Strange electrical issue

[bogus]

1994 k2500 5.7L 3/4 ton 6 lug
seems I can't post a video here so I'll leave a link to the subreddit where I posted this problem:

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I have cleaned or replaced every ground that I can think of.

I replaced the fuel pump when I got the truck in November 2023
New oil pump
oil pump pressure switch
EGR
EGR solenoid
vapor canister purge valve
MAP sensor
PCV valve
IAC
TPS
ICM
ignition coil
distributor cap
sparkplugs
plug wires
and all vacuum lines are okay.
replaced the inlet and outlet fuel lines to the TBI

 

[GoToGuy]

So what's the problem your posting on? What, it stopped running? Won't start now? Place in drive stalls out?
Did you do the IAC reset , check the length before install.
We're all those items broke? New fuel pump, what pressure after replacing?
You missed the O2 sensor? If it's lazy or not reading it affects all running conditions, no O2 sensor feedback, ECM cant see to control A/F ratio= poor performance.
Have you ran a scanner to see if sensors are reacting and reading normally? Not just a code reader.
Ya gotta explain a little , since we're standing next to you.

 

[bogus]

So what's the problem your posting on? What, it stopped running? Won't start now? Place in drive stalls out?
Did you do the IAC reset , check the length before install.
We're all those items broke? New fuel pump, what pressure after replacing?
You missed the O2 sensor? If it's lazy or not reading it affects all running conditions, no O2 sensor feedback, ECM cant see to control A/F ratio= poor performance.
Have you ran a scanner to see if sensors are reacting and reading normally? Not just a code reader.
Ya gotta explain a little , since we're standing next to you.

My bad. It starts and then stalls after an unpredictable short time (could be 10 seconds, could be 2 minutes before stall). I've replaced the O2 sensor, forgot to mention that.
I'll check fuel pressure after work, today.

 

[bogus]

So what's the problem your posting on? What, it stopped running? Won't start now? Place in drive stalls out?
Did you do the IAC reset , check the length before install.
We're all those items broke? New fuel pump, what pressure after replacing?
You missed the O2 sensor? If it's lazy or not reading it affects all running conditions, no O2 sensor feedback, ECM cant see to control A/F ratio= poor performance.
Have you ran a scanner to see if sensors are reacting and reading normally? Not just a code reader.
Ya gotta explain a little , since we're standing next to you.

You must be registered for see images attach

Fuel pressure is good

 

[1998_K1500_Sub]

Fuel pressure is good

Tell us more:

Spark?

Injectors firing?

Fuel pressure when it's dying / won't run? You may have an intermittent problem with fuel pressure / fuel pump electrical circuit, so this info would be useful at some point.

Engine temp? Ambient temp?

Any accessories "on": AC comp? Other?

Will it restart immediately after stall?

Tach showing any motion whatsoever (when cranking-no-start, if this happens)?

ECU codes?

ECU sane when it's dying / won't run?

Tell us everything, because "it dies" doesn't give us much to go on although the fact it's a "sudden death" is of interest.

You're replaced a lot of parts but that doesn't mean that those areas can now be overlooked; in fact, it may make them suspect...

Was the replacement ICM given a thin coat of heat-sink compound before installation on the dizzy?

 

[bogus]

Tell us more:

Spark?

Injectors firing?

Tach showing any motion whatsoever (when cranking)?

ECU codes?

No codes, spark is excellent, fuel pressure does not change when surging, only stops pressure when it cuts out. The injectors have pulse, and are firing.

The tachometer only slightly "jiggles" under the 0 mark when cranking, until the truck starts, then normal readings.

The oil pressure gauge is good

 

[1998_K1500_Sub]

No codes, spark is excellent, fuel pressure does not change when surging, only stops pressure when it cuts out. The injectors have pulse, and are firing.

So the engine dies then the pressure dies, or the other way around?

Ditto for the ignition.

I'm not being a smart-a$$, I've personally debugged and repaired a situation on a 1994 B-body where the fuel pump had an intermittent, poor ground (it didn't go open circuit, it just showed high resistance) that would cause the fuel pressure to sag and then the engine to die.

The fuel pressure looked fine every time it was checked, otherwise. The poor ground was the true cause.

Dig hard and dig deep, because it sounds like your problem is something evasive, like this B-body's was.

 

[bogus]

So the engine dies then the pressure dies, or the other way around?

I'm not being a smart-a$$, I've personally debugged and repaired a situation on a 1994 B-body where the fuel pump had an intermittent, poor ground (it didn't go open circuit, it just showed high resistance) that would cause the fuel pressure to sag and then the engine to die.

The fuel pressure looked fine every time it was checked, otherwise. The poor ground was the true cause.

Dig hard and dig deep, because it sounds like your problem is something evasive, like this B-body's was.

The engine dies and then pressure drops.

I cleaned the ground from the fuel pump to the frame, could it be the ground strap around the fuel take inlet?

 

[1998_K1500_Sub]

The engine dies and then pressure drops.

I cleaned the ground from the fuel pump to the frame.

How's the ground strap from the frame to the engine? Ditto, the strap from the body to the frame?

There are two, up front just behind the passenger's side exhaust manifold.

One strap runs from the back of the engine head to a stud on the body, and the other from the same body stud to the frame. Those form the ground return path for the fuel pump, and other circuits.

could it be the ground strap around the fuel take inlet?

I don't expect it to be; I believe that's there to prevent static charge issues on the fuel inlet.

 

[bogus]

How's the ground strap from the frame to the engine? Ditto, the strap from the body to the frame?

There are two, up front just behind the passenger's side exhaust manifold.

One strap runs from the back of the engine head to a stud on the body, and the other from the same body stud to the frame. Those form the ground return path for the fuel pump, and other circuits.



I don't expect it to be; I believe that's there to prevent static charge issues on the fuel inlet.

Replaced those straps as well