Help, I think I may be having some ECM problems. here's what is happining.
It started last fall when my 88 started fumbling and running rough, I attributed it to injectors as I took it to someone and had it checked and 3 of the injectors failed and another 2 were not doing well. of course I had it in the chevy shop. well I took it upon myself to change out the injectors and it seemed that it went well, the chevy dealer wanted 1300 bucks, but I could not get it to start on it's own without soem ether in the plenum. my injectors are showing 13 ohms each, the tps is where it should be, but a funny thing happened when I was checking the injector connections. At first all of the clips were checking out ok on both wires each, they were lighting up my tester. That was last week and I checked them out pretty quickly. well last night I had the ignition on for a while and now I am only getting power in one side of the connector wires. I think I have checked every thing by the book, I have a gm, both the electical and other red books as well as the haynes. But... I have checked the threads out pretty intensly but don't really find anything like this, what do you guys think?
My vette is an 1988 L98 no mods yet. would like to stay stock just as a daily driver but I've had this thing for going on a year and haven't had the chance to put on more than 500 miles... oh it's got around 79000 on it. help please, sound like the ecm?
thanks,
Kent

 

Ok, you say it runs with starting fluid sprayed in the TB...so you know you have good spark. Now, do you hear the fuel pump run for 2 seconds when you first turn the key to on? If not, check the FP fuse, it should be pigtailed off of the positive battery cable somewhere. Next, put 12v to terminal G on the ALDL. You can run a long jumper from the battery + post and insert the wire in pin g. If you don't know, the ALDL is pinned like this (looking at it from the seat)
F E D C B A
G H J K L M

Putting power to terminal G will run the fuel pump, see if the car will start with it jumpered. Be careful with that jumper wire with the engine running.
If the pump doesn't run you are most likely looking at a pump change. If it does run, check the pressure (looking for around 43psi). If all that checks out, check the injector fuses, inj1 & inj2. If that is good, get a noid light and hook it to an injector connector and watch it as you try starting the car, it should flash. If it doesn't flash then the ECM probably isn't seeing the refrence pulse from the distributor, and if that is the case, it won' fire the injectors. The most likely suspect in that case is the ignition module...but you need the check the wire going from the dist to the ECM to make sure it isn't broken or grounded first.
Also check all grounds for the engine, you may have one rotted off or otherwise broken.

 

thanks for the reply Morley,
i've checked out the pump, it works and my fuel pressure is staying at about 42-43 lbs, the fuses are ok as well as the 3a fuse for the ecm i've tried my noid light at the injectors and it is not lighting but does on the cold temp inj. i'll check the dist wire and the grounds and let you know.
thanks,
kent

 

finally,
well Morley you were right, I had unhooked the dist wire to ecm to keep from firing as i set #1 for timing and forgot to rehook it up. that problem fixed, now it still won't start. i am going to go through the checklist again before reposting. i was thinking about loosening up the injectors enough to see if fuel is coming out of them as my pump is ok, i have pressure at the rail, the lights are blinking and do have constant 12 v. at on ing. these are used injectors that i bought from someone here on the forum and they check ok for resistance, i've replaced a lot of parts but feel i need to recheck everything. will let you know.
thanks for listening to my ramblings,
Kent