Lull 944E42 that won't run after bad fuel

[roveer]

We've got a Lull 944E42 with a Cummins diesel engine that was running rough last week (sputtering and stalling) then wouldn't start. After looking at the fuel it was pretty dirty and so was the fuel filter. All changed, tank drained lines blown out. New fuel and filter and now it won't start. Had mechanic come to job site and he was able to get it to run on ether. He could see fuel up to and past filter and could see fuel after injector pump. Injector pump raises pressure to 1600psi? Injectors pop open at high pressure? I'm no mechanic, but I know the basics and can follow the conversation.

He's suggesting new injectors and if not that then new (or rebuilt) injector pump. He's skeptical that 4 injectors would all be bad at same time.

Just wondering if I could point more definitively at the injector pump at this point. Really trying to cut down time as I need this machine working at critical point in build. Based on everything I saw It looks like pump to me. They have ordered injectors but not pump and I think that is wrong direction, we should have pump ready to go.

Ideas / comments / suggestions...

Thanks,

Roveer

 

[Delmer]

I don't know what kind of injection pump that is, so I'm talking in general. If you had bad fuel and replaced the filters etc. then you did bleed the injector lines, right? and there was or wasn't fuel squirting out of them? I agree four bad injectors aren't likely.

The other thing to check is any other restrictions in the fuel system. You could tee a pressure/vacuum gauge into the line before the injection pump to be sure there's pressure there when you crank it.

Also, check the inlet fitting and return fitting on the injection pump for clogging. Fuel going in under some pressure, and fuel going out without air, and nothing squirting out of the injector lines is making the pump look bad.

 

[roveer]

I don't know what kind of injection pump that is, so I'm talking in general. If you had bad fuel and replaced the filters etc. then you did bleed the injector lines, right? and there was or wasn't fuel squirting out of them? I agree four bad injectors aren't likely.

The other thing to check is any other restrictions in the fuel system. You could tee a pressure/vacuum gauge into the line before the injection pump to be sure there's pressure there when you crank it.

Also, check the inlet fitting and return fitting on the injection pump for clogging. Fuel going in under some pressure, and fuel going out without air, and nothing squirting out of the injector lines is making the pump look bad.

I do know that when the mechanic opened several of the fuel lines they were all squirting fuel including in and around the lift pump (I'm now learning some of the terminology through my research.) He even opened the line up by the injector and there was fuel there. His problem was that he said that while it "appears" that the pump is working he couldn't tell if it was actually feeding the injectors at the high psi level required to get them to pop.

I've also read that if the pump doesn't get fuel that it can be damaged as the fuel also acts as a lubricant. I pulled down the owners manual and they have a bleed procedure which I will look at but with the amount of fuel comeing from ever connection the mechanic opened I'm not thinking there is air in the lines but you never know. I'll also see if we can look at those inlet/return fittings for debris. He didn't feel that enough debris would get past the filter to actually clog the pump but again, you never know. Time to get down and dirty and see if we can't get this problem licked.

I still think it's the pump, they are set to change the injectors tomorrow which I don't think will solve the problem. Unfortunately the pump is expensive >1k rebuilt and I don't have a good bead on where I could get one. My local equipment guys are telling me to call cummins directly.

Thanks for your help.

Roveer

 

[Delmer]

Yes, the "VP" pump can be damaged by lack of fuel if that's the pump you have. The one dodge with that pump that I've seen failed would start and run fine for a while then lose power under load. I don't know if that's typical or not.

The high pressure line at the injector is the one that needs to be bled last. The injection pump pumps very little fuel and doesn't bleed those lines very easily. You may have to open more than one and crank until there's no more air bubbles in the fuel squirting out. If there's no smoke or mist visible in the exhaust, then you're not getting any fuel out of the injectors. If there's fuel squirting with no bubbles from the injector line, but it doesn't make any smoke in the exhaust, then pulling an injector and hooking it up outside will tell you if it's not spraying.

 

[roveer]

Yes, the "VP" pump can be damaged by lack of fuel if that's the pump you have. The one dodge with that pump that I've seen failed would start and run fine for a while then lose power under load. I don't know if that's typical or not.

The high pressure line at the injector is the one that needs to be bled last. The injection pump pumps very little fuel and doesn't bleed those lines very easily. You may have to open more than one and crank until there's no more air bubbles in the fuel squirting out. If there's no smoke or mist visible in the exhaust, then you're not getting any fuel out of the injectors. If there's fuel squirting with no bubbles from the injector line, but it doesn't make any smoke in the exhaust, then pulling an injector and hooking it up outside will tell you if it's not spraying.

All makes sense. We weren't getting any smoke and would run on ether until depleted then engine would wind down. Was getting fuel at the line to the injector but I don't know if he was checking for bubbles or pressure. Tomorrow we will be pulling injector to see if we get mist. I believe it's the pump but somehow hoping we can clear/fix without having to send out for rebuild. That would take lots of time. We'll know more tomorrow once we pull an injector. From what I've read we are leaving that to the mechanic as it seems like you can screw things up if you don't know what you are doing with the injectors.

Roveer

 

[roveer]

Ok, mechanic came back to our jobsite on Thursday. Before putting in the injectors he pulled one, connected a new injector to the fuel line and before installing it cranked the machine to see if the lift pump would cause it to pop with a spray of fuel. It did not. Now the culprit seems to be this lift pump which is going to cost over 1,500 bucks for a rebuilt.

Any suggestions before biting the bullet and shelling out the bucks. Anything we can do or try with this pump that might get us running? Any partial tear down? blow out or other that we might try? Pump looks pretty complicated so I'm guessing this is not a simple tear down / repair. Especially based on the prices we are seeing on this thing. Told a new one is 3k.

Thanks.

Roveer

 

[Delmer]

A lift pump is a low pressure transfer pump. The pump that the lines to each injector are connected to is the injection pump.

Did he crank it with the line loose before tightening the nut on the new injector? If it squirted fuel with no bubbles but failed to spray out of the injector, then I'd go with the new/rebuilt injection pump.

 

[02Dmax]

Some of those pumps have a very specific bleeding procedure and if you don't do it, they will not run.

My honest opinion is you probably don't have anything actually wrong. There's a screen going into the lift pump on the suction side. That should be checked.

A picture of the injection pump would be helpful. I highly doubt it has a VP pump on it. A VE is more likely or even a Bosch M or A.

 

[roveer]

Some of those pumps have a very specific bleeding procedure and if you don't do it, they will not run.

My honest opinion is you probably don't have anything actually wrong. There's a screen going into the lift pump on the suction side. That should be checked.

A picture of the injection pump would be helpful. I highly doubt it has a VP pump on it. A VE is more likely or even a Bosch M or A.

As best as I can tell the Cummins engine is a QSB4.5 and the pump part number is: 4988593. Any help on how to purge/prime would be helpful.

Roveer

 

[roveer]

Mechanic came back today and swapped the pump and the machine is once again running. Was an expensive fix but we have to work... Thanks everyone for your help and tips.

Roveer