M818 Cummins lift pump?

[TheBuggyman]

All,

Has anyone ever put an electric lift pump on a five ton with a Cummins? Seems that I am drawing air in from somewhere and I cannot find it. I have even pressurized the entire fuel system including the tanks. All of the selector valve lines have been replaced that were in question.

If my air leak was in the injector pump itself (possible?) do you think that a lift pump installed just after the selector valve and before the filter would help keep everything primed?

One last thought- what if the fuel tanks were pressurized to 1/4 to 1/2 psi to keep air out of the entire system?

Thoughts???

 

[timntrucks]

the thing that jumps at me and is over looked many times is the square washer in top of your fuel filter. it must sit in the square hole for that o ring to seal. take a look see that little booger sucks just a little air and will drain all the fuel back into the tank. keep us posted on what you find, does it do it on both tanks?

 

[TheBuggyman]

I will double check that washer again but the engine had the issues when I got it and I changed the fuel filter first to eliminate that possibility.

And yes, it does this on both tanks.

 

[jwaller]

you have to find and fix the leak. putting a band air on my using a pump will only show signs of the problem and not fix it. now if you used pressure on the system and didnt find any leaks then the pump or injectors could be be. leaky injector or worn pump.

does it smoke a lot when running?
does it make good power?
whats the fuel mileage?
there are 100 places to cause a air leak in the system and I think I have looked at every single one of them before I finally fixed all mine.

 

[TheBuggyman]

Does not smoke alot when running, just a little.
Power is poor compared to my M813/super singles.
No idea of fuel economy.....

Wouldn't any air leaks have to be on the suction side of the injector pump?

One thing to mention is that if I let the truck idle for 10 minutes or so, turn it off and remove the fuel line that goes from the filter to the pump at the filter end there is not much fuel in that line. Shouldn't that line remain full even at idle? Is there a check valve somewhere to prevent fuel from returning to the tank when the engine is off?

 

[73m819]

no just the fuel shut off solenoid, i have been wanting to put a one way valve right at the line where it connects to the tank, at work thay use air one way valves for that fuel valve

 

[JWenig]

The FIRST thing I would do is to replace all eight fuel hoses. (6 on the selector valve, supply off the filter and return off engine) These hoses have reusable ends, so buy some 3/8" and 1/2" fuel hose of that type at your local hose shop. The old hoses will NOT show any signs of leakage but 9 times out of 10 that is where the air comes from. While you have the tool box off replacing the hoses on the selector valve go ahead and disassemble the valve and replace the two o-rings in there as well. I put a light coat of grease on the valve parts before putting it back together. These hoses are old and cracked. If you do this FIRST, you will be doing something that needs to be done regardless of where the air leak is, and more than likely fix the leak/problem in the process. Use a razor knife to remove the old hoses being careful not to cut into or scratch the brass barb fittings. I lube the fittings with oil before inserting them into the new hose. Do Not unthread the fittings out of the selector valve, just cut the hoses off the fittings, that way all the hoses are headed in the correct direction. Make sure you measure hose lengths first. Good Year brand hose is Insta-Grip 300 psi WP. ACE Hardware o-rings are a #9 and #25. Let us know how this turns out. Good luck, Jim

 

[WillWagner]

First you should troubleshoot it so you avoid throwing parts and unnecessary amounts of $ at it, The FSOV isn't the only thing in the pump that can cause this symptom. If you have a gut feeling it is a F/P, here's an easy check you can do. Get some 1/2 in. id clear line at the hardware store or from McMaster and a push on swivel. Fill a 5 gal. bucket with fuel and hook the line dirctly to the pump. Start it and run it a min. then shut it off. If the fuel drains back into the bucket, there is an issue in the pump...FSOV, front seals, worn main shaft, gear pump seals, a worn gear pump, etc. If the fuel stays in the line, the issue is before the pump.
McMaster p/n's...hose, 5195T77...fitting, 53485K26

 

[TheBuggyman]

JWenig, already replaced all of the hoses to the selector valve and the o-rings in the valve. The hoses were pretty rough. I have not replaced the hose from the filter to the IP yet. How would the return line off of the engine draw in air? Isn't this line pressurized while the truck is running? I suppose I could see it on the off cycle......

Will, the hose in the jug of fuel is a great idea and I was thinking along the same lines myself, just ran out of time. Does anyone know what a rebuild for that pump would cost?


FYI, thanks everyone for the input, I appreciate your help!!!!!!!!

 

[73m819]

it would be nice if someone on site rebuilt them, im SURE we could keep him busy

 

[WillWagner]

I don't do it anymore, but, I know a guy that still does them. The only issue is that there is 3 or 4 different pumps used on the 855's in the 5t trucks. The cost SHOULD be between $200. and be up to around $650., exchange. Just depends on what is wrong with your pump. Like if there is an issue of not holding a prime and it is just seals that are hard as a rock, east fix, minimal parts, low price. However, if, let's say, the weight carrier comes apart, that is an expensive part, so the price would be more, or there is too much throttle leakage, that means the housing needs to worked to accept an oversize throttle shaft. There are lots of things that can go wrong inside the pumps. If someone were to offer an exchange pump, what do YOU guys think a fair pricing would be? Just charge a flat, fixed price of say $350 to $450 with a core, no matter what is wrong with the core. That enables a person to just ship the core and pmt to the rebuilder and the rebuilder just ships another pump right away, almost no downtime. However, the rebuilder has no clue if the internals are FUBAR, so the repair price could easily exceed the price that is fixed. Or, ship the defective pump to the rebuilder, repair as needed, send a bill to you, you pay and the rebuilder ships it back. Sometimes this can lead to a week or more of down time and transit time. Look at the poor scetch below. How 'bout a few of you 5t guys snap a pic of this area on your pump, a good clear one so I can see all the numbers on the tag, along with a pic of the pump from the side, and post it here. I will see if I can come up with a core pump for the different types and do some ground work to get a real world price for a good pump.