I have a lift pump similar to the BD diesel units offered at summit racing, as to the actual brand I'm unsure at the moment. I have the edge juice w/ attitude monitor and chip and lately in oregon we've had a lot of snow and below freezing weather. My monitor has been showing that my fuel pressure is very low (rarely it'll hit zero at idle) but I'm not convinced its the lift pump.

Before the issue I'd run 20-25 psi at idle and 12-14 at wide open throttle, chip turned to the max. Now i'll run 6-10 going down the freeway but the second I step into it the pressure jumps to 17psi or so and will bounce from 9psi all the way up to 23psi and back. I'd think it was a failing lift pump ( replaced shortly before i purchased the truck 2 years ago) but the pressure loss is totally backwards from what i would assume it to be. Is it possible that the pressure sensor for the chip that I installed in the vp44 is going out? or that the chip itself has something screwy? I did buy the chip as a remanufactured unit. I have yet to spend the money to have a shop confirm the lift pump pressures and I'm totally basing this on the readout of the edge monitor.

 

From the pressures you are saying it appears you are running a pusher pump setup. If that's the case, it certainly sounds like the bypass is sticking and the pump needs to be replaced.

Dave

 

the pump is on the frame rail close to the tank and the block mounted lift pump is no longer there. I assumed this was a sort of aftermarket solution to the problematic pumps they had for awhile. I had no issues until the temperature up here dropped below freezing then it started acting up and its been doing it since.


What would the bypass do on the pump? Is it just a safety deal to avoid over pressuring the system and causing the "hard starts" I've read about?

 

You could be having fuel gelling problems, but it's hard to say from my warm living room.

The fuel pump has a method of controlling pressure through the use of a bypass system. Basically, it just limits the max pressure of the pump and prevents it from working too hard.

Usually, this bypass will stick open. When this happens, it's all but over. The pump will still run, but pressures will often dump to half of what they would be and a quick stomp on the throttle almost always restores pressure for a time. This is a signal to change the pump immediately.

And as always, check all your gauge readings with another known good gauge. It may say you some bucks if you have a bad sending unit or the like.

Dave

 

I was looking into the fass systems as a possible replacement, are these worth the money? I've been working on larger diesel trucks for close to six years and see the fuel/water separators on everything, but a fuel/air separator? seems somewhat odd that could / would be an issue let alone a power gain.

 

An aftermarket fuel system can be a great value. It all depends on what you are trying to do with the truck, how long you are going to keep it, ect.

That said, The FASS brand has a very loyal following. Do your research and find the system that fits the bill for you. Whether it's with filters or not, you get a lifetime warranty if you buy the system and some great customer product support.

Dave

 

down the road I'd like to see the truck get a set of twins, probably being a kx35/40 and hx55 i believe it is, ( friend has it but I haven't talked him out of it yet ), and bigger injectors. My clutch is supposed to hold up to 600 hp and I don't need anything more than that in all reality. I'd like to set it up to handle at most something in the 500 hp range when all was said and done. I've seen some Walbro alternatives without the filters as well, are there any good places to see dyno proven results, or at least a comparison somewhere?

oh and now the truck ran 20-25 psi cruising at 18 psi wide open throttle with the chip maxed out then shortly before i pulled into my driveway it dropped to 6 and started acting up. I have about a 25 mile each way drive and it was fine until then, today at least.

Thanks for your help so far, I really appreciate it.

 

I'm going through this right now, when i start out the pressure is up after about 20 minutes it starts to fail and the pump makes a louder buzzing noise and the pressure fluctuates sometimes when u step on it it goes up. But thats the same way my last one died. I have the big line and relocation kit and just put this pump in a year ago. No more carters for me.

 

have you found any of the pumps that would relocate to where the carter is? All the stock stuff was long gone when i bought my truck

 

I had ( sometimes still have ) the same symptoms as you did, and it turned out to be the FP sending unit. I have a low psi warning light kit that I trust more than the gauge. When all is normal, the light corresponds to the gauge within a pound or two at first turn of the key when the pump does its split second turn on before cranking the engine over. When it acts up going down the road, like bouncing from 14 all the way down to 0 at times and all numbers in between, I know it's the sender and not the pump because the light never comes on. And before I had the gauge, the light was what saved me when my carters were going out. Give a short floor board of the pedal and it clears up for who knows how long.

The low psi kit does use a sending unit as well, but it is strictly an on/off switch type set at 5psi, and built different and stronger than the other one. Where as the one for the gauge is a variable resistance type that floats from 30 to 230 ohms. So there is a lot more internal movement on this one that leads the way for more reasons for failure. Even with a snubber installed, as Diesel Dan suggested to do, I'm not sure if the HD sender I'm using is going to last.

On the area of the pressure relief valve, you also have one on your VP itself. It's the banjo bolt for the return line. Had to replace mine after they wouldn't include one with the new pump and my old one tested faulty. It was opening prematurely ( before 15psi ), plus was the original from mile 0.

 

Been running the Airtex replacement and getting 19-20 at idle and 14-16 highway speed depending on how my foot holds it.