There is no open that I can detect. I can see power going throught the injector to the ECM side of the circuit and ground from the ECM through the injector to the power side of the of the circuit. That doesn't leave anywhere for an open to hide, does it? Is there a way the ECM could be putting out its pulsing ground signal without it being detectable?
------------------ 1988 Fiero Formula 25k miles, garaged since 1988
I don't know the answer to that...maybe Phonedawgz does. I do know that injectors typically have about 20 ohms resistance built in, so they are not 'open'. Perhaps if they are stuck, they can't provide feedback to the ECM to send a pulse...but I am guessing now.
Originally posted by Gall757: If you know you have a bad fuel pump and injectors, why not fix what you know and deal with what issues remain after that?
It wouldn't surprise me if the injectors were bad, but don't know that they are. If it would be easy to replace the fuel pump or have it replaced, it would be fixed now. What I do know and what should be easy to fix is that there are no pulses going from the ECM to the injectors. -Paul
I don't know the answer to that...maybe Phonedawgz does.
I hope so, he is very knowledgeable about this area of a Fiero. I wouldn't be this far along without his insight and tips.
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I do know that injectors .......... are not 'open'.
That is what my tests are showing.
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Perhaps if they are stuck, they can't provide feedback to the ECM to send a pulse...but I am guessing now.
the only thing electrical in an injector is an electromagnet, just a long coil of wire. No sensor so the injector has no idea if its valve is stuck or not. Besides, the connection from the ECM to the injectors is an output, not an input. -Paul
------------------ 1988 Fiero Formula 25k miles, garaged since 1988
Correct me if I am wrong but we think the ECM IS running because it turns on the SES light correct? A non-running ECM because it has no power on either it's pink switched power input or it's orange constant power input would cause the ECM to not fire the injectors. If you have a SES light that would indicate the ECM is getting power and at least that part is working.
A wide open throttle causes the ECM to go to flood mode and for it not to fire the injectors. Unplug the TPS and confirm no pulses to the injectors.
If you do have the powers, you do not have a TPS that is showing wide open, and you have an ignition signal going into the ECM then the ECM sure looks like it is bad.
---- I corrected my misread on my last post.
--- No the injectors won't make the ECM not fire the injectors.
---
At 20 ohms the injectors will be the highest resistance in the circuit. So when the ECM is trying to fire the injector you should read +12 on the pink wire and almost 0 on the other wire.
[This message has been edited by phonedawgz (edited 11-30-2014).]
Correct me if I am wrong but we think the ECM IS running because it turns on the SES light correct?
Correct.
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A non-running ECM because it has no power on either it's pink switched power input or it's orange constant power input would cause the ECM to not fire the injectors. If you have a SES light that would indicate the ECM is getting power and at least that part is working.
I am with you here.
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A wide open throttle causes the ECM to go to flood mode and for it not to fire the injectors. Unplug the TPS and confirm no pulses to the injectors.
Ahh... easy to test and and sounds cheap and easy to replace, I like it! Will be doing the test first thing tomorrow, with my fingers crossed.
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If you do have the powers, you do not have a TPS that is showing wide open, and you have an ignition signal going into the ECM then the ECM sure looks like it is bad.
Looks like we will have our most likely suspect soon. Many thanks, -Paul
------------------ 1988 Fiero Formula 25k miles, garaged since 1988
I thought you already tried unplugging the TPS from my post from back on the 25th?
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one idea - unplug the throttle position sensor & see if it will start. if it's stuck/shorted above 2.5 volts it will put the ECM in the clear flood mode disabling the injectors.
if still no pulse try this: Injector "scratch"test
1) with key off, unplug the distributor 4-wire connector, locate the purple/white stripe wire in plug 2) connect a regular test light to the POSITIVE side of the battery 3) connect your other test light to the injector green or blue wire to check for pulsing 4) turn key on, momentarily tap the regular test light tip to the purple/white stripe wire terminal in the 4-wire plug the ecm should pulse the injector each time you tap test light on the terminal if nothing else is wrong.
If this works you probably have a bad ignition module (no reference pulses to the ecm)
[This message has been edited by AL68 (edited 12-01-2014).]
I thought you already tried unplugging the TPS from my post from back on the 25th?
I remember the post. I think I put the test on hold because of the “see if it will start” part. I know it wont start because the fuel pump is dead. I'm going to have the car towed to get the fuel pump replaced and I am trying to get the car in condition to drive back once it has a new pump.
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if still no pulse try this: Injector "scratch"test
I like this test, it will let me double check my earlier test of the ICM that I am not sure of and it can be done with a bad fuel pump!
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2) connect a regular test light to the POSITIVE side of the battery
Is the regular test light being used for more than an easy electrical connection? I would rather use a wire with a push-button, I don't know if I have enough hands to get 2 good test light connections at once. Are you sure it should be connected to the positive terminal? When I tested the ICM it tested like a normally open relay that was putting out ground pulses (on the purple/white wire). Should I have been seeing pulses of +V? -Thanks, -Paul ------------------ 1988 Fiero Formula 25k miles, garaged since 1988
[This message has been edited by Paul.S (edited 12-01-2014).]
no change with the tps unplugged eliminates a tps problem.
The test light bulb adds resistance, you don't want to touch 12 volts to the purple/white wire.
You can connect a piece of wire to a pin & backprobe the injector wire like the picture in Phonedawgz's post, connect the other wire end to your HF test light tip to test for injector pulse without having to hold the light.
You need to be able to do a fast tap-tap-tap-tap... on the purple wire to see if the ecm will pulse the injectors. The module should put out a positive pulse, the ecm would not recognize a negative pulse and do nothing.
Looks like 3 possible common problems left: bad module (most likely), bad ecm or the purple/white wire between them.
[This message has been edited by AL68 (edited 12-01-2014).]
no change with the tps unplugged eliminates a tps problem.
One more off the list.
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The test light bulb adds resistance, you don't want to touch 12 volts to the purple/white wire.
Thought it might be something like that.
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The module should put out a positive pulse, the ecm would not recognize a negative pulse and do nothing.
My module shows no connection, not +V or -V at rest. When the distributor is turning, it pulses between no connection and ground. Is it defective?
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Looks like ........... bad module (most likely),
I am going to pull the module and have it tested. If for no other reason, so I can stop wondering about it.
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bad ecm or the purple/white wire between them.
Will check them out with the scratch test as soon as I am sure I am not going to kill whatever is left of the ECM. Can I just go ahead and do the scratch test with both +V and -V and not worry about frying something in the ECM? Thanks, -Paul
------------------ 1988 Fiero Formula 25k miles, garaged since 1988
Results tend to be dependent on the competence of the tester, (the box and the person).....The module can pass in the store and still fail in your car.
Results tend to be dependent on the competence of the tester, (the box and the person).....The module can pass in the store and still fail in your car.
Thanks for the heads up. Tested fine at Auto Zone on 5+ tests, 10+ test at O'rielly showed half of the tests good, the other half tested fine in all modes except BYPASS. Anyone know what that means? O'rielly didn't and Google wasn't much help.
I think there is a new A1 Cardone distributor in my future. -Paul
------------------ 1988 Fiero Formula 25k miles, garaged since 1988
[This message has been edited by Paul.S (edited 12-02-2014).]
I did the Injector "scratch"test, no pulses with +12V or ground.
There was one strange result: with the test light probe hooked up to +12V, whenever I touched it to the purple/white wire that connects to the distributor there was a sharp snap, followed a second or 2 later by a dull thunk. It was quiet but distinct if you listened for it. It sounded like a single pole relay clicking when the contacts close, and then when it de-energized the relay arm hit something softer and vibrated like a tuning fork. Kind of like a turn signal blinker relay. What the heck could that be? -Paul
------------------ 1988 Fiero Formula 25k miles, garaged since 1988
[This message has been edited by Paul.S (edited 12-02-2014).]
What did the HF test light do - solid green with no changes?
With the ignition on solid red with no changes, as I expected. I backprobed the connector while everything was plugged in and with no ground signal coming from the ECU, the probe was seeing +12V from the fuse box coming through the injector. -Paul
------------------ 1988 Fiero Formula 25k miles, garaged since 1988
I now know that the culprit is most likely the output circuitry in the ECM controlling the pulse outputs to the injectors.
It might have taken me another 7 years or a lot of $$$ without all of you. Every post has been helpful. Those that didn't point directly at the problem helped me focus my attention and rule out what wasn't the problem so I could find the way to what was.
Looks like everything else in the car worked so the car could start and run on the fuel it was getting from the cold start injector while the key was in the START position. But when the key was released the cold start injector shut off and the ECM wasn't running the main injectors so it died. It seems obvious now, but it wasn't immediately clear that the cold start injector was completely independent of the main injectors, and the ECU tested good and did everything but generate the injector pulses.
I am going to be ordering the following: A-1 CARDONE remanufactured ECM BOSCH fuel punp ACDELCO fuel filter ACDELCO Fuel Tank Sending Unit Gasket
Most likely from Rock Auto tomorrow. Any other parts I should order? Any other distributor I should consider? Thanks again, -Paul
------------------ 1988 Fiero Formula 25k miles, garaged since 1988
Glad you found the problem, fixing problems over the internet is a pain sometimes. My shop gets DOA's towed in almost every day, some of the problems are really fun to fix. Just had a Sunfire towed in today - no fuel pump noise, no check engine light, no injector pulse or spark, power/grounds good & no scanner communication - dead ECM.
Rock is where I get parts for myself that I can wait for - NAPA and the other local stores are a lot more expensive on a lot of the parts, just stay away from the no-name stuff, a lot of it is cheap junk.
You should also get a new filter ("sock"/strainer) for the pump, most of them don't come with it but it usually comes with the o-ring seal, see if the pump picture from Rock shows them.
Hopefully the tank looks good inside, I have a couple Formulas, one sat at least 5 years, the tank was fine but the injectors were stuck from the old gas. You won't know until you try to start it.
Good luck getting it fired up, I couldn't go that long without driving one - I bought another one just to drive while I finish my 3800 swap.
============edit========== just looked at the Bosch pump at Rock auto - comes with the O-rings but no strainer - should get one also. the pump also comes with a hose and clamps to replace the pulsator, they can leak & bleed off fuel pressure.
[This message has been edited by AL68 (edited 12-04-2014).]
I wish your shop were closer. Omaha isn't in towing distance from Grand Rapids, is it?
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Rock............, just stay away from the no-name stuff, a lot of it is cheap junk.
There and everywhere else. I can't believe the low quality of some of the parts I've seen. House brands too. Especially Duralast.
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Hopefully the tank looks good inside,
What if it doesn't? I saw a post about having it cleaned and coated at a radiator shop, but I don't know if all of them can do a good job, or what kind of coating to look for.
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just looked at the Bosch pump at Rock auto - comes with the O-rings but no strainer - should get one also.
Thanks for catching that. I thought it had one, I was probably thinking of other pumps I looked at. Thanks, -Paul
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the pump also comes with a hose and clamps to replace the pulsator, they can leak & bleed off fuel pressure.
I'm guessing that Bosch's turbine design doesn't need a pulsator?
[This message has been edited by Paul.S (edited 12-04-2014).]
I had a Nova tank done by a radiator shop several years ago, came out clean with a reddish-clear coating inside, seemed to work good. Might have to check with some car people in your area for a shop that can do it - repair shops, car clubs/shows, etc.
Most pump kits eliminate the pulsator - don't know why GM ever used them, no one else did & most other pumps were the same style.
