Cold Weather Starting NHC-250

[6x6junkie]

get a block heater on and e site cheap plug it in 20 min later truck will fire right up . do not use either bad news

 

[Csm Davis]

get a block heater on and e site cheap plug it in 20 min later truck will fire right up . do not use either bad news

6x6 he has no fuel flow, how is a block heater going to fix that?

 

[doghead]

It just will, I read it on the internet...

 

[rangereter]

Vgunner, Just to give yourself a sanity check, you could break the fuel line between the PT pump and your fuel tanks where it transitions from rubber to copper. I think you can do this on the drivers side frame rail above the starter. Use a clean 5 gallon fuel can with known good fuel to pull from. If it primes and runs fine from the gerry can, then it is just a matter of back-tracking down stream. Good luck.
Regards, Bob

 

[dreameweaver]

Like a lot of others have said, put in a block heater keep it plugged in. If having fuel problems put in some anti-gel and then make sure you put stuff in to keep the fuel good. I live in North Dakota and run an M816 and have no problems

 

[Triple C]

Csm davis has you on the right track, you have a fuel delivery issue not a cold start issue. Sounds like you need to replace your fuel filter, drain your tank (you posted the fuel looked dirty) and check all your connections. Personally I wouldn't put fuel conditioner in the fuel just to get it to flow if there are contaminants in it. Better to drain the tank and clean it first. THEN make sure you have winter blend fuel in with conditioners and a good filter. Good luck and keep us posted, a lot of us are going to be having starting problems in the cold.

 

[wheelspinner]

do not use either bad news

NOTHING wrong with using ether correctly on a 939 series trucks

I shoot a little shot of ether into the snorkel on my M923. Starts right down to 10 degrees F.
Pete

Absent a full canister this is the ONLY way it should be added if working alone!

Yes, I shoot it in that big plug hole up on top of the elbow, just up from the factory cold start injection point. I can't do it while cranking, was by myself climbing up & down doing the 5-ton boogie.

By doing this, whatever cylinder has an open intake valve will overload and bad juju will happen. That's why the instruction tag states the engine MUST be cranking when hitting the ether.

Ok, I read the cold start procedure & yes, I did everything you can do with no ether bottle.

I did not use much ether at all on either truck & shot it in the big 3/4" pipe plug just above the ether injection port on the intake manifold.

Again if the truck is not cranking BAD things can happen by doing this. By adding it at the mushroom, you give the engine a chance to pull it in evenly.

 

[VULCANGUNNER]

Thanks wheelspinner, I will shoot it down the stack then. How many engine rotations does it take to get to the engine?

Yes, it is a fuel delivery problem.

The pump is pulling hard, the fuel filter is clean, the line between the two flows 100%.

It has to be a clog up in or around the fuel tank selector switch.

(Air pressure for all work is 75 psi)

I took the fuel filter feed line off & blew air back through the selector valve into one tank & then the other. They blew bubbles.

I pressurized the selected fuel tank & the fuel filter feed line flowed good for a moment & then just drizzled.

Switched tanks on the selector & pressurized the other tank. It flowed about 1.5 quarts & then slowed to a drizzle at the fuel filter feed line.

* My plan is to pull the fuel selector valve out, disassemble/inspect/clean/rebuild on the bench.
* Blow air back through all 6 lines at the valve, establish flow from tanks to selector valve.
* Establish flow from the fuel selector to the fuel filter feed.

One of the times I was pressurizing a tank a small piece of what looked like charcoal (soaked in diesel) fell out of the fuel line. It was too hard to disintegrate from fuel flow or air blasts but crunched between my fingers under light pressure. A piece that size up around the selector valve could clog up the whole shebang.

 

[VPed]

If you remove the selector valve and blow back to the tanks, whatever might be causing the problem will probably come back. If the problem debris was a single piece, then you would think you would only have problems while on that tank. It sounds like your problem is similar despite which tank is selected.


We once had a pressure problem on a new, large, low pressure natural gas line at work. First course of action was to blow back through the line to unclog. That appeared to work as there was no restriction. System was but back on line but the problem soon returned. Engineers figured a regulator was needed so a $20K regulator was installed. Problem soon returned. Eventually, the whole thing was disassembled, flushed, and inspected. Found a potato chip bag a worker had thrown into the pipe during construction. Expensive to say the least.

 

[VULCANGUNNER]

You are right, I will make the majority of my effort pressurizing the fuel tank & pushing the obstruction forward away from the tank.

I drove the truck 650 miles up from Texas & it never gave me a hassle. Filled & drained both tanks twice during the trip. I guess I just lucked out it didn't stop flowing on the trip!

I'd rather have it break down in my back yard than out on the highway.....

 

[Csm Davis]

But don't over pressure the tank 5psi max.

 

[VULCANGUNNER]

I removed the fuel selector valve, lines a little bit dirty but nothing major.

- Fuel selector to fuel filter line = Clear blowing both directions.

- LH tank feed hose to selector valve = Pressurize tank, no fuel flow to valve, vent & return line vent air slowly. (Blow back from valve toward tank = bubbles in tank)

- RH tank feed hose to selector valve = Pressurize tank, no fuel flow to valve, vent & return line vent air slowly. (Blow back from valve toward tank = bubbles in tank)

- Vent lines flowing to both tanks & stack exhaust line

I pressurize either fuel tank & the fuel should be blasting out of the corresponding feed line at the selector valve, correct??
Neither of my fuel tanks will flow to the valve when pressurized.

My next step is to pull the deck plates above each fuel tank & remove & verify flow to all vents & returns. Remove feed tubes from each fuel tank & verify flow.

Should probably drain & flush both fuel tanks too.