Strange fuel pump problem

[rickf]

I have a problem that is bothering me. I suspect the lift pump is going bad but I want to be sure before Idrop the money on a new one. This has been a rough couple of weeks and money is tight.I had my gauge acting up and bouncing all over (Glowshift). They sent me a new sender and all was good. Took it for a test ride and verified that I had pressure. Not real good pressure but 12lbs. at idle and 6 at WOT with the Quad on. Was talking to a friend and the pressure just dropped to zero. Power off type of drop, not gradual. Truck stayed running. Shut it down and restarted it and pressure came up for a little bit and then off again. Put a mechanical gauge on along with the electrical and verified that it is shutting down. Tapped on pump to no avail. This was a NAPA pump bought three years ago. At that time I had bought the truck and found that it had no fuel pressure, Nobody knows for how long, previous owner told me it always ran well. So this si the second time. My VP is on borrowed time but right now I need to know what you guys think is the issue here?Rick

[War Eagle]

Not sure what your vehicle is but I understand a third gen truck with a CP3 probably won't mind at all but if it's a 2nd gen with a VP44 then you are playing with fire. The VP44 can't suck worth a darn so it needs a lift pump to deliver fuel and it needs more pressure to provide fuel for cooling the electronics. Without these it will commit suicide. Just a matter of time.:2cents:If it is a non VP44 and non CP3 then I can't offer much insight.

[JAG1]

When mine did this two times I needed a new lift pump. A big line kit will gain you about 2 psi pressure on a stock pump. The big line kit with a bigger draw straw will gain another 1 lb of pressure on the stock pump. The biggest advantage with the big line kit though, is the pressure won't drop even under wot. I know this by experience.Big line kit helps to afford another filter before the lift pump which helps it last longer if there are any dirty fuel purchases. The prefilter on mine dropped it from a steady 15 to a steady 14. Not too bad.

[rickf]

Not sure what your vehicle is but I understand a third gen truck with a CP3 probably won't mind at all but if it's a 2nd gen with a VP44 then you are playing with fire. The VP44 can't suck worth a darn so it needs a lift pump to deliver fuel and it needs more pressure to provide fuel for cooling the electronics. Without these it will commit suicide. Just a matter of time. If it is a non VP44 and non CP3 then I can't offer much insight.

[towhungerford]

Need to know if you have a in-tank pump or a engine mounted. If it is an engine mounted pump locate the two wire connector at the pump and backpin into it with a DMM and watch the voltage whenever you see the pressure drop. If the voltage drops when the pressure drops you"ll either have a wiring or pcm issue. If it is a in-tank pump the test is the same you"ll just need to backpin directly at the connector on the top of the tank module.Hope this helps.

[rickf]

Need to know if you have a in-tank pump or a engine mounted. If it is an engine mounted pump locate the two wire connector at the pump and backpin into it with a DMM and watch the voltage whenever you see the pressure drop. If the voltage drops when the pressure drops you"ll either have a wiring or pcm issue. If it is a in-tank pump the test is the same you"ll just need to backpin directly at the connector on the top of the tank module. Hope this helps.

That was going to be tomorrows step. I will hook my Vantage into it and see what is happening. I just wanted to get opinions on whether this was a common type of failure. My luck will be that I put a meter on it and it will not fail, Happens every time.:rolleyes:

[gassernomore]

Towhungerford brings up a good idea. I have personnally been battling problems with my Lp. Thought it was on its way out. I wired directly to a power source and all of my problems have gone away. If it were me, I would turn off my Quad until I had better FP. With pressure like you are saying, you are going to fry your VP sooner:2cents:.

[rickf]

I have the XZT so it is just a switch on the dash. I turned it off as soon as I saw how low the pressure was going. It did not drop at all with the Quad off. The symptoms remind me of a motor overload switch which I seriously doubt this pump has or a coil which gets hot and goes open circuit. If this is an induction type motor that could be it. It will do ot at idle or if I hold it at 1500 rpm, makes no difference. I hope I find it is just the motor. If it turns out to be the ECM I might just find another ignition controlled circuit and use that to trigger a relay for a new pump mounted on the frame rail.

[towhungerford]

I had a motorhome with an 8.3 that I worked on a while back with a liftpump issue that bit me in the butt. The lift pump was not comming on so I unpluged the connector and put my DMM on to verify voltage and I had good power and gnd, or so I thought. So I put a new liftpump on it, hooked it up and ... nothing:banghead: So I put my meter back across it but this time I left the pump plugged in, no voltage, unplug the pump and I would get voltage. So I had to also replace the ecm. I learned a valuable lesson that day, now I issolate and load test EVERYTHING. Just because you get voltage on the meter does not mean the circut can handle the load.I even bought a fancy circut load tester (which I've never used, prefer the headlight)

[rickf]

Need to know if you have a in-tank pump or a engine mounted. If it is an engine mounted pump locate the two wire connector at the pump and backpin into it with a DMM and watch the voltage whenever you see the pressure drop. If the voltage drops when the pressure drops you"ll either have a wiring or pcm issue. If it is a in-tank pump the test is the same you"ll just need to backpin directly at the connector on the top of the tank module.

Hope this helps.

[jumpjg]

Rick, After reading about all the problems people been having over the past year with the big dollar electric systems, I'd say try your luck on a mechanical system. There is an "Assasin" mechanical pump kit available that has a good reputation that might be a few bucks cheaper and most use it without an electric back-up. I think someone on this list wrote about his experiences with an Assasin pump. I went the cheap route 2 years ago with an Airtex; mounted it on the frame rail then added a Draw Straw & big line kit (3/8"). I had the Airtex replaced twice under warrantee. With the third pump I installed an in-line filter/strainer from Geno's Garage on the pump suction side ( http://www.genosgarage.com/FLEETGUARD-UNIVERSAL-IN-LINE-FUEL-FILTER-SCREEN/productinfo/FF5079/) & it has hung in there for 18 months now; still delivering 19 psi at idle, 17 at highway speed & never going below 15. My truck is pretty much stock & I drive with an egg under my foot. Good Luck Joe in St Louis

[rickf]

Well I called Geno's and talked to Andy and told him my plans about remote mounting the FASS DDRP. He asked if I already had the remote mount and I told him no I didn't. He said not to get it, the DDRP is substantially larger than the stock pump and the remote puts it in the way of road debris. He also told me it is a gear pump and not a rotary vane type and the engine vibration would not bother it at all. So I have the pump on order and we will see what happens. I will be mounting a filter ahead of the pump. Anyone else running this setup?Rick

[Ilikeoldfords]

I am running the DDRP with a big line kit (3/8). It is mounted on the frame well a could feet before the back tire. I am not sure how old the pump is because it was in the truck when I bought it. I just got a gauge on it finally last week and am kinda scared at what I found. At idle, I am holding 15 psi, cruising I am around 12-13 psi, at WOT it will drop as low as 8:ahhh: I found a filter inline before the pump so I am going to try changing that and the stock fuel filter and see what happens. The truck has everything in my sig. I dont think I would even mess with an electric pump. To many things can effect it. If it were me, I would go straight to a mechanical pump. Hope this helps !!

[Mopar1973Man]

Depending on the series of DDRP pump it could be a older 45 GPH or the newer 85 GPH pump.

[Yankneck696]

I have the DDRP on my truck. Block mounted & 18 PSI at idle, 15 PSI WOT. No prefilter (seems to be not suggested for this pump). All I have is an Edge EZ.Ed

[Ilikeoldfords]

Ok so I got curious and crawled under the truck again. I was trying to find a date of manufacture but I didn't see one. At a closer look, the tag actually says fass hpfp. But, I have no idea which one. I read that some of the hpfp's are adjustable? Any ideas?

[Ilikeoldfords]

Depending on the series of DDRP pump it could be a older 45 GPH or the newer 85 GPH pump.

Do you remember when they made the switch to the higher flow pumps?

[rickf]

Depending on the series of DDRP pump it could be a older 45 GPH or the newer 85 GPH pump.

Mine is the 85GPH with the filter in the box and directions to install it ahead of the pump. No filter, no warranty! You better believe it is going in. Rick

[Mopar1973Man]

Do you remember when they made the switch to the higher flow pumps?

Sorry I don't know.

No filter, no warranty!

Seriously that what kills the Raptor series pumps more times out of ten is something suck into the pump wedge the rotor and burn the motor up with the fuse blowing out. Then some add bigger fuses to help it burn out better. I would suggest just getting a remote filter mount and getting a nice spin on pre-filter and then protect the pump from damage too.

[rickf]

If I get good pressures from this pump I may add a filter and water separator down on the frame, get it all before it even gets to the pump. If that affects the pressure to much I will just move the setup to my Chevy CUCV military pick-up with the good old mechanical pump. That way I do not lose any money.