I'm starting to think about some sort of improved, reasonably priced, /mechanical/ fuel pump for an IDI.

This spring I'm going to be building a fairly high end engine, and I /do not/ want an electrical fuel pump - I just plain don't trust them not to fail at the worst possible time.

I know that the stock lift pump is reasonable, but really isn't enough once you get into the 150-180CC range that I expect to be running in - At that point, you'll probably be pulling fuel through it, instead of it creating pressure.

Now, the question is: What other options are available?

Constraints are:
1. Reasonably cheap. I'm hoping to find a design that involves an off-the-shelf pump of some sort, something that's not a $500 part. I'd like to find something in the <$100 range, not including modding.
2. Machining adapters and such is not an issue(they are effectively free for me due to having access to the machines myself).
3. Cam-powered or belt driven is fine - though I worry about the belt at that point.

One option I've been thinking about is the plunger lift pump used on some Cummins engines: Diesel Fuel Lift Pump 3936316 P7100 Fits 6BT Cummins 94-98 Dodge RAM Pickup 5.9L | eBay

It seems like it might work, though it would require an angle adapter for mounting and probably a plunger extension.
It might not be able to handle the flow, though.

Any thoughts? And please, no electric pump suggestions(Unless you are thinking about removing the electric motor and installing a pulley...)

 

Interested, I too have a distrust of electrical components, which is why I dive an old dinosaur of a truck!

 

I bought an electrical but Mac said there performance was suspect at WO compared to the mechanical and others say the fuel flow is more precise on the electrical ?


I have decided to run my mechanical and have the electrical wired in so if the mechanical fails I just flip a switch and change the fuel lines over. Why not run 2 electrical if you are worried ? that should move enough fuel ?


I was all paranoid about a air start issue so I bought an electrical but I learned something myself when I put the PM starter in with 2 new 31 batteries. You gotta be able to turn these babies over like a Honda Accord and you will have a lot less problems when you run into a air problem or other hard start issue. but I'll have the electrical backup for a just in case.


Just saying....... Good luck with your hunt.

 

Those piston lift pumps will feed a 400 HP Cummins so unless the IDI takes a lot more fuel, it will keep up.

I would get a 20 PSI pressure gauge and plumb in after the fuel filter. This will tell you if the lift pump can't keep up (I.E. pressure drops to zero) and will also let you get the maximum life out of your fuel filter (I.E. run it until it limits your pressure to zero at WOT).

That way you could make sure that the stock pump won't keep up before you have to fix something that might not need fixing.

 

contact holley, they may have a rebuildable mechanical pump, or hell, get one for a chevy small block, and change out the lever.
as I have not done any research on this, the pumps look exactly the same externally,
(lever fulcrum, and bolt circle of the mounting)
may need to grind it a bit to fit the lame IH block machining.
I suspect for 100 bucks you could get this to work, and have a pump that lasts a lifetime, and with added extra flow.

 

Even the valley mounted lift pump in the PSD has a hard time keeping up with a modded engine.
I am planning at some point to replace my mechanical pump with a frame mounted fuel conditioning module from a 6.0 truck. They flow a lot, and are very reliable.

 

How about a FASS or the like?

 

Reliable also. The Airdog I messed with had some filter issues, but once that was addressed it was OK.
The nice thing about the FCM is that you can get a filter with a waterproof wrap to prevent any water in fuel issues.

 

More like stock pump turned up two flats. At least that was the case with the one i got from O riellys, at 3/4 throttle it was below 1 psi, at WOT it was negative pressure.

Im interested in this as well. Never carried around a spare fuel pump until i went e-pump.

 

One thing I'm also going to be looking at is fuel pickup efficiency. If there's some restriction or blockage, you could easily be dropping flow.
I've got one truck that I /know/ isn't pulling as much fuel as it should be; I'll probably just mod everything with bigger fuel lines and make sure the pickup etc is clear.

I'm definitely going to look at that.

 

This was my exact thought also. Don't people use a BBC fuel pump block off plate on these already?

I'm also interested in this as I prefer the mechanical pump.

 

the spring rate of the check valve in the pump on out put side determines the out put pressure, as fuel will push back on the valve and hold it open, in this way self regulating the pressure, holly has several mechanical pumps or did, as I worked on many some years ago, to provide a carbureted 360 with methanol, changing or fabricating a arm is possible.

 

some one should set up a test with a truck with mechanical pump installed, and when running on e pump, do pressure and GPM tests a differing RPM to collect data on stock pump..

 

Well, I've got a gauge coming, I'm going to zip-tie it to the hood one of these days and see what I get on my current truck.

I also have a data point on a Facet Duralift - my dad had a gauge on his for a while.
Idle was like 7 PSI. You rev it in neutral, and it drops to 4 or 5. Haul a load and floor it, and it drops to zero, and the truck doesn't feel as powerful at the upper end either.
With a banks turbo like mine, it ought to produce quite a bit of power in the upper end, but it's kind of anemic and retarded up there(I'm assuming due to lack of fuel pressure).
Needless to say, I'm not entirely happy with it for that reason.

 

OK. I have more info! I'll have video of this one of these days, when my phone and computer cooperate again...

Yesterday, I zip-tied a small mechanical fuel pressure gauge to the grill above the hood, so I could see it while driving.
I replaced the 'vacuum switch' on the filter with the line for it, so that it would be on the output side of the filter.

When I fired the engine up(it fired right off, no issues with leakdown or anything from breaking the vacuum), I got around 4 PSI. Revving made it drop a little.

After warming it up and taking an actual drive, I found that at idle I'm getting 4 PSI. Flooring it, I'll hit 3 PSI minimum.
I could not make it go under 3 PSI, or above 4 PSI at any time.
For this application, this is extremely good. It may be a hair low(probably due to losses from the filter, which is new), but the consistency is more important.

Note that this truck is my '93 F-250 with 'factory turbo' engine, stock IP that may or may not be turned up(I tried to turn it up and couldn't get the screw to turn in any further).

The lift pump in it is... whatever was in it when I bought it. Definitely not new.

Anyway, there's a data point for y'all.