Om 617a Electric fuel pump conversion?

[ThisIsZane]

I've read the few threads that speak about the topic but all seem to refer to having both an electric fuel pump and a mechanical fuel pump running. None of this was tuned to the idea of performance.

I'm not the most mechanically inclined and this is all still a learning experience for me. I'm wondering if it is possible to disable/remove the mechanical pump all together and use an electric fuel pump to deliver the needed fuel (the MW pumps with 8mm elements claim 120cc's of fuel delivery) I'd imagine this would save me a considerable amount of money seeing that it will cost ~$1200USD to have the dieselmeken pump built and shipped.

I currently have plans to ship the mechanical fuel pump to dieselmeken to have it built with 7.5mm elements with the goal of around 250HP. BUT would want to run this idea by those who know what they are talking about first.

[diesellover 92]

i know nothing about the om617 lift pumps but i can guarantee you can find something on the shelf to run inline for you needs. You can buy a walboro 255lph in tank pump for $80 now. i Know they sell inline versions also.

[Rogviler]

It sounds like you're talking about (or confusing) two different things to me. The lift pump is what sucks fuel from the tank and delivers it to the injection pump. The injection pump is what delivers the fuel to the injectors. You can bypass the lift pump with an electric one but not the injection pump. At least not without getting crazy technical and expensive, since it involves high pressures and precise timing.

-Rog

[ThisIsZane]

Ah yeah, it appears I'm an idiot. Looks like I'll go with the dieselmeken pump after all. Thanks

[diesellover 92]

Originally Posted by Rogviler

It sounds like you're talking about (or confusing) two different things to me. The lift pump is what sucks fuel from the tank and delivers it to the injection pump. The injection pump is what delivers the fuel to the injectors. You can bypass the lift pump with an electric one but not the injection pump. At least not without getting crazy technical and expensive, since it involves high pressures and precise timing.

-Rog

this makes way more sense than 1200 for a lift pump rebuild

[OM617YOTA]

To answer what can be answered(mostly for future people searching), yes you could replace the lift pump with an electric pump. You'd need to use an EFI pump, as the pressures needed exceed what a carb'd pump would be capable of delivering, but it'd be no trouble. The IP has a built in fuel pressure regulator and would just bypass any flow that it can't use, as it does now with the mechanical pump.

[NZScott]

This is why the forum exists, for learning

In fact most people with superpumps have to run something better than the standard lift pump. Bosch 044's are popular but have their own drawbacks (ie noise).

[Junkman]

Fass Fuel Systems | Fass Fuel Pump | Thoroughbred Diesel

From the Cummins crowd.

[BillGrissom]

I have also considered alternatives to the lift pump since replacements are ungodly expensive (though rebuild kits are fairly cheap). There are electric pumps for gas/diesel on ebay ~$40. Mount one on rubber isolators since some are "rattlers". I have seen some spec ~12 psig, which is what your IP inlet needs. Some "carburetor" electric pumps like Holley radial-vane or Carter can produce 15 psig, indeed Holley sells a spring upgrade kit (for bypass regulator) for their blue pump and I used that long ago on a TBI upgrade on my 1965 Chrysler (gas engine).

An EFI pump (Walbro, Bosch, ...) is a bit over-kill, but not much more expensive. They are designed for ~60 psig outlet, but will work OK at lower pressures, and give much more flow-rate there. Cheapest would be one for a 1990's Ford truck which was frame-mounted (have bought new for $20). But, more plumbing needed. EFI pumps are positive-displacement, so must have a pressure regulator and these aren't integral like in "carb" pumps. You need a "back-pressure" regulator. I don't know of any ~15 psig automotive ones, only "pressure-reducing" reg's for carburetors. You might use the 90-04 Corvette filter/reg (Wix 33737), popular among hot-rodders. It relieves at 56 psig, but that shouldn't over-whelm the IP. The IP needs a minimum ~12 psig, but more pressure "should work" (quote to shove in my face later). It simply needs to fill the IP cylinder each stroke, and 56 psig is nothing compared w/ the 1950 psig output pressure (OM617 turbo injectors). On the plus side, our diesels already have the needed "return tube" to the tank, which people retrofitting EFI on classic gas engines must run, so tee into that for the regulator return flow (5/16" quick-connect).

If one does use an in-tank EFI pump (post 2), it must still have a bypass regulator. The reg is usually built-into the entire "tank assembly" in new cars which is a big plastic unit w/ level sensor, etc, which would require a big hole in the tank top. You can install just the pump, but passing the wiring thru is a pain, and no real advantage over an external pump. Those w/ later cars may have provision to mount the Bosch pump & reg assembly used on gas cars of the same car body. It mounted in front of the rear axle (seach Google Images). Like the Corvette reg, it would supply ~55 psig to the IP.

[Junkman]

Pressure is one thing. What volume does a 617 need? I suppose this may become an issue in the future as pumps begin going out but it hasn't been much of an issue for a stock engine.

Just because there is an over flow valve doesn't mean that you can randomly turn up the pressure. There will be a happy range perhaps slightly above stock pressure.

[OM617YOTA]

My experience with fuel pumps for carb'd applications is that they run in the 4psi range. Not enough for our engines, hence my recommendation of an EFI pump.

The built in overflow valve on our IPs mean that unless you very significantly turn up the flow, you CAN'T turn up the pressure. The spring on the overflow valve is what controls the pressure, opening at a set pressure and venting anything extra back to the tank. Just like a FPR on a gasser.

Not sure what the stock lift pump GPM is, but when I emptied my tank by running the return line into a fuel can and idling the engine, it pumped ~10 gallons in ~20 minutes. At idle. Obviously it'll pump more at higher RPMs and the overflow valve will have to(and therefor is able to handle) vent more.

With that in mind, my conclusion is that the built in overflow valve can handle just about anything a reasonable gasser EFI pump will put out. Probably less spring wear also, as it'll be a steady flow instead of pulsing all the time.

[Junkman]

Somewhere there are fuel pressure specs. I've seen requirements calculated for the 24V Cummins but haven't paid attention to 10#. The sweet spot appears to be between 12 & 17# on that engine. The overflow valve begins opening at 14#. IP is lubricated by fuel and stock Dodge lines lines are not sufficient to avoid significant pressure drop at WOT. A fuel pressure gauge is routinely installed permanently on that vehicle because the engine will run with the IP only and cause the IP to die from lack of lubrication.