1987 GT V6. I've got good fuel pressure and spark and engine starts-up initially from the cold start injector then stalls and won't run. Fuel pump runs fine and pressure at the rail is good. Problem started with a blown injector fuse that I traced to a bad injector (very low resistance). All injectors are now replaced as well as the ECM (thought I had blown the injector drivers), but the problem remains.
Checked with a noid lamp and there is no signal at either the injectors or the 6 way plug just ahead, although there is 12V - it just never gets grounded.
Engine does run if I add fuel manually and I checked all the injectors for firing when I changed them. All the fuses are good and no longer blow.
When you turn the key to on, without cranking, does the fuel pump run for two seconds and then turn off? It should. Does the check engine light come on? It should. If both of these tests fail then look to see why your ECM isn't functioning. The #1 cause of Fiero ECMs not functioning is that they are not receiving power, both switched and constant (unswitched) power.
Is your ECM reset connector connected? If it is not then your ECM won't be receiving it's unswitched power and won't run.
Now ONLY if the above two test ARE WORKING then try bumping the starter and see if the ECM again turns on the fuel pump for two seconds and then turns it off. If the two above tests pass but this one fails then look at the distributior 4 pin connector wiring.
NOTE - If you crank your engine past a bump, you can build oil pressure. The fiero also has an oil pressure switch. So if you crank the engine a revolution the oil pressure switch can close and that will power the fuel pump. So don't let that confuse you when doing the above test.
On the Fiero V6 ECM check for constant (unswitched) voltage on pin B1 abd C16 (Orange) Check for switched voltage on pin A6 (Pink or Pink/Black)
Key on, engine off, fuel pump runs for 2 secs as it should, also SES light is ON as it should be. Bumping starter causes fuel pump to run again for 2 secs as it should. ECM therefore appears to function correctly. I'd already tried these tests with no luck. Also rev counter registers movement correctly. Engine does run briefly on first try up to 1500 rpm (fuel from cold start injector) then stalls and won't run since no more fuel supplied from regular injectors. Fuel pressure is good at around 40 psi.
Everything seems good except there are no pulses to the injectors - noid lamp does not flash when cranking. There is 12V on one pin, but the ground signal from the ECM on the other pin never arrives. When manually grounding the injectors I can hear them fire.
Take the secondary pin retention clips out of the ECM connector. With the key on apply ground to first pin D15 and then D16. Do the injectors fire? If so then the wiring to the ECM is good. If not then look at wiring.
While cranking read the voltage on each of the grounds of your ECM. If you see a ground wire that has voltage on it fix it.
If neither of these show a problem then your replacement ECM is bad.
[This message has been edited by phonedawgz (edited 07-06-2014).]
Yeah it is. The little gray or blue plastic clips in the ECM connectors on the engine wiring harness that keep you from probing into the connector with it still plugged into the ECM. Usually one has a clip on it to hold the connector to the ECM however sometimes that clip is metal.
A little screwdriver untangs them.
Blue in this picture
Ignore the "release slots" - this is a googled pic
[This message has been edited by phonedawgz (edited 07-06-2014).]
That's great thanks - sorry for the silly question, but I was wondering how to probe it with it plugged in!
I'll let you know the results. The latest ECM was a "new reconditioned unit" right out of the box with just the PROM and CALPAC switched, but same result as the one I removed. So "thoeretically" it shouldn't be the ECM.
Out of curiosity, what injectors did you put in? Its a possibility that since you replaced all of the injectors they may all be from a defective batch or pinned out slightly differently than factory. I never had any luck with aftermarket injectors... I'm new to Fieros but this is what I would check first since you said the wiring seems OK upon initial checks...
Take at least one out and perform an injector test to see if they function correctly... Similar to this procedure.
This will rule out any problems with the injectors themselves. Make sure the power and ground comes from the same pins they would from the car...
Edit: Just realized you said there is no ground at the connectors. That may be an ECM problem after all...
[This message has been edited by Shho13 (edited 07-07-2014).]
Injectors are reconditioned units from Precision Fuel injectors and I checked them before I installed them. They are all good resistance and the plugs fitted fine. Also manually grounding them with the plenum off I could hear them firing no problem.
I've removed the clips and probed the two grounding circuits which have 12v with key on. However, when I ground them it's impossible to tell if the injectors fire or not - how do I know? I have checked the wires alone to the 6 way connector and they appear OK with 0 resistance (disconnected from ECM). Also when cranking I do get a voltage drop on my voltmeter between D15/D16 and ground which implies the ECM is sending a ground signal - my test lamp doesn't flash but dims a lot. I still have to check all the ECM grounds when cranking - lost my helper
Can anyone give me a picture of the 6 way connector with the pins labelled to help me? I know its two/two/two for the two banks of injectors and the cold start, but I'm not sure which is which.
You may/are going to get a voltage drop (dimming) during cranking anyways. That is why it is important to check the difference between what happens on the pink and what happens on the Lt. Blue/Lt. Green wires to see if the dimming is just the cranking or it is the ECM firing the injectors.
Depending on your wiring the injector to engine harness plug might be a 6 in a row weatherpack connector (85 - 86) or a 2x3 metripack(88). I don't remember which way the 87 went, and even then they might have changed it mid year. The color of the wires vs their function doesn't change however.
The injectors wires can be installed either way to you have to look to see which wires are connected to which bank. The ECM batch fires the injectors so it doesn't even matter which injector plug is on which injector.
Weatherpack 1x6 connector
A - Pink/White - Switched power - runs to the injectors with the Lt. Green wires B - Lt. Green - Injectors to ECM C - Lt. Blue - Injectors to ECM D - Pink - Switched Power to the injectors with the Lt. Blue wires E - Purple/White - Cold Start Injector F - Tan - Cold Start Injector
[This message has been edited by phonedawgz (edited 07-07-2014).]
Thanks - that'll help with the connector - yes it's 6 in a row. I did check all the injector wiring, from plug to injectors, when I had it all apart and it checked out OK with my ohm meter and yes I know it's batch fired, 3 and 3. New injectors are from Precision Fuel injectors and are Fiero reconditioned units - looked EXACTLY the same as those I took out and I was able to exchange the locking rings.
I am going to try one hail Mary and change the ICM - just in case, I changed it once before a couple of years ago - it would really piss me off if I've misread some of the symptoms and that's the issue.
All this started with blowing one of the injector fuses and finding a bad (low resistance/shorted) injector. Then I got it to run enough to get home with a bigger (10A) fuse. Then it ran REALLY rough (worse than just the 3 cylinders) stalled and wouldn't restart. At that point I changed the ECM, all the injectors and replaced all the proper fuses and here I am.
Yes (stupid but) I replaced the blown 5A injector fuse with a 10A to get me home, since the 5A's kept blowing - ran for about 3/4 miles. It enabled me to run on about 5.5 cylinders instead of 3.
Everything now replaced and set back to OEM specs and since I thought I could have damaged the ECM drivers I changed it for a new (reconditioned) one.
That's what I thought and that's why I've replaced the ECM with a rebuilt one, but still have the same issue. I confirmed I have a spark, but still no fuel.
Still checking the wiring, but haven't found any issues so far.
I'm going to try starting it with some quick start spray to see if it runs and confirm that all it needs is fuel - waiting for another helper to turn the key
I've checked for spark and I see my tester flashing on all plug leads, so looks OK. I've sprayed in starter fluid and NOTHING at all. Changed the ICM (in case) still nothing. Pulled a spark plug and it's wet and smells like gas. So I appear to have spark and fuel (at least temporary) and no fire - engine cranks fine.
What else to try? I did see another post where they finished up changing the coil and it fired up, but I'm skeptical since the car was running fine up till I had the injector problem. BTW: I did not disconnect the plug leads so they're not changed from when it was running.
Is your spark tester an older one that just jumps a small gap or is yours designed for HEI ignition. An high energy ignition spark plug tester has a bigger gap in it than just a spark plug. The reason is that under compression there is more air in the cylinder. That more are results in the coil having to generate a higher voltage to jump the gap, when the plug is in a cylinder that has compression. So you can get 'fooled' into thinking you have spark with a lower voltage ignition tester and then you don't have it when the spark plug is in the cylinder.
Also
Cranking the engine with spark plug wires disconnected or having marginal spark plug wires or having a plug gap that is too large can cause the insulation in the ignition coil to fail like this. The insulation can fail to where it only fails (arcs internally) under very high voltage.
[This message has been edited by phonedawgz (edited 07-16-2014).]
I've ordered a replacement coil anyway. They're not expensive and I've already spent the $$ on changing the ECM, ICM and injectors, so another $30 isn't going to break me!
My spark tester isn't an in-line type and you leave all the plug wires connected, you just hold it against the wire while cranking and it flashes to indicate the presence of "high voltage". I tried it on my "regular" car and it flashed the same way. However, maybe the voltage isn't sufficient. The plug I pulled looked in good condition other than being wet. What is the correct gap? I didn't measure it, but it looked in the range of .040 -.050
OK new coil installed and NO change. I have changed fuel nozzles (one was bad), ICM, ECM and the coil. I have a good spark, my noid lamp is now flashing indicating firing signal to the injectors, the plugs are wet with gas - and NO fire. I've tried starting fluid as well and also NO fire. Fuel pump runs fine and I have a good indication of engine rpm on the tach during crank. I haven't checked the actual fuel pressure, but pressing the schrader valve gas squirts about 1 foot high. Plug leads were never moved since the engine was running - so they're good as well.
Dave, pull the 4-pin connector from your ICM and look at the female pins in the harness end. I think it's the 2nd from right as it's installed that runs the fuel pump. The ICM isn't in play at first ignition on. That's controlled by the ECM and as you know cycles the pump for 2 seconds or until pressure is reached, whichever comes first. That's where you get your 'start-stall' effect. As soon as the ECM sees spark signal from that ICM terminal, it takes over and turns on the fuel pump.
With age, the barbs that hold the harness ends in the rubber terminal can turn loose and if the ICM male pin should happen to hang on the end, it will push it back into the rubber harness end. All the female terminals should be flush with the end of the plug. A friend fought your problem for 4 years and could never get his 88GT to start, so it sat beside the house. We decided to work on it together and I had it running within about 10 minutes. The car's now a happy highway cruiser again. His wasn't the only 2.8 where I've seen the same problem.
Not much on the Injector circuit besides the vacuum reg valve .
Fusible Link F ?? to ECM 20A
. . . Crazyred84 solved his no spark problem:
" I figured it late the other night. When I installed my ICM I plugged in the wires going to the ECM backwards. The ECM wasn't getting the signal from the ICM to fire the Injector. So, lesson learned. Double check your connectors!" .
so simple! . . ----------------- Mark ' 85 2m6 3.4PR In the Great Northwest!
[This message has been edited by NW-Fiero (edited 07-25-2014).]
Still no joy so I gave up and took it to my mechanic. He's also had no luck so far - and he races old GM's plus rebuilds motors etc. He's going to work on it over the winter. He did manage to get it running and driving, but the mixture was WAY too rich.
For the no spark signal condition, especially after having unplugged or changed the ICM, look at NW-Fiero's diagram. I think B3, the blk/red wire is the spark signal. Sometimes the wire will recede back into the plug and lose contact with the ICM pin.
Not much on the Injector circuit besides the vacuum reg valve .
.
The "vacuum reg valve" is the EGR solenoid. They WILL short out and take out one (only) of the injector fuses. The result will be a 3 cylinder engine. You can simply unplug it to test, although you will likely get a quick code 32.
