I got my pump back from rebuild and installed it. I also replaced the lift pump for good measure (didn't like the resistance on the primer. It was really soft.). I am now back to the same problem I've always had with bleeding the lines. The number one line is somewhat okay, but all the other 5 lines are basically fuel bubbles and nothing else. The fuel pressure is 9 to 10 psi with the engine cranking. I bled the fuel lines from the tank at the lift pump, then the filter, then the return line at the IP until there was no air in the fuel. I then (with all lines loose at the injectors) pumped the primer 60 strokes. I had raw fuel coming from number 4 at the injector. I've tried bleeding at 1, 3, 5 followed by the remaining lines with no good results. I then spent several hours bleeding each line individually as well as repeating multiple lines. Results are still a very low volume of frothy fuel. I don't see any apparent fuel leaks anywhere in the system. I know that the system from the tank to the lift pump is good and the volume is good. I was bleeding my line to connect my pressure gauge and on the third stroke I got soaked in diesel. I feel that something is allowing a massive amount of air to enter the system. Can anyone figure a spot where I could be drawing air (filter or heater)? Anyone got a different bleeding procedure? I've bled a lot of Cummins 6 cyl. engines in my Army years without a problem, but this one has me stumped. I appreciate any help and I guess I'll order a new filter while I'm waiting. The one on the truck is several years old but very little use. I may have messed up the heater gasket though.

 

Assuming fuel isn't coming from the fuel filter gasket when you prime pump the lift pump the only place it could be sucking air is the fuel line from the tank to the lift pump. Try using a can of fuel with a hose in it to the input of the lift pump to bypass the tank/line.

I usually prime until fuel comes from the return line. Then tighten it down and crank until fuel comes from all injector lines. then I tighten them down one at a time while the wife cranks the engine. After about 3 of them are tight the engine starts running on it's own then I tighten the rest of them down. There may be a bit of rough running until all of the air works its way out but it smooth's out after about 30 seconds.

Edwin

 

Thanks Edwin. I already tried that. That's how I eliminated the lines from the tank to the lift pump being bad. I remember that when I changed the fuel filter before that my preheater spun loose. I just tightened it back as best I could. A search for preheater on the forum turned up that that oring is notorious for leaking air into the system. I don't understand how it could draw that much air but not leak fuel but strange things happen. I've had that pump off several times and was never able to bleed it correctly (always difficult). I managed to get it started before by spraying fresh diesel into the turbo intake until that got it running and it bled itself. Last time I pulled the pump to change orings on the head, it worked but only long enough to get me broke down on the road and a towing charge. I'm gonna be really upset if I spent that much money on a 7 dollar oring.

 

I would delete that fuel heater. Those things are notorious for sucking air. Genos has the delete nipple, which is a Cummins part, so you may be able to source it locally.

 

Last spring I had trouble bleeding my pump and it turned out to be an injector problem. Still haven’t sent those injectors off to be checked. Swapped injectors out with another set I had and the truck fired right up.

 

Suction side air leaks are difficult to find. I would suggest putting 8-10 psi into the fuel tank then look for leaks. Mine turned out to be a crack in the lift pump...Mark

 

Thanks Mark. I tried that putting pressure in the tank first time I pulled the pump. That was a nightmare. After I sealed the tank vent I was able to build pressure to check leaks and found none. Someday I will build a fuel cap with an air connection. My fuel filter and square cut o-ring arrived last night so I will do that job today. The heater delete is on the list for later..

 

I’m going to star the obvious. Have you tested the fuel shut off sealanoind. Last time I changed the pump on my 93 I had hooked the wrong wire to it. It would still let fuel come to the injector line but not enough to run. I spent hours priming till I figured it out. It hit the first time when I fixed it

 

I bought a new fuel tank cap then I took the screw in part out of the old one and drilled a hole in it. Then I screwed in a quick connect fitting in the hole. Works like a champ but I have to plug the air vent on the tank to build pressure. My problem turned out to be crud in the tank plugging the screen over the pickup tube. I cleaned it off but I need to drop the tank to clean it out eventually. My problem is when the tank gets down to 1/2 full it doesn't want to start and I have to crank it a while before it picks up. Normally I just have to touch the key and it's running.

Edwin

 

Who rebuilt your injection pump? Sounds like what happened to me once...there is a metering sleeve/collar that needs to have the ball end of the governor lever assembly firmly in place. If this collar has slipped loose you will never be able to generate enough fuel pressure for a proper injection pulse. And unfortunately it usually means the pump has to come apart to get things back in alignment.

 

I pulled the fuel heater today. The stud backed out with the filter. The square cut ring was flatter than a pancake. I replaced it with a new oring and reinstalled with a new filter. The old filter was still good but since I had a new one "so be it". I bled the filter. and reinstalled everything I removed to work on the fuel heater. I then loosened all the inj. lines and gave the lp about 50 strokes. It had raw fuel at 3 and 4 injectors. I tightened 2, 4, and 6, and bled 1,3, and 5. I then reversed the procedure. After doing this for about 3 hours, I cursed for a few minutes and loosened all the lines and bled them in 15 sec intervals for about the next 20 minutes (had to pause after each bleeding for the battery to recover). It was getting dark and cold so I tightened the lines and was giving up. I bumped the starter and the beast coughed, ran rough for a few seconds and smoothed out. The beast seems to know when I have reached the end of my patience (the next step would be getting the torch out to cut it into manageable pieces for the scrap heap). Thrash, the pump was rebuilt by United Diesel in Montana. Job looks good and they have been in business for decades. I'll review them in my other post later when I've driven the beast for awhile.

 

Sorry I'm laughing, but I've been there and made the same mistakes. There are many places for air to hide. If you don't bleed the system in a specific order and way, all you do is move the air around and never get it out. Loosen EVERY fitting including the filter between the lift pump and injectors. Prime then tighten each line and component starting with the lift pump and slowly work your way to the top. Air compresses, so unless is has a place to go, like out, it stays right where it is.