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Old 05-17-2008, 02:13 PM   #1
xxbobbyrxx
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car cranks but won`t start

1990 L98 car cranks & wants to turn over but will not,,,no pulse to the injectors..i know this is pretty much an open ended question,& it could be a long list,,but other than a battery/starter/injectors what could the culprit(s) be here?
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Old 05-17-2008, 03:43 PM   #2
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L-98 Engine Start Sequence

Posted by Grumpyvette


Info that might help - (before you ask, yeah the LT1 is very similar).

This flow chart might help.

http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf

L-98 Engine Start Sequence

When you start an L-98 engine Corvette, a series of events take place that causes the engine to run. Knowing the sequence will help you troubleshoot no start conditions.

Fuel Rail Pressurization:

When you first turn the key to the “on” position, the fuel pump will run for 2 seconds pressurizing the fuel rails. There is a Shraeder valve on the passenger side fuel rail near the rear of the engine and if you measure the pressure there after the pump runs, you should see between 40-42 pounds of pressure. The reading will go to 38-40 pounds nominal once the engine is running.test by attaching a fuel pressure gauge to the fuel rail at the shrader valve, on TPI and LT1 engines its located on the pass side fuel rail.

Initial Crank Action:

If you then rotate the key to the start position (assuming the anti-theft system has not disabled the starter), the engine will rotate.

Once the oil pressure has reached 4 PSI, the oil pressure switch will close allowing the fuel pump to run. (Note that you should have a black oil pressure switch/sender. It is mounted behind the distributor on the driver’s side and if it is not black, it is suspect due to a run of bad units that stayed in the GM parts pipeline for some time).

The distributor will send a string of pulses to the ECM (Engine Control Module) in response to the engine being rotated by the starter. These pulses continue as long as the engine turns (both starting and running) and if they are not present, the engine will not run.

ECM Reaction:

If the ECM sees oil pressure greater than 4 PSI and the reference pulses from the distributor, it will energize the injector drivers which will begin pulsing the injectors on for 4 ms (milliseconds) periods. (In the L98, all injectors on one side of the engine fire at the same time followed by all injectors on the other side firing at the same time. On the LT-1, the injectors are fired individually at the appropriate time).

The ECM will also pull in the fuel pump relay in effect paralleling it electrically with the oil pressure switch. (If the fuel pump relay fails, you can still normally get the car to start and run unless you can’t make at least 4 PSI oil pressure. This is a “limp home mode” feature put in place to allow for a fuel pump relay failure).

The ECM also monitors the TPS (Throttle Position Sensor mounted on the throttle body assembly) and wants to see .54 volts at this time. If it sees appreciably more than 0.54 volts, it will assume the engine is flooded and the driver has pressed the accelerator to the floor to clear the flooded condition and restrict the fuel flow as a result. (.54 volts during start and at idle from the TPS is very important to both starting and run performance.)

Assuming the ignition module is good (meaning there is a spark of sufficient intensity to ignite the fuel), the engine will “catch”.

Engine "Catches":
When the engine catches, the MAF (Mass Air Flow sensor mounted just ahead of the throttle body) sends a signal to the ECM advising that air is flowing and also just how much air is being pulled through to the intake manifold. The ECM takes note of the amount of air being consumed and adjusts the injector pulse width to around 2.2 ms nominally so as to attain a proper air/fuel mixture to insure combustion. (This is how the 1985 through 1989 L-98 works. For information on the 1990 and 1991 L-98 variant, see the Note below).


The engine should show an initial idle speed of around 900-1100 RPM and then slowly diminish to 600-700 RPM unless the air conditioner is on in which case it will run at around 800 RPM.

If this does not happen, the Idle Air Mixture valve (located on the throttle body) may be misadjusted. Alternatively, there may be a leak in the intake manifold or another vacuum leak may be present. Listen for hissing sounds---there should be none.

ECM Mode:

The engine will now be in Open Loop mode meaning that the ECM is controlling the air/fuel mixture by referencing values stored in memory.

Once the Oxygen sensor (mounted on the exhaust pipe) reaches operating temperature of several hundred degrees, the Manifold Air Temperature (MAT) sensor shows an intake air temperature of more than 140 degrees and the Engine Coolant Temperature (ECT) has reached 160 degrees, the computer will switch to closed loop mode meaning the Oxygen sensor’s output is examined along with the MAT and ECT outputs and the ECM adjusts the injector pulse widths (more “on time” or less “on time”) to constantly strive for a 14.7:1 air/fuel mixture which is the best mixture to hold down pollution.

Note that prolonged idling can force the computer back into open loop mode.

Note: In 1990, the MAF was eliminated from the engine in favor of a speed/density system. This system uses a sensor called the MAP sensor which measures the Manifold Absolute Pressure (hence the name MAP) and compares it with the atmospheric pressure outside the intake manifold. This information, coupled with the Manifold Air Temperature, Engine Coolant Temperature and Engine RPM is used by the ECM to determine the amount of air entering the cylinders. It is a different way of reaching the desired 14.7:1 air-fuel mixture ratio but functionally is like the MAF system in that the ECM uses the feedback to control the "on time" for the injectors.

Corvette used this approach in the 1990 and 1991 L-98 engines and in the 1992 and 1993 LT-1 engines. With the 1994 model C4, they went back to the MAF system. Note that MAF based systems are far more accurate since they measure air flow directly whereas the MAP system infers air flow indirectly. A multitude of things can throw the calculation off and Corvette returned to the MAF system beginning with the 1994 C4 (with a MAP backup). From a troubleshooting standpoint, the MAP operation comes into the sequence the same place that the MAF does.

Summary:

If you have a no start condition or if the L-98 starts and then dies, check the above items in sequence to see if all the events are occurring as required.

A Scan Tool makes this job much easier and is a highly recommended troubleshooting aid for these sorts of problems.

http://www.harborfreight.com/cpi/cta...emnumber=46030

Most of the C4 Corvettes used a MAF (Mass Air Flow) sensor to determine how much air is being pulled into the intake manifold. The exceptions are the 1984 Corvette that used a speed density system--a sort of predictive method of measurement---and the 1990 through 1993 C4 models which were also speed density based. In 1994, Corvette went back to the MAF based system but used the speed density approach as a back up. (1989 Bosch MAF installation shown at right).

A Mass Air Flow sensor has an extremely fine wire inside its bore. The 1985 through 1989 C4 engines used a Bosch MAF sensor that heated the wire to 100 C. The 1994 and later C4 models used a AC/Delco MAF that heated the wire to 200 C. The amount of current required to reach the temperature is measured in each case. (Note: the LT-5 engine used in the ZR-1 used a speed density system and continued to use that system in 1994 and 1995 since the engines had already been made prior to the last two years of production. The ZR-1 therefore has no MAF even after Corvette went back to the MAF based system).

Theory of Operation

As the air travels past the heated wire enroute to the intake manifold, it will cool the wire and additional current is added to again heat the wire to the design temperature. Since the amount of air moving past the sensor is directly related to the amount of cooling experienced by the heated wire, a feedback condition is established whereby the exact amount of moving air is directly related to the amount of current passing through the wire and the intake air is therefore precisely measured.

Once the amount of air is known, the computer controlling the engine can add or subtract fuel as required to maintain the magic 14.7:1 air-fuel mixture resulting in the cleanest burn possible from an emissions (pollution) standpoint.

It does this by varying the "on time" of the fuel injectors. The injectors are pulsed on and off and the width of the pulse is lengthened or shortened as required. When you first start a typical engine, the pulse width is around 4 milliseconds but as soon as the engine "catches" the pulse width is shortened to about 2.2 milliseconds for idle. During operation, the measured air flow through the MAF will cause the computer to increase or decrease the pulse width as explained above.

MAF Operating Conditions

The Bosch MAF is more complex than the AC/Delco version. Both measure the air flow but the Bosch MAF has a circuit called the 'burn-off circuit' that cycles on for about 2 seconds when you shut the engine down. This circuit heats the wire to a high enough temperature to burn off any residue that may have collected on the wire during operation. If you are in a quiet area, you can hear the relays click on and then off on a 1985-1989 C4 as the burn-off cycle occurs.

There are two relays involved with the Bosch MAF: A power relay that passes current to the MAF wire during normal operation and the burn-off relay that provides the current for the cleaning cycle. Both are located on the firewall in the engine compartment, just behind the battery on the drivers side. Bad MAF power and burn-off relays can cause hard starting problems and should be changed periodically as preventative measure and any time you experience hard starting conditions.

The AC/Delco MAF has a power relay but no burn-off relay. For this reason, you should pay even closer attention to the condition of your air filter on a later model C4 than normal since a contaminated wire in a AC/Delco MAF is going to stay contaminated for the most part and cause false signals to be passed to the computer.

Also, the Bosch MAF outputs its information as a analog signal to the computer but the AC/Delco sends its signal as a digital component of varying frequency. For this reason, you cannot measure it's operation directly.

A scan tool is generally the best way to troubleshoot engine problems and with the 1994 and later Corvette, it is virtually mandatory. (An oscilloscope will also work on the AC/Delco MAF but a regular test meter will not).

MAF Problems

Faulty MAF sensors will normally light the check engine light on the drivers information center if the problem is constant and store a trouble code. If intermittent, a trouble code will still be stored as long as the battery is not disconnected.

Normally, the problem is a poor connection at the sensor and wiggling the wires, unplugging and reinserting the connector will often cure the problem.

A faulty MAF will normally cause a no start or difficult start condition and although you can eventually get the car into the "limp-home" mode in most cases, you need to attend to the problem ASAP.

This flow chart might help.

http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf

AC/Delco sensors can become intermittent or give false readings if the wires become contaminated as explained above.

The MAF is a critical part of the emission control system and as such will cause the computer to react to problems very quickly, setting trouble codes and reducing performance in ways that cannot be ignored for long.

MAF Mods

The Bosch MAF is often modified by removing the two screens that are present in the front and rear of the cylinder. Removing these screens significantly increases the air flow through them and this results in more horsepower. Removing the screens is an old trick from the Corvette Challenge days in 1988 and 1989. It does work but is illegal in many states so be advised not to do anything that will get you arrested for a pollution violation.

The AC/Delco MAF is not readily modified. It is what it is but since it is a larger diameter than the Bosch, it responds well to changing the air filter to a free flowing type such as the K&N filter.

Welcome to C4 vette codes it is very ....repeat very important that if you are not savvy of working on your Vette ...you would be better off - taking your car to a dealership for repairs on your trouble codes. However if you feel that you want to dive right in ..than you have come to the right place. First locate your car's alcl this component is located just below the instrument panel and to the left of the center console. Remove the plastic cover the first two slots to your right are the A & B slots for a drawing of the alcl module's picture is added below.

The A slot is the diagnostic slot and the B slot is the ground slot. insert the computer key into these slots (with the engine off) this is very important...now only put the ignition key to on ( not start !!!) the check engine light will display a code 12 which is one flash followed by two flashes. This code will be flashed three times ..followed by the trouble code stored in your car's computer.

What ever the code is it will be flashed three times. Have a paper and pencil ready and write down the code.

code 13 =1 flash followed by 3 flashes =>oxygen sensor
code 14 =1 flash followed by 4 flashes =>coolant sensor
code 15 =1 flash followed by 5 flashes =>coolant sensor
code 21 = 2 flashes followed by 1 flash =>throttle position sensor
code 22 = 2 flashes followed by 2 flashes=> throttle position sensor
code 23 = 2 flashes followed by 3 flashes=> manifold air temp sensor
code 24 = 2 flashes followed by 4 flashes=> vehicle speed sensor
code 25 = 2 flashes followed by 5 flashes=> manifold air temp sensor
code 32 =>egr system
code 33 =>map sensor
code 34 =>maf sensor
code 35 => idle air control
code 41 => cylinder select error
code 42 => electronic spark control
code 43 => electronic spark control
code 44 => lean exhaust
code 45 => rich exhaust
code 51 => PROM
code 52 => fuel calpak
code 53 => system over voltage
code 54 => fuel pump circuit
code 55 => ecm
code 62 => oil temp

Please remember that if you have the computer key installed in the alcl and you start the engine (you will ruin the engine's computer) only put the ignition to on (not to start).

If you should get a check engine soon display.. you can use the above procedure and codes to buy the right part or at the very least to keep from getting taken for a ride and be made to pay hight prices for some inexpensive module that you could have installed yourself.

If your engine displays a trouble code ... your engine will go into limp mode ..it will still run but very poorly. You might be able to reset the computer if it will not start (just to get home) by disconnecting both battery cables and re-installing them ...this is not recommended ..but if you are stranded it might help unitl you get your car home or to a repair shop..good luck.

1985 TO 1991:

Code #12: Normal No Codes.
Code #13: Open Oxygen Sensor Circuit.
Code #14: Coolant Sensor Circuit Low.
Code #15: Coolant Sensor Circuit High.
Code #21: Throttle Position Sensor High.
Code #22: Throttle Position Sensor Low.
Code #23: Manifold Air Temperature Circuit High.
Code #24: Vehicle Speed Sensor.
Code #25: Manifold Air Temperature Circuit Low.
Code #32: EGR System Failure.
Code #33: Mass Air Flow Sensor High.
Code #34: Mass Air Flow Sensor Low.
Code #36: Mas Air Flow Sensor Burn-Off Function Fault.
Code #41: Cylinder Select Error.
Code #42: Electronic Spark Timing.
Code #43: Electronic Spark Control.
Code #44: Lean Exhaust indication.
Code #45: Rich Exhaust Indication.
Code #46: Vehicle Anti Theft Fault.
Code #51: Faulty Mem-Cal.
Code #52: Fuel Calpak Missing.
Code #52(1990-91 Corvette Only): Engine Oil Temperature Sensor Low.
Code #53: System Over Voltage.
Code #54: Fuel Pump Circuit Low Voltage.
Code #55: Defective ECM.
Code #62: Engine Oil Temperature Sensor Circuit High.

ECM CODES 1992 TO 1993:

Code #12: Normal No Codes.
Code #13: Left Oxygen Sensor Circuit.
Code #14: Coolant Temperature Sensor Circuit High.
Code #15: Coolant Temperature Sensor Circuit Low.
Code #16: Opti-Spark Ignition Timing System.( Low Pulse)
Code #21: Throttle Position Sensor Circuit High.
Code #22: Throttle Position Sensor Circuit Low.
Code #23: Intake Air Temperature Sensor Circuit Low.
Code #24: Vehicle Speed Sensor Circuit.
Code #25: Intake Temperature Sensor Circuit High.
Code #26: Quad-Driver Module #1 Circuit.
Code #27: Quad-Driver Module #2 Circuit.
Code #28: Quad-Driver Module #3 Circuit.
Code #32: Exhaust Gas Recirclation Circuit.
Code #33: Manifold Absolute Pressure Sensor Circuit Low.
Code #34: Manifold Absolute Pressure Sensor Circuit High.
Code #36: Opti-Spark Ignition Timing System. (High Resolution Pulse.)
Code #41: Electronic Spark Timing Circuit Open.
Code #42: Electronic Spark Timing Circuit Grounded.
Code# 43: Electronic Spark Control Circuit.
Code #44: Left Oxygen Sensor Circuit Lean.
Code #45: Left Oxygen Sensor Circuit Rich.
Code #51: Mem-Cal Error.
Code #52: Engine Oil Temperature Sensor Circuit Low.
Code #53: System Voltage.
Code #55: Fuel Lean Monitor.
Code #56: Vacuum Sensor Circuit.
Code #61: Secondary Port Throttle Valve System.
Code #62: Engine Oil Temperature Sensor Circuit High.
Code #63: Right Oxygen Sensor Circuit Open.
Code #64: Right Oxygen Sensor Circuit Lean.
Code #65: Right Oxygen Sensor Circuit Rich.
Code #66: A/C Pressure Sensor Circuit Open.
Code #67: A/C Pressure Sensor Circuit. (Sensor or A/C Clutch Circuit Problem)
Code #68: A/C Relay Circuit Shorted.
Code #69: A/C Clutch Circuit.
Code #72: Gear Selector Switch Circuit.

CODES 1994 TO 1996:

DTC #11: Malfunction Indicator Lamp Circuit.
DTC #13: Bank #1 Heated Oxygen Sensor #1 Circuit.
DTC #14: Engine Coolant Temperature Sensor Circuit Voltage Low.
DTC #15: Engine Coolant Temperature Sensor Circuit Voltage High.
DTC #16: Distributor Ignition System Low Pulse.
DTC #18: Injector Circuit.
DTC #21: Throttle Position Sensor Circuit Voltage High.
DTC #22: Throttle Position Sensor Circuit Voltage Low.
DTC #23: Intake Temperature Sensor Circuit Voltage High.
DTC #24: Vehicle Speed Sensor Circuit.
DTC #25: Intake Air Temperature Sensor Circuit Voltage Low.
DTC #26: Evaporative Emission Canister Purge Solenoid Valve Circuit.
DTC #27: EGR Vacuum Control Signal Solenoid Valve Circuit.
DTC #28: Transmission Range Pressure Switch Assembly Fault.
DTC #29: Secondary Air Injection Pump Circuit.
DTC #32: Exhaust Gas Recalculation.
DTC #33: Manifold Absolute Pressure Sensor Circuit High.
DTC #34: Manifold Absolute Pressure Sensor Circuit Low.
DTC #36: Distributor Ignition System High Pulse.
DTC #37: Brake Switch Stuck On.
DTC #38: Brake Switch Stuck Off.
DTC #41: Ignition Control Circuit Open.
DTC #42: Ignition Control Circuit Shorted.
DTC #43: Knock Sensor Circuit.
DTC #44: Bank 1 LF Heated Oxygen Sensor #1 Circuit Lean.
DTC #45: Bank 1 LF Heated Oxygen Sensor #1 Circuit Rich.
DTC #47: Knock Sensor Circuit Or Module Missing.
DTC #48: Mass Air Flow Sensor Circuit.
DTC #50: System Voltage Low.
DTC #51: EEPROM Programming Error.
DTC #52: Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #53: System Voltage Low.
DTC #55: Fuel Lean Monitor.
DTC #58: Transmission Fluid Temperature Sensor Circuit Low.
DTC #59: Transmission Fluid Temperature Sensor Circuit High.
DTC #62: Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #63: Bank 2 RF Heated Oxygen Sensor #1 Circuit Open.
DTC #64: Bank 2 RF Heated Oxygen Sensor #1 Circuit Lean.
DTC #65: Bank 2 RF Heated Oxygen Sensor #1 Circuit Rich.
DTC #66: A/C Refrigerant Pressure Sensor Circuit Open.
DTC #67: A/C Pressure Sensor Circuit Sensor or A/C Clutch.
DTC #68: A/C Relay Circuit.
DTC #69: A /C Clutch Circuit.
DTC #70: A/C Clutch Relay Driver Circuit.
DTC #72: Vehicle Speed Sensor Loss.
DTC #73: Pressure Control Solenoid Circuit Current Error.
DTC #74: Traction Control System Circuit Low.
DTC #75: Transmission System Voltage Low.
DTC #77: Primary Cooling Fan Relay Control Circuit.
DTC #78: Secondary Cooling Fan Relay Control Circuit.
DTC #79: Transmission Fluid Overtemp.
DTC #80: Transmission Component Slipping.
DTC #81: Transmission 2-3 Shift Solenoid Circuit.
DTC #82: Transmission 1-2 Shift Solenoid Circuit.
DTC #83: Torque Converter Solenoid Voltage High.
DTC #84: 3-2 Control Solenoid Circuit.(Auto Only).
DTC #84: 2nd And 3rd Gear Blockout Relay Control Circuit.
DTC #85: Transmission TCC Stock On.
DTC #90: Transmission TCC Solenoid Circuit.
DTC #91: One To Four Upshift Lamp(Manual Only).
DTC #97: VSS Output Circuit.
DTC #98: Tachometer Output Signal Voltage Wrong.

You really can't be effective at playing mr-fix-it with out the correct tools especially on the more modern cars that are computer controlled, the days of effectively tuning by ear and vacuum gauge and engine sound went out with carbs.
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Old 05-17-2008, 05:13 PM   #3
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Fuel pump. Pull the cap off the shrader valve on the fuel rail and push in the valve needle to see if you are getting fuel to the rails. It should spray out ,so be careful
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Old 05-19-2008, 09:37 AM   #4
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Quote:
no pulse to the injectors
The Grumpsters info on the C4 'start sequence' is really great.
That was posted seems like years ago and it's one of the main sources of info I used to learn about our TPI engine controls.

But back to the 'no pulse to the injectors'.... That's an interesting aspect of your no start issue to me ....

Did you use a NOID light to determine there are no injector pulses?

Maybe a better question is; How did you determine there are no injector pulses?
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Old 05-19-2008, 10:05 AM   #5
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with a noid light,,
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Old 05-22-2008, 11:25 AM   #6
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Quote:
Originally Posted by xxbobbyrxx View Post
with a noid light,,
Good check with the NOID light.............bobbyrxxxx.....

Question: Did this symptom start after any work was done to the engine?

Hmmm.... That would lead me to think there is a problem in the distributor.
There is a pickup coil and a reluctor ring IIRC that sends tach pulses to the ECM. When the ECM receives the pulses it activates the Injector Drive circuitry which then pulses the injector low side to ground thru the electronic injector driver circuit.

But before we go that far, can you check to make sure one side of the injectors are getting +12 Volts?
It's ALWAYS a good idea to eliminate the MOST SIMPLE cause of a problem before going to the more complex ones.

A little 'Troubleshooting 101' there, LOL.

Use any old multimeter, set to 20 volt scale or whatever scale you have above 12 volts. If it's an auto range meter just set it to chsck DC voltage.

Pull any one of the injector plugs.
Pick one up front that's easy to get to.

You will see TWO little metal contact or connectors in the injector harness plug connector.
Turn the ignition key to the 'on' position.
Place the negative meter lead to ground. (engine metallic surface)
Place the red or positive lead on one of the two injector plug metal connector surfaces.
See if you have +12 volts there. If not, move the meter lead to the other injector plug connector surface.
See if you have +12 volts there.
Turn the ignition key off.

The injectors are wired in PARALLEL for each BANK. This is a 'batch fire' system for the injectors. Fuel is 'made available' but there is no individual injector pulse for each cylinder as in the Sequential Fuel Injection systems.

They ALL turn on at the same time but are split up into TWO sides like a stereo.
The ECM 'fires' one bank then the other.
+12 VOlts is supplied to ALL the injector 'positive' terminals whenever the key is on.

So make sure you have +12 volts at the injector plug.
You really only need to check ONE injector plug on each side of the engine to determine this..... because they are wired in parallel.

If you have the +12 volts there then the distributor ignition module may be bad or the distributor may have 'pickup' circuit trouble.

TIP: Check the connectors on the side of the distributor to make sure they are plugged in well to the distributor.
Check the large flat connector coming from the distributor to make sure it is plugged in good.
You guys don't laugh, I've left them unplugged a few time myself.


TIP: If the +12 Volt lead going into the distributor is not connected or not making a good connection, the engine will not start AND IIRC the tach pulses will not be fed back to the ECM so.... the injectors will not pulse.

Don't rule out ANYTHING, no matter how simple, as being a LIKELY SUSPECT.
More Troubleshooting 101, LOL.

The 'reluctor ring' is a round device inside the distributor housing with 8 'tips' on it sort of like an 8 sided star. As the tips pass by the pickup coil, a 'reference pulse' is generated that is wired back to the ECM.

THis let's the ECM detect the engine is turning and supplies reference for the ignition module.
Until the engine is turning, the injectors will not fire as ther is no reason for them to OTHER than the ECM does 'prime' the engine during the before start sequence.

That's why these things normally fire up soon as you engage the starter.
The ECM has done all the 'work' to set the correct start conditions before the starter has a chance to turn the engine over more than a couple of rounds.

My 91 fires up in about 1/2 second even if it's been setting for weeks.

BTW, this doesn't sound like a 'too difficult' problem so hang in there, you will find it.

Post back here with you reserach and I or someone else here will give you more tips on finding the problem.

Last edited by VetNutJim; 05-22-2008 at 12:00 PM.
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Old 05-23-2008, 06:47 AM   #7
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vetnutjim,,,thanks for this info,,to answer your question,,yes i did have work done,,,my car was running sluggish,,(1990 auto) took it to my neighborhood mechanic,,had a tune up & he replaced 3 bad injectors ( i probably should of changed out the other 5),,car ran like a champ,,,a day later..wife and i went to see a movie,,came out of theater,,opened her door, unlocked (power locks) my door,,,as i walked around,,she didn`t know i unlocked the doors,,and she re-locked the doors,and alarm went off...i opened my door with key,,alarm stops ,,,,i start the car up,,no problem,,,6 seconds later engine stops,,.try to restart..car cranks,,but won`t start,,,i wait awhile,,,try again,,samething,,,,towed it back to him,,,,,come sunday morning,,i ride back to his shop,,with my other key,,,car starts up...i let it idle,,about 3 minutes later,,car dies,,,,,i don`t think it`s a vats issue,,,he changed out the ecm,,that didn`t work,,he`s using a noid light to the injector,,but can not get a pulse,,not being a mechanic,,i`m stumped,,i don`t know if that alarm going off had anything to do with it,or was it just a coincidence,,he might think there`s a short somewhere maybe the theft deterent relay,,,,,,,,i`ve read other posts.here and other forums,,about cars cranking and not starting,and the nightmares they went through,,until they changed their injectors (all of them),even though they didn`t think that was the problem.
and voila there cars started,,i will pass this info on,,have a great holiday weekend to all bob,,,,
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Old 05-23-2008, 08:34 AM   #8
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Just to let you know. I had a VATS problem a month ago. I found out the VATS has control over the starter and the fuel. There is a starter enable relay and the VATS module, The module sends a signal to the ECM to turn the fuel injectors on and also sends voltage to the starter enable relay to allow the starter to operate. Since this happened right after the VATS was triggered I wonder if it is allowing the starter to operate but not sending a signal to the ECM to turn on the fuel injectors? I wanted to bypass the VATS in my car but I was told that I would have to buy a new chip for the ECM that bypassed the VATS or buy a square wave generator to tell the ECM to energise the fuel injectors. My VATS module is located in the upper right hand side of the dash and was a pain to get to. Also the grounds for the fuel injectors are located on the left side of the transmission bell housing if they are not clean and tight they could shut off the injectors also.....Just my 2 cents worth hope this helps
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Old 05-23-2008, 11:06 AM   #9
VetNutJim
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This is a long shot but....clean up the little 'pellet' on your ignition key.

It's just a resistor inside the key shaft so you can stick it under the faucet and wash'er off then dry it and try it.

Check the condition of the two little 'tabs' on each side of the key as well.
Do they look worn or damaged?

I believe if VATS is activated the starter won't engage.

Clean up the key pellet and see if you get injector pulses.
That would be the most simple of solutions for your no start condition.
Remember: Never rule out ANYTHING as a LIKELY SUSPECT.......

If it's the key, that would be grrreeeattt!!!
Like I said, this is a 2000 meter shot, LOL.
My key pellets are worn down to little nubs and the key still operates the VATS system.

But. . . . I noticed that I have to 'wiggle' the key now to get my 'Lights On' reminder chime to work now when I open the door with the lights still on.

If your mechanic doesn't know a lot of nuances about Corvettes, it could take him a long time to fix it.
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Old 05-23-2008, 11:12 AM   #10
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Quote:
Originally Posted by hoopty View Post
Just to let you know. There is a starter enable relay and the VATS module
Not on his '90. Both the Fuel Enable and the Starter Enable (energizing the Starter Enable Relay) functions are performed by the CCM. There is no VATS Module on the '90-'96.
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Old 05-23-2008, 02:02 PM   #11
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mechanic did resistance test on injectors,,was told it read "11" on 7 of the injectors a "2" on the last one.......hmmmm..i called up jon from FIC,,who ACTUALLY called my mechanic to help me out,,( a fellow ex-jerseyean who was smart enough to leave this state,,did you know that jersey charges an EXIT tax of 2 % when you sell your house & if you leave the state) but that`s another topic,,,,,,,,,,,,,,any way ordered new injectors from Jon,,,mechanic told Jon & me there is a ground issue,,there is spark,,,hoping the new injectors solve it,,if not???,then looking into vats, and hoping it`s not ccm trouble,,thanks to all
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Old 05-23-2008, 08:37 PM   #12
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mechanic did resistance test on injectors,,was told it read "11" on 7 of the injectors a "2" on the last one.......hmmmm..i called up jon from FIC,,who ACTUALLY called my mechanic to help me out,,( a fellow ex-jerseyean who was smart enough to leave this state,,did you know that jersey charges an EXIT tax of 2 % when you sell your house & if you leave the state) but that`s another topic,,,,,,,,,,,,,,any way ordered new injectors from Jon,,,mechanic told Jon & me there is a ground issue,,there is spark,,,hoping the new injectors solve it,,if not???,then looking into vats, and hoping it`s not ccm trouble,,thanks to all
What happened to the original issue of 'no pulse to the injectors' ?

I may be a little unorthodox but......
If I found ONE suspect injector, I'd UNPLUG that one and start the engine up to make SURE I didn't have additional problems to go along with that one injector.
............I'd do that BEFORE...EVER,EVER taking anything else apart.
Yes, it WILL run on seven cylinders.

Stupid question: Does your 'mechanic' not know how to use the SEVEN injectors he 'thinks' are good to troubleshoot and analyze the rest of the engine control system?

Pardon me but, I think when the injectors are replaced there's a GOOD chance you'll get the news that; "Oh, after we put the new injectors in we found 'such and such' bad along with 'so and so.' Sorry, we'll have to order up a new 'so and so'. Should be here in a few more days."

The 'Shotgun' approach to fixing things can get awfully 'extensive'.
Methodology seperates the 'ordinary' from the 'extraordinary' guys.

Good luck with it podner.

Last edited by VetNutJim; 05-23-2008 at 09:10 PM.
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Old 05-30-2008, 04:52 PM   #13
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recieved the 22# bosch injectors from JON at fuel injector connection,,great guy,,he even called my mechanic,,,anyway,,they changed them out,and what do you know,, car started ,,,so far so good,,,obviously i can`t explain it,,but was this all it took?,,,thanks to everyone who chimed in,,have a great weekend
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Old 08-10-2008, 02:31 AM   #14
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Cool cranks but wants to start

fuel pump tap on the fuel inlet where u put gas in take cap of bang it with hard rubber malet few times might work happen to me
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Old 04-17-2009, 06:03 PM   #15
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95 Corvette Won't Start and major coolant leak

Hi All,
I've been scouring the internet looking for a solution to my problem but I can't seem to figure it out. My 95 Corvette will not start... I've done all of the standard checks and I'm down to the injectors not firing. I am getting a strong signal to the injectors but they aren't pulsing when the car turns over. The car will run for a few seconds when I spray ether into the intake so I know it is getting spark.

Regardless, I changed the distributor, the spark plug wires, and the spark plugs. The fuel pump is working and I'm getting excellent fuel pressure with the key on and it's holding when I shut the car off. I brought the car to the dealer and had them install a brand new computer. I checked the connections to the distributor and they are all connected, I even disconnected and reconnected them. There was water in the lines and the injectors were gummed up. I pulled the fuel pump out and cleaned all of the gas, I then blew out the fuel lines. I pulled the fuel rail off and bench tested each fuel injector. I was able to get them freed up and ran some alcohol through the injectors. They all worked great. I got some fresh high octane gas in the car right now... I am also getting 12V at each injector.

Do you think it's the fuel injection ground? Is that on the drivers side of the car on the bell housing with about 3 or 4 other wires?

Also, I have a major coolant leak coming out of the right side of the block above the starter. I mean... it's draining as fast as I'm pouring water into the cooling system. I got under the car but can't see where the leak is coming from. I also pulled off the body panel on the right side to see if I could get a better view but I can't see where it's coming from. Any ideas??

Thanks in advance.

-Larry
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