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What the $&*!#! is this?! Is undocumented 2.8L part the cause of 7yrs of frustration? by Paul.S
Started on: 11-21-2014 08:29 PM
Replies: 101 (2191 views)
Last post by: AL68 on 12-05-2014 01:06 AM
Paul.S
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Report this Post11-30-2014 06:06 PM Click Here to See the Profile for Paul.SSend a Private Message to Paul.SEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Gall757:


You are correct. Open circuit = no pulse.


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?

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Report this Post11-30-2014 06:35 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
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.
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Report this Post11-30-2014 06:37 PM Click Here to See the Profile for Paul.SSend a Private Message to Paul.SEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
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
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Report this Post11-30-2014 07:04 PM Click Here to See the Profile for Paul.SSend a Private Message to Paul.SEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Gall757:

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.

 
quote
I do know that injectors .......... are not 'open'.

That is what my tests are showing.

 
quote
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

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Report this Post11-30-2014 07:13 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
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).]

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Report this Post11-30-2014 10:03 PM Click Here to See the Profile for Paul.SSend a Private Message to Paul.SEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by phonedawgz:

Correct me if I am wrong but we think the ECM IS running because it turns on the SES light correct?

Correct.

 
quote
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.

 
quote
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.

 
quote
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

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Report this Post12-01-2014 12:31 AM Click Here to See the Profile for AL68Click Here to Email AL68Send a Private Message to AL68Edit/Delete MessageReply w/QuoteDirect Link to This Post
I thought you already tried unplugging the TPS from my post from back on the 25th?

 
quote
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).]

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Report this Post12-01-2014 08:19 AM Click Here to See the Profile for Paul.SSend a Private Message to Paul.SEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by AL68:

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.

 
quote
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!

 
quote
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
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[This message has been edited by Paul.S (edited 12-01-2014).]

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Report this Post12-01-2014 12:48 PM Click Here to See the Profile for Paul.SSend a Private Message to Paul.SEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by phonedawgz:

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.


Tested for ground pulses from the ECM with the TPI disconnected, no change.

 
quote
Originally posted by AL68:

if still no pulse try this:
Injector "scratch"test

Will run the “scratch” test as soon as I am sure how to do it right. -Paul

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Report this Post12-01-2014 11:12 PM Click Here to See the Profile for AL68Click Here to Email AL68Send a Private Message to AL68Edit/Delete MessageReply w/QuoteDirect Link to This Post
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).]

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Report this Post12-02-2014 08:28 AM Click Here to See the Profile for Paul.SSend a Private Message to Paul.SEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by AL68:

no change with the tps unplugged eliminates a tps problem.

One more off the list.

 
quote
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.

 
quote
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?

 
quote
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.

 
quote
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

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Report this Post12-02-2014 09:37 AM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
Just a note of caution with the module test.

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.
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Report this Post12-02-2014 02:02 PM Click Here to See the Profile for Paul.SSend a Private Message to Paul.SEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Gall757:

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


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[This message has been edited by Paul.S (edited 12-02-2014).]

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Report this Post12-02-2014 07:41 PM Click Here to See the Profile for Paul.SSend a Private Message to Paul.SEdit/Delete MessageReply w/QuoteDirect Link to This Post
Had more tests done on the ICM. None showed a problem. My conclusion: ICM most likely good, O'Reilly's tester, probably a little flaky.

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Report this Post12-02-2014 08:15 PM Click Here to See the Profile for Paul.SSend a Private Message to Paul.SEdit/Delete MessageReply w/QuoteDirect Link to This Post
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

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[This message has been edited by Paul.S (edited 12-02-2014).]

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Report this Post12-02-2014 11:05 PM Click Here to See the Profile for AL68Click Here to Email AL68Send a Private Message to AL68Edit/Delete MessageReply w/QuoteDirect Link to This Post
If the noise was near the air cleaner it was probably the fuel pump relay, it's on the firewall behind the driver's seat.

Sounds like your ECM driver circuits are dead but it is receiving the reference pulses and turning the pump relay on.

What did the HF test light do - solid green with no changes?
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Report this Post12-03-2014 04:57 AM Click Here to See the Profile for Paul.SSend a Private Message to Paul.SEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by AL68:

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

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Report this Post12-03-2014 05:50 AM Click Here to See the Profile for Paul.SSend a Private Message to Paul.SEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by AL68:

If the noise was near the air cleaner

It was....

 
quote
it was probably the fuel pump relay, it's on the firewall behind the driver's seat.

ahhh.... at first I thought something might miswired but that explains it.

 
quote
Sounds like your ECM driver circuits are dead but it is receiving the reference pulses and turning the pump relay on.

It sure does. Thanks, -Paul

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Report this Post12-03-2014 07:07 PM Click Here to See the Profile for Paul.SSend a Private Message to Paul.SEdit/Delete MessageReply w/QuoteDirect Link to This Post
THANK YOU SO MUCH EVERYONE!!

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

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Report this Post12-04-2014 12:54 AM Click Here to See the Profile for AL68Click Here to Email AL68Send a Private Message to AL68Edit/Delete MessageReply w/QuoteDirect Link to This Post
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).]

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Report this Post12-04-2014 09:08 AM Click Here to See the Profile for Paul.SSend a Private Message to Paul.SEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by AL68:

My shop gets DOA's towed in almost every day,

I wish your shop were closer. Omaha isn't in towing distance from Grand Rapids, is it?

 
quote
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.

 
quote
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.

 
quote
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

 
quote
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).]

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Report this Post12-05-2014 01:06 AM Click Here to See the Profile for AL68Click Here to Email AL68Send a Private Message to AL68Edit/Delete MessageReply w/QuoteDirect Link to This Post
Probably a little far for AAA to tow

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.
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