Truck information:
2002 Dodge 2500 QCLB Cummins 5.9 with 6 speed Manual. 129K miles
Bone Stock except for fass fuel pump located on side of engine block.
Fuel level between 1/4 to 1/2 tank.

I purchased the truck back at the beginning of December, truck ran great, lots of power. Three weeks ago I went to get on the highway and truck began spitting and sputtering at 2500 RPM, no issues under 2000 rpm. Drove truck the rest of the way home taking it easy. Assumed that plugged fuel filter was to blame. Change filter, bled air as directed. Truck started up, ran great, took for test drive, and was worse than before. Limped back home. Using a fuel pressure testing gauge connected to the shraeder valve was reading 10 psi when bumping starter to energize LP, as soon as truck was started the fuel pressure would drop to 1 PSI. Decided the LP was shot and ordered a Raptor FRRP. After installing the Raptor I was unable to get it to prime. Tried many many times. Finally came to the conclusion that the polarity was backwards on the Raptor. Snipped harness connector wires, flipped and shazam, the Raptor primed and supplied fuel to the IP. After bleeding air for a really long time I was only able to get 1 PSI when bumping the starter. Just to be on the safe side, I tried a second gauge to verify that I didn't have a bad pressure gauge on my tester. Also, reinstalled my old Fass pump which primed immediately and supplied 10 PSI while not running just to verify there wasn't a kinked line. Contacted Air Dog, discussed pump with tech and they mailed me a replacement. While waiting, I did quite a bit of research on the fuel system. Ordered a Vulcan big line kit with pump relocation bracket. Mounted new pump just ahead of fuel tank, and ran the new 3/8" hose with quick connect to top of tank, 1/2" from pump outlet to stock fuel filter and from there to the IP. Also installed a ISSPRO mechanical gauge with isolator at same time. After bleeding the system I was only able to achieve 5 PSI when bumping the starter. Decided that due to the larger volume of fuel line I should adjust the FRRP a little higher to accomodate the needed volume to maintain correct fuel pressure. After adjusting, bumping the starter fuel pressure goes up to 15-18 PSI. Truck takes a long time to start, once started runs smoothly, but fuel pressure begins dropping as soon as truck is running. Fuel pressure will drop to below 5 PSI so I shut it off as soon as it hits 5. In addition, if I bump the starter the fuel pressure rises 15-18 as mentioned but as soon as the pump times out, it quickly drops back down to zero. In researching I thought that the overflow/return valve could be stuck open/partially open allowing the fuel to go right back to the tank. I pulled it out and tested with air pressure at 10 psi, seemed to stay closed, and at 16 seemed to open correctly. I've already spent quite a bit of money on the pump, relocation/big line kit and monitoring gauges. My next resort is to drop the tank/lift the bed and see if I have a cracked pick up tube in the tank (1/4 tank syndrome). I pride myself in not being a parts changer to find the problem but this truck is testing my patience. What am I missing????? If it happens to be the pick up tube in the tank sending unit, what is my best resolution?
I appreciate any direction/advise given, sorry for being so long winded, just wanted to get all of the facts out there right up front.

Also, before being asked, I did go thru all of the fittings/connections to verify that there was no leaks from tank top all the way to the IP.

 

for one, verify your new isspro's accuracy against your other test gauge. sometimes isolators can leak and cause inaccurate readings...(I thought my airdog had failed a while back because my gauge said 5psi...when in reality I had 20psi the whole time...my isolator started leaking on the gauge side making the gauge inaccurate. I run fuel directly to the gauge now and its dead on accurate now.)


So I would first rule out gauge inaccuracy. once you verify its accurate 100% of the time, next step is to check the tank/fuel basket. your screen under the pickup tube might be clogged up with dirt. You would be surprised to find out how much stuff makes it into your tank from dirty fuel nozzles at the fuel stations.

if no clogs, check the straw for cracks or if it came unclamped from the bottom of the basket. also check the quick connects for air leaks.

hopefully pureflow has fixed their pump seal problem. they have has an issue with diesel leaking past the pump seal and into the electric motor, causing pressure issues and pump failures.

 

Update

As suggested I checked the fuel pressure with my tester gauge at the IP. Same results as the ISSPRO mechanical gauge with isolator. Bumping starter builds 15-18 PSI, truck takes 15-20 seconds of cranking to get to start, then fuel pressure quickly declines.

Dropped the tank this evening and found that the truck must have had the pump in the tank originally. Found some rubber hose and clamps connecting the ribbed straw to a piece of steel tube with a filter sock on the end.Rubber hose didn't look the greatest but didn't see any obvious holes. Removed filter sock, heald up to the light and can see through easily. Only a few chunks of debris located in the basket and the tank itself is very clean. Steel tube had no cracks and I looked around at the ribbed straw a bit but didn't find any cracks that were visible. I'm going to look for a replacement unit at the dealership tomorrow. This is the last part to change out in this adventure besides the pressure valve on the IP.

 

the valve on the injection pump should have nothing to do with it.

ideally you want that valve open at all times...

I run 20psi at idle and 17 at full throttle.

you can bet that overflow valve is open the entire time because it opens at 13-14psi.

your pump should be able to hold pressure with the valve open...if it can't then there is something either wrong with the pump, or the fuel lines/draw straw.

 

** Update

Jigabop, you know your stuff!

So, I ordered a Vulcan draw straw 5, installed it last night. Once I had the tank back in and everything hooked up the truck fired right up and running great! I'm frustrated with the fact that I spent so much money but I guess I'm ahead of the game. For the cost of taking it into a shop/dealer I spent the money runnig the Vulcan big line kit, Raptor FRRP pump and ISSPRO gauge set.

If I can offer anyone some advise, the easiest way to solve my problem (1/4 tank syndrome / cracked draw straw) would be to cut in a clear piece of hose to see if your sucking air bubbles from the tank! This $60 fix ended up costing me almost $1200. Live and learn.

 

How and where do you hook the clear hose. I need help. Think I have a air problem also

 

Chris38piatt,

You could cut in a clear piece of hose temporarily along the frame ahead of the tank before the lift pump to visibly see if your pulling air while someone bumps the starter. Obviously take all precautions, you don't want to get run over. My truck was pulling some serious air from the tank. I listed this as something to try as a last ditch effort before dropping the tank or lifting the bed. I was frustrated enough that I didn't try it myself, I just dropped the tank and put in a Vulcan draw straw to eliminate the problem. Hope this helps, good luck.