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Discussion Starter #1
I'm having fuel pump problems again I replaced the fuel pump because the fuel pressure would just drop off and the car would die. Turning the key on and off did nothing but putting the jumper in the oil pressure switch and tapping it on and off quickly would make the pump run and the car will start and run but the fuel pressure will just drop off and the car will die I thought I replaced the fuel pump relay but aparently not. I replaced the one near the wiper motor. But when I jump the oil pressure switch connecter I hear a click from behind the battery is that the fuel pump relay ?
 

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putting the jumper in the oil pressure switch and tapping it on and off quickly would make the pump run and the car will start and run but the fuel pressure will just drop off and the car will die
What does engine do if you leave jumper in place?

when I jump the oil pressure switch connecter I hear a click from behind the battery
is that the fuel pump relay ?
No
FP relay is on firewall

Clicking is most likely from MAF relay getting power when OP switch bypassed

see circuit diagram


 

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Yes and if your going to replace that I'd suggest you replace the maf relays as well.
WRONG
Check out the diagram above.

Power from the OP switch does not go through the control side of the pump relay so how can it
" make it click "
 

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Discussion Starter #5
If i tap the jumper quite a few times until I hear the fuel flowing by the fuel regulator I can push the jumper in and the pump will stay running for a couple seconds to 5 or 7 munutes then it stops on it's own and the fuel pressure drops off. I definitly replaced the correct relay I replaced the one on the firewall. I don't use the MAF I have an aftermaket ECU but the factory ECU is still in place to run the dash and the fuel pump.
 

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Discussion Starter #6
If you follow ORN 340 around to the oil pressure switch it goes thru the oil pressure switch then comes around and connects to RED 120 just after that it has a symbol what is that symbol ? and what does it mean ? It's just above where it says "fuel pump" is that a fusible link ? could this be my problem ?
 

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If you follow ORN 340 around to the oil pressure switch it goes thru the oil pressure switch then comes around and connects to RED 120 just after that it has a symbol what is that symbol ? and what does it mean ? It's just above where it says "fuel pump" is that a fusible link ? could this be my problem ?
That's the Fuel Pump Fuse in the Fuse Box at the outside edge for the passenger side dash. 10 Amp Fuse, I believe it is in the lower right corner. May be labeled FP or FR.
 

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It is NOT that fuse. If that fuse were blown then the fuel pump would NEVER power up.

Its sounds as if your FP relay is indeed the culprit. But if you did replace the correct one and still have the problem then you have a wiring problem going to the FP relay or coming off the FP relay. Check that fusible link too! You can do that by checking at Terminal E of the FP Relay for 12vdc+ (doesnt matter what position ignition is in this spot is hot all the time).
 

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It is NOT that fuse.
Let me get this straight, you're saying that the device circled in red is not a fuse? Oh dear!



If that fuse were blown then the fuel pump would NEVER power up.
I never said the fuse was blown, I answered the OPs question about what the schematic symbol was and also where that device was located. It is possible for a poor contact in the fuse block to cause intermittent current flow through the fuse without it blowing. Again, I'm not insisting that this is the OPs problem, just that the whole circuit needs to be looked at.
 

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Let me get this straight, you're saying that the device circled in red is not a fuse? Oh dear!

Nope...not what i wrote... You forgot to quote the next sentence also! It says "it is NOT the fuse" It does not say "it is NOT A fuse". It is not the fuse blown causing his problem. If the fuse were blown he would NOT get any power to the fuel pump no matter what he jumpered out. (excluding jumping out the fuse itself of course).



I never said the fuse was blown, I answered the OPs question about what the schematic symbol was and also where that device was located. It is possible for a poor contact in the fuse block to cause intermittent current flow through the fuse without it blowing. Again, I'm not insisting that this is the OPs problem, just that the whole circuit needs to be looked at.
Possible....but very unlikely.

First thing i would do is check for 12vdc+ at relay terminal (E) or on the supply side (left) of the oil pressure switch. This will rule out the fusible link( (the fusible link is marked "fusible link" at the very top of the schematic and is wired directly to the battery) and all wires that lead to those points. Check for the 12vdc+ at those points with IGNITION in the OFF position.
 

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I think some people might be misunderstaning this FP circuit.

The only purpose of the FP relay is to give power to the FP when you FIRST START the car, after the car is running the oil pressure comes up and CLOSES the oil pressure switch which is in series with the fuel pump. This oil pressure switch is a SAFETY to keep the car from running when there is NO oil pressure (or atleast not enough to keep the OIL Pressure switch from closing whatever that value may be).

Here is how it works... There will be 12vdc+ sitting at terminal E of the FP relay at all times. When you put the key in the ignition and turn it to the start position 12vdc+ is sent from the ECM (terminal A1) to the coil of FP relay (term C)which energizes that relay and closes contacts on the FP relay terminals A to E and that gives the 12vdc+ sitting on FP relay terminal E (remember term E is hot at all times) a place to go...across E to A then to the fuel pump (assuming FP Fuse is good). Then sometime after that (i would have to hunt that time period up in the FSM) the relay deenergizes. But that doesnt kill the power to the FP because remember the engine is running and your oil pressure has come up and closed the oil pressure switch. Now power for the fuel pump is coming from the fusible LINK across the closed oil pressure switch and across the Fuel Pump fuse to the fuel pump. Now if you lose oil pressure the fuel pump will shutoff and the engine will die. (out of gas).
So you see the FP relay cannot be used for anything other than starting the car up....otherwise you would not have the advantage of the oil pressure switch safety circuit for loss of oil pressure. If the oil pressure safety switch opened because of loss of oil pressure and your FP relay were powering the fuel pump the oil pressure safety switch would not kill the engine upon loss of oil pressure because the FP Relay would be powering it also at the same time.

Dont confuse oil pressure safety switch with oil pressure sending unit. The sending unit is used to tell your oil pressure gauge how much oil pressure there is (PSI).

So you see the FP Relay is kind of a misnomer. It is not used while the car is being driven. You are running on the oil pressure switch during that time.
 

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Discussion Starter #12
Where is the fuel pump fusible link? and does anybody know where the wires from the fuel pump relay to the fuel pump itself are hidden?
 

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Nope...not what i wrote... It says "it is NOT the fuse" It does not say "it is NOT A fuse".
Right you are! My apologies. Can we agree that I never said THAT fuse was the problem? In fact the only input I've made to this thread to the answer the OPs question about what the symbol was.
 

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Right you are! My apologies. Can we agree that I never said THAT fuse was the problem? In fact the only input I've made to this thread to the answer the OPs question about what the symbol was.
nope too bad you are forever to blame... lol


The fusible links are all located behind the battery coming off the terminal. Which one it is? Dunno.

Just speculating but I wouldn't think it to be the fusible link. you really have to pull some amps for that to break. I would look more along the lines of the oil pressure switch. Easy enough to check. just pull it and make a simple jumper. If the car starts and stays running.. you have the culprit.

Also pay attention to the wiring around and inside the relay connectors. they can look solid but be broken at the metal and the wire covering still inplace.
 

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Discussion Starter #15
I have already jumped the oil pressure/ fuel pump safety switch but I would have to touch the jumper to the connector a few times before the pump would run for a short time
 

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with the car off.. Have you installed a jumper and tried to run the car.. not something you just touch.. but a piece of heavy guage wire across the two terminals?

if so and it runs constant only when pressing on the wires then a wire is broken inside the connector back shell at the wire connector.
 

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Discussion Starter #17
I jumped the terminals on the oil pressure/ fuel pump safety switch with the key both on and off with piece of 10 gauge wire with 2 male spade connecters on it. I had a fuel pressure gauge hooked up and the gauge didn't move. but after tapping one of the spade connecters on the terminal a few times the pump would run and I would get fuel pressure so I pushed the spade connecter all the way in and watched the fuel pressure gauge it would sit at 47 PSI for a few seconds to a few minutes I tried to start it it ran for a few minutes then the gauge dropped an the car died. This happened a few times.
 

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I think some people might be misunderstaning this FP circuit.

The only purpose of the FP relay is to give power to the FP when you FIRST START the car, after the car is running the oil pressure comes up and CLOSES the oil pressure switch which is in series with the fuel pump. This oil pressure switch is a SAFETY to keep the car from running when there is NO oil pressure (or atleast not enough to keep the OIL Pressure switch from closing whatever that value may be).

Here is how it works... There will be 12vdc+ sitting at terminal E of the FP relay at all times. When you put the key in the ignition and turn it to the start position 12vdc+ is sent from the ECM (terminal A1) to the coil of FP relay (term C)which energizes that relay and closes contacts on the FP relay terminals A to E and that gives the 12vdc+ sitting on FP relay terminal E (remember term E is hot at all times) a place to go...across E to A then to the fuel pump (assuming FP Fuse is good). Then sometime after that (i would have to hunt that time period up in the FSM) the relay deenergizes. But that doesnt kill the power to the FP because remember the engine is running and your oil pressure has come up and closed the oil pressure switch. Now power for the fuel pump is coming from the fusible LINK across the closed oil pressure switch and across the Fuel Pump fuse to the fuel pump. Now if you lose oil pressure the fuel pump will shutoff and the engine will die. (out of gas).
So you see the FP relay cannot be used for anything other than starting the car up....otherwise you would not have the advantage of the oil pressure switch safety circuit for loss of oil pressure. If the oil pressure safety switch opened because of loss of oil pressure and your FP relay were powering the fuel pump the oil pressure safety switch would not kill the engine upon loss of oil pressure because the FP Relay would be powering it also at the same time.

Dont confuse oil pressure safety switch with oil pressure sending unit. The sending unit is used to tell your oil pressure gauge how much oil pressure there is (PSI).

So you see the FP Relay is kind of a misnomer. It is not used while the car is being driven. You are running on the oil pressure switch during that time.
OK, I don't want to misquote you again, so I'm including everything. To sum up your position, you are saying that the ECM does not keep the Fuel Pump Relay energized while the engine is running as in whenever the ECM is receiving Distributor Reference Pulses. Do I have this right? Have you ever verified that the ECM does not keep 12vdc+ on Fuel Pump Relay terminal C as long as the engine is running? Would you be willing to measure Fuel Pump Relay terminal C and start your car to see if 12vdc+ is there after the engine starts and remains as long as the engine runs? I'd rather see this than ALCL pin G as it will minimize confusion with Fuel Pump Relay NO/NC contacts.

Apologies to the OP, but this circuit is on topic and this could be a valuable learning experience.
 

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OK, I don't want to misquote you again, so I'm including everything. To sum up your position, you are saying that the ECM does not keep the Fuel Pump Relay energized while the engine is running as in whenever the ECM is receiving Distributor Reference Pulses. Do I have this right? Have you ever verified that the ECM does not keep 12vdc+ on Fuel Pump Relay terminal C as long as the engine is running? Would you be willing to measure Fuel Pump Relay terminal C and start your car to see if 12vdc+ is there after the engine starts and remains as long as the engine runs? I'd rather see this than ALCL pin G as it will minimize confusion with Fuel Pump Relay NO/NC contacts.

Apologies to the OP, but this circuit is on topic and this could be a valuable learning experience.
Thats exactly what i am saying. The Fuel Pump relay is deenergized not long after the car is started. Have a look at the Oil Pressure switch part of the circuit first. Lets say the oil pressure went to zero because oil pump has failed. Your oil pressure switch would electrically open up and remove 12vdc+ to the input side of the Fuel Pump Fuse. That safety right there would not do ANYTHING to cutoff the fuel pump if the FP Relay were energized at all times which would cause terminal A-E of the FP Relay to be closed which would send a hot at all times feed from the fusible link straight to the fuel pump. It would be pointless to even have the oil pressure safety switch in the circuit if the FP Relay were energized at all times(while engine is running).

I think the "timed" 12vdc+ to the fuel pump actually comes from B2. If you notice on a GM car that when you turn the ignition to on (not to be confused with start/crank) you will here the electric fuel pump kick on for about 2-3 seconds then turn off. This is the prime to get the fuel rails up to pressure until engine is running.
 

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Now for the OP.

Sounds like you have a Fuel Pump problem, FP Relay problem or associated wiring.

Here is where i would start......

With a friend in the car have them crank the engine over while you are checking for 12vdc+ at term A of FP Relay. If it is NOT there while engine cranking then check Terminal E. If it is at terminal E then your relay is NOT energizing. So check Term C of FP Relay for 12vdc+ during engine cranking. If it is there then your relay is BAD (open Coil Term B-C or Contacts A-E are fried).
The above is assuming From FP relay Term A all the way to the fuel pump is good as far as the wiring is concerned.

If O vdc at Term E of FP Relay at ANY time then you have a wiring problem from or to the fusible link at the top of the schematic OR the Fusible Link is Blown.

If 0 vdc at Term C of FP Relay during engine crank then you have a bad wire from Term A1 ECU to Term C of FP relay OR The ECU is bad (bad transistor output for term A1).

Let us know what you find.
(this is assuming the ground at Term B is good)
 
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