2001 Suburban stalling issue

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kbuskill

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First off, not my truck, just trying to help a buddy.

My buddy just got a 2001 Suburban and it will randomly stall for no apparent reason.

It has 275k miles on it but "supposedly" had a "new" engine put in it with "only" 100k miles on it by the previous owner.

I noticed right away that someone had cut 2 of the small ground wires that break out of the main harness, toward the back of the intake manifold and normally go the back of the passenger head/block, and added wire to them using the cheapest butt connectors available and ran them to the ground stud on the firewall where the braided ground strap bolts.

First thing I had him do was remove the butt connectors and solder and heat shrink those 2 wires. The next thing we did was wiggle and move every harness under the hood to see if we could get it to act up... nothing obvious.

I checked under the under hood fuse box and found nothing obvious wrong.

I next had him remove and clean the ground wires on the drivers frame rail. He drove the truck for 2-3 days without any issues but it has now started stalling again.

When it stalls, sometimes it will crank right back up, other times it will not. It cranks fine but acts like its not getting fuel or spark.

The one thing I noticed the other night is that when it won't start the fuel gauge reads empty. When the fuel gauge reads proper the truck will start and run.

I am leaning towards bad grounds or negative battery cable.

When I first checked the codes it was throwing codes for everything. There must have been 50+ codes showing but after cleaning the ground on the frame and clearing the codes the CEL stayed off.

Any help would be appreciated. I have never owned a GMT800 so I am not familiar with possible common problems.
 
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kbuskill

kbuskill

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check and clean the harness for the fpcm, next time the fuel tank shows empty check the fuel pressure

If it were in my possession it would be easier to diagnose. It cuts off on him randomly while driving and I'm not there to check anything... lol

Unfortunately he is not very mechanically inclined so it makes it difficult.

I didn't have a fuel pressure gauge the other night but it did shoot fuel out of the rail when I depressed the schrader valve.
 

exp500

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Following the clues- are fuep pump relay and gas guage seperate power leads? probably but I'd have to check diagram.
It does sound like attack of the electridal gremlins! I would also look at underhood power distribution box/fuse panel for corrosion, Verify battery connections both ends.
 
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kbuskill

kbuskill

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Following the clues- are fuep pump relay and gas guage seperate power leads? probably but I'd have to check diagram.
It does sound like attack of the electridal gremlins! I would also look at underhood power distribution box/fuse panel for corrosion, Verify battery connections both ends.

We pulled the underhood fuse box up and everything looked good under it. I wiggled all the connectors under it to see if it would act up to no avail.

I think the next step will be to pull and clean the ground at the battery cable/engine block.
Maybe replace the cables as a precaution.

Do the GMT800's cables suffer from the internal corrosion as bad as the GMT900s do?
 
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kbuskill

kbuskill

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No start and fuel gauge showing empty would lead me to look at the fuel pump module. I seem to recall an issue with the harness at the fuel pump getting crispy.

I knew the GMT900s had a fuel pump module, wasn't sure about the 800s.

Is it mounted under the truck above the tank or ???
 

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