1986 GT 5 spd. Car had been down for about a year before purchase and rodents ate many of the wires at C500 and a fuel injector wire. Cut/sliced/soldered all wiring back together and the car ran fine. Had it out about one month ago and it still ran fine, but was starting to crank slowly. Tried starting it a couple of days ago and it hardly turned over at all. Tried jumping it, but the battery and alternator wire started to get very hot. Pulled the battery and attempted to recharge, but couldn't get it past 8 volts. Replaced battery today and it turns over very well ... but won't fire. Found a couple of threads by phonedawgz (copied and pasted below) and checked against my car.
Tach will run a couple of hundred RPM when cranking. Fuel pump doesn't cycle when turning the key on (just short of crank). Check Engine light doesn't illuminate. Not sure if it did before, but all other electrical systems in the car where working properly so I suspect that it did previously illuminate. Have power on both sides of the ECM connector. Have power on both sides of all fusible links.
Not sure what/where to check next. Could something have happened to the ECM while trying to start with the jump start? I had the cable connected properly so that's not it. "Does the check engine light come on, key on engine off? It should.
After you turn the key to on, but before you crank it, does the fuel pump come on, run for two seconds and then turn off? It should.
If both of these fail then look to see why your ECM isn't working. Most likely the problem with the ECM not working is no power to it but they do also go bad. Just don't assume the ECM is bad before looking to see why it isn't working.
IF
IF the two above tests pass then crank it and see if the tach rises to 200 rpm and then falls back to zero. I that fails then look to see why the primary side of the ignition system is failing.
----- Since you said the engine cranked, fired and ran for a very short period of time, that does sound like a non-working ECM. The 2.8 has a 'cold start injector' that squirts fuel into the intake WHILE CRANKING and while the engine is cold. There is also an electric heater so it basically only does it at the start of the first crank or until you let the car sit for 15 min.
A common failure of the power to the ECM is an open ECM reset connector. If these two parts are not plugged together the car won't start and you will get the failure on the first two tests. It is located under the big electrical plug next to the battery.
Some fuses don't have power with the key on? You mean like the dash light fuse? Yep that is normal.
Also do make sure you have +12v on both of the studs of the power distribution posts shown above. They should have +12 all the time (unswitched)"
I had this issue after replacing the fuel pump, and noticed the check engine light was not turning on with the key in the on position. I found that I could bump the fuse box with a decent thump and get the check engine light to illuminate, at which point it would start when cranked. So I cleaned the fuse box up and sprayed much of it with something like wd40 (I was awfully frustrated and it was a long day, for some reason I forget what spray I used, may have been silicone ) and the problem has not come back since. I had also removed the center console and fidgeted with the wiring at the computer to see if I could get the CEL to turn on in the process. Worth a try.
Well, I went through all the flow charts in the factory service manual and the next step appears to be replacing the ECM. Anyone out there got a know good 1227170 ECM for a 1986GT 2.8 V6?
Well, I went through all the flow charts in the factory service manual and the next step appears to be replacing the ECM. Anyone out there got a know good 1227170 ECM for a 1986GT 2.8 V6?
Did you check your fuses? Spray a little starter fluid into the intake and see if it fires right up. Wait and check for other forum responses first. My goof I see that yours is a stick and the ECM I have probubley wont work, its for an automatic 2.8 GT and probubley wont work (???).
[This message has been edited by James Bond 007 (edited 01-23-2017).]
James Bond 007, I think that the ECMs are the same. Do you see a part number on yours? Maybe the PROMs need to be changed, but I think that otherwise they are the same.
Gall757, I did follow the service manual under "No service engine soon light". The SES light wouldn't go on when turning the key to "run". It didn't go on when putting the ALCL key into pins A & B either. When I put a test light to the brown and white wire, circuit 419, the SES light would come on. The next steps were to check for power on circuits 240 and 439 (large orange wires) located in the two ECM connectors. Both had power. The last check was to check the ground circuit 450 (black wire) and it had continuity. The last dialogue box on the chart is to replace the ECM.
The ECM on my 85 GT doesn't seem to be working (no SES, no upshift) for whatever reason, but car still runs. The car runs when you set the timing with the ECM bypassed. Seems to me it should run even if the ECM doesn't.
Just FYI the car will start/run on starter fluid with out an ECM even in the car. (I have seen this) Check the grounds bolted to the head, trans side, that will cause no CEL and a no run condition. Easy way to check is leave the key on and start shaking the grounds, if you hear the pump kick on that is your problem. (I had this happen) also look at the fuse box, all the connections should be "bright and shiny" if dull and discolored, there is probably cracks in the connectors. I have also run into to this.
Edit to add: all of this is not in the trouble shooting tree of the service manual. And if you do need an ECM I have some(any model any code, I have all, or very close to all). PM me
[This message has been edited by sardonyx247 (edited 01-24-2017).]
thanks guys. The ECM is universal. The PROM makes it work for a specific vehicle. I may have an ECM locally that I'll pick up at our club meeting Saturday. If that doesn't pan out I'll let you know about buying yours.
Check and make sure you also have power on the switched power input to the ECM. That is the Pink/Black wire on A6.
Also if you are testing with a meter with the ECM disconnected, you might have a good enough connection to get +12v reading on a meter, but not a good enough connection to get +12 with the ECM connected. Backprobing the connectors with the ECM connected would show you the voltage with the ECM in place, or using a 12v test light instead of a meter would put a load on the circuit that would load a possible high resistance trouble spot.
You are on the right path. Everything is pointing to the ECM not functioning. The question is why is it not functioning.
[This message has been edited by phonedawgz (edited 01-25-2017).]
phonedawgz, The precheck for Chart A-1 in the service manual for no "Service Soon" light had open circuit checks for circuit 240 (orange wires) and circuit 439 (pink/black) wire. Both had power at key on with the ECM connected. Also, probed circuit 419 (brown/white wire) which illuminated the dash SES light. The SES light wouldn't illuminate at key-on. I did check the ECM grounds and they have continuity so the final dialog box is for a bad ECM. I will be picking up a couple at our Saturday club meeting and hope that one will get the car going. One "Note" in the manual states that prior to replacing the ECM I should measure resistance of all solenoid coils and relays that the ECM controls. Looks like the IAC valve, fuel pump relay, AC relay, EGR solenoid and injectors are the ones that I need check. Both ECMs are part number 1227170. I have a picture of one of the ECMs and it looks like it may have had a PROM update at some point. The number below the ECM part number on mine is M611641752. The one I have a picture of is M721889760. It has a second bar code label with number 16083382. Not sure what any of these numbers mean and the origin of the ECMs are in doubt. Could have come from automatic cars and mine is a stick. One of the ECMs is said to have a hyper tech chip, but he isn't aware of the donor vehicle. I could install one of these ECMs to at least see if the car will start? I may swap my current PROM into another ECM afterwards to ensure the correct controls for my car's build. Any special considerations in swapping PROMs? The service manual states to use a special tool (looks like a fuse removal tool, but for a PROM).
Ahh - Pink/Black and the two Orange wires. When I saw only the "large orange" I thought they had you only testing the two places the switched (constant) +12 reached the PCM and not the switched (Pink/Black). Yep if you have grounds, you have power and your SES light circuit is intact, then the conclusion would have to be a bad ECM. 85 2.8 ECMs are internally different but the wiring didn't change. 86-88 are all the same. The PROM will be programmed auto or manual. There is a slight tune difference plus the auto tune activates the locking torque converter. In a manual car GM used that output for the shift light. So if you are running an ECM with a PROM programmed for an automatic, the shift light would come on when you reached the speed where the ECM would want to lock up the TC. It will however run just fine with only the tune difference being slight.
MT 7170 PROMs differ slightly in how they activate the shift light. On the MT, the shift light programming activates only in the lower gears, and you might have a 4 speed or 5 speed prom so the light might not activate right. This assumes you haven't removed the annoying and worthless light.
California PROMs are detuned a bit also.
I have yet to find anyone who was pleased with the Hypertech tune of a PROM in a Fiero. Try it if you want but it most likely will kill your MPG without adding anything for performance.
Almost all 7170 ECMs have the PROM in a black carrier. Pry up on each end a bit with a small screwdriver and the carrier should come up and out. The carrier is keyed so it can only be inserted in the right direction.
Some early 86 7170s however have a pin socket for the PROM. The PROM can be carefully pried up at each end. Be careful not to mangle the pins when pulling the PROM out. Prying alternatively from each end should get you there. Prying from one end and then pulling it with your fingers will bend the last pins to be released from the socket. so don't do that.
Considering how cheap you can get a Fiero ECM, idk how much time I would spend trying to look for troubles in the wiring. Plug in the ECM and see what happens is my first thought. That is assuming you don't have some physical damage to your engine harness.
[This message has been edited by phonedawgz (edited 01-25-2017).]
It was the ECM. Put in a replacement and it fired right up. Thanks for all the helpful replies. Special thanks to phonedawgz for his insights and diagrams.
) and the problem has not come back since.
