Engine/Transmission (1998.5 - 2002) Have a fuel pressure problem question...

[DLausche]

Mine is acting weird like this as well. I get a fairly consistent 6 to 7psi in most conditions. But, if I floor it, the FP gauge "pops" up to 12 or 13. The way that is pops up suddenly is leading me towards thinking the bypass valve on the VP is somehow sticking. I've had mucho problems with fuel delivery lately and have had 4 lift pumps on within the last several months. I'm also wondering if powering the pump from the ECM is causing my problems. The heater grids cycling on and off dramatically affect my FP after startup. Heater grid comes on and FP goes to zero and I can hear the pump change tone like it is running slower. I think I'm going to hook up the pump through a relay to make sure it is getting a full 12+ volts to it at all times.



-Deon

 

[Texas Diesel]

Two (more likely) - the lift pump is cavitating and does not catch back up until a demand is put on fuel flow by way of flooring it.

Interesting thought, I wondered the same. I put a clear line between the FF and VP to look for bubbles but none seen.

 

[CCutshaw]

. The heater grids cycling on and off dramatically affect my FP after startup. Heater grid comes on and FP goes to zero and I can hear the pump change tone like it is running slower. I think I'm going to hook up the pump through a relay to make sure it is getting a full 12+ volts to it at all times.



-Deon

Are your batteries up to full charge? Can you check the voltage at the battery when your hearters come on. Just an idea.

Calvin

 

[Weidner]

Deon- Your truck looked fine when you smoked my out in the car pool lane last week! Maybe we need to have a garage night and get to the bottom of the lift pumps... I just put a new one in yesterday and hit 0 psi on the way to work today. I have a mechanical test gauge sitting on my desk for tonights test...



I think I am going to double check my lines for kinks and test the gauge...

 

[DLausche]

Deon- Your truck looked fine when you smoked my out in the car pool lane last week! Maybe we need to have a garage night and get to the bottom of the lift pumps... I just put a new one in yesterday and hit 0 psi on the way to work today. I have a mechanical test gauge sitting on my desk for tonights test...



I think I am going to double check my lines for kinks and test the gauge...

Well, it sat broken for almost two months. Partly because I am building a new shop attached to the house and that has consumed a lot of time and partially because I was WAY frustrated with it. You sound like you are heading down the exact same path of frustration that I was on. I finally got it to work. Yep, it runs fine but I'm not very happy with my FP right now.



I knew that was you behind me when I let out a bit of smoke. Sorry about that :-laf My foot slipped I think.



Glad to get together and combine thoughts on how to solve our fuel problems. PM me and we can figure out what might work.



-deon

 

[Kwoolley]

I just got my FP gauge hooked up this afternoon and it is doing the same thing. I'm leaving in a week to drive 1/2 way across country and back again. It doesn't sound like a new LP always cures this. Bypass valving? Relay? Dirty pickup in the tank? Gremlins?

 

[dnesbitt3]

LP for me

Fuel pressure did the same thing (new LP in July 13,000 miles ago) I checked the 2 plugs going to the LP. Took it to Cummins South (they have done all of my service work). Two days of trying to pinpoint why the LP was dropping off... .



They agreed to replace the LP under warranty and that has fixed all of my FP problems for now. 15 at idle 10 at WOT. I've been down the VP44 road and vowed to not go there again. I also wanted to not believe the guage, but with the poor performance of these crappy carter pumps I don't know why I didn't believe the guage.



Peace,

Don

 

[LMausolf]

My fuel pressure suddenly dropped to around 3-5 psi on the highway last weekend so I let up on the throttle (natural reaction), and when I slowly pressed the throttle again it dropped to 2-3 psi so I let off. It jumped to it's normal 13 psi for no apparent reason so I continued driving with no more problems that day. I put on another 100 miles on Monday with no problems however, when I turned the key to “run” it didn’t sound like it normally did. Wednesday, I was about 20 miles into an 80 mile trip and again lost pressure, I figured my best bet was to go to the nearest dodge dealer (5 miles) and get a new LP. The dealer told me that they only had the new in-tank conversion, the closest place that had an old lp was about 40 miles away. Off I was with intermittent fuel pressure, although it never fell to zero. I saw a Freightliner dealer about 1 mile before the Dodge dealer so I stopped there, gave the parts guy my engine s/n and he gave me a new lp. I did go to the Dodge dealer because the curiosity was killing me, $164 cheaper at the Freightliner dealer!

Anyway, since I replaced it my fuel pressure is higher than it has ever been (16) since I put the gauge in last summer and it again sounds normal when I turn the key on.

 

[RAJohnson]

Boy with all the money you boys are spending on OEM Fuel Pumps you could have each had a FASS :-laf :-laf :-laf

 

[Weidner]

mechanical test gauge showed 15 at idle and 11 at wot. I guess I have no problem... besides a dead electronic gauge sending unit...

 

[stg2500]

Where can I get a mechanical test gauge? my fuel pressure guage drops occationally as mentioned above. I want to rule out the gauge before I change the pump.

 

[Texas Diesel]

Autozone sells a test setup that fits right on the VP schrader, for around $30

 

[Bob Cochran]

Be careful with the Autozone test setup the one I seen was not rated for deisel and I think it can damage it to push deisel in it. Maybe others here can verify that for both of us.