New Thread, issue no longer related to car sitting and the battery dying. To keep my efforts going, broke out my gmsm > led me to Code 54 troubleshooting flow chart > Completed all steps up to "Diagnosis = faulty FP Relay" however when I slapped in a spare nib/nos relay I got the same very frustrating outcome. Could I have a faulty Oil Pressure Fuel Pump switch? and of course I don't have a spare.

* It may be worth noting the manual states there should be 12v at ckt 120 for 2 seconds after ignition turned on (confirmed in troubleshooting), or anytime references pulses (no clue what these are) are received by the ECM. Does this mean my ICM is involved and not listed? As in the Fuel Pump ckt is fine based on troubleshooting but the ECM isn't seeing these references pulses (from the distributor/icm) to keep the pump running? With k.o.e.o. I get 44psi at the rail so the pump has to get power to prime.

Which of the two parts (ops / icm) would you try first?

 

I think you can rule out the OPS by disconnecting it and jumping the C and D terminals to "fake" a closed OPS to the ECM.

In the bottom of schematic below is the fuel pump circuit.

Since you can rule out the OPS for free, I'd start with that.

 

Jumped C&D (fused jumper wire), connected battery, attempted to start = no dice.

 

so with a bad ICM, you get no spark. But it still may not be the ICM.

Maybe take the coil wire off, put a screwdriver in the wire boot touching the metal, and hold the screwdrive close to a ground point like an engine bracket or something. Have a friend crank the engine over and see if you get spark arcing to ground. If you get no spark, then either a bad coil, bad input into the coil (i.e., no 12V to the coil during crankng), bad ground from the (-) side of the coil, bad coil wire, or bad ICM. Again, check all the "free" stuff first like wiring.

 

Connected spark checker between coil and cap = Spark
Connected spark checker between cap and sp#1 (checker @ each end) = No Spark

Prelim... Dead JEGS icm... roughly 1yr 24 days after purchase, less than 1 month after warranty expiration.

 

There designed to crap out just after warranty lol

 

So the coil is producing spark ? How much kv?
have you pulled the cap to inspect the cap and rotor conditions?

 

So the coil is producing spark? The test light in the spark checker flashes when connected between the coil & cap.
How much kv? Unknown - How do I test this?
Have you pulled the cap to inspect the cap and rotor conditions? Yes, both look nearly new to the naked eye. Found a bag-o-icm's from my jy trips, located a GM module stamped 369, swapped, no dice. However this module did produce a flashing light on the spark checker connected to sp#1, light flashed on the checker connected to the coil while cranking too.

If the ops died, would it still operate the dash gauge? (Gauge operates bau when cranking)

Is it time to break out the noid lights?

 

That OPS only drives an indicator light. Is that what you're referring to? The light will be on until you start cranking.

If you're not sure you're getting fuel, then yeah you need to rule that out too. A noid light on an injector is a good test.

 

That OPS only drives an indicator light. Is that what you're referring to? No, the dash gauge with the oil can, never seen a light, just a swinging needle. Just looked at a 90-92 110mph cluster & don't see a removable bulb in that spot.

If you're not sure you're getting fuel, then yeah you need to rule that out too: I have 44psi @ the rail w/ ignition on, I thought this meant power to the pump was good?

 

 

See the note at the bottom, how can I even complete that test if the engine won't run long enough to reach operating temp? How am I supposed to measure oil pressure? Battery on charge overnight, will try the test light on ground to fp test terminal at daybreak, if the light is on I'll hit the jy tomorrow and grab a cheap ops for testing.

Anyone know if the noid light labeled Bosch2 will work on the Bosch 3's?

 

Just because the pump is working doesn't mean the injectors are working. Though the noid should work on Bosch-III's. All it does is detect the ground switching from the ECM. Before even that though you can verify you're getting 12V to the pink wire on the injector harness during cranking with a DMM.

Again, the OPS can be ruled out by simply removing the connector from the sensor and jumping the C and D terminals on the harness. It'll simulate a closed OPS. If the engine starts, you know you have a bad OPS.

 

Well the Harbor Freight Noid Light & IAC test kit was BS. The light labeled Bosch 2 had one of two blades so loose it pulls from the slot. I used a different one labeled GM PFI (On Inj #2) and of 3 tries, I got a blinking light once. Since your assistance ruled out the ops and the service manual ruled out wiring or relay issues, I might have to buy a new icm to completely rule that out.

 

Did you verify you're getting a constant 12V on the pink wires on the injector harness? The noid light suggests you're at least intermittently getting it...

 

Tried today, on Inj # 2 harness connector, voltage never passed .5V when cranking. It moved from 0V fluctuating to .48V or so and back to 0.

If I understood your above post & the gmsm the ECM controls the ground side, power comes from the Inj 1/ Inj 2 fuses. Don't the injectors run off the reference pulses from the ICM? Or they should have 12v in cranking and their on/off times are ICM controlled? I'm lost and the only things that's ever left one of my ThirdGens running one minute & dead the next is a battery and fregging icm.

 

What voltage do you get with just key on but not cranking?

 

I'm pretty sure 0v, I didn't see voltage move until key was in the start position trying to crank. let me head out and retry.

 

0v @ inj#2 harness connector w/ key in run position.

 

Try unplugging all the injectors and check voltage again.

 

If you're getting 0V, that's most likely your problem. Verify it's the same for all injector plugs on that side (after doing what Tuned just said).

In which case, you need to check the fuse that's in line on that circuit (see the schematic I posted earlier).

It could be that one of the injectors shorted out and blew the fuse. In which case, pull all the plugs off and measure the impedances on all the injectors.

Also, check the other side as well since the two sides are on separate circuits.

 

Unplugged all inj connectors > Checked voltage @ inj#2 > 11.8V/11.9V with key in run position

 

Sounds like you have a injector or two that are shorted.
start homing them 15-16.5 with a difference of .5 .
if there grey body multecs there junk

 

Yep

 

https://www.thirdgen.org/forums/memb...-1990-a-2.html Post #62 has a pic. They're these orange Bosch III's (says ford on em) I bought off a member here just over 1yr ago. I'll head out for some testing.

EDIT: Set DMM to 200Ohm's > Tested all on the passenger side > 14.4ohm's once the value settled, one may have been 14.7ohm's.

 

Check drivers side too. Seems like something is shorted turning off injector driver.

 

The passenger and driver side appear to be on different circuits. Though, what you could do is plug each passenger side injector in one by one and see which causes the 12V to be pulled down to 0. Could be something where the application of 12V itself induces the short (I'm not electronics expert, so just a guess).

 

Checked driver side 2 @ 14.6Ohm's 2 @ 14.7Ohm's. Found my old injectors, right out the ziplock one tested @ 16.2Ohm's.

 

And no power to the drivers side bank with the injectors unplugged?
and the fuses are fine for bank 1&2 no corrosion in the spade socket?

 

Well if they're on different circuits help me comprehend the following...

Bank 1 > All connections unplugged > 12V @ each harness connector w/ key in run position
Bank 1 > Plugged in the 1st injector (to the rear of the engine / pass side) > Moved DMM to Inj harness connector next to it > 0V w/ key in run position
*Moved to Bank 2*
Bank 2 > All connections unplugged > 0V @ 1st harness connector I tried checking w/ key in on position

Found I left Bank 1 Injector 1 plugged in > Unplugged Bank 1 Inj#1 > DMM still hooked to Bank 2 Inj harness connector > Now seeing 12V w/ key in run position like they're on the same circuit. I'm lost...

EDIT: Bank 2 > Plugged in the 1st injector (to the rear of the engine / driver side) > Moved DMM to Inj harness connector next to it > 0V w/ key in run position

any ideas?

 

Since the fuses didn't "look" blown, and no corrosion in their cavities I've gone as far as testing the resistance of the Inj # 1 & 2 fuses, 0. Any other tests I can try?

 

Do you have a spare 730 ecm ? Seems like plugging in injectors shut off the driver.

 

opps double post

 

I've been doing most all troubleshooting with my spare 730, conditions were the same w/ my original ecm that came in the car and memcal I purchased from you. To prevent them from being damaged while troubleshooting I switched to my spare.

I just went as far as taking a old injector (16.2 Ohm's reading) outside, plugging it in Inj # 1 harness connector spot, DMM in harness connector next to it = 0V with key in on position. So if NO injectors are connected i get 12V at all connectors on both banks, with any injector connected when key hits on position DMM reads 0V. Injector driver shutting off? How can his happen with 2 previously operational ecm/memcal combos?

 

I'm not following this. Later today, I'm going to make a spreadsheet for measurements that I'd like you to fill in so I can see what causes which measurement. Stand by.... I'll post it up here later (looks like we can attach Excel files).

 

Standing by for spreadsheet...

 

Ok, plug one injector in at a time and then record the voltage on both sides with key-on, engine off.

 

I can say in advance as soon as I plug in any injector with Key On / Engine Off DMM will show 0V period. I did that test earlier by mistake. I left an injector connected on the pass side and got 0v testing on the driver side BUT...

I'll start on this at daybreak... Thanks a mill for the excel spreadsheet in efforts to help!

 

You may have done it already... I just can't follow it in the posts. I'm a mechanical engineer by trade, so I need crisp data organized neatly so I can see what's going on... lol.

BTW, I ran the same test on my car... key-on, I get 12V at the pink wire on the injector plugs with 7 out of 8 plugged in (unplugging one to make the measurement).

 

Also, the way to rule out the ECM is to disconnect the connector that contains the Dark Green and Dark Blue injector wires. Then turn the key on and make the measurement again. The pink wire gets 12V regardless of the ECM. I believe it's the large black connector.

If it still goes to 0V, then you know it's not the ECM. But at that point I wouldn't know where to go from there...

 

I tried to get done what I could before dark...

EDIT: Would a TunerPro RT datalog of an attempted start help?

 

Just so I understand the data...

For example on the #7 injector... when you plug in the #7 injector, you get 12V on every plug except for H5 and H8?

 

When I plug in Injector # 7 the connector to the left of it, INJ # 5 Harness Connector has 0V, so does INJ 8 Harness Connector directly across from it.

 

Now take one of your old injectors and plug it into #7 and see what the result is.

 

Correction on my part. With Old or New Injector plugged into # 7, Harness Connector 5 is 0V but Harness connector 8 has 12.3V.

I'm going to repeat the entire test tomorrow. Let me ask, as I plug in an injector I should be testing the pink wire in the harness connector next to it going left to right? So when I plug in injector 1 i'm testing the pink wire of injector 3 harness connector? Should I be unplugging each injector as I move forward? Like when I plug in injector 1 to test that side and the other, when I move to injector 3 do I unplug injector 1 and repeat? I might have done the test wrong.

 

Ok, let's do this... When you plug in an injector, measure the voltage on the pink wire on every other plug.

For example, plug in injector #1, leave all others disconnected. Then measure the pink wire on every other injector plug. Put the ground side of the DMM on the engine somewhere to get ground, not the other wire in the injector plug.

AFter that, disconnect #1, plug in #2, and measure all the other injector plug pink wires.

Keep moving around the engine until all are measured.

Here's a revised matrix. Blacked out cells are because for example you can't measure the #1 injector when it's plugged in.

I know these injectors are wired in parallel, so you should get the same results across injectors... but all the same, let's just measure everything.

Try to be as methodical and careful as you can.

 

Here's what we've got, 12.1V-12.2V at each pink wire following the above instructions.

 

Ok, this is what I wanted to see. We just proved out this part of your injector circuit schematic below). Everything upstream on the 12V keyed voltage circuit is good. Also proved that none of the injectors are shorted internally or fail in the presence of 12V.

Now repeat the measurement, again key on, engine off, but instead of putting the (-) probe on the DMM to ground on the engine, put it to the ground side of the injector plug. You should get 0V on every injector, since the ground side in the ECM should be open. It only grounds when it's time to fire the injector. If you get 12V or something else >0, likely you have an ECM problem.

After that, still leave everything disconnected, but put the noid light on any one of the drive side injectors and crank the engine. Then any one of the passenger side and crank. Make sure during cranking you get a good strong pulsing light. They're all in parallel, and we will have already proven your wiring is good so only need to do one per side..

If both these additional tests pass, then it's not a fuel problem. It has to be spark (I'm assuming you were also pushing the pedal down a little during cranking and it wouldn't start... in which case, it's not an airflow problem and therefore not an IAC motor issue).

I'll re-read through this thread again to see what you've done on the ignition side for next steps if the above test passes.

 

Additional Test # 1 - Pass

Additional Test # 2 - Fail: The noid light isn't bright or consistent. Takes me back 5 days to post # 14... might need to buy a new ICM since it provides the reference pulses used to fire the injectors aka tell the ecm to do the "ground switching" thing. Edit: Might even add new plugs & wires to the list.

What are your thoughts?

 

I'm stuck between a rock & hard place. I've taken every troubleshooting step offered. I've measured resistance on all accessible engine ground points and 0.00 - 0.05 Ohm's. Again, conditions the same with 2 operational ECM's. I've even pulled plugs and cleaned them, no dice. I haven't tried a spare ignition coil. I'm NOT wasting $40-$70 on an ICM without knowing for sure. I've tried searching HIGH and low for a concrete answer here on TGO... What tells the ECM to ground the injector circuit?

All info I can find on Reference Pulses, Injector Pulse, Injector Power, TPI Cranks but won't start lead to users reaching the replacement ICM point and going ghost. Never reporting back as to issue identification or resolution. Many old threads may mention what brand ICM someone's going to try but NOT it's success rate or avg life cycle. One thread mentioned an ICM marry-go-round, and I'm not trying to ride that ride... Options are slim, basic parts store modules (Lifetime Warranty), GM Parts Direct OEM Delco (1yr), Davis Unified (Unknown Warranty), Summit Racing (1yr) or JEGS (1yr). It won't be another JEGS module if it comes down to it...