Fuel Return Line Pressure?

[WillWagner]

Oh, again, the screen in the pump, the one under that big azz flat head screw, is only there so that in case of a catastrophic fuel pump failure, the debris from the pump will not get into the injectors. It isn't a maintenance item. HOWEVER, in the case of something sitting and getting gooed up fuel, having water infused fuel run through the system, that screen will get plugged. If when removed, the screen filter was plugged with rust or gelled fuel, the injector screens are 99% full of the same stuff.

Rust, if the screen filter in the pump was rusty on the outside, that means the injectors are too. That filter filters backwards, filters inside out, hence the magnet inside the filter. So, if there are rust stalagmites on the outside of the fuel pump screen filter, the injectors are the same way. SOMETIMES the screens can be removed, the plunger pulled from the body, cleaned with scotch brite, cleaned thoroughly, lubed with clean fuel or WD40 and put back into the body, and things will work fine.

DO NOT pull all of the plungers out at one time, remember those parts, the plunger and barrel are lapped to one another and cannot be inter mixed. Do them one at a time.

To the OP, If you do end up pulling the injectors, PM me before you start. I can give you some hints.

 

[Wreckclues]

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It is part of the "tamperproofing"
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With the nuts missing could engine vibration over time have worked the screw and throttle shaft out of alignment? If so what direction should I turn the screw to get the angle between idle and full throttle back to 32 degrees?

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Rust, if the screen filter in the pump was rusty on the outside, that means the injectors are too. That filter filters backwards, filters inside out, hence the magnet inside the filter.
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May have dodged that bullet, the outside of the screen was clean. The inside was coated with what looks like rust.

 

[msgjd]

With the nuts missing could engine vibration over time have worked the screw and throttle shaft out of alignment? If so what direction should I turn the screw to get the angle between idle and full throttle back to 32 degrees?

several years ago i pulled a 290 out of an M818 dump conversion that is (still) missing the cover plate on the side of the PT pump as well as the pivot shaft nut. .. It came from a different town than yours, but the 290 clearly was tinkered with .. I stuffed it in a commercial dump last year but soon I need to finish hooking up all the hoses etc and address the PT pump stuff

i wish i could answer you but i have never touched a PT pump other than replace that little screen on these trucks from time to time .. Your situation reminds me i need to look at the 290 for the lever being out of position

 

[WillWagner]

It is part of the "tamperproofing"
[/QUOTE]

With the nuts missing could engine vibration over time have worked the screw and throttle shaft out of alignment? If so what direction should I turn the screw to get the angle between idle and full throttle back to 32 degrees?

[/QUOTE]

It is going to be the screw toward the front of the pump, the one you can't see.

Remove the linkage and see if it idles w/o the linkage connected. Should be 600-700 RPM. That screw that should have the nut and tamperproof nut is to set throttle leakage so that the engine doesn't die on decel and/or stick the injectors from lack of fuel flow on off throttle events. It is screwed in pretty far, there is usually 1/2 inch or so protruding past the thin lock nut. The actual idle is set through the governor cover.

My guess is that the pump isn't set up correctly, but, the allen you can try turning is under the flat area in front of the house shaped aluminum cover. Turn lefty loosie, keep track of the amount of turns in case it is set sorta right. If you go too far, the holes in the shaft will pass the passages in the pump and start closing them off.

 

[Wreckclues]

Ran her directly from a boat tank connected to a compressor. She will not start from the fuel tank or with the exhaust pipe attached. Even with the pipe off it's a hard start.
Ran clean fuel and Sea Foam injector cleaner through the injectors. At first couldn't get her over 600 RPM but later got her a little over 1000 RPM but with no pedal response.
At this point I removed the linkage spring and let the linkage hang free. It "Idled" at about 950 RPM, little difference from full throttle. Hung the boat tank and compressor in the wheel well and idled the rig out of her winter storage tent.
The adjustment bolts on the PT Pump won't budge.
Just for review when I bought the truck and solved the initial problem with the pickup tube, it drove good. After changing the oil it ran great...and then it didn't, devolving to where we are now. So if the pump was initially set up wrong why did the truck drive good initially?
Could the problem be the muffler? The internal colander like pipe at the exhaust pipe end has detached from the muffler body. Don't know what the other side looks like. What follows is a video link showing the exhaust.

 

[msgjd]

i am at a loss of ideas .. it ran strong for me as well until i started having trouble with it sucking air after it sat around a lot during its last years here .. i can only think "injector screens" however my only experience i've had with a clogged screen was one of my M818's and the errant cylinder had a skip

maybe injector nozzles are sticking and not opening all the way? idk .. what i know for sure is these particular cummins systems are prone to sucking air

 

[WillWagner]

Me, I would pull injectors, BUT, if you aren't familiar with the tune up procedure, not an option, it could cause you more issues.

I would pull the pump and find a shop that can stand test it to see if there is an issue. 4 bolts, a couple of lines, and it's off. Faster and easier to do this. Not technical at all.

IF the exhaust was an issue, it would start, run OK for a second, then die, it's gotta get out to get in, and have black smoke as it died. BUT, just for S&G, take the pipe off the manifold and see what happens.

There are some really rare things I saw happen that could cause this, the drive coupling between the accessory drive and compressor can split and mak it so it will not start, but, yours starts. The drive gear on the input shaft spins on the shaft. This will cause what you are seeing, but unless the pump is torn down, no way to tell.

The fuel shop will see that issue when they do a stand check.

Other than that and not being there, it is a guess on my end.