Broke down this morning...AND again tonight :-(

[FSJ Guy]

Post up which voltages are measuring incorrectly. That could help us diagnose...

If it runs while you "hot wire" the fuel pump, then we know the ECM is working EXCEPT for the fuel pump relay. Next, try hot-wiring the fuel pump relay. If it works only with the relay hot-wired, you've narrowed things down even more. Next, check your power to the fuel pump by bypassing the relay.

[243]

Voltages checked out, system grounds were 130+ ohms at the ECM, still no power key off key on at A1 to the fuel pump relay.

Power to the ECM is 12v.

Ground system from the beginning:

Negative battery cable to frame.
Frame to engine block.
Negative battery cable to ground distribution block.
Fuel and Start relays to distribution block.
System grounds to distribution block.
Sensor grounds to distribution block.

Added yesterday for insurance:

Cable from distribution block to core support.
Cable from core support to cab (used for testing at ECM).
Second cable from negative battery to front of engine block.


Even with this minor setback, I am a carbuhater and will never go back, ever.


.

[FSJ Guy]

Should you really be getting that high of a reading on your grounds? I don't recall seeing 100+ ohms on ground connections. I don't remember really looking either.....

[243]

I was wondering about that, I checked the resistance the same as voltage, key on with the connectors plugged into the ECM. With the connectors un-plugged, I found 0 resistance in the system and sensor ground circuits A11, A12, D1, D2 and D6 back to the ground distribution block confirming the ground path is sound.

I think the ECM puked, but it would be nice to know if the cause was old age or my harness.

I am leaning towards old age since I have been driving it a long time with no issues and not touching it.

[Tatsadasayago]

Methinks both ECM switching diodes for your fuel pump outputs got smoked from low voltage/high current/high resistance.
This is probably what took out your first pump relay.

[243]

I opened the box to see what there is to see this morning, it was like I was asked to read this:

l;aksjdf;kuqewokvn;lkjao;elkfna
aodjkf;lakenovk2098430jqe;lrkjfa;elkdmf;oa
aoejrf;alkejfd;oskefoajse9872435jl
al;ksdjfoaeijfoakjefoajedo3042985-fvkdv ,mzxclkvjad
daoekf/aldf';ald'flakdf;lkas;dlfka's;ldkfa
a;odjf;akjfda;aa;lfkej09485f;alksdvlkasdf;lk

But I didn't see anything melted, bulged capacitors or obvious signs of damage.

I found *ONE* 7747 box within 75 miles of town, I will go get it at lunch.

O'reilly has a re-manufactured box for 99.00, the junkyard box is 50.00 and I hate to pay that, the boxes should be laying in every junkyard.

[243]

Installed the chips in the junkyard ECM and turned the key and no power for 2 seconds at A1.

The retainer clips are removed for testing so I took the tip of the test light and pushed the A1 connector towards the ECM and it moved a fraction of an inch. Second try and I had power at A1 and the fuel pump primed, key off and key on and it fired right up.

I will re-check the voltages again now that it's running to see if there are any strange numbers.

[243]

Checked system and sensor grounds with the engine running and found 130+ ohms again, I un-plugged the ECM so I don't fry a third one, raised my hands to the sky and said why, why did you invent fuel injection???...just kidding, I am still a carbuhater

[Nikkormat]

I've got a 2150 I can box up and send down...

[243]

As you poke fun, zero resistance indicated on the multimeter on system or sensor grounds, key on or engine running and it's purring like a kitten now...

[Nikkormat]

I poke fun but I too am fool injected.

[Tatsadasayago]

Glad you got it sorted out.
What did you find that was causing the high resistances on the ground circuits?

[243]

I *believe* this was due to a bad connection where I tied the multiple TBI grounds together, I ripped the harness apart to confirm I had the sensor and system grounds tied together, found the end point and cut it loose from the other grounds and ran it direct to the battery post that is also connected to the engine and frame directly.

WinALDL only indicated 12.2 volts even though the TBI power is direct to the battery "fused".

What I noticed this morning, there is no direct connection between the alternator charging post and the starter solenoid post/battery cable connection.

The ~10ga wire at the solenoid, runs into the cab, I believe through the bulkhead connector and back to the engine bay and alternator.

I am going to ground the alternator this afternoon and add a direct connection between the solenoid and alternator.

Next will be finding out why the alternator charging wire runs through the cab.

[Nikkormat]

The ~10ga wire at the solenoid, runs into the cab, I believe through the bulkhead connector and back to the engine bay and alternator.

I am going to ground the alternator this afternoon and add a direct connection between the solenoid and alternator.

Next will be finding out why the alternator charging wire runs through the cab.

Yeah the whole system charges through those 10 gauge wires. Great huh?

I ran a starter cable from the alternator up. I've got the TBI grounds grounded directly to the negative battery cable where it connects to the block. All of that for my beefy 40 amp alternator!

Glad it worked out, and it was fun to learn some trouble shooting with you.

[243]

It's not over yet and I am learning as I go.

[243]

This afternoon I replaced the positive cable that had a broken lug, added a ground from the starter to the frame where the negative battery cable ties to multiple other grounds, added a charge wire from the solenoid to the alternator and a ground from the alternator to the negative battery post. Voltage looks good now, 12.9-13.3v depending on rpm.

I grabbed a handful of tools, tow rope, cell phone, charger, spotlight, flashlight, called my kids to see if they were home or working and headed out for a test run. It ran damn good, I was also datalogging and glancing at the computer, temperature and voltage were looked good and stable. Took if from a 55 mph State highway to a 75 mph State highway and hammered it, running 75-90 mph.

Lost 2nd, 3rd and reverse, 27 mph for 12.5 miles and I am home.

[serehill]

Yeah I don't have a lot of knowledge but I i know the prime is not dependent on the oil pressure switch. the ECM should bypass oil pressure to prime. After the rig is up & running the issues should not be a prime problem. It does sound a lot more like a connection problem because of the inconsistency.