NHC 250 missing out, bogging, then revving up on its own

[hellpounder]

When I got back from driving yesterday and was draining the tanks, I heard the engine start to idle erratically - it would bog down, then speed up, but not quite surge. Blipping the throttle didn't make any difference. I left it on the block heater all night and started it again today, and it had a very stumbly start, whereas it usually starts immediately. It smoothed out after a couple minutes. Let the tanks build up air and test drove it, it almost stalled halfway down my drive, and then would just randomly miss out.

The previous owner had a shop completely overhaul the fuel system - new tank, filter, pump, lines, etc. I have about 3/4 a tank, can't find any fuel leaks, I've made sure to use winter diesel and a proportional amount of antigel each time I add fuel, and haven't had a single issue with it running until this.

I've been trying to search the web for info, but haven't come across much that seems relevant yet. I'll start scouring the TMs and continue independent research, but would really appreciate any input in the meantime.

Thanks a bunch.

 

[hellpounder]

Going to try replacing the fuel filters with my next check. It has the dual spin on upgrade, just NAPA filters.

 

[M35A2-AZ]

Sounds like it maybe sucking air in from someplace.

 

[hellpounder]

I finally got around to testing more and replacing the filters. It has the dual spin on upgrade, with the water separator and particle filter. Using NAPA filters.

Last night, before replacing the filters, I opened the water separator and drained it until a steady stream of diesel poured. I primed the fuel pump using the factor primer on the side of the engine. Pumped until steady stream of diesel. Started it, it stumbled slightly, but after a few seconds it idled smoothly, I could rev it, and I test drove it around the block. Starting off in 1st gear it had no power, flooring it, it was just choking out, then after a few seconds, it gained power and accelerated normally. I could hold the throttle and it would go just fine. Come to a stop, it sputters, does the same thing, after about 5-10 seconds of flooring it, it clears up and accelerates. Anytime I come to a stop it behaves the same way.

Replaced the filters today. The old ones had almost no diesel in them when I removed them. Filled the new filters with fresh diesel and antigel, oiled the gasket, hand tightened them, used the fuel primer on the side of the engine and pumped until it produced a steady stream of diesel, then started it up. Stumbled slightly, but evened out after a few seconds, revved fine, and idled smoothly for about 10 seconds, then sputters and dies. Try to reprime it, almost nothing but air is coming out of the primer. I take off the filters and they have maybe 1/5th of diesel in them. Refill, tighten, reprime until steady supply of diesel, starts up, same thing - dies after a little bit, primer just spits out air, filters are mostly empty. It seems like the fuel supply between the tank and the filters isn't supplying. The fuel tank and lines are only a few years old, and the tank is stainless steel.

Going to try to disconnect the line between the filters and the tank and see what I find, but any suggestions would be greatly appreciated.

 

[M35A2-AZ]

You may look at the pickup tube in the tank. They can get a crack at the top of the tube and pull in air.
It happen to my truck many years ago.

 

[M35A2-AZ]

Here is my thread about it.

M923A1 losing prime

I have a M923A1 that was losing prime. I checked and checked for leaks and found none. But GL damaged my fuel tank mount before I picked up the truck, so I removed the tank to repair the mount. Now that I had the tank off I removed the fuel pickup tube from the tank. The tube was about ready...

www.steelsoldiers.com

 

[Wreckclues]

You may look at the pickup tube in the tank.

My pickup tube rotted out. I have an 813.

 

[reloader64]

My M813 started acting like it wasn't getting fuel, beginning with hard starting, then losing power while driving. I put an external lift pump on it, and that fixed the problem...for a little while. Turns out that my injection pump needed to be rebuilt, and the internal lift pump failing was just the first symptom. I had the IP rebuilt, and the trucks starts and runs normally now.

Scott

 

[hellpounder]

My M813 started acting like it wasn't getting fuel, beginning with hard starting, then losing power while driving. I put an external lift pump on it, and that fixed the problem...for a little while. Turns out that my injection pump needed to be rebuilt, and the internal lift pump failing was just the first symptom. I had the IP rebuilt, and the trucks starts and runs normally now.

Scott

Good to consider. Would you mind sharing how much that costed, and roughly what the process was like?

 

[hellpounder]

I

Here is my thread about it.

M923A1 losing prime

I have a M923A1 that was losing prime. I checked and checked for leaks and found none. But GL damaged my fuel tank mount before I picked up the truck, so I removed the tank to repair the mount. Now that I had the tank off I removed the fuel pickup tube from the tank. The tube was about ready...

www.steelsoldiers.com

I
Sweet, thanks. I'll see what I run into. The tank and all of it's lines and fittings were all custom made about 9 years ago, after speaking with the previous owner over the weekend.

I got the line to the tank disconnected, but didn't have the correct wrench to get the fitting out. Previous owner said he had the pickup tube custom machined to attach to that fitting, and that it should pull right out once I can get it unscrewed. Going to see if I can borrow my neighbor's adjustable wrench - I'm snowed in, and I let someone borrow mine (of course).



While the line was off, I decided to stick it in a 5 gallon jug with some antigelled winter diesel. It primed just fine, and it started. Ran until I shut it off, which was about 5 minutes. Revved and idled without sputtering. I took the filters off afterwards and this time they were full of fuel instead of being mostly empty.

I think I may see some wear at the end of the line, where it connects to the tank, so I'm going to trim it back some. Once I can get the fitting off I'll inspect the pickup tube and go from there.

Thanks for the input, guys. Hope to have another update shortly.

 

[reloader64]

Good to consider. Would you mind sharing how much that costed, and roughly what the process was like?

I pulled the pump off myself and had it rebuilt by a diesel shop in Austin, TX. The rebuild was just shy of $1,000. R&R'ing the pump is pretty simple, as there's no timing to worry about. Disconnect the inlet hose and the outlet pipe, and the cables and wiring, then pull the 4 mounting bolts. The 2 bolts closest to the engine had to be wrenched out as I recall. It took me about 45 minutes to pull it, and about an hour to get it back in.

Scott