Biting the bullet: Converting to electric fuel pump

Cubey · Feb 23, 2020

Maybe it's a pressure problem. I guess I should have stuck with the Mr Gasket 105p or ordered a Holley blue.

Half way typing this while walking my dog so I don't remember who pointed that out before, but I guess they were right.

Once I hook up my fuel pressure test gauge, I will know better.

The charts again for comparison:

Holley Red:

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Holley Blue

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Holley Black

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Cubey · Feb 23, 2020

Ok so it's not the pressure. At idle, it's about 6.5psi. Driving, 4.5-5. So it must be flow.

I removed the filter head bleeder valve's core and shoved my test gauge hose on the fitting and zip tied the gauge to the cowl.

The fastest I got up to in this video was about 45mph but that gives you a good idea. I had it floored at one point.

https://photos.app.goo.gl/JNZrYscV3VuUrdaD8

So, I wasted $100 on the Holley red basically. It's a good emergency backup I guess. Maybe on an NA IDI it keeps up ok, but not turbo.

I guess I will order a Holley blue for $128 shipped and swap it out, plus add the regulator. I just hope the 5/16" return line is enough for the freaken regulator since it calls for 3/8 or larger.

I really don't want to throw in the towel and go back to mechanical. :/

Any suggestions before I proceed?

Selahdoor · Feb 23, 2020

Cubey said:
Crap!!!

Low flow definitely seems to be a problem. I jumped on the interstate for a couple miles, and with the pedal to the floor, I was staying steadily at 68mph!! Letting off a bit maintained it. 70 was the best I ever hit, trying to floor it.

An IDI needs more than 97gph?!

EGTs were lower than normal. Used to run at 900ish at 65-70, it was around 700-750 I'd say.

Could off-timing cause that?

Very possible.

Recently I pulled a several mile long, very steep grade at over 85mph... (Started the grade at about 50, and steadily climbed in speed)

Without it ever down shifting. Never got above 2200rpm. And never had the pedal all the way to the floor.

Of course, this is an empty truck, and not a loaded RV...

By the way, I am running a cheap ($65.00) green pump from O-Reiley's. With no mechanical pump.

But I am also going to plumb the mechanical back in, with check valves.

Cubey · Feb 23, 2020

Selahdoor said:
I am running a cheap ($65.00) green pump from O-Reiley's. With no mechanical pump.

My F250 has one and it does decently except on big hills. But it's NA like yours. Turbo'd engines need more flow, I guess.

I can either buy a Holley blue w/ regulator (100gph @ 5psi) for $128, or Holley Black plus regulator (138gph @ 5psi) for $195. (Both prices incl. tax).

The $128 is more tempting but what if 100gph is still too low? I'd be out even more money and still wouldn't have proper flow. So, I guess I might just have to sink $195 into the Holley Black.

I'm already out $100 for the Red pump, unless I can resell it. Better off keeping it as an emergency spare though, since it can get me down the highway in a pinch.

The red is only putting out about 50gph at 5psi though, so... yeah. 100gph might be enough but should i risk it? Probably not.

Booyah45828 · Feb 23, 2020

If you're getting 4.5-5 psi while driving, I'd say your pump is providing enough fuel. Did you change anything else on it? Forget to go install something back? Pinched a return line while installing the new pump?

Cubey · Feb 23, 2020

Booyah45828 said:
If you're getting 4.5-5 psi while driving, I'd say your pump is providing enough fuel. Did you change anything else on it? Forget to go install something back? Pinched a return line while installing the new pump?

Pressure isn't the same as flow. And based on the dyno chart for this pump, 5psi = 50gph. Driving around town and getting up to about 45mph is fine. After about 55mph, it starts to lack power. By the time I'm at 68, there's no more flow possible at 5psi than 50gph, even though I need 60-75gph, if not more.

Supposedly the 7.3 093 turbo engines need 15gph per 700rpm. So at 2800rpm (700rpm x 4) it would need 60gph (15gph x 4). At 3500rpm, 75gph. This pump falls short by at least 10gph which is a lot when putting the hammer down but getting no reaction.

Flooring a turbo IDI on a relatively flat highway shouldn't make it sit at 68mph with no change in engine rpms. It's fuel starving, it seems.

I did go under and look for leaks and messed up hoses, but I didn't see anything obvious.

Cubey · Feb 23, 2020

Hmmm, maybe it's the Racor R26P, being rated 45gph. I guess I will try deleting that from the system tomorrow (it's raining now). It's just a matter of swapping a couple of hoses to do that, so it's a good thing to remove first to see if it makes a difference.

But eh, even without that, 50gph from the pump is still too low.

chillman88 · Feb 23, 2020

I'm betting if you left that gauge there and started on the interstate at 68-70 you'd probably see that pressure go a good bit lower.

Does your fuel filter restriction gauge function properly? NA 68-70 was about all she would do on hills with an e-pump on mine. The filter gauge kept lighting up when I laid into it too hard because the e-pump couldn't supply enough.

Cubey · Feb 23, 2020

chillman88 said:
I'm betting if you left that gauge there and started on the interstate at 68-70 you'd probably see that pressure go a good bit lower.

Does your fuel filter restriction gauge function properly? NA 68-70 was about all she would do on hills with an e-pump on mine. The filter gauge kept lighting up when I laid into it too hard because the e-pump couldn't supply enough.

I don't think 6.9s have such a gauge. The only fuel light is "water in fuel', which is useless since it's harness isnt hooked to anything anymore.

I will put the test gauge back another day (maybe tomorrow) then check it at 65+mph. I removed it to prevent theft and possible rain damage today/tonight. But assuming pressure does drop futher, flow should increase.

The big question is more... blue (100gph @ 5psi) or black (138gph @ 5psi)? I'm thinking black. It should never fuel starve at 138gph max.

Thewespaul · Feb 23, 2020

Where is your pressure sensor located?

IDIBRONCO · Feb 23, 2020

Cubey said:
It should never fuel starve at 138gph max.

I don't think that it would. I'm pretty sure that is what Wes runs and we all know how much fuel his Shop truck needs.

IDIBRONCO · Feb 23, 2020

I can't rememeber what type of set up Wes has on his for the return. I wonder if running a separate return would be the way to go?

Cubey · Feb 23, 2020

Thewespaul said:
Where is your pressure sensor located?

For the test gauge?

It's a HFT fuel pressure/vacuum tester. I used it previously for vac testing, so I already had it on hand.

https://www.harborfreight.com/Fuel-Pump-and-Vacuum-Tester-62637.html

To attach it, I removed the valve core from the factory filter head bleeder valve stem, and just pushed the hose onto the bleeder valve stem.

Initially I just unscrewed the whole stem but I didn't have the right thead size adapter.. then I dropped it when I tried putting it back. Stupid thing is aluminum so I had to use a wire coat hanger to slide it to a place I could reach it. Luckily, I got ahold of it and got it threaded back in. That's why I ended up removing the core and shoving the hose on there. Works great though for quick tests, no leaks even without a clamp.

Cubey · Feb 23, 2020

IDIBRONCO said:
I can't rememeber what type of set up Wes has on his for the return. I wonder if running a separate return would be the way to go?

Maybe, but then I'm dropping the tank to install a second return line somehow. Unless I feed it into the filler vent but then we're back to air bubbles being created in the tank.

The Blue pump wouldn't be pushing as much back to the tank, since it's lower flow, so maybe 5/16" would be ok considering the IDI's consumption rate. Black? Dunno. It would mainly be a problem at idle and low RPMs when consumption is low.

The tank transfer pump has been off during testing, so we can rule that out as being the problem. Plus it's installed off of a tee, so engine to tank return is completely unrestricted.

Cubey · Feb 23, 2020

OH!!

A return isn't even needed on the standard (non-bypass) $30 Holley regulators! You just plug the extra port.

The more expensive $90 bypass ones need a return line.

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So, I should be able to install a Holley Black and non-bypass regulator and be done with it.

It's the cheaper, less great way of doing it, since the pump and regulator gets deadheaded a lot more, meaning they may not last as long but ehhhh.

Biting the bullet: Converting to electric fuel pump

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