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Lift Pump Not Working, Where to Start

WarWagon said:
You have a shaft driven vane pump in the IP between the fuel inlet and the rest of the IP. Unless it's turning the only fuel you see is leakage through it. The engine must be turning the IP to flow fuel.

Spin the engine over and see how much fuel you get out.

IMO with the past 9 pages the point is reached where the shaft has sheared off in the IP or something else is refusing to flow fuel through it.

Compare the fuel return on a running 6.5 when cranking (unplug PMD) and this problem will become very clear. :wideyed:
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Replaced the IP today with the same result. No fuel coming out of the IP going to the injectors. We had the whole left side injectors cracked and glow plugs removed. All told probably cranked the engine 3 minutes with brakes in between with no fuel coming out of the injector lines. The clear line we have on the fuel return line has fuel in it so fuel seems to be flowing through the IP.

I tried hooking up a second PMD with hopes that the PMD was the issue. Same issue.
 
Is Pmd is proven good? I have replaced bad ones with new ones that were bad also. That got me to the point of under what is meant by “known good”.

Pcm is option.

Before that I would remove the fitting going into your ip that the fuel line connects to. Have it hooked up to fuel line and check flow through it. There is a screen there that could plug.
 
Next we need to installed forged Lower Control arms with new bushings and ball joints (have all the parts). Probably have to cut off the stamped steel ones as I could never get them off the torsion bars. While doing that, replace the boots on the CV axles (already have the thermoplastic boots Ferminator recommends). Then the final project will be to install the already prepped GMT 800 rear axle with disc brakes. Damn truck could use a paint job after sitting out and new leather upholstery or seat covers.
 
Longer term is to prep the engine we saved from the '95 wreck for when this engine gives it up. Just simple stuff like gapless rings, new timing gears and chain, new water pump.
 
Big T said:
That and a faulty IP we jerked around with for two years. When your time is extremely valuable, it’s better to throw parts at it.
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This was delayed by Covid interruptus “forcing” us to socially distance in Montana with infrequent visits to CA home. Also impacts with my being slowed by recovery on 3 different foot surgeries which made it uncomfortable doing the work. Throw in the typical 6.5 troubleshooting headache starting with the typical problem solutions starting with grounds and proceeding to PMD, lift pump, etc. I think the interruption of continuity of work really hindered the whole process, but it’s running and we’ll get this one back on the road.
 
Big T said:
This was delayed by Covid interruptus “forcing” us to socially distance in Montana with infrequent visits to CA home. Also impacts with my being slowed by recovery on 3 different foot surgeries which made it uncomfortable doing the work. Throw in the typical 6.5 troubleshooting headache starting with the typical problem solutions starting with grounds and proceeding to PMD, lift pump, etc. I think the interruption of continuity of work really hindered the whole process, but it’s running and we’ll get this one back on the road.
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How would you like a 1995 Tahoe to get going again. LOL
 
jrsavoie said:
How would you like a 1995 Tahoe to get going again. LOL
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I'll pass. Between work and two home in various stages of remodel, plus a boat I need to finish after repower and another I need to replace fuel tank and prep for sale, I have a long list still on my plate. The good news is the longer I stay in Montana, the more I can be irresponsible and just fish away on my free time, thus not attacking that list.
 
@Big T Here ya go, fixed it for ya.
“Throw in the typical 6.5 DS4 troubleshooting headache starting with the typical problem solutions starting with grounds and proceeding to PMD, lift pump, etc.”

If only you knew the amount of headaches you eliminate with db2. We don’t care about ground wires, sensors, nothin.
 
Rockauto shows two different AC Delco IPs for the ‘94 Suburban with different prices:
C3F50D79-01D3-42FF-A691-2F8B02BF98F5.pngABBDBFB0-5FC7-43FE-829D-AA358B83526C.png

They identify by engine code. Where do I find that? Here’ the VIN:

8FB18956-E6FB-4D4F-A75F-207E83B0B022.jpeg

So which one?
 
Will L. said:
@Big T Here ya go, fixed it for ya.
“Throw in the typical 6.5 DS4 troubleshooting headache starting with the typical problem solutions starting with grounds and proceeding to PMD, lift pump, etc.”

If only you knew the amount of headaches you eliminate with db2. We don’t care about ground wires, sensors, nothin.
Click to expand...

Yes but the conversion to db2 seems like a PITA.
 
Big T said:
Yes but the conversion to db2 seems like a PITA.
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Pedal swap. 2 hours at junkyard, 2 more at home for r&r.
Ip which you are a pro at now.
Buy aftermarket trans controller- that will be a 1 day thing in itself.
Mechanical boost control if it isn’t already on that truck.

Only other thing to complicate it is if you must have cruise control, and don’t want to do throttle cable cruise control.

Then at 30,000 mile intervals you bump the timing 1/16” advance to make up for timing chain stretch if you are really worried about it. But most just do that around every 100,000 miles.

Last step is sell off ds4, pmds, throttle pedal.

and incase you think I am being biased (which I am) can everyone who ever had a db2 die in under 200,000 miles please chime in. And compare that to everyone who had to replace pmd or ds4 or APP or ground wire issues in 200,000 miles.

yes swapping to db2 is a little more work than just ds4 swap. Until you add in the first pmd swap and any other issue at all.
 
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