Engine/Transmission (1998.5 - 2002) In-Tank Pump Issue

[MMoyle]

Hi All,



Back in 2006 the dealer installed the in-tank fuel pump under warranty and because of the low pressure that still existed after the installation, I installed the stock carter pump in the stock location to aid in pulling the fuel from the in-tank pump. With both pumps running I would get 23 psi at idle. I haven't notice any issues until recently.



When I start the truck, the fuel pressure runs up to 23 psi for about 5-10 seconds then drops down to 11 psi. I temporarily disconnected the carter pump to determine how much pressure I was getting from the in tank pump and I found it to be close to zero.



What would cause it to jump to my normal 23psi for a few seconds then drop to 11psi? Do I have a blockage on the in-tank pump? Can I some how try remove the blockage (if that is what it is) without dropping the tank?



Thanks in advance.

 

[JLandry]

Hi there,



Is is safe to assume you've changed the fuel filter (no blockage there)?



How are you powering both of these pumps? What are the electrical connections?



It almost sounds as though the in tank pump starts and runs for a few seconds then stops for some reason.



I doubt it's blockage in the tank, but to satisfy your curiosity you could blow compressed air back through the fuel line where it connects to the Carter pump. Be sure and remove the tank fuel cap first of course.



If you become convinced the in-tank pump has failed, then in might be best in the long run to drop the tank again, but this time install a Draw Straw V from Vulcan Diesel Performance. It uses the tank module but eliminates the pump completely. If you want a second lift pump, mount one on the frame rail right in front of the tank. Vulcan also sells lift pump relocation kits and hardware.



Good luck,



John L.

 

[jcwehking]

Can't help but share what you find out. I'm running nearly the same set up except running a 7lb pressure Carter pump and the in-tank pump for a total of 15 psi.



Seem to remember reading that on start up, voltage is cut by 1/2 to the pump and then full voltage on run. Not sure if it could be cutting the volts back down once running.

 

[grimesja]

I have had similiar situtations in my truck. The culprit was the screen in the tank module bgetting clogged. If you pick up some dirty fuel or get some algae, the screen will difinitely clog up and it is a pain to remove and clean. An easy wauy to check if the screen is clogging is to 1. remove the fuel cap 2. disconnect the fuel supply line to the stock carter pump 3. blow air thru the supply line. If you are having clogging issues, the fuel pressure wil be normal for a short time then drop back off (within minutes). A clogged screen acts the same way as a clogged fuel filter. You will have good pressure at idle but then it drops off with the least amount of acceleration. Just my two cents from my experience.

 

[MMoyle]

Thanks to all that replied. When I get some free time (working to much these days) I am going blow air thru the supply line to see if that helps. I will let you know how I make out.

 

[Jacobe]

I had a in-tank pump put on my 01 as a warrentty replacement. My mpg dropped really bad. iwent to the fass system and still had a low pressure reading . the original factory pump mount was left on at the in tank conversion. there was to much restriction throu that old pump mount block. I removed it and has a steady 20 psi.