M923 fuel problem

[rcb]

Hello to all MVers:
My newest M923 arrived, checked all fluids, drove on the farm for an hour, parked on slight grade, an hour later would not start ! Topped off tank, hit the primer
pump until I had fuel, still will not start. Not even a sputter, absolutely nothing.
Your collective thoughts please...
Thanks...
Bob

 

[wreckerman893]

Does it have the turbo Cummins engine in it?

If so the fuel shutoff solenoid may be hung open (see pic). Note the solenoid with the rubber boot and the silver thing sticking out of it. This is controlled by the battey switch.

These things will de-energize and not allow fuel to get to the engine. You have to hold the thingy open and have soldier be crank the engine. Usually that will energize the soleoid and the silver thing will pull back into the housing. If I do not crank my M927 everyday mine will de-energize every time. These trucks are notorious for this.

If you have the NA 250 engine did you pull the Emergency fuel shutoff when you turned it off......you should not do that with a 900 series truck. If you did reset the shutoff on the engine and it should crank.

If neither of these works you should start checking to see if air is being sucked into the system.

Hope this helps.

 

[MyothersanM1]

Check everything rubber from the tank to the IP. More than likely you have dry rotted fuel lines and the system is sucking air somewhere. It does sound like a loss of prime due to drain back. I was taught by a well known Cummins guy around these parts to put my foot into the accelerator and crank, baby, crank. Soon as it fires let off.

 

[wsucougarx]

How did you shut the truck down? Did you pull any levers? Thinking he may have used the Emergency Shut off Valve when he shut her down.

 

[M35A2-AZ]

Here is my tread on my priming problem.
http://www.steelsoldiers.com/5-ton-up/79327-m923a1-losing-prime.html

 

[Reno]

I accidentally pulled out my emergency cutoff switch while driving it home from the base. I was looking for a vent switch.
Had to manually push the lever back at the pump on the 250. Relieved that was all it was.

 

[Over]

Fuel Pump problems:

I too just picked up a M923 nhc-250. It was driven here about 320 miles from CA to AZ. The former owner shut it off then when we hopped back in it, fired it up it died. Would not start. We checked the fuel tank, fuel filter and air filter. In the end we disconnected the fuel line to the fuel pump and turned it over. No suction at all while turning over. So to check the fuel line we pressurized the fuel tank with air and fuel came thru the line, ok that's good. Then reconnected to the fuel pump, pressurized again and tried to fire up. It started then ran. I am guessing on the way in the fuel pump crapped out and the IP was sucking the fuel. Funning thing is when they pulled in at the end of the road they shut it off for a couple minutes then hopped in fired it up and brought it in to the property. All I can figure is as it sat the fuel ran back and the IP didn't have enough suction to compensate for the bad fuel pump. Any thoughts of what to check on the fuel pump? Can the fiber star that connects the fuel pump break or wear out and now its not turning? Any help is appreciated as we are out there now looking it over.

 

[Csm Davis]

Fuel Pump problems:

I too just picked up a M923 nhc-250. It was driven here about 320 miles from CA to AZ. The former owner shut it off then when we hopped back in it, fired it up it died. Would not start. We checked the fuel tank, fuel filter and air filter. In the end we disconnected the fuel line to the fuel pump and turned it over. No suction at all while turning over. So to check the fuel line we pressurized the fuel tank with air and fuel came thru the line, ok that's good. Then reconnected to the fuel pump, pressurized again and tried to fire up. It started then ran. I am guessing on the way in the fuel pump crapped out and the IP was sucking the fuel. Funning thing is when they pulled in at the end of the road they shut it off for a couple minutes then hopped in fired it up and brought it in to the property. All I can figure is as it sat the fuel ran back and the IP didn't have enough suction to compensate for the bad fuel pump. Any thoughts of what to check on the fuel pump? Can the fiber star that connects the fuel pump break or wear out and now its not turning? Any help is appreciated as we are out there now looking it over.

What fiber star? There is no pump other than the IP.

 

[Over]

According to the tm there is a star washer between the air pump and fuel pump. Is the fuel pump the IP? Is there a fuel pump in the gas tank? As I mentioned there was very little suction when we disconnected the line to the pump that is attached to the air pump.

 

[redneck20]

Emergency fuel shut off valve ? If the valve is closed it cant let fuel out this resulting in no suction on the incoming side

 

[Over]

Reset that. Close then opened the lever. Electric fuel pump in tank?

 

[redneck20]

Emergency fuel shut off valve ? If the valve is closed it cant let fuel out this resulting in no suction on the incoming side

Pretty sure there is only a pickup tube in the tank, which Is why you have to prime the system. Have you tried repriming it? How about the filter?

 

[Csm Davis]

According to the tm there is a star washer between the air pump and fuel pump. Is the fuel pump the IP? Is there a fuel pump in the gas tank? As I mentioned there was very little suction when we disconnected the line to the pump that is attached to the air pump.

No pump in tank, no pump inline, and yes the pump bolted to the air compressor is your high pressure pump.

 

[Over]

So the only pump that draws fuel from the tank is the one bolted to the air motor on the engine. This is the high pressure pump ie the injector pump, correct?

 

[162tcat]

There is one pump in the system, the high pressure injection pump aka PT pump. No other pump. Sounds like you have an air leak somewhere between the PT pump and the tank. 30 year old fuel lines are probably due to be replaced.

 

[Over]

Thansk!
That's what I needed to know. Looks like the pump is bad. The seller is sending me one so I can replace it. All fuel lines, returns and vents are good.
Thanks again!

 

[162tcat]

You said that it started again after pressurizing the tank, the pump is probably ok just an air leak somewhere. How do you know the fuel lines are good? Just because you don't see a leak doesn't mean they are fine. Air leaks in while they are under vacuum, fuel doesn't always leak out.

 

[1 Patriot-of-many]

I have an A2 where the fuel lever hangs up on the cable not allowing it to move fully forward sometimes, it will either not start at all or run very rough. Just something to make sure of, the fuel lever is fully forward when cranking.

 

[goldneagle]

It's probably the rubber hoses going from the fuel filter to the IP. It took us 5 or 6 times pressurizing the fuel tank to see a little weep of fuel on the side of the fuel line. It had a rub through from being clamped in place. We replaced it with a take off and we were back on the road. On mine it is 3 feet of fuel hose and reuse the fittings (push on type).

 

[Over]

Took me awhile to log in. I guess I went from "WTFOver" to "Over". I go by that because years ago one of my old friends that was in Vietnam used to say "Wiskey Tango Foxtrot Over, that's radio talk". But Over will do. Anyhow we found the problem. My son and I found a leak in the old hardened primer pump hose plus the primer pump didn't work. We took it apart and got some of the carbon off the 2 ball bearing/spring valve assemblies. Then found some o-rings in the shop that fit the plunger. Then off to Home Depo where believe it or not they have the soft fuel line (marked as such) and ferules. Put it together and primes strong! Just got back from putting 50 miles on her thru a REALLY BAD mining road we live on. Road barely fits the truck and the drop in going thru some of the washes are pretty steep and rocky. Got 6 mpg at average speed of 27 mph (5mph to 60 mph).This whole purchased happened because I bought a generator and a M105 trailer. Suburban didn't like the trailer especially when it had to bring it all back from 7000 feet to 1000 feet and 150 miles

Thanks to everybody that chimed in! After listening to folks here and printing up the TM I now know there is only the High Pressure pump which feeds the computer fired injectors. And it's vital to check for leaks. Also thanks to Joel for driving down (320 miles) and delivering it. First time it didn't start was with us the new owners. I guess these trucks have to train their owners. Now my son is looking for one. Registered with GL to see what pops up.