MMroc86

Car=1987 Trans AM GTA 5.7 TPI All original.

The title says it all. I cannot find a clear answer for this question. My car wont turn on, I checked spark & I have none. Could a bad ECM cause a no spark issue? Or does the ECM soley control the injectors in terms of starting the car?

I guess my ? is, would I have spark if my ECM/Prom were bad?

The dizzy has no cracks & is in fact practically new, as well as the ICM, but I took it apart and will have it tested. Fuel pump is new as well & hear it priming. Sending unit is also new BTW.

Sparkplugs new
Wires tested fine so I did not replace them.
Rotor is also new....

Any and all help getting this thing running is greatly appreciated. THX

Six_Shooter

iTrader: (2)

The ECM does not control spark at start up/crank.

In a properly operating spark system the ECM could be removed from the car and there would still be spark.

The ECM does control spark timing after the engine is running. Most of the time 400 RPM is the threshold for GM OBD1 ECM to take over spark timing control duties.

MMroc86

Exactly the answer I was looking for. THX. I suspect the ICM is the culprit. I purchased a dizzy for 89$'s and it came with the ICM. Probably a crappy cheap one. I drove the car for about 1000 hard highways miles in about 2 days. Perhaps that fried the piece of crap....

gw082008

Had a similar issue with a new distributor - removed the ICM and took it to Auto Zone - it tested ok.
Made a cheap tester with a spark plug and a battery - the ICM would not fire the plug
so it obviously was faulty - so much for Auto Zones diagnostic equipment.

MMroc86

Replaced the ICM & I now have spark!

Unfortunatly my car still won't run.... This can only mean that the ECM is not telling the injectors to fire right? BTW I replaced the fuel pump & I hear it priming so I know its not that.....

gw082008

Try this site - it's a trouble shooting starting point for you from a factory service manual.

http://www.hotrodlane.cc/ONLINETECH/TPIwontstart.html

Make a test light from a Radio Shack LED assembly - catalog #2760270.
Unplug all the injectors from one bank - check one injector source to GND - should be dim light with key on.
Good Luck!

MMroc86

So I did the test on the injectors & they check out as okay. No short to ground & resistances are good. I just so happen to have another ECM lying aound from an 86 with a 305 so I swapped the ecms & put the prom from the GTA with the 5.7 in the ecm from the 86 & it still would not run.

Looks like it may end up being my prom...

I have spark.

MAF is practically new

My Fuel pressure is at 41-43 with ignition on

What else could it be guys? Want to make sure its the damn PROM b4 I jump the gun on it, cause that sucker is about 100$'s

BTW I did check & the ECM from the 86 is the same one used in 87, the prom is what changed.

sailtexas186548

iTrader: (2)

Are you sure you don't have fuel? Are you getting anything from the engine, misfires, poops, any noise at all? Fuel smell, wet plugs?

Check your grounds on everything fuel system related, the ECM, and injector circuits, check the ECM fuse, pull the (-) battery cable off and let if sit for 30 minutes then hook it back up.

I'm not real familiar with the older ECMs but my '91 has the prom (chip) and a second one that's a limp home mode, I can pull my prom out and the car will still run, or at least try to fire off. If the older ECMs are the same try removing your prom completely and see what it does?

Street Lethal

iTrader: (16)

Remove the stock Multec injectors, when one shorts they all do...

CRASHANDBURN_01

first try spraying a short burst of starting fluid in the throttle body. if that starts the car for a second then you know you have a fuel problem. if so next check your injectors to make sure you have 12v at key on. 41-43 psi seems a little low for key on but should still try to start. if injector voltage test good, find a noid light and make sure ecm is pulsing the injectors. if bad or no voltage, check fuel inj fuses and wiring. if i recall there is a connector near the dizzy that attaches the injector part of the harness to the main harness. you might have knocked it loose swapping parts or may have bad connection.

MMroc86

Alright so Im still working on this thing. Im on vacation this wk so I am putting some time into it.

I tested the resistances on the injectors & they are pretty high.

2 of them are reading 16.5 which is not the terrible, but the rest of them are well into the 20s.

I read somewhere that if 1 injector goes out it takes out the entire cluster & that could be why my car will not start. I also bought a noid light & will be checking to see if the ecm is sending a signal to them as soon as my battery gets charged up.

Im pretty sure the ecms are completly different Sail, mine just has a prom, if I take that out the ECM is **** on a bull.....

-srs-

Someone correct me if I'm wrong but those injectors should all read in the 14-16 range. Injectors reading impedance in the 20's seems really odd.

MMroc86

Yeah I thought them being the 20s was weird to. Checkd em multiple times tho. Two of them are in the 16s the rest are in the 20s....

MMroc86

Just got done checking the injectors with a noid light & all connections are pulsating.....

This leads me to believe that ECM is in fact sending the correct signal to them.

Im going to re-re-test the resistance on the injectors.

BTW sail I do have a strong fuel smell.

I also read somewhere else that a bad pickup coil would keep the car from starting, has anyone had any experience with this? Im thinking if the ICM on the new distributor went bad theres no reason why the pickup coil could not of gone bad as well.....

Again this a 1987 GTA 5.7 TPI All original.

MMroc86

UPDATE

I retested my injectors & they are all right around 16.3 & 17.0 on the ohm meter. So heres what we got....

Injectors pulsating
We have spark
Resistance on injectors are good
MAF is new
Dizzy checks out fine no cracks
Wires are good.
Fuel pump is priming
All fuses are good.

Car will only crank no start.

I now suspect the pickup coil.....

ChevCamZ28

Not to state the obvious, but did you test your cars battery? could be weak.
Also, did you set the distributor at TDC with the rotor facing the #1 cylinder.
Double check your firing order and trace the ignition wires to the correct plugs.
Not sure if VATS would cause your issues, but you can see if the security light lights up on the dash or you can jump the A & B terminals to read codes
if any are stored.

MMroc86

All of the above has actually already been done & ruled out as well.

NemeSS-TyranT

iTrader: (1)

U gonna sell that firebird?

gw082008

Brand new distributor had a bad ICM - took it to Auto Zone - tested good - made my own ICM testor with an extra coil and a spark plug. ICM would not fire the plug - so much for Auto Zone testing. Replaced the ICM - fired right up.
Go to these sites - lots of tips.
http://easyautodiagnostics.com/gm/4....-of-articles-1
http://easyautodiagnostics.com/gm/4....ed-icm-tests-1
Good Luck

MMroc86

Dont think so NemeSS.