Dies in gear when throttle applied

[92GMCK2500]

Got a little bit of time this morning. Some updates:

1. Scanner is out but I am yet to figure it out. Stay tuned...
2. Truck start fine. Tested voltage at fuel pump harness connector at fuel tank. I got 13.8v, whilst back probing Grey wire. Per the FSM this is within the 13.5-14.5v spec at idle. Is 13.8v optimal though?
3. Immediately tested voltage at fuel pump relay, orange wire. Got 14.34v.
4. That's 0.54v voltage drop - is this acceptable?
5. Stopped truck. Checked codes. Code 15 still, no surprise. Code 54 has not appeared again since disconnecting battery last night.
6. Went to start truck again. No go. Crank, no start. Verified spark and fuel, all ok, following FSM Chart A-3. Landed on "no trouble found, see diagnostics aids on facing page".
7. Here are the diagnostics aids

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- Fouled plugs - known fact.
- EGR Valve - code 32 diagnostics needs resolving.
- Low fuel pressure - doubtful, but entirely possible. I could rent a pressure tester again to verify new pump. Could be wiring, 13.8v an issue?
- Contaminated fuel system. No, all new.
- grounded CKT 423 - ?? What is this?
- basic engine problem - probably!

Edit: tried starting truck again, it started with throttle at wide open.

Low fuel pressure?

Low fuel pump voltage? Problem in fuel pump circuit?

 

[1990Z71Swede]

13.8V is not a problem.
It sounds like it gets flooded, most likely because CTS says its cold, when it is not. The scan tool would tell you for sure. But I'm surprised fuel enrichment for 20 degree centigrade is enough to cause a no start. Also TPS position might affect your CTS reading if there is a bad connection in the Return B circuit.

EST = Electronic Spark Timing.
CKT= Circuit, I think.
423 goes from ECU to ignition Module.

 

[92GMCK2500]

While testing crank, no start condition it started with the fuel injectors unplugged, no spray coming. Flooded for sure.

 

[92GMCK2500]

Can I now be confident that the fuel pump wiring is "good"? Or, are there other tests to be done?

Once the truck started again, it actually ran "normal", not surging, no stumbling while in gear at different throttle amounts. Hilarious.

 

[1990Z71Swede]

Can I now be confident that the fuel pump wiring is "good"? Or, are there other tests to be done?

Once the truck started again, it actually ran "normal", not surging, no stumbling while in gear at different throttle amounts. Hilarious.

For now I would focus on the flooded when starting hot issue, could be leaky injector or injectors or the already identified problems in the CTS circuit

 

[PlayingWithTBI]

EST = Electronic Spark Timing.
CKT= Circuit, I think.
423 goes from ECU to ignition Module.

Yes to all 3. CKT is a standard abbreviation for Circuit even though there's no "K" in circuit

Here's a schematic from an 88/89 (1227747 ECM). #423 is the white wire.

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[92GMCK2500]

For now I would focus on the flooded when starting hot issue, could be leaky injector or injectors or the already identified problems in the CTS circuit

I'll start at the CTS stuff cause that makes the most sense right now. Got a game plan, just gotta make some time to work on it, usually evening/night hours (in my driveway)

 

[92GMCK2500]

Yes to all 3. CKT is a standard abbreviation for Circuit even though there's no "K" in circuit

Here's a schematic from an 88/89 (1227747 ECM). #423 is the white wire.

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So, it's Cir-kit.

Thanks for the schematic!

 

[92GMCK2500]

Here's my old scan tool. Anyone familiar?

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[Schurkey]

I've seen those. A company I worked for had one for use on city buses, but it wasn't part of my job with them to use it.

The way I remember it, those were mostly used on trucks and diesels, but there was software available to use with passenger cars and light trucks.