Ph4tty

So maybe its the vibration that the LP experiences while mounted on the block that leads to failure. Thats enough reason for me

Take it easy Mr SuperD. If you put this thread on a conveyer belt,...I got your point in post #3

Now I remember why I didn't follow the walbro threads

Superduty

"So maybe its the vibration that the LP experiences while mounted on the block that leads to failure. Thats enough reason for me"

I'm not disagreeing that people should relocate their pumps. For the reason of vibration, heat and ease of access, I think frame rail mounting versus engine or in tank is the best.

I just didn't want people thinking that they will pick up 2 PSI by moving the pump, all other things being equal.

Having said that, I am done fighting this fight and all the others concerning fuel pumps. I am happy to hear that at least someone understood the point I made here.

I'm out.

csutton7

SD--ok I'll agree that the pressure will not increase, that wasn't my point---and it looks like I was on one point and you another, but your other point about mounting locations doesn't hold water or fuel in this instance about pump performance over the long haul--

and you're telling me that just because it's a race pump then non-race pumps don't have to follow suit in mounting locations--why not---don't we use racing setups in our vehicles today to make the cars better, so why not in the fuel pump mounting world?? (please don't read diagrams so literal that you'd have your pump dragging on the ground--that's funny)

I'll agree that once it's primed though it should put out the same pressure no matter where it's located--unless there's some restriction or line change size--
but the longer it takes a pump to prime itself is shortening the life of that pump--pumps like to be cooled by the fuel(or at least it helps) and even short durations of no cooling will add up over time and kill the pump prematurely--

nuff said unless I have to say more.........chris

Superduty

"but the longer it takes a pump to prime itself is shortening the life of that pump"

That is what checkvalves are for. They will keep the pump primed at startup. And you can get them with low restriction too. I suspect the trucks with engine mounted pumps have a checkvalve somewhere in the suction side otherwise the engine pump would lose prime all the time.

"don't we use racing setups in our vehicles today to make the cars better, so why not in the fuel pump mounting world??"

I think the thing with the aeromotive pump instructions was for drag racing. They don't want the pump to starve when the fuel all goes to the back of the tank. And if it does temporarily starve, if the pump is mounted below the tank, it will sell prime. We don't really have those conditions with our trucks and thus it is OK for us to mount the pump above the tank if we need to. It is interesting that aeromotive doesn't say those installation tips are for drag racing. What if I was road racing a vehicle and all the fuel went to the front of the tank ? It wouldn't help to have the pump mounted at the back of the tank.

Anyway... I am happy that we agree the placement doesn't make a difference as far as the pump output is concerned.

I don't care where people mount their pumps and I don't care what pump they run. I just want them to understand what they are doing when they do things with fuel pumps.

Added as an edit. I've been told that the Dodge fuel pickup has a built in checkvalve. I've also been told that the Walbro and Bosch pumps both have built in checkvalves.

csutton7

I don't think there's a check valve or any way I don't remember seeing one on my truck when I dismantled the fuel system--so this may be another reason for their short lives--still I say a 100% gravity fed pump is the best location for a pump and there's no way you will convince me otherwise--chris

Clunk

I believe the few feet of larger than stock rubber hose on a LP relocation helps dampen the pulses from the VP to the LP check valve.

MVIEIRA

I haven't seen anybody comment on the design of the pumps. The little Carter electric pump on our trucks is a vane pump and vane pumps don't work well at drawing a fluid. A twin gear pump is the best, but every pump has a limit of how far they will draw a fluid with the effects of atmosphere and gravity. After 14 years as a heavy equip. mechanic for the Caterpillar dealer I work for and taking many hydraulic training courses I feel that where a pump is mounted in the system is important. I see most CAT applications where vane hyd. pumps are used, the pumps are mounted at or below tank level and not very far from the tanks. As you look at where our factory pumps are installed on the engine, they are mounted higher than the tank and at least 6 feet from the tank on my longbed truck. It's just my opinion but I don't feel that it is a good design. Most CAT diesel engines use a mechanical twin gear fuel pump, & some use a mech. single piston/plunger style with check valves, which I feel are better supply pump designs but they are on larger more expensive engines. You can say it doesn't matter where the pump is mounted and whether they suck or push but it won't change my mind. I relocated my OEM fuel pump just in front of the tank and my idle,cruise, & WOT pressures are alot better than when it was mounted on the engine. Just my $.02 worth.
Regards, Mike.

J BODY

I think you have a very valid point MVIEiRA. Same reason the 12 valve diaphragm pumps had very few issues. They were better suited to pull the fuel.

Bart Timothy

I've never believed it was cavitation of the vane pump, while in the stock mounting location, which caused pump failures, although it has the potential to contribute. There is something else going on with engine vibration, or fuel flow harmonics/pulsations to the VP44, which destroys or weakens the internal bypass valve of the pump. Failure of the internal bypass, which is a spring loaded ball and seat, is why fuel pressures gradually drop over time. The spring ends being weakened for some reason. The vast majority of failuers are either a failed bypass and sometimes the pump to motor coupling. The vanes and chamber are almost always in good condition if the fuel has been clean.

P.J

Relocating the stock LP helps?

Going just off of the thread title:

YES! It helps me to be able to swap it out in a fraction of the time and from under the truck, not leaning over and scraping up my forearms trying to fish out it out of the factory location.

A creeper, and some fuel down my sleeves and I'm off and running.

Jim Lane

At 100 MPH it is easier to BLOW the fuel to the front of the truck than it is to SUCK it to the front.
A small vacuum leak will aerate the fuel and you loose power and are very difficult to find where as a small pressure leak will just drip and be easy to find.
Location does make a difference.
But if you install an electric pump at the tank in addition to the diaphragm pump you might rupture the diaphragm from the pressure and dilute your oil.
Also connect it through a relay and an oil pressure switch or Murphy Switch so if you get in an accident you won’t pump out your fuel.