XM818 a semi failed recovery

[mattgunguy]

XM818 a semi failed recovery (It's alive)

So we decided we wanted a 5 ton to run with our deuce. Did a lot reading & a good bit of shopping around. Finally settled on a XM818 from a member here. Timntrucks who is a first class dude & has been great to deal with.

The wife & I left Springfield early Friday morning heading to scenic southern Louisiana. Got there in the late afternoon. Did the usual walk around, test drive, chit chat, & did the usual things that most folks do when buying a used truck. Let alone a 23,000 pound beast. Did the money & title exchange & things were good. Left out around 6:30. Made it to Magnolia Mississippi & wham the truck dies. Two hours on side of the road and some phone calls to Tim we got him running enough to limp to a truck stop. 10pm & called it a night. Off to a hotel. 7 am & time to start working. Tim drove the hour & a half up to help out. Narrowed it down to a fuel problem. Managed to find a new filter, replaced the old rubber lines, bypassed the selector switch. Now I have a very large yard ornament that will mostly idol fine but cuts out over 5mph. Been a good day. I managed not to throw any tools, cuss a lot, or punch any doors. I must be growing up finally.

In the end we've conceded defeat. Just can't figure it out here. He's going on a trailer tomorrow, & taking the ride of shame back to Springfield & a hotel again tonight.

 

[dawico]

Dang, hate to hear that.

Hopefully you get it figured out soon.

 

[R Racing]

there is a secondary fuel screen in the injector pump on the top of it. its either a large straight blade in some I think either a allen or hex head on the other style. look and see how it looks?

 

[mattgunguy]

The screen wasn't bad. The screw is a pain to get out of there though.

 

[turnkey]

Sweet looking ride...Sorry to hear about the trouble...Like you said makes a great Pink Flamingo...

 

[doghead]

The intank fuel pickup tubes are known to deteriorate above the fuel (near the top) and suck air. I'd pull the pickups and look them over.


A quick test , you could drop the rubber line directly into a fuel can and see it it runs better after a little time to get any air out.

The primer could be sucking in air also. Does it function properly?

 

[Csm Davis]

Sorry guy I tried to help as much as possible, if I didn't have a bus full of females to drive around I would have drove over.

 

[Trailboss]

Sorry to hear your problems. I've been broke down in MVs four times and know the feelings that run through you.

If you've bypassed the selector, replaced all the fuel lines and filter, that leaves either end of the fuel system. Just throwing out possibilities from my vast level of ignorance as I armchair quarterback from a distance. You've probably already considered these -

1 - Something clogging the fuel intake in the tank, or restricting fuel flow in the new lines like a pinch or kink
2 - All the injector lines not completely bled
3 - Trash in the injector/fuel pump that made it past the screen, possibly clogging the injectors
4 - One of the new fuel lines or fittings is allowing air in
5 - Fuel shut off valve not fully open
6 - Hate to say it, but fuel pump may have failed.

I love my XM818 and have driven it several thousand miles. Fuel issues are frustrating, but once you figure out the problem and fix it, your truck should be very dependable. Hope you find it quick.

 

[goldneagle]

If you didn't use the proper fuel lines they could collapse under suction. On the suction side you need stiff lines.

 

[mattgunguy]

I'm learning towards a air leak i can't find, or a something is stuck in a line somewhere. I hope it's not the pump. The truck itself just about broke the bank, the trailer home has more than smashed the bank. So a new pump would be many many months out.

I do suppose the fuel line could be collapsing. The truck runs great most of the time at a stand still, but it could be the extra pull on the fuel system while gaining speed could be collapsing the hose/hoses. Something to think on anyways. I'm not going to get to down about it though. I've gotten to spend some extra time with my wife, & she likes to jump in as well to help. Thank you for the kind words y'all. Y'all are a pretty good group of folks

This truck has been named P.I.T.A. Pain. In. The. Arse. That seems fitting after the last few days.

 

[EMD567]

The fuel system is dead simple. You are getting air in the system at some point, and 250's do not any air at all. Start at the tank, and work forward. Things to check for:
1)intake pipe inside tank. This is steel tubing, and after a number of years, water condensation will rust holes in the tube. I had to replace mine with a piece of brass tubing.
2)Flare fitting at top of tank-make sure it is clean and tight.
3)tank selector valve- O-rings will rot, and stop sealing. There is a thread on SS about rebuilding the valve.
4)Filter loose or sucking air around the gasket.
5)Flexible line from filter to IP- it can go bad over time, and suck air though the casing. This was the major problem with my M814, and took me 6 months to find it.
My experience has been that if the IP goes, the motor won't run. I have never found any gunk on the filter at the IP, the filter under the fender goes down to 5 micron, and filter at the IP has way bigger holes then 5 microns.

 

[mattgunguy]

Once we get him home I'm gonna strip the system completely & replace every line front to back. Probably stick with just one fuel tank. Might put the extra in tank deuce pump we've got in there as well. Do t know yet on that. Requires more reading and thought yet.

 

[timntrucks]

here are some more pics

 

[goldneagle]

It took a few tries of pressurizing the fuel tank on my M820 to find the air leak on the hose going from the fuel filter to the IP. It was under the strap that holds the fuel hose to the frame. In my case we could not start the truck due to loss of suction. In your case it seams to be not enough fuel getting to the injectors. That could be a constricted line. You can always try adding 5 PSI air pressure to the tank (continuous) and see if you get more speed out of the engine. Pushing the fuel through the hoses (instead of pulling) should keep them from collapsing inward and let more fuel through. If that seems to solve the problem then you can try replacing all the fuel lines with the stiff type lines. (or flexible copper tubing) to the filter and then hose to the IP.

EXAMPLE: That is why water pumps (none automotive) use a very stiff hose on the suction side and a soft collapsible hose on the discharge side.

 

[Csm Davis]

Okay if I were to try to fix this problem once at home I would do it with an eye towards less connections in the lines like the line from the filter to the pump it's what about 3' long and has 4-6 connections make it one flexible line with 2 connections. You get the picture and I would keep the dual tanks and valve, yes the valve can leak sometimes but not normally and is easy to repair and will not give you any more problems afterwards. You have got to remember these trucks are 40+ years old and any small o-rings and such have probably never been replaced. They are great old trucks and you have a great one there, it just has a very small problem that needs to be found, take your time and enjoy the search and getting to know your new truck.

 

[mattgunguy]

On the road again. We be on the road again

 

[doghead]

The filter bolt is a known to be challenging to get leak free also.

 

[goldneagle]

The filter bolt is a known to be challenging to get leak free also.

That is another reason I upgraded to a spin-on filter. If you check my latest M820A2 thread you can see the replacement filter mod I did. Very cheap and effective. All my 5 ton trucks will have the same upgrade.

 

[mattgunguy]

And home at last!!! Thank you to all for the help and the ideas. My eyes are to heavy for more right now. Good night.

 

[mattgunguy]

PITA with his not so little sister Meradith a 1970 Kaiser Jeep M35a2 rolling on MRAP's and 395's. So I guess they're non-identical twins since both are 1970 manufactured year.