[reeferdale]

First I have to tell you all this is my first vette in 15 years and I am not a mechanic. I am capable of following instructions though, and I am not incompetent when it comes to doing repairs. It has just been a long time. I bought this 91 vert and drove it for 2 days before this no start problem. I drove it home (130 miles) and to work one day (80 miles) with no problems other than a slightly rough idle when stopped in park and a very slight hesitation when acccelerating.

Originally I was working from a post by red90vette "Starts but will not run". I started this thread because of a new problem.

Recap - 1991 L98 Car stalled and would not restart. over the next 3 days would start and drive randomly. Now just will not start at all, Turns over and will catch for a second then immediately dies.

I followed all of the diags listed in the starting sequence. I checked fuel pressure 44+, Pump is working and holding pressure, replaced TBS, MAP sensors. Wantred to wait on Fi replacement till I got the car running. Long story short, I caved in and took the car to the dealer. Here is there diagnosis so far.

Bad PCM. Fuel injectors show they are "grounded from both ends"? I ok'd the new PCM. They called back later in the day, the car started and ran for a while, I don;t know how long, then died again. The PCM was bad again. They have now diagnosed that injectors 2 and 3 are shorting out and causing the PCM to go bad.

So, at this point I am sort of at their mercy. I wish I would have had the time to take this apart and replace the FIs myself, but over a week I could only get 2 hours to even look at the diags. I have a few questions I hope someone can provide their advise/opinion on

what is diff beteween ECM/PCM. I thought they were the same thing and that pre 1993 cars had a computer calle da ECM and then the name changed to a PCM? Does a 1991 vette have both a PCM and an ECM?

If the PCM was fried, how could the car start and run at the times it did? After the initial stall/no start, I was able to start and drive the 3 times, even though they were only brief (drives 1 -3 miles)

Does the diagnosis from the dealer sound like a reasonable scenario? What causes a FI to short out?

I am afraid that if I have them replace FI 2 & 3 that another one may short and fry the PCM again? I do not want to pay them to do all 8 injectors because it is about 5 times the cost I can do them for myself.

If they get the car running should I just drive it home and replace all 8, including the 2 they just did so that I don't fry the PCM again?

If I have a short in the 2 FIs couldn't the cause of the short be corrected? What would casue a short in the FIs anyway.

Is it normal for the PCM to be unprotected against a short in a FI? Seems that there would be some sort of circuit protection.

Would it be wise to try to get my original PCM back from them so I can have it tested?, Or see if the car runs with it after they finish there work?

I probably would not mind this cost so much if I had been able to drive the car for a while. But it is almost anti-climatic at this point. To drive the car for < 250 miles and get stung for a 2k repair bill really hurts. I could have bought a 93 for what I will now have into this vehicle. I just hope that the FIs are the final issue for now. If the car runs then I do not mind doing the rest of the maint items myself. It was a drag to see it sit there for a week, a week of 90 degree plus weather, not be able to drive it, and not have the time to work on it either.

Any input would be appreciated, also if anyone has any advise/questions I can bring to the dealer when I talk to them that would be great. It is not that I do not trust the dealer (yet), I would just like to have some reassurance that they are not just replacing parts until they fix the problem, I could do that.

 

[Vis Croceus]

what is diff beteween ECM/PCM. I thought they were the same thing and that pre 1993 cars had a computer calle da ECM and then the name changed to a PCM? Does a 1991 vette have both a PCM and an ECM?

When it controls more than the engine it's a PCM. In the Y-body that switch happened in 94.

If the PCM was fried, how could the car start and run at the times it did? After the initial stall/no start, I was able to start and drive the 3 times, even though they were only brief (drives 1 -3 miles)

If an ECM injector driver was fried from a short, it would remain fried. It wouldn't work intermittently.

I would just like to have some reassurance that they are not just replacing parts until they fix the problem, I could do that.

Very few GM dealers know anything about a car more than 10 years old. Most likely they are throwing parts at the problem. I'm sure with the dealer price of things like ECMs and injectors this bill is going to be ridiculous.

Surely this isn't your DD, so what's the hurry that made you take it to them? Bring it home and fix it yourself or bring it to somebody who actually knows these cars.

If you don't have the FSM, get it.

Would it be wise to try to get my original PCM back from them so I can have it tested?, Or see if the car runs with it after they finish there work?

Doubt they'll give it to you, or at the least there will be a core charge which will be more than the price of a used ECM, so not worth it.

 

[reeferdale]

Initially I planned on driving the car for a few months then parking it and giving it a thourough inspection/clenup/repair. It wasn't so much the "hurry" to get it fixed as much as I faced the fact that will not have much time, if any, to work on this until the fall. The work issue is my problem, but I did want to drive the car the rest of the summer.

Since this is my first vette in 15 years, and I only had the car for 4 days I do not have any relationships at this point with a known good corvette shop or mechanic.

I ordered the FSM last week, should have it by Friday.

I was wondering if jump starting the car would/could have fried the ECM? I did jump the car Sunday evening after work cause I actually had a few hours to work on it and wanted to finsih the start seq diags.


I went into the dealer this morning and talked with the mechanic. He is a veteran GM guy and showed me the actual diagnostics he had doen to this point. When the car came in, both wires on the FIs had a 12V charge on them. This is where the bad PCM diagnosis came from. After the replacement PCM went bad after the car running for a while, he discovered the 2&3 FI being shorted.

SO, I am having him replace the 2&3 injector so I can at least drive the car home. Once home, hear is the sad part, I am going to replace all 8 injetcors. I took Th and Fr off next week. Anybody have a brand of FIs they want to plug? Also, a good online source of FIs? I am going to order them Friday so I will have them for next week.

Also, if anyone is in the SE Michigan area, Ann Arbor/Novi, and knows a good shop or mechanic I could hook up with I would appreciate it.

 

[Vis Croceus]

I was wondering if jump starting the car would/could have fried the ECM?

It's not impossible, but it's not likely.


Racetronix is a good source for injectors. I don't know what size your car takes, but a search on corvetteforum should turn that up.


I would post on corvetteforum.com or camaroz28.com in the regional section for your area asking if anyone can recommend a good shop.


If you end up working on it yourself, those are better forums to post tech questions as well. This place has very low traffic.

 

[88TxVette]

In another thread in this forum a member suggested using these:

http://store.summitracing.com/partd...0824&view=1&N=700+150+4294908216+&appfilter=1

ACCEL fuel injectors help you get the most from your fuel injection.
ACCEL Performance fuel injectors provide precise control of fuel delivery and atomization for increased power, improved throttle response, and better fuel economy. ACCEL fuel injectors feature either a high or low-impedance design to function properly with your vehicle's ECU. These injectors also utilize a precision-ground, Bosch-style pintle design to produce a wide-angle conical spray pattern for ultra-fine fuel atomization and improved burn efficiency. ACCEL fuel injectors come complete and ready for installation with precision-molded O-rings and fine-mesh fuel strainers.

Brand: ACCEL
Product Line: ACCEL Fuel Injectors
Part Type: Fuel Injectors
Injector Advertised Flow Rate (lbs/hr): 24 lbs./hr.
Injector Advertised Flow Rate (cc/min): 255.0cc/min
Quantity: Sold as a set of 8.
Injector Impedance: 14.4 ohms
Driver Type: 12 V saturated circuit
Overall Height (in): 2.880 in.
Seat to Seat Height (in): 2.270 in.
Manifold O-Ring Outside Diameter (in): 0.573 in.
Fuel Rail O-Ring Outside Diameter (in): 0.574 in.
Outside Diameter (in): 0.943 in.
Injector Plug Style: Bosch/Amp Style
Wiring Harness Included: No
O-Rings Included: Yes
Notes: **See application notes.

*After reading more you might want to ACC-150826 26#/hr. flow if you plan on doing any other mods to your car later down the road.

Fuel Injectors, 24 lbs./hr., 14.4 Ohms Impedance, 12 Volt, Ford/GM/Lincoln/Mercury, Set of 8

$269 + ~10 bucks shipping.

 

[Vis Croceus]

I suggest a search on the major SBC/LT1/LS1 forums for threads about Accel injectors before buying those.

 

[extanker]

yes jumping starting can cook an ecm.ecu,pcm etc. injectors ? go GM my opine.change fuel filter also when doing injectors

 

[reeferdale]

thanks, I took the car back home. Just too muh for GM to do the work, plus, I will learn a lot doing it myself (with the halp of DC crew I hope) I am going to just take my time and work on it. I got the FSM and it seem pretty good for folling through a the proper diag path to take. I am going to start a new post with FSM quesstions

Thanks to all

 

[reeferdale]

All done

Thanks to all for the info, I put the new FIs in and the car fired right up and is running GREAT. I held off on the rest of the tuneup till the flal. I am having toooooo much fun.

It has been 15 years since I ahd my a#@ in glass!