RockysInMyBlood

****. Climbing Lizard Head Pass in southern Colorado today, towing my 5th wheel, about 18k lbs. combined. Fuel pressure as reported by my Edge Attitude dropped to 0. Question is what's wrong and how to fix it?

Details: Dropping off Mesa Verde last week I noticed low (0-2) fuel pressure. Strange, I wasn't even on the pedal, exhaust brake was holding it back, revs were about 2000. I figured a plugged fuel filter, so I swapped it out in Cortez. I'd run about 10000 miles on the existing filter. Funny thing, though, it'd didn't look all crudded up, like the last time I had bad diesel ...
Running empty around town fuel pressure was 12 psi at idle and 4-6 psi when I got on it.

Today, with a load coming up Lizard Head, which about a 4000 foot climb from Cortez, I got 0 PSI. When I pulled over, shut it down, wait a few minutes and then hit the starter, the pump cycled, pressurized the filter to 12 PSI, just like normal. I fired it up, when up the road and completed the climb with about 5 PSI.

Then, when I dropped down and climbed the Dallas Divide, I got the same darn thing, 0 PSI at the top. I pulled off, shut down, waited a few, fired it up and fuel PSI has looked good all the way into Ridgway CO, which is where I'm at now.

So, truck runs empty OK, but with a load on the big hill the IP is starving for fuel. What do y'all think? Lift pump? (It's got about 20k miles on it) Something else? I gotta figure this one out since I've got some big hills to climb.

Thanks for any help y'all can be!

rich

i would say lift pump is going or maybe a pick up tube problem since it seems to be doing it climbing. some guys have said they have gotten pin holes in them see if it does it at certain fuel levels

RockysInMyBlood

I don't know anything about the pick up tube. Is that what the fuel pump sucks the fuel from in the tank? How the heck do you test for that? Alternatively, is there a simple test for the lift pump? If the lift pump is going, is it typical to show good pressure except when towing a heavy load on a steep climb?

rich

no most lp dont care the only way i can think of testing the tube is till fill the truck up and see what level it starts having a fit on or drop the tank and look at it

RockysInMyBlood

Turns out to be the ~!@#$%^&*! lift pump.
Test drove it this morning. Got it to drop to 0 at WOT climbing a steep hill not pulling the 5th wheel. So I replaced the lift pump. Now, climbing the same hill empty at WOT I don't drop below 5 psi. I figure the wacky pump performance is explainable if the pump was just now starting to go bad.
I'm glad the new lift pump did the trick, since I sure couldn't drop the tank in the state park where we're staying. Thanks for your suggestions, Rich.

badme

The only way I know to test the tube is to take it out of the truck, put it in a pail of fuel, put a vaccume pump on it, then lift it out of the fuel. If it holds vaccume all the way to the filter it is good. If it does not the leak is at the point where the vaccume drops. Mine had a pin hole in it and that is how I found it. Mine also would suck air and quit running under a heavy load. I would lean to the lift pump if I were you.