Hey guys this is whats been happening. Its a 1987 305 TPI formula auto

It'll start and run great but then suddenly as youre driving or idling it'll act as if its getting no fuel then die and not restart. Sometimes it'll just stall as if you turned off the ignition. Recently changed the cap rotor and coil.

It wont restart..it'll crank but not start. I noticed the check engine light does not come on when you try to restart it.

Sometimes it'll start right back up (check engine light on) or it wont (no check engine light) and it'll only crank

Could this be a ECM failing intermitentley?When the light goes on it shows no codes at all except 12.

Any help would be appreciated!

 

Check your ignition module, located on distributor. Alzo check wirring going to coil, pink and white if im correct.

 

i shall try that! but would it cause the check engine light to not go on??

 

The car is almost 25 years old...you should definitely check all of your wiring. I do mean ALL of it. Your symptoms do sound like a failing ECM though. Start with the obvious first though - check all the wiring.

 

just got done installing a new ignition module and checked all the wiring.


Wiring is good, but the car will start run fine but stall as if you turned off the key, and there is no check engine light. (no codes, and the light does not come on when the car is off and the run position so its like theres no signal from the ECM)

could it be the ECM is on its way out? I was thinking pickup coil could be bad but would that cause the check engine light to not come on when the key is in the run position but engine not running?


Thanks for all the help guys

 

Have you checked your MAF?

 

Yes, i tried checking the MAF and the computer i tried tapping... It seems that when the car gets a little warm something cuts comunication with the computer. Would a bad Pickup coil interrupt communication with the computer?

The car will run for less than a minute before it cuts off... After that it needs to cool for a minute or more before the ECM will come on.

Any ideas??

 

Did you check the engine harness ground connections? There are two, one on the back of each cylinder head. They're a ***** to get to...but if they're loose it causes all sorts of silly problems.

When you say the ECM "won't come on", what exactly do you mean? How do you know the ECM isn't turning on? If you are not getting 12V to the ECM when the ignition is on, then it sounds to me like your problem is probably the ignition switch itself.

 

I'll check those grounds. basically the service engine soon light does not come on when you turn the key to the on position. It doesnt do that initial blink to tell you the compter is working. Everything else works though, radio wipers, gauges etc...

When the SES light doesnt come oon itll crank but thats all. It doesnt do the initial fuel pump prime and theres no spark.

but when the SES light comes on itll fire right up....itll run bt then it just dies

How can i check if im getting 12 v to the ECM?

 

Are you loosing spark and well as fuel injector pulse at the same time when enigine is slightly warm? sorry, missed the mil lamp not coming on and to comunication.....

 

Also, a long shot, but recently I thought my ECM was on it's way out as well. I was experiencing the same symptoms with the SES light and no codes. When I examined the connection to the ECM under the passenger side dash, some of the terminals in the connector had pulled out just enough to not make contact with the pins, one of which was the ground. When I secured them in the connector, everything was back as it should be. I actually almost bought a new ECM.

 

Yes no spark, im not to sure about injector pulse but i'm pretty sure theres none. Its as if the computer was just disconnected whicle the engine was running. Usually if the engine stalls out the SES light comes on but it doesnt. Today it ran for less than 30 seconds before it died.


87IROC: I was hoping ths was the problem but alas no.

 

http://easyautodiagnostics.com/gm_ic...n_module_1.php

you can have someone crank it while this happens and use a noid light on a injector or place your hand around the injector body and see if you feel it pulsing.

 

ok i shal lcheck that. if theres none does that mean the ECM has gone bad?

 

the dist sends a signal to the ecm the ecm will fir the injectors. If you ignition coil module is bad or the pickup coil is bad in the distributor. you will loose spark and injector pulse. The link I posted has some good information for you to go through and test. If the module is bad I always replace both together " have been bitten bye not. You would need to pull the distributor.

 

Hmm I just changed the ignition module but not the pickup.


If the pickup is bad would that make the SES not come on on intiail cranking?

 

You either have a bad ground or a bad ignition switch or possibly some faulty wiring related to the 12v feeding the ECM. That's best arm chair troubleshooting I can offer, the rest is up to you.

Hint: your pick up coil and dist module have absolutely nothing to do with the SES light working, or not....you're wasting your time lookin up that horse's ***. Check your grounds first, then locate the wire that feeds 12v to the ecm when the ignition is on and hot-wire it. This will take the switch out of the loop; if it runs then and doesn't cut out, then you know your swtich is bad. Start with the grounds first.

Check grounds. Grounds good? Go to next step.

Check 12v to ecm - hot-wire ecm. Fix the problem? Replace switch. No? Replace ECM.

 

it may ! depending if the ecm is getting the hight low distributor pulse. If your not getting spark you need to go through the trouble shooting tests listed. Since this only fails under heat soak the pickup coil may test ok. Disconnect the pick up coil from the dist module and use a ohm meter to check the resistance on the pick up coil. It should be 800 to 1300 ohms. If this is ok the next step is to set your meter to A/C volts, now with the meter on the pick up coil crank the engine and read the meter. Should show voltage of around .2 to .7 volts. I'm thinking the pick up coil or the mainshaft in the dist is bad. The mainshaft has a magnet in it and this will crack or loose it's strength, now it won't send a signal to the module for spark.

 

It might? Either it does or it doesn't. Which is it? My gut tells me it doesn't. The SES light should come on when the key it turned on....before any spark pulse ever gets generated.

 

if you need a pinout of the 1227165 go here. Put seriously check you basics are you getting power to the coil ! if so do the distributor trouble shooting.

http://www.chevythunder.com/fuel%20i...ecm%20#1227165)

 

Thanks guys!

I'l lcheck all these things...I totally didnt think of it possibly being the igntion switch.

I dont think the pick up coil would send a signal to the SES light....I check on my s10 with a 4.3, disconnected the wiring to the distributor but the SES stil lcame on.

So I'm guessign its what you guys suggest, wiring, ground, ignition or ECM. I'll check al lthese things and let you know what I find

 

Ok, grounds are good, theres no spark or pulse ging to injector when the ses doesnt come on and it just cranks.....

so i disconnected the harness from the ECM when the engine would cut out and not have a SES light. Im not to good at this electrical stuff but id shove my probe into the pin and see if i got current....I hope i explain this well.....

I found that the pin that controls the SES light...it always had current and lit up my light probe when the key was on....so basically it lit up like the SES light would normally do....it would blink when the key was turned on jst like the SES light is supposed to. So current is going through there...but for some reason the ECM isnt lighting up the SES light when the car cuts out and doesnt start.


For pin A6 that says its for the ignition, I never had current when the car wouldnt start, or when the car would start...maybe i was doing it wrong? Is this pin spposed to be measured with the connector attached t the ECM and current flows from the ECM to this pin?

Anyway, what wre your thoughts on the SES scenario above?

 

The wire that lights the SES is always hot. It functions via ground. In other words, when your ECM wants to turn on the light, it closes a switch, grounding the light and completing the circuit. The wire coming from the ECM and going to the SES is usually a brown wire with a white stripe on it. If you ground this wire, the light should come on when the ignition is turned on.

Typically, the hot wire coming from your ignition switch that powers up the ECM is a pink wire with a black stripe on it. When 12v appears on this wire, it tells the ECM to turn on. That is all...this is not the wire that supplies service voltage to the ECM. The ECM always has 12v on it as long as the battery is connected. Any orange wires you see in any of the connectors going to the ECM are battery power and should always be hot.

 

This is great info, Thanks!

I think im leaning towards the ECM being bad, but I'l have to go redo my tests first to confirm

 

I'm not thinking ecm if you don't have spark. ignition switch or distributor/ coil issue. you can have a working ignition system ecm aside.

 

hmm interesting. maybe I'll look more into the ignition switch. This isnt the part you insert the key into right? I looked online and it looks like a 9 prong distribution block or soemthing...its cheap so I wouldnt mind trying that before anything else.

Would you happen to know where this is located? Im hoping its not in the steering column.

 

were you put your key is called a ignition lock cylinder. your ignition switch is that piece lower down on your column. Like I have said before if you don't have spark start with going through the ignition trouble shooting steps don't just throw parts at it.

 

Thanks! Ill go over my checks again, im not to good at trouble shooting unfortunately, but what youre saying is true.

Wl llet you guys know what I find.

 

update

ok so i retested and i did get spark....my spark tester was bad so i was getting spark but no injector pulse when i first checked it.

I was able to get a used ECM out of a camaro to play with to see if my ecm was bad. i swapped it in ad it ran. but later when i turned it off and what not i got the same symptoms....

I went to go see if i was getting power to the ecm again and noticed i wasnt....i kinda scratched at the ecm harness connector (the one attached to the wiring ) and now it runs great...tried many times and no problems. Im guessing before i was getting intermitent connection through my tester?

So so far so good. im thinking it was a case of oxidation / corrosion on the ecm plug which was blocking the current and what not...

seem like a good explanation? I suppose its pssible because its so old... Hoping that cured it !!!

 

little update

still running good, so far problem hasnt reoccured

 

Sweet !!!

 

Glad you got it somewhat figured out! I don't know if you watch NASCAR, but wait until next year when they switch to Fuel Injection. The car will need some type of computer to run it and they will need to come to this site to figure it out!