For a few months, I've been using an electric Duralift fuel pump on my 7.3. No problems.

I timed my van well before I installed the e-pump. I was concerned, because I learned that changes in Outside-of-IP fuel pressure can affect timing. Hopefully, my e-pump pressure matched my former lift pump pressure.

I also installed a shut-off switch for the pump. I didn't want it to be chugging away whenever I had the "key-on" but had no intention of starting the engine (like working on the van or troubleshooting something). Also, I figured it could be kind of a security system. If I parked my van for a long time, I turn off the pump. Since the thief doesn't know the location of the switch, I figure the thief could drive for a block before it'll shut down.

The reality:

My van drives fine with or without the pump on. Sometimes, I'll drive for miles before realizing my pump was never turned on. Not only that, but I honestly can't tell the difference between on or off? Highway or city driving is not affected. It drive completely normal with zero fuel pressure. I'm kind of bummed, because I was hoping the anti-theft plan was going to work.

So, I'm wondering.... What's all this hubbub about fuel pressure outside the IP?

 

I have no idea what the "hubbub" is you speak of - but I don't come to this forum very often. The Stanadyne pump needs NO fuel pressure to work correctly. It has its own fuel pump built inside the injection pump that can draw fuel from 20 feet down. But - it cannot draw fuel through a plugged or non-working mechanical fuel pump. So - regardless if the fuel at the inlet of the injection pump is zero -or 10 PSI - it will run just the same. If inlet pressure is higher then 10 PSI - it might activate the automatic timing advance and make it cut in prematurely. The injection pump has a automatic timing advance that works off of fuel pressure. It starts to advance at around 10 PSI and reaches pressures over 60 PSI as RPMs increase. The main purpose of having an extra fuel pump (outside the injection pump) is to make bleeding and filter filling easier. There were a few diesel cars and trucks sold in the USA with no separate fuel pump at all (like an Isuzu PUP, Trooper, Chevy LUV/Chevette). They had to add a hand-primer pump on the filter housing to make it possible to bleed the filters when needed.

 

Is there no performance drop even at WOT?

 

No performance drop. The rotary-vane fuel pump built into the rear of the injection-pump housing supplies more then it can ever send to the injectors.

 

The problem comes in the calibration of the pump though. If the pump is calibrated at 6psi inlet pressure, it needs to be within 2psi either direction, or the timing will be effected.

The recommended range is 4-8psi, and that is to cover variations in stand supply pressure at calibration.

It is true that the IP will run without a lift pump, but the pump will be out of calibration. The 90 is calibrated at 6psi inlet, and your timing will be effected if your lift pump isnt working.

 

Completely different style pump.

 

What PSI is your Facet rated for and have you tested the inlet pressure at all? Maybe it's running 4psi or below and as Racin said, below a certain amount effects timing...maybe your is always affected so it all feels the same.
Just a thought though, I'm messing with my IP all the time trying to figure out how all the different adjustments affect my power output and MPGs, and currently dealing with input pressure and it's affect on power. I can say I have the 9-11psi Facet and when the truck is running I NEVER see psi over 7. And once the throttle is open it only drops.

I just changed my fuel filter two days ago and it made a significant difference in PSI at the gauge once the throttle opens, but oddly it seems to have lowered my power output. No idea on that one.

 

Completely different how? In this context, they are very similar functionally. Bosch (German, not American) and Diesel Kiki pumps were built under license from USA Stanadyne. Different - yes. But both have rotary-vane low-pressure fuel pumps in back and both are rated to draw fuel from 20 feet below them.
"Completely different??" I don't see it that way.

 

PSI is somewhat dependent on flow rate. E.g. - a pump cannot sustain its rated pressure if demand on it is more then it can flow. In an absolute worst-case-scenario - I doubt you can make your truck demand more then 1/4 gallon per minute no matter what you do to it. Most any electric fuel pump is going to be rated at 1/2 gallon per minute or more. Sounds like you've got fuel restriction problems somewhere.

 

The engines you quoted use a Bosch VE style pump. The VE is sleeve metered, contains a timing mechanism that bias's housing pressure versus spring pressure, and housing pressure is regulated by an orifice on the housing return circuit. Regardless of how much pressure, or lack thereof you put into the VE's transfer pump, your housing pressure is going to remain constant because the regulation is on the back end. The Roosa-Master style inlet metered pumps we have have the regulator on the front side of the transfer pump via a small orifice and max pressure relief valve. When you run more or less inlet pressure to the transfer pump on these, it alters transfer pressure via the regulator. When you alter transfer pressure, you alter the pressure differential of the timing mechanism (There is no spring like a VE pump, just transfer to housing pressure differential) which will cause your pump to advance or retard based on inlet pressure. Thats why any stanadyne DB test plan has a specific spec to run your inlet pressure at.

 

I know for sure on mine when my pump died it ran alot quieter... and could be my imagination, but i swear it was easier to make it smoke. Went about 45 miles this way before it started surging and intermitten stalling. I assume that is due to small air leaks somewhere, as with the carter multi-fuel on there now, its easy to hit 0 psi at half throttle (wont smoke) and i can keep walking into it down to the floor where it will roll coal making a pathetic 10lbs of boost which is all my clapped out, leak plagued, tired turbo can muster.

 

I understand that. My comment was about the two makes of pumps being similar in design as they are both rated to feed themselves fuel from a 20 foot drop.

As to DB or DB2 or DC or CBC etc. Stanadyne/Roosamaster pumps and the effects of inlet pressure on the timing advance? I can't say I've experimented with it on a stand. I've checked the timing advance on many a DB or JDB pump on a running engine and observed little to no difference in the advance operation between a gravity feed zero-pressure hookup versus 7-8 PSI on the inlet. Seems to me - at least in theory - if it takes 10 PSI to push against the advance spring to begin timing advance - anything below 10 PSI will make little difference. That is unless the housing-pressure-regulator valve gets plugged and internal housing pressure spikes too high. We did not work on DB2s in our shop. Just DBs which did not require a test-stand to check advance operation as long as we had a running engine to mount the pump on.

 

Even the AG advance mechanism is different, but even then, bottom line is this. The T.P. pressure is above 10psi just off idle... That being said, its moot... Inlet pressure effects overall pressure, and overall pressure effects timing. I understand it may not be much, but in terms of how the engine acts, its a ton.

One of the first lessons I learned in dealing with these pumps, was a direct influence of lift pump pressure in terms of timing advance at the pump, and timing advance, at least in a turbo application, is almost always a negative, with the only exception being the size of the turbo. I didnt see the numbers a test stand put out, I saw a 20whp gain on a 200whp truck, just going from 9psi inlet, to 6.5psi inlet... Those are real world numbers. So in terms of lifting fuel from 20ft vs. a 7psi inlet pressure, the engine still may run, but the difference in the way it acts is going to be dramatically different.

 

That all being said... all of these facts apply only to a well-timed engine that's running correctly using good injectors and such. After 100K miles, the timing will be out of whack anyway, injectors may or may not be firing anywhere near consistently.
So, you may not notice any difference at all... If only because things are nowhere near 'optimum' in the first place.

I'm one of the few people running a mechanical low-pressure pump with a higher end setup - I like the reliability(and cost), but I do understand that it may well mess with the timing. I've sort of adjusted my timing curves to compensate, which may or may not be perfect... but works well enough.

Honestly, if I were to go to an electric setup, I'd be using something like a Powerstroke high-PSI pump with a regulator; That way I could be assured of constant pressure.
(Note: /I/ would actually use two in parallel, with a switch so I had a backup)

My dad has one of these Faucet Duralift pumps on his truck, and I'm very disappointed with how the pressure drops under load. It puts out perhaps 7 PSI at idle, and flooring it can actually make it hit 0. And this is measured /before/ the filter.

That's just my 2C; take it or leave it.