Biting the bullet: Converting to electric fuel pump

Cubey

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Really return volume at different loads and rpms comes down to the pump, especially the advance piston wear. You may see the most at idle or the most at low load but high rpm, or high load high rpms, just depends on the pumps condition and efficiency.

The injection pump, I'm guessing.

Considering I had zero problems before switching, it must be something directly related to the Holley conversion, not an IP problem.

Doesn't the filter head return line connection have a check valve? Perhaps it's weak and is bleeding pressure from the supply. Just a thought.

The fuel pressure drops when shut off, as if it's going somewhere. Wouldn't it normally hold pressure? Maybe it's how Holley pumps just are. I had no starting problems with the mech pump so it wasn't losing prime.
 

Thewespaul

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I would plug the return port in the filter head if you have it, I do it on all e pump setups since the e pump has a much easier time pushing air out of the system than the stock pump.
 

Cubey

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I would plug the return port in the filter head if you have it, I do it on all e pump setups since the e pump has a much easier time pushing air out of the system than the stock pump.

Will do. I specifically remember replacing that piece of hose when I did the return lines and o-rings a year ago.
 

Selahdoor

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That's easy enough to change. I can let the engine return go straight through the tee and use the side connector go to the transfer pump. I just gotta dig put a longer piece of scrap hose from my stash to change it. I will only run the transfer pump with the engine off so it can't cause problems.



Oh, I see. I looked up a diagram. The IP itself pushes returning fuel too, not just injectors.

My thought is that yes more fuel will be flowing to the IP, but at a lower pressure, so the return pressure might go down too since the IP will be getting less pressure.

The engine will be using 4-5x fuel as much fuel than at idle so that will probably eat up the extra flow.

But, I was wrong about pressure/flow from the Holley, so maybe I am again.
Put a check valve in that line from the transfer pump.
 

Cubey

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Put a check valve in that line from the transfer pump.

Yeah, might a good idea. I think the pump has one.... but there is also still a ball valve before the transfer pump, so i can manually cut off the flow.

But that shouldn't mess with return line pressute.
 

Selahdoor

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I was just thinking that if there is no check in the pump, you could be returning fuel to the wrong tank.

Think I'd add the check valve just as extra assurance.
 

Cubey

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I was just thinking that if there is no check in the pump, you could be returning fuel to the wrong tank.

Think I'd add the check valve just as extra assurance.

I just ordered this. It'll be here around Monday.

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I probably won't get to install it until next Thursday due to rain Mon-Wed, but I'm hoping to just sit here parked for at least a week more. Gonna hit the road again soon and won't be back here for at least a year, so maybe my mom won't mind another 7-10 days.

I will straighten the return line from engine to tank at the tee (no more 90° turn) and check the pressure again. Then I can put on the check valve and reconnect it to the transfer pump.

I will see if I have the materials on hand for disconnecting the filter head return line connection. I have spare injector caps, clamps, and old used hose bits, so maybe I can come up with a bolts shoved in a hose ends with clamps to plug off both connections.
 

Cubey

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Edit: nevermind. I'm a dork. This post was me being totally wrong. :oops:
 
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Selahdoor

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Where is the "view post before it was edited" button?

:rotflmao
 

Cubey

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Where is the "view post before it was edited" button?

:rotflmao

I got confused for a few minutes. I mistook the steel supply line from the filter to IP as another return because it's teed off with return.

So um yeah :joker:

As in, this:
(pic from my truck because it's easier to see, but RV is the same)

You must be registered for see images attach
 

Booyah45828

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No, the little bit of fuel that the tee lets pass into the return system is moot. Truthfully, the return system should be sized large enough that there should be 0 psi present.

That Tee is designed to bleed air present in the supply system directly to the return, without it having to go through the injection pump. Such as air that would be introduced when changing fuel filters.

Sometime during 7.3 production they changed to a check valve/nipple on the filter head, vs a nipple on the elbow.
 

Selahdoor

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Yep. And note, there was a check valve.

I removed that line and plugged the filter head.

Re-routed the line to tee with the other line that comes off the top of the IP.
 

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