Cliff notes version first for those who hate long post. Over several days I have had intermittent fuel pressure loss, just to return to normal pressure the following morning. Filter changed and new lift pump installed. Overflow verified not stuck. Problem still there. Whats up?

Detailed version below.
On the way home from work last Thursday the fuel pressure began to fall as I went up a hill. Eventually fell off to zero. Arrived at home and drained a little fuel with the water drain at the filter , then cycled the lift pump. Repeat 2 or 3 times and got fuel pressure back. I then took it for a 25 mile round trip (all flat land)and just as I got near the house lost fuel pressure again. It slowly fell over a couple of miles until dropping to zero again. Early Friday morning I made the same trip and fuel pressure stayed above 10 psi. Drove a differnt vehihcle to work.

Saturday, I fired it up and it had good fuel pressure. Drove it for a 14 mile round trip and fuel pressure was low, but stayed above 10 PSI. It did set several hours before I retuned home.

Sunday afternoon came and I changed the fuel filter. It was very slow to build pressure through cycling the pump after the filter change.

So I swapped the lift pump out with a used one that I had replaced just before having the VP44 rebuilt and installing the fuel pressure gauge back in early 2005. It built pressure sooner so I was hopeful.

Monday came and I made the 35 mile trek to work with the pressure only maintaining around 12 psi. On the way home, coming up the same hill I lost pressure again. Stopped at Advance Auto and got a new pump. Installed it Monday night. I did a visual inspection of the lines from the tank to see if there were any worn spots before putting the pump in and saw no indications of a problem.

Tuesday came and I made it up the same hill without losing pressure down to zero but it did drop to about 10 PSI. Further down the road on a much smaller hill and in a 55 mph zone versus 75 mph of the larger hill I lost pressure again.

Cycle the pump once this morning and got only a few psi. Repeat and get 16 PSI. Went through an hour of cycling the pump, firing it up, repeat and it always hit 16 psi. Drove it to work again with about 13 psi maintained, dropping to 10 psi on the hills.

Driving home I mashed the hammer down pretty far in fourth gear on flat ground and the pressure dropped to about 7 psi and would not recover. Over the next five miles or so it went to zero again.

Stopped beside the road and did the filter drain and pump cycling routine a few times and got it back up to 6 PSI. Over the next twenty miles it slowly faded to zero again. When I turned on the 1/2 mile long dirt road to my house I hammered down on it once I got in third gear and into fourth. It pulled strong with no sputtering and the psi went from zero to about 3 psi.

Shut it off at the house and cycled the pump several times. Nothing. I am unsure if the pump was running with those cycles. This is a bump the starter for the 25 second run time cycle I am speaking of. Go out about 2 hours later to put it in the barn for further diagnostics and get 16 psi when I fire it up. Pulled the overflow valve out and checked it with air pressure to see if it was opening and closing. Yep. I don't have a pressure regulator on the compressor right now so I can't say just what pressure it was opening at but I could see the piston moving. I know I was getting air through even after I let the compressor bleed down to under 10 psi.

I am going to try to get a new overflow valve tomorrow. This is driving me crazy! Any ideas?

How much fuel is in the tank? You need to drop it and inspect the filter system in the bottom .
It won't get much better with the stock carter lift pump!! They are junk before being boxed to ship to dodge.

Fox,
The fuel level is above 1/2 tank and dropping as I drive it. Don't get me wrong, I appreciate your attempt to help, but the stock lift pump bashing does nothing toward that end. And yes, dropping the tank is next on the list if the overflow valve replacement doesn't do the trick. Just not looking forward to that given I will be working by myself. I may have to rig a hoist and lift the bed instead. I remain unconvinced that the sock plugging is causing such an intermittent problem though. I may soon be proven wrong though.

As for the carter pump, I realize I am not going to get 20+ psi of fuel pressure with it,(don't need it)and that most feel they are junk. However, with a completely stock engine and tunning, that stock pump has maintained a minimum of 10 psi under the heaviest loads, or better over the last eight years and 80 thousand miles. Even while pulling my 11,000 lb 36 foot travel trailer up steep grades here in Colorado. Normal running empty pressure is 14 to 16 psi.

The issue is this intermittent pressure loss. What ever is driving that would have the same effect no matter what kind of pump I was running.

And BTW I never bought a pump from a Dodge dealer.

Wow sorry about your trouble, what a b!tch.
I wonder about the inside of your fuel tank? There is a growth that can grow in your diesel tank and plug the strainer inside the tank. It's a black colored slime that is actually growing in the fuel.

But first I think I would find a way to pressure test the line going from front to back or replace it. Sounds like a pin hole from rust possibly causing the problem? Have you blown it out?

Sounds like you do have a inlet restriction to your lift pump. Could be a plugged strainer like suggested or posibly a tank venting issue. Check your tank vent/rollover valve and make sure its not clogged with dirt. Easy way to check for a venting problem is to drive it with the fuel cap loose and see what happens.

Where is your lift pump mounted, on the side of the engine still ? If it is and you plan to keep it there your best lift pump option is the FASS DDRP , it is designed to be mounted on the engine even though it SHOULD be back as close to the pickup point as possible.

I've only run the Carters on my RAM for 230k miles , they aren't the junk some think they are if you MOVE them back to where they should be , The morons at Chrysler is the reason they are on the engine , not Cummins or Carter.

I battled the same problem with my '95.

I would check the fuel pick-up in the tank. Mine had a hole worn in the tube, and was sucking air.

Had the same problem with '98 12 valve. The fuel tower in the tank has a filter in the bottom and it was plugged. Removed the tank, took the fuel tower out and cleaned the filter and tank, fixed the problem. It was plugged with a black slimy residue almost like thick paint. Got a bad batch of fuel somewhere.

Thanks all for your input. Here is the update. I had to order the overflow valve and picked it up Friday. I got it put on this morning after which I took it for a drive and hammered on it. Through multiple full throttle runs and full throttle roll on's in 4th and 5th gear the worst I saw has just under 10 psi. On the other hand the best it would do is about 13 psi when running down the highway. Idling is about 15 psi. Although it didn't drop to 0 like it has been, it is obviously still not right.

My bet at this point is you guys who are pointing to a problem at the pick up in the tank are right.

John,
Yes it is still mounted on the side of the engine. The pickup has just under 230K on it now. Since I just replaced the stock pump and highly unlikely to shell out the coin for another, I am curious as to what you did for moving yours back closer to the tank. Do you have any pictures or can you point me in the direction of resources to do this?

The picture below was taken 3 or 4 years ago at Yellowstone and shows what the pickup now sees most of its miles pulling.

71yelladustr

When I went to the dealer Friday at noon to pick up the overflow valve, the pressure had dropped to about 6 psi just during city driving. I stopped and left it idling and the pressure stayed at 6 psi. I got out and took the fuel cap off and let it continue to idle for about 30 seconds with the cap off. No change.

put a vacumn gauge inline and watch it what it does...Ill bet like people have said your pickup is plugged up in the tank, when you drive it collects more and more and under a heavy load it clogs up tight...ie no pressure...Ive got a customer with a diesel van that this happens to often...ive cleaned out the strainer more times than I care to remember. Its a ford van but symptoms are the same...thats where id start!

Before taking the tank or pickup out, get some Algicide killer for diesel fuel from most any decent auto parts stores. They used to not carry the algiced in small bottles but they do now. Dump it in your fuel tank and drive it a little while to treat the whole fuel system.
Not winter anti gel, not that at all.
They make a product to kill this growth and use it really strong at first treatment to KILL and then you use it in lower amounts for maintance.

That way if it's a problem, you already did the first part, KILL it! Then you have to clean out all that dead bacteria or whatever it is.

Otherwise it's very contagious and will spread from the top inside of your fuel tank if it's not all treated at once, it'll regrow without treatment.

My