Truck died and will not start. Checked fuel pressure, 10 psi.  Decided to change fuel pump to Airdog FRRP-100.  Now with Airdog FRRP-100 pressure is at 10 psi (which I believe is low for priming pressure) with Airdog pressure screw all the way increase via screw.  Cracked VP44 return line banjo bleed than tried to bleed at 1,3,5 but pressure was low very little flow. 

What would cause the pressure to be so low?  There seems to be air still in the lines and can't seem to get it out- think be cause the pressure is so low. 

I did change the VP44 out in December & fuel pump (Airtek) ~year ago

 

any suggestions?

 

 

 

How are you checking for trouble codes? Do you have code scanner.?

I use the OBDLink LX- the green one- scanner.

Ok this is probably very obvious, so don't be offended, but are you tightening down all the lines once it's starting? The bleed process should go, loosen fuel filter, bleed it, solid fuel flowing then tighten. Then the same process at the VP, and then the same process at the injector lines on the head. That's how you'll get all the air out. Once the truck starts with injector lines cracked it'll run, but it'll run like crap and you'll need to tighten down the lines to smooth her out. 

 

If if your already doing this then please pay no mind! Just wanted to make sure that was happening since it never was really mentioned. 

 

I I do agree though. If the trucks starting and dying then it sounds like it's either being starved for fuel, or it's leaking. The leak would be pretty obvious I'd imagine. Otherwise make sure no lines are kinked and you have everything plumbed and routed the right way. That could explain your low fuel pressure readings.

Yea I follow that process but don't have the fittings at the injectors cracked with the truck running. I bleed them by bumping the starter loosen & tighten.  Do you bleed the VP by loosening the return line?

Thanks Cumminz

Starting consistently now & stays running, but haven't had the guts for a test drive.   Changed the return valve on the vp44 (Had the original which I replaced with the replacement vp44 in December. So, I re-installed the original. ), bleed the system at inlet of vp44, return of vp44 & cracking with the 1,3,&4 injectors cracked than tightened (all injector had fuel coming out), tighten all fittings on system except on the top of the fuel tank. 

At one point the airdog FRRP-100 didn't start when bumped. Checked the voltage going to it (with key in 8.5V when bumped 12V- it's always at 8.6v with key in- not sure if that is proper.    It's starting consistently and stays running.  I'm going to let the company, Diesel Auto Power, LLC

Is there any way to update the Title of this thread from Wii to Will?

Good to hear it is running. What is it you are going to let DAP do?

The return valve from the VP44 was the faulty component that came with the VP44 I purchased in December.  I was just going to let them know it failed.

Glad to hear you got everything figured out and good to hear the symptoms of what a bad return valve will create! 

Well, the old return valve stuck also after ~20 miles and the truck died again.  I live very close to work ~2 miles.  I unstuck the return valve, purged the air & it started right up.   I did notice #1 & #4 in are leaking & have them as tight as I can get them.   Any suggestions on how to stop the leak at #1 & #4- already as tight as I can get them by hand?   Also, any thoughts on what maybe causing the return valve to stick- that's two return valves that have stuck. 

I'd be cautious about cranking down those injection lines too tight. I can't remember off the top of my head but I believe the torque specs aren't that high. If they're leaking I'd imagine that it might be your crossover tube O-rings are shot.

 

On the return valve side, have they both been new? Only thing I could think that would cause it too stick would be debris in the fuel or just bad fuel, but I doubt the truck would run if conditions were that bad so it is a bit weird. The return valve was installed with the two O-rings on both sides correct?

The return valves, one was new and the other original.  New valve was installed in December 2015 with rebuilt VP.  It's odd both would stick since it's just a spring & ball.   It was installed with O-ring on both sides. 

 

Do you have a link or describe how to change the crossover tube O-ring? Haven't done any thing with the injectors.  I'll be looking it up right after online.

I'm not 100% sure if the crossover tube o-ring would cause a leak out of the injector lines, so don't go ripping into it just yet, I'm hoping someone else will chime in to either confirm or deny that. I can't remember if there's anything on the inside portion of the threaded nut on the injector that connectors that connectors to the head.

 

In short though to replace the O-rings on the crossover tubes, you remove your injector lines completely. Keep them in the bundles that they're are in due to the blue fasteners. Then get a crossover tube removal tool, thread it on and gently remove the tube.

 

I haven't personally done it, I was getting ready to while chasing a fuel leak but fixed the problem before actually changing the o-rings. The hardest and most tedious part of the job seems to be removing the injector lines and not bending/kinking them AND keeping them in their respective groups for easy re-installation. I'm sure a quick google search would show a write up or two on how to do it.

 

TOOL HERE

 

You might be better off just getting a new NEW return valve.

Thanks Notlimah.  I'm ordering new valve and O-rings today. I don;t have a parts store that carries parts for the truck that is easily gotten.  The Cummings (Pacific Cummings) usually only has the pasts in Los Angeles.

Ok, I hope that fixes it. I would recommend doing them all if you're going to do one. I'd also recommend cleaning up the mating surfaces as well just to make sure there's no debris in there as well.

I had very similar issues with having leaks at the head. Even after all new delivery tubes, O rings, lines, still had issues. Finally, fixed it by cleaning up the mating surfaces of the delivery tube and injector lines with scotch brite, then cleaning them with brake cleaner and compressed air, then very carefully tightening each end a little at a time. You have to make sure you get the line perfectly seated, then hand tighten the nut, then wiggle the line and make sure its seated. I had to take the two lines I was having trouble with, out of the blue hold downs so I could move them around enough to get them seated. The torque on those nuts is 35 ft lbs btw. I would get yourself a crows foot line wrench in either 3/4 or 19mm, whichever fits better on your injector line nuts. Even after all that, I still had to snug them a little past the 35 ft lbs. They still seemed a little weepy after that, but I just let it go and they stopped. Also, I would make sure the engine is cold when you first do this.

Edited June 18, 20168 yr by leathermaneod

Glad leather chimed in with some first hand experience! 

 

I wonder if the 'leak' could be caused by excess fuel sitting in the nut from the bleeding process and then once tightend down causes a 'slow leak?' That could've been why yours was happening for a little and then stopped leather. Just a theory though. 

That's definitely a very good possibility notlimah. That wasn't my issue originally, because I made sure to clean everything off, and then it would make a puddle just sitting idling, but toward the end when it just seemed to be weeping, that could have been the cause. That would explain why it eventually dried up. The annoying thing with diesel is how it creeps because of how oily it is. Makes it really hard to track things down like this. Hot water helps wash all the residue away though 

 

one other thing to add, don't get frustrated and put a thread sealer on the nut that threads into the head. Back when I had a local shop do some work on my truck they tried to do that and told me it was perfectly fine and there was nothing else they could do   This is a very bad idea because, if I'm not mistaken, fuel can get into the oil if the line isn't sealing to the delivery tube. That why the O ring is on the tube, to prevent fuel from getting out and down into the crankcase. Even if fuel can't get into the oil, it's still bad to have a leak there because you won't be getting all the pressure from the injection pump and so your injectors won't operate as efficiently. The threads on that nut are not meant to seal anything, but rather only to put pressure on the line and delivery tube to press the mating surfaces together. 

Edited June 19, 20168 yr by leathermaneod

You can remove the cross over tubes with a thick bladed screwdriver. No need for the special tool unless you just want it. Unless you have removed the tubes and injectors I would suspect shot o rings on the tubes. They are easy to replace.