Cuts out after start ups

Hi all it’s been a while. My truck cuts out after start up, sometimes went putting it in gear. New Optimizer build. Everything is pretty much new. See Signiture . Never while driving. It will do it every morning and then after going somewhere and restarting it. But not every time. Checked all Grds., wiring harnesses and connectors. no DTC. Fuel press good.
no air in clear return line going to IP. LP volume test.
The only thing that i transferred from the old motor was the PDM and extension harness. They worked fine on the old motor. I did have another known good PDM and tried it. No dice. I was going to bypass the extension harness by plugging one of the PDM,s directly to the upper engine harness connector by the IP but neither one would plug in. Wrong connector on the upper harness. It takes a PDM that has the square ears on it . Mine are both the curved ear type. I sure hate to buy another extension harness just to check the one on there now. I tried using my Tech 2 to see what the IP pump is doing. But it happens right after start up and I have to re- enter motor info after start up because the scanner disconnects when cranking on start up. It happens to fast. I sure hope someone on here experienced this problem before. It’s getting very annoying. Worried about reliability. Thanks.
https://youtube.com/shorts/59tbVMGnJ...xQYUw_C6V8Ri9f

watch the RPM gauge it’s just a fast stutter.

Hi all, this is a continuation of my first post. I took some videos of my truck when the event ( cut out , stutter ) happens. My first video has been removed. Don’t know why. Hope somebody sees these . What do you guys think. Thanks Gus.

First video is of the clear return line to the IP check for air in the fuel system when the event happens.
https://youtu.be/0--ulrqD0xs?si=zJmmXTsVvvOlqsAS

Second 2 videos is of Tech2 IP data and voltage readings on the battery checking to see if voltage drops off. Both when the event happens.

https://youtube.com/shorts/ibnH9ehCD...M8YbBbWfGiDWtz

https://youtube.com/shorts/eR6XuhrAo...XaRxM5KkfVCV-8

I don't see or hear anything abnormal. If you mean the little ignition blip and voltage dip immediately after start, it may be something or nothing. I only saw that once in your second video. A lot of things happen after a start, and more so after a cold start. It could be glow plug controller or fuel lift pump related. The 1995 models have 2 operating modes of the lift pump (your sounds a bit noisy), when the key is turned to start, and after the oil pressure comes up to OPS switch pressure. Neither of these should affect ignition events. A failed PMD/FSD harness should cause the issue, either. If it's failed, it would be either more often and random, or stall for longer periods. Even so, it usually takes some movement to cause the intermittent connection, such as a really rough running engine (yours seems normal), or worn out engine mounts, allowing the engine move a lot in response to torque outputs. It's possible your FSD (Fuel Solenoid Driver, what the PMD -Pump Mounted Driver- is called when it's no longer mounted to the pump), is failing or has a poor connection. If the ignition blip is intermittent and limited to after a start, it won't be easy finding the cause. You'll probably correct the issue by adjusting connectors, or the suspect component will just fail. It wouldn't hurt to have a known good spare FSD on hand, in case it fails on the road somewhere.

According to YouTube, your video in the first post was "removed by the uploader". I recall seeing that video when you first posted it, and it didn't show me anything remarkable. It was just a very short clip of the instrument panel after a start. I had nothing to reply, so I didn't. I suspect no other replies for the same reason.

Thank you for your reply. Yea this is going to be a hard one to figure out. It’s just so weird it does it like clockwork in the morning and then randomly through out the day depending on how long my stops are. Very frustrating. I have spent a lot of time on doing the wiggle test on all the harnesses while the truck was running. I am concerned about the reliability of taking the truck on long road trips. I always carry a spare FSD, OPS and LP. I do have a brand new Raptor LP sitting on the work bench. I am in the middle of getting the “Wait to Start light” working. Problem with the trace circuits on the PCB on the back of the cluster. I’m saying this because I do seem remember on the old motor the WTS light blinking and the stutter after start up. Could be I’m overthinking this? I also have the bigger starter installed on this motor but I didn’t upgrade to the bigger cables because it starts so good. I wish I could narrow it down if the event is fuel related or electrical. I may come back on here w/ a video after fixing the WTS light. Thanks for the help.

A lot of this isn't adding up. There's only a couple common suspects for most, if not all, of the issues. The Ign. Switch. If your IPC (Instrument Panel Cluster) is flaky, get it refreshed. There's outfits that do rebuilds for not much, and it retains your original odometer. If you have the direct drive starter (the big one), make SURE you have the forward support bracket installed. That start is heavy, and it will break the block if it isn't supported. The smaller gear drive starter isn't as bad, but it will also break the block, it just takes a little longer. Your problem is not fuel supply related. It's electrical or electronic. Fuel supply issues cause stalls, hard restarts, and wild RPM flares.

Thanks Dmax for your input. I too was thinking ign. switch. I’ll probably just replace the switch. And the FSD extension harness because it was carried over from the old motor. Thanks for the tip on the IPC. Wasn’t aware anybody repaired them. I do have the Powermaster gear reduction starter from Quadstar. I do have the rear bracket installed and new starter bolts, I do not believe I have the starter listed in my signature. Thanks again for all your help.

When I first joined here I had a 94 K2500. After reading about electrical and ground problems I picked up a can of oil electrical cleaner. I attacked every connector I could find. I also got some dielectric grease and sanded and greased every ground. I had it from 96 to 2014 and never had any electrical problems.

Of course, the Nut is right about the importance of good grounds. And, speaking of grounds, there is one in particular that is exceptionally important, and my be related. The PMD/FSD harness (OEM or otherwise) has an independent ground wire, and it MUST (MUST!), be attached cleanly to the injection pump. This is the ground for the driver transistors, and if it's anywhere else (such as any more convenient location), can, and will eventually, effect the engine running quality, to put it simply, to include unexplained misfires.

all, I’m back on here working on my truck doing the stutter after startup. I do have another thread started about my instrument cluster. I’ll probably be jumping back and forth between the threads. Ok you all recommended checking all the grds. and wiring harnesses. I have checked the grds. And wiggle test all the engine bay harnesses. Also yesterday went through all the harnesses unplugging the connectors and applying dielectric grease in the engine bay. Still have to do ECM harnesses and the ones I can get to under the dash. Like you guys suggested.’Did some voltage and amp readings videos while the event happened.




If the videos get mixed up I can’t see which is which. The video with the big molded lead connector plug into the Big meter is the one showing the GP amp readings.
First video: Big meter voltage reading of the fuel shut off solenoid back probing the connector

Small meter: voltage at the ECM-B fuse
Not sure I seen anything on the video. Did see the voltage reading fluctuating on the fuel solenoid (Big meter) not sure.

Second video: Big meter amp readings during GP cycle. You have to read the amps. On the MV scale because of the type of DC clamp used.

Small meter: voltage at the ECM-1 fuse
Not sure either on this one too.
Did see a small voltage drop (small meter ECM-B) when the GP were warming up and also on the second little stutter. You can see on the amp meter the GP firing again on the second stutter. There are two stutters you have to zoom and play it a couple of times and listen.

Did see the voltage drop on the the small meter on the second stutter. You have to play it a couple of times and zoom in and listen and stare at the small meter (ECM-1fuse). What do you guys think?Sure looks like the GP,s fire again when the event happens. When I finally get my WTS light worked my I’ll be able to tell if they fire out on the road after a start up. I am not sure if that will tell me anything or not. I’ll just keep plugging along my.

Some things I thought about: still haven’t changed out the FSD ext. harness (work on the old engine). Still have the stock smaller battery cables but it does start very easily. I do have a new gear reduction Powermaster starter installed. In the process of upgrading to the Raptor LP. Still have to go through the ECM connectors and the connectors I can get to without pulling the dash back out. Final thought it is so weird that it does it like clockwork in the mornings and sometimes if I stop for awhile depending on how long it sits. I haven’t started it for the day and have a battery charger on it to boost the battery voltage to see if the stutter happens. Not very optimistic.
Sorry for the long one boys. Thanks.



1995 K3500 6.5 TD silverado dually. 4L80E, New Optimizer 2/28/25 from Leroy’s new IP from Quadstar 4” exhaust deleted muffler. New GM8 turbo . Relocated FFM. Relocated Fuel PMD to bumper w/ Leroy Deisel,s cable kit. Relocated OPS. Rebuilt 4L80E, new aux. coolers, new aluminum radiator, upgraded oil cooler lines from Leroy’s
New an-6 trans. lines. New fuel tank, and steel and rubber fuel lines. Pre- LP fuel filter kit from Leroy’s AC Delco GP,s and injectors.

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Well boys it wouldn’t let me transfer the videos. I’ll try to upload from my you tube
https://youtube.com/shorts/i4JTP90fw...1O1pNmePxTyF2h
https://youtube.com/shorts/S1ucSDeLF...RlDsy-q9JD_rj2
like I said in my previous post if the videos if get mixed up I have descriptions of which one is which. I sorry for the confusion and the long post.just trying to figure this out. Thanks guys.

Goose57 your second video is marked Private and wont play. . . . .