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.

 

[Wreckclues]

Thanks guys, next steps are;
1. re-re-rebuild the fuel side of the pump, replace all the O-rings in the filter and test each fuel circuit for air using the transfer pump.
2. Detach the muffler
3. Before sending the pump out for testing, open the "house" cover and see what's going on with the adjustment screws. The screw to the right of the "house" is only sticking out about 5/16". Seems I remember Will saying it should be closer to half an inch?
In the mean time I found this great animated video on how our pump and injectors work

 

[WillWagner]

One thing at a time so you know what the issue was.

 

[msgjd]

In the mean time I found this great animated video on how our pump and injectors work

wow , that recent video is WAY better than the cummins technician training film i saw on there some years ago !

nice find !

 

[msgjd]

In the meantime I found this great animated video on how our pump and injectors work

since i am in the process of reconverting a militarized NTC290 i took out of an M818 to put back into a commercial truck application , i have run into several little issues getting the "new" engine to receive all the commercial truck's additional fuel hoses, air lines, and oil lines that the M809-series doesn't have .. This requires me to R/R certain military-specific parts on the NTC290 and replace them with parts and assemblies taken from my old original NTC230

This is a slow tedious task being mostly done one item at a time because it's been a dozen years since i removed both engines, and the labels on every hose and line have since deteriorated .. To add insult to injury, i cannot locate pictures i took at the time, which detail the location of everything

Of interest to you and your PT-pump curiosity, i have discovered i need to reconfigure the NTC290's militarized PT pump by adding the screw-on fuel fllter assembly from the old engine, which bolts directly to the tail of the PT pump .. I've never been into these pumps before, but there's no hurting a cadaver parts engine .. So, here's a couple pics of the gear pump end, which draws the fuel from the tank(s)

You can easily pop the gear pump head off with a 3/16" allen , apparently there's no wire seal used on that particular piece.. I suppose we need to be careful not to lose the mating mesh of the two gears , i also made sure i didn't pull the gear shafts out of the main PT-pump body much, not knowing what issue that would cause inside or not ..

There's an o-ring in a detent at each of the two ports on the gear pump housing to seal it to the passages on the main PT-pump body .. I suppose if those o-rings were bad they could cause a loss of fuel pressure or a diversion of fuel elsewhere ..

I also have to wonder if low-sulphur fuel would create excessive gear pump wear however your engine has low hours..

As you can see, the gears on this one are gummed up just like my short-term memory is nowadays







the donor cadaver

 

[Wreckclues]

Update: Tearing into my checklist I found that the gasket between the fuel filter bell housing and the upper part may not have been diesel certified, it had swollen to the point that it no longer fit the groove. Also found the water trap petcock was clogged solid. Currently waiting on new O-rings, in the meantime I removed the home plate from the pump. Not going to touch the adjustment bolts until I troubleshoot the fuel system, until then I'm soaking the bolts in penetrating oil.
What were the plate's attachments? One source said they were screws, but what I found looks like some kind of soldered stud.
Also found the vent lines on my tank are rusted shut, will replace with brake line as soon as I source the right size, but for now just replaced with some spare fuel line.
Thanks for the pics JD, I recently scored Bulletin No. 3379084-00
Group 5 Fuel Pump PT Rebuilding, should I ever want to go where you're going...

 

[WillWagner]

The little round head things that hold the cover on are drive rivets. Don't touch anything else until you get things back together, otherwise, you will not know what the issue was. Do one thing at a time. Picture of a drive rivet attached.

To get them out all you do is use chisel with a very fine point and give it a little love tap alternating side to side. It will eventually back out and then use a good set of dikes to finish prying it out.

 

[msgjd]

Update: Tearing into my checklist I found that the gasket between the fuel filter bell housing and the upper part may not have been diesel certified, it had swollen to the point that it no longer fit the groove.

hey we can't forget to pay attention to the oh-oh ring (and groove) on top of those fuel filter cans (retaining bolt) .. That spot up there collects a lot of environmental crud and the o-ring can get deformed during tightening enough to suck air .. another issue i've run in to is the fuel tank selector valve on the cummins trucks sucking air, but your's is a M813 and fortunately doesn't have that ornery item

perhaps the gasket didn't like seafoam or some other additive? ..

rubber just isn't as good as it used to be .. case in point is a failed goodyear tire dated 2016 on my M116 gen trailer compared to the 55yo bias relic shown below, which has been up and ready to roll at any given time for all these years ..

okay, now that i said that, murphy (or mullaney) is gonna strike

 

[Wreckclues]

rubber just isn't as good as it used to be .. case in point is a failed goodyear tire dated 2016 on my M116 gen trailer compared to the 55yo bias relic shown below, which has been up and ready to roll at any given time for all these years .

Too funny, when I was airing up last year, found one of the duallies had zero air pressure but wasn't flat. As far as I could tell it had always been that way with me repeatedly crawling over a stone wall in my yard and driving around town...go figure.

 

[Mullaney]

hey we can't forget to pay attention to the oh-oh ring (and groove) on top of those fuel filter cans (retaining bolt) .. That spot up there collects a lot of environmental crud and the o-ring can get deformed during tightening enough to suck air .. another issue i've run in to is the fuel tank selector valve on the cummins trucks sucking air, but your's is a M813 and fortunately doesn't have that ornery item

perhaps the gasket didn't like seafoam or some other additive? ..

rubber just isn't as good as it used to be .. case in point is a failed goodyear tire dated 2016 on my M116 gen trailer compared to the 55yo bias relic shown below, which has been up and ready to roll at any given time for all these years ..

okay, now that i said that, murphy (or mullaney) is gonna strike

View attachment 946647

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Hey! I resemble that remark...

 

[msgjd]

you might want to carry a hammer or billyclub in the cab for when you do your walkaround .. those who are not tone deaf can hear different pitches of notes being played when the air pressure isn't the same among them


they don't look flat if their circumference winds up the same as the tire next to it but sometimes you can spot a different contour .. the sidewalls on those tires are solid and i've seen situations where a driver ran his 5T around all day on tank trails and never knew he had a flat or two back there until he got back in for the night and did a walkaround.. one of those guys was me, i had picked up a 7.62 casing , the (unpunched) primer was outward and the bullet had penetrated the valley between the nubs ..

I removed the wheel from the truck and rolled it over to the BN maint tent, but BN maint refused to fix it .. i had been shot before, but they apparently were chicken-sh&&s

 

[msgjd]

Too funny, when I was airing up last year, found one of the duallies had zero air pressure but wasn't flat.

it might've had pressure if you had parked that tire in the sun

 

[msgjd]

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Hey! I resemble that remark... View attachment 946679

just checking whether you really read everyone's posts, or just click the "like" button ... lol

 

[Mullaney]

just checking whether you really read everyone's posts, or just click the "like" button ... lol

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Nope. I spend more time than I should, but I read and even understand most of what I "like". I worked on military trucks back in the early 80's for a steel high-line company. Rebuilt from the ground up. Worked on trucks, then got into hydraulics. Not claiming to be the all knowing. Just somewhat experienced maybe?