So I've been doing some reading and since I haven't been able to find any thread with the exact symptoms I'm experiencing. Hopefully someone might be able to point me in the right direction so I won't end up throwing alot of money after this problem.

First the car is an LB9 and before it decided to not start at all its issues began with hesitation/stumbling under anything but gentle acceleration. If you were gentle with the throttle it would rev normally if you got in a hurry it would protest. The next day it refuesed to start, it will crank just fine but will not run. Pulled a plug this afternoon and found that I have spark. Fuel pump is only a few months old as is the fuel pressure regulator but I checked them anyway. Pump primes and fuel filter was pulled to make sure it wasn't clogged, which it wasn't. Fuel pressure regulator and the hose attached to it is as dry as a bone so no leaks there. I checked for codes yesterday and the computer is not storing any. My SES light is on although as I understand it that is not the last word on whether a ECM is good or not.

Any ideas?

 

Did you pull the codes? Get a paperclip and read:

https://www.thirdgen.org/service-eng...ht-error-codes

 

Sorry, let me clarify, the SES light is not out it lights up as normal. When I did the paperclip test the other day all I got was 12 meaning it did not flash any error codes of any kind. Whatever the problem is it seems the computer is not aware of it.

 

And the ACTUAL fuel pressure reading is ????

 

The anger sharks stopped swimming so I reinstalled the fuel filter to run a pressure test.

Gauge reads 40psi and holds. It takes about 10 min before it begins to drop. Still no codes??? Any ideas?

Checked the MAF sensor by attempting to get the car to start by unpluging it to no avail. So that is ruled out...

 

cam/crank sensor or ecm

diagnoss it! alldata.com

 

well I changed the ICM today along with the distributor cap and rotor while I was in there. Result...no joy. I also checked the injectors with a probe and I am getting power across both pins on the connector but unless I am doing something wrong it appears that I am not getting any injector pulse.

My test light should flicker as the engine cranks right?

 

I'm begining to think the ECM may be the cluprit. Anyone else have any ideas before I go about removing it?

 

yeah bro my 91 formula is doing the same exact thing as yours. i checked the same exact stuff as you. the only way my will start is by spraying gas directly into the intake. i think my computer is my problem as well. can you let me know what you find i dont have another computer by then

 

The fuel pressure should be more than adequate.

Yes, the ECM side of the injector harness should ground at every pulse and either show up on an analog meter or a test light. If the ECM is not receiving distributor reference pulses it will not operate the injectors. The reference pulse comes from the distributor. If the ignition is making spark the pickup coil is not in question, but the connections might be.

 

well new pick-up coil (I was tempted to try anyway Vader) and ignition coil (broke a tab off the old one) and still no start. Still getting spark and when I stick my finger in the spark plug hole I get fuel??? If I'm getting both what can the matter be?

I should add that it occasionally fires but won't quite catch in order to run

 

I would spray some starting fluid into the plenum and see if it fires up, runs, and then dies.
If it fires up and continues to run, I would think it is the Ignition Module (which you said you changed but could be bad out of the box.)

 

A couple suggestions:

1. Did you put plenty of dielectric grease on the new ignition module when you installed it? They short out pretty easily if that grease wears through.

2. I would not rule out a bad MAF. I was having similar problems with my 88 LB9 and tried almost everything only to find out I had a bad MAF sensor. I had no codes, and tried running the car with it unplugged also. I know people claim different ways to test them but the only way I've found to be sure is to plug one in that you know works. If I were you I would go buy a new MAF and plug it in just to be sure, you can always return it to the store if that's not the problem. I returned many parts in the process of diagnosing my bad MAF lol.

 

I had a couple other ideas I wanted to run past you guys.

1. Since it was falling on its face unless you gave it throttle gently. Could it be a bad tps? I also read that the tps can put the comp in flood clear mode thus inhibiting a start.

2. Bad coolant temp sensor?

 

I use every last bit of the thermal paste supplied and spread it around evenly. I'll give a new MAF a shot later today.

 

TPS could absolutely be a possibility. Have you checked the voltage on it? If it jumps around or drops off as you're opening the throttle it's bad. Could also just be too far out of adjustment.

CTS also plays a role in determining a/f ratio. Thats a cheap part and really easy to replace so it might be worth replacing it just as insurance.

But if you haven't checked the voltage on your tps do that before you go any farther.