jaqxun

I'm not a mechanic, but I do love my truck. I'd really appreciate figuring out what to do with this problem...
About a week ago, I was driving fine but up a steep grade, when I suddenly lost fuel pressure, them power to to the truck. I assumed I'd run out of fuel, and then when I determined I had had fuel, that I was sucking air in the line somehow.
I took it to a mechanic, who replaced a leaky fuel line, and sent me home.
Then, the truck had very low power, and my fuel pressure gauge (an ISSPRO) was reading at 0. It seemed, from research on these forums, and also from checking out the truck, that the proble could very well be with the lift pump.
I took it back to the mechanic, and told them that I wanted the fuel pressure fixed and that it may be the lift pump.
They replaced the lift pump, the fuel filter (which was only a few months old anyway) and cleaned a screen that the fule goes through, and sent me on my way. Th truck dorve great for a couple of mile, and steadily lost power- no pick up, slow, would cut out if i tried to go any faster than 40 mph or so. I took it back to them, and they blew out the lines, and said they couldn't find a restriction. They also changed the return valve, which they said controls fuel pressure, but it didn't help.
So my truck is still not running the way I need it to. I am totally stumped (and no longer working with the mechanics I took the truck to..)

The truck has a new WVO system and has run flawlessly for six months or so. We use a FASS pump for the grease, and have an auxiliary tank for diesel- the stock tank we use for veg.All the problem have come up while I was running on diesel, though.

Can anyone point me in the right direction to getting my truck up and running again?

Thank you.

CamperAndy

Did your supply pressure come back when you installed the new lift pump?

Any smoke to to along with the loss of power?

You indicated the WVO system had worked fine but does it still work fine since the issue began?

kthiemann

A couple thoughts off the top of my head, when they cleaned the pre-filter at the fuel heater did they replace the o-ring that seals the thing? I've seen a couple of those where the o-ring got cut and while it didnt leak fuel it allowed it to suck air and lose fuel pressure, another thing down in that area is the electrical connection for the fuel heater, sometimes it will become distorted and while it may not leak fuel it will allow enough air in the system to cause fuel pressure issues, simple way to check that is to take some silicone and pack it in around the connection.

Another thought is that if I understand correctly you have 3 different fuel sources, perhaps the switching valve or valves are stuck somehow restricting your fuel supply.

Something else you can do is to put some clear hose in between your fuel filter and injection pump and watch it for air bubbles and fuel volume, that should help determine if the problem is at the fuel supply end or injection pump end.

macattack_ga

I am having similar problems.
When I start the truck I get about 20psi, but then it drops very quickly to 10-15psi.
running down the road w/ a VERY light foot I see about 10. Hills it drops to 5 or less!
New Lift pump, good filter and return valve...

What I SHOULD have done is pulled the fuel heater off. Like kthiemann said... they can leak.
See: http://www.cumminsforum.com/forum/94...m-writeup.html
I'll be pulling mine tonight or this weekend and will report back.

jaqxun

The supply pressure came back temporarily (for about five miles of driving or so) after installing the new lift pump.

I did notice when the truck got started up after the mechanics had been running the engine really hard ( 3-4000 rpm for several minutes at a stretch, with the fuel heating up to 140 or so) that there was a cloud of black smoke. I've never seen that before.

I haven't driven on WVO since the problems began, mostly because I don't have any filtered to use. I did switch to/from grease as an experiment, and lost power as I switched back to diesel. I don't think I had enough grease in the tank though- the grease felt somewhat sluggish... But the truck did stop running altogether at that point, on diesel, and had to bleed air out of the lines. This was right before the new lift pump was installed.

Busboy

You could have some bad fuel or something in your tank that's plugging the filter. That could be why your FP came back temporarily. Try changing the filter again and see if the pressure comes back right away. If it does clean out your tanks.

macattack_ga

Why are you using an eletric fuel pump? When working properly, the stock mech LP should work just fine.

Can you use the FASS to push fuel to the stock LP?

With the truck NOT running, you should be able to build up ~20psi of fuel pressure and it MIGHT help you find any air leaks you have... like around the pre-filter/fuel heater.

I doubt it is a fuel filter problem, but it's an easy fix if it is...

Do you have a diagram of your modified fuel system?

mine:

rebal

when the mechanic blew out the lines it just pushed it back in the system. I would pressure the tank to 5psi (no more or kaboom) and look for leaks, also how much fuel is in the tank? you could have a cracked draw straw?

RCW

If you are still running an OEM pickup tube in the diesel tank, replace it with a decent aftermarket kit. The OEM versions crack and then suck air. The problem usually happens as the main tank gets below the top third of the tank. The lower the fuel, the harder it sucks and the more air it gets.

RockysInMyBlood

One other thought - flexible fuel lines can look ok, and function ok at idle, but then collapse under load. I've had it happen to me with the peice of flexible line than runs to my lift pump - it had a very slight kink it. OK at idle, got sucked shut under load. Have you checked yours?