the.hogman

I need some help.

Back in March put in a new lift pump, pressure guage and checkvalve. Ran better than she ever had. Not a lot of miles on it now and then the other day I was heading home and she was wanting to die at lights and run rough until the rpms came up. Pressure guage is under the hood so I pulled off to look. At full throttle it was only about 10 psi. Lift pump I figured.

Picked up another new pump from O'Reilly (Airtex 73104) and popped it in.

Now my fuel pressure varies wildly from 5 psi up to 30 psi and the truck won't stay running. It will run for a bit and then the pressure just plummets until the truck dies. I sometimes can feather the throttle and keep it running but not for long before the pressure goes too low. I doublechecked everything I did for the install and it is all good with no leaks. I got under and see no issues or wetness from fuel anywhere.

What is the potential problem here? Would it be the new pump acting up? I took out the overflow valve and it looks good and clean with no seeps either.

Help!! I am ready to get rid of her right now, any takers?

patdaly

First thing, with it running, clamp down on the fuel return line and see if it steadies out and raises the pressure. If so, your overflow valve is acting up, looking good or not. If not, the only other possible thing would be wither the new lift pump or perhaps the strainer in the tank. ( partially plugged.....)

John_P

hogman:

DTR Member patdaly is giving you good advice on checking the fuel return line to see if the overflow valve is bad. I would also make sure your fuel filter is clean and if you still have the fuel heater etc. check all that too.

FWIW,....I have seen new lift pumps and overflow valves be bad right out of the box.

Good luck and keep us posted.

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John_P

the.hogman

New fuel filter and check the screen makes the truck run now.

I was lazy and should have done that in the first place. I didn't expect to have to with so few miles since the last change.

Pressure is a steady 10 psi at all rpms. Quick pinch of the return line sends it right up. As stated before this must be the checkvalve. A new one is on the way. Once again, I didn't expect a Bosch to last from 3/11/11 to 11/10/11. Pretty poor longevity. I won't be buying another one of those...

Thanks for the quick replies. I appreciate it!

John_P

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hogman:

From my end, you are very welcome Sir! Glad to hear your truck is doing better! I would like to see your pressure higher than 10psi though. When my truck was stock I would see 18-20 at idle and 22-24 underway. I am HIGHLY modified now (see signature) and I see 40 almost all the time.

I wanted to also add that some of the aftermarket parts we all buy for our Dodge CTD Trucks IMHO are INFERIOR to what was available a few years ago.
Heck, I recently bought a new shut-off solenoid for my 1996 and it was stamped; "Made In China." Pretty disgusting really that we buy new parts and they can't even last a year.

the.hogman

Sorry for the delay! I got the new overflow valve and the pressure runs between 25-30 psi. Now get this, it won't keep its prime. I am guessing a feed fuel line issue? What is the best way to prove this? I know it is best to replace with marine rubber and I probably will, but I want to analyze to be sure that is what the trouble is.

patdaly

Not holding prime can be sooooooo many places. I would start simple and make sure everything is snug, fuel filter head is tightened, etc. All it takes is a micro crack in any of the rubber.........

Some people say they can find the leaks by the pressurize the fuel tank trick, I never could. I will say this, your fuel lines from the engine to under the drivers side floorboard are in the failure range time. I have replaced both my 97's, Brownie a couple of years ago, and Greenie just last week.

I just used SAE J30R9 hose, it is fine for all fuels.

the.hogman

Update. I ran fuel line from O-Reilly for the supply. They just got it in this week and it is WAY better than the J30R9 according to the SAE specs and it is fresh on the market. About $4.50 a foot. I used 11 ft of 3/8 and it took me all the way from the tank, along the frame attaching to the old and onto the metal stub at the engine. I simply removed the quick couplers and then removed the retainers from the metal tube stubs. I was able to push the 3/8 over the quick coupler ridge (hard to do!) and then put a clamp on either side of it. Sure to seal!!

Guess what? The return line is now leaking exactly where I pinched it to check the overflow valve. I looked at my hose pliers and found that they have a burr that cut the line!! Once I replace that line, I should be good to go.....

Let's see, replaced filter, cleaned the screen, replaced the lift pump, replaced the overflow valve, replaced the supply line, will be replacing the return line. I am pretty sure this will be everything. Should be good to go for quite a while now!

infidel

Since you messed with the lift pump you might also want to take a look at the hose from the pump to heater.

the.hogman

Just came in from replacing that short return hose behind the fuel filter. Wasn't a bad job at all, about 20 minutes tops. Did see that the hose was an original dated back in late 1997 and was split, it wan't from my pliers...

Plunged the pump and watched the pressure climb up until the overflow valve kicked out the excess pressure. Fired it up and checked for leaks. Currently no fuel leaks but I will go out later tonight or in the morning and see if it lost its prime. I appreciate the comment about the hose to the heater. I checked it out thoroughly when I was doing the pump and made sure it sealed when I was done. I think it is ok...

I'll post tomorrow. Right now it runs like a top but was losing its prime. Hopefully I have it all of the way fixed now.

the.hogman

Well no change. Lost the prime in about 1/2 hour. It runs with 28-32 psi but after going about 8 miles it idles rough and will die while I watch the gauge still read at least 28. No fuel leaks at all. Any suggestions?

the.hogman

New discussion dealing with the prime problem here

https://www.dieseltruckresource.com/...d-t298095.html

infidel

Since it runs rough after a few miles it indicates the problem is on the supply side of the low pressure fuel system.
That eliminates half of the system anyway.

the.hogman

Excellent info. This is the kind of help I am needing. I'll start to concentrate on that side of the system. I feel I am good from the tank to the hard line at the engine. I am leaning towards a heater issue and the lines/gaskets around that area. I'll pull and doublecheck and replace as I can.

the.hogman

Got back in town to do some work on the truck. Here is the final tally of things performed to it:

New J30R14 3/8 fuel line from tank to all the way to the heater-no steel lines,
removed steel lines from heater and replaced with brass elbow fittings and barb,
took heater completely apart and cleaned all surfaces prior to reassembly,
inserted dielectric grease into the wiring connector on heater,
tightened heater retaining bolt (I think this was the culprit for air infiltration to the system!),
new screen and bowl gasket gently tightened,
new 1/2 elbow hose from heater to lift pump,
put studs in block to ease reattachement of the heater and pump,
new lift pump,
new overflow valve,
new overflow J30R14 5/16 return rubber line behind filter,
used high quality fuel injection hose clamps and tightened them appropriately!

Runs like a top. In all of this it seems the first problem was the bad lift pump, it then proved a bad overflow checkvalve, then the overflow line split where I pinched it to test overflow pressure, then I had air getting in because of the heater.

Note to self, when tightening the screen bowl on the bottom of the heater, TAKE IT EASY! I think that I had overtightened it previously so when I took the bowl off this time it loosened and partially backed out the special bolt that holds the heater in tight. When I took the heater apart on the bench, the inner bolt was barely finger tight...