My electric fuel pump dual with manual setup. And alternative.

[Selahdoor]

The way I have my electric and manual fuel pumps set up right now, in a dual configuration:

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Note that the check valves are backwards in the pic. I didn't take another pic before I installed them. The arrow should be pointed the other way.

Here's a drawing to show closer to what it looks like, installed.

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The check valves are aimed at the fuel filter. This keeps either pump from being able to pump fuel back through the other.

The electric fuel pump is set up on the wheel well right beside the engine.

The advantage to this setup is that the engine can be primed with the electric fuel pump, every time you start it up. And any time that you run out of fuel. Etc...

I run the electric all the time. As long as the key is in run position. Doesn't hurt it to keep it running all the time. But you can put yours on a toggle if you wish. I just kept forgetting to use the switch, or to turn it off after I turned off the engine.

As long as the fuel is flowing correctly, I think it is probably better for the electric pump to be used, than to just let it set there.



Now the electric does just fine in this application. In fact, it ran just fine, (And I have very steep hills in the 30 miles between here and town.), when the electric was the only one hooked up.

But technically, it is made for pushing fuel, rather than pulling.

So if you would rather have the electric pump down on the frame, closer to the source, here is a drawing I made to show how you could set it up in the same fashion I have mine set up... But with the electric pump down near the selector valve...

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[gandalf]

Lets be sure I understand this. You run the electric pump all the time, and apparently the stock pump also all the time. You have check valves after each pump to prevent one from backfeeding through the other. So, they're both running all the time, each supplying fuel to the filter through parallel lines. They both pump fuel, draw fuel, through the FSV on the frame rail. The output from the FSV is 3/8 if I remember correctly. You split that 3/8ths with half going through each pump, through the check valves, and them combine them once again into a single 3/8th. Theoretically you have half your fuel going through each pump. I don't believe you're going to get any additional fuel to the filter because the line(s) start and end at 3/8th.

I'm not sure I see what the advantage is. You'll have to explain that part to me. If you could shut the stock lift pump off that would give you a choice between the two, the ability to use one as a backup. I need more explanation as to what you're thinking is on this.

 

[Selahdoor]

Mostly my thinking is that I want to keep the IP supplied, no matter what. And I want the system to prime with the electric pump, no matter what.

I'm not trying to overthink this.

In fact, I am trying not to overthink this.

That said...


The truck runs just fine off of either pump.

The truck only needs as much fuel as a 3/8 line will supply.

But sometimes, one pump simply doesn't move enough fuel all by itself.

If you are running both pumps at the same time.... Then in any conditions where one pump might not be supplying enough fuel, the other is backing it up.

You always get as much fuel as a 3/8 line will let through.



I have noticed a MARKED difference in the 'get up and go' of this truck, after getting both pumps plumbed in, in parallel.

It used to do just fine at 65 down the highway. Just felt like you'd better not ask for any more than that, or you'd be disappointed.

Now, you can be doing 70, and hit the go pedal, and it will threaten to leave you behind...

Response has improved in all speed ranges.

And shifting has improved as well, for some reason.


At the same time it is not using any more fuel than it was. In fact efficiency seems to have increased a bit.

 

[hacked89]

Edit: actually what model is the electric pump you are using?

 

[IDIBRONCO]

In fact efficiency seems to have increased a bit.

It could be that your pump timing has increased slightly. It could have been slightly retarted before and now runs better/more efficiently using both pumps.

Edit: actually what model is the electric pump you are using?

IIRC, it's a generic in line pump.

 

[Selahdoor]

Here's the pump.

https://www.oreillyauto.com/detail/...02/5569385?q=electric+fuel+pump+deisel&pos=11

Note, buy an extra fitting for the thing, and throw away that tiny metal filter they include with it. That thing gets clogged in a heartbeat, and I'm convinced it is what gives these things such short lives.


IP timing. No doubt it increased it a bit. But I had already increased it by 2 and a half dime's thickness, after I bought it.

 

[Fort Ford]

Sorry to bring this back to life but I've been contemplating this type of mod. I'm wondering why you felt it was important to have them in parallel instead of inline like seems to be more common? I've seen lots of people add an electric pump before the mechanical pump, and I've seen at least one guy add the electric pump between the mech and the filter. My understanding, based on the flow-through design of a mech pump, that this shouldn't be a problem? Or do you feel it will put undue strain on the pump diaphragm? I've been contemplating upgrading the stock filter assembly to something more robust with an integrated electric pump, but I don't like relying entirely on an electric fuel pump. Mechanical redundancy appeals to me. I like the idea of the parallel system with check valves. In my case, I am planning to upgrade my rear tank to a 38gal from the late 80's model, and do away with the midtank and fuel selector valve assembly, since it and most of my fuel lines are heavily crudded up and need replacing anyway and it just seems simpler having one tank and fewer potential fuel leaks. I could run the pumps both directly off the tank, and now I'm even imagining making a custom pickup so they'd each be on their own pickup. That way they wouldn't be starving each other sharing the same 3/8 supply off the selector valve.

But that feels like overthinking it, when I could just plumb it all in-line for a lot less work. So I'm hoping you have thoughts on why parallel is superior to justify the extra work accomplishing it?

 

[IDIBRONCO]

His aren't quite truly parallel. They are separate. They are parallel, but they do share the same pick up. This was mostly (I think) to avoid the pressure on the fuel pump diaphram like you said. He says that his truck runs better while using both pumps. Also, the electric is one of the small, universal ones that will work fine for a gas engine with a carb, but they don't have enough flow to run a fuel system with a constant flow through a return line like our engines or gas engines with EFI have.

 

[Selahdoor]

If the diaphragm in the mechanical pump goes south... As in it punctures, or tears... Starts leaking in any way. Even a tiny leak... If you have the electric inline with it, the electric will be dumping fuel into your oil pan, regardless of whether it is before or after the manual pump.

While the engine is running, BOTH will be dumping fuel in. But if you have the electric, it will dump fuel in, even if the engine is not running, if you have the key on.

I was actually concerned that if the manual pump got a bit old, and wasn't compromised on it's own, it might more quickly become compromised by the pressure from the electric pump.

I put them in parallel to prevent that from happening, either way, (naturally, or because of the extra pressure.). Neither pump can push fuel through the other.

I am considering putting check valves just before each pump as well. So that neither can end up somehow PULLing fuel out of the other.



And mine are truly parallel. They have the same source and the same destination. They are side by side. And neither feeds to or from the other. You don't have to go all the way back to the tank and make two separate sources for it to be parallel.



@Fort Ford You could run a single line to the old location of the selector valve, then split the line and put the electric pump on one line right there. To get better performance from the electric pump.

I would still put the check valves on the two separate lines, just before you tie them back together and feed them to the fuel filter.

And possibly go the extra step of putting two MORE check valves on the lines at the old location of the selector... Then feed each check lined valve to a fuel pump. (Then of course, the original check valves after each pump.)

Like this: (Simpler than it sounds.)

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The truck truly does run better at all speeds, like this, than it did with either fuel pump alone.

 

[Cubey]

Sounds like you have a timing issue, if it takes 2 pumps to run it right. My RV's timing has been so thrown off when running at 5-6psi with the Holley Red electric fuel pump conversion that it tops out at about 55-60mph on a flat highway with the pedal to the floor now. Prior to that with the mechanical pump, it had no such problem. I didn't touch the IP or injectors, so nothing else was changed. Sadly, I didn't check the pressure of the mechanical pump before pulling it. I measure it now by removing the filter head's bleeder valve core and pushing on the fuel pressure test gauge hose on the fitting. Now, it could be the HFT fuel pressure gauge is crap and the pressure is higher, but that seems a little unlikely. The bleeder valve fitting should be a fine place to check the pressure without restriction, since the core gets removed. Plus, the Holley Red is only rated up to 7psi so it sounds about right, since it has an extra W/S filter between the pump and stock filter.

 

[hacked89]

I find it interesting that you mention it runs better with both.
I'll skip the detailed math unless anyone wants more info.

Let's talk a stock 7.3 N/A motor with stage 1 injectors/rebuilt injectors.

Max Calculated GPH requirements - 30gph
What does a 3/8" hose system @ length of truck flow @5psi - 28 GPH.

So this is kosher and lines up.
Your electric pump model does 38 GPH at similar PSI.
That should meet the system requirements.

The injection pump takes 5psi at the inlet, creates pressures of up to 5-6k psi and the injectors open at 1700-1900k psi.

That said, I'm assuming there is a variable in the mix that you either aren't meeting your calculated flow requirements or not achieving a proper burn before your duel pump setup. Where right off the showroom the truck was. It should have been fine with just the electric though.

Now on my engine build which is coming up next I calculated 70GPH requirement so really only way to get that is to bump the inlet side pressure up.

Ill be testing this as well and putting both supply and return gauges on my truck to observe.

Math is just the hypothesis before the real world testing.

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[Selahdoor]

My electric pump is in the doghouse. On the wheelwell.

It's pulling, not pushing. I believe this type was intended to push, not pull.

@Fort Ford will probably have even better luck than I, if he puts the electric pump down near where the selector valve was.



Also, with either pump, I would lose 'gumption' at higher speeds, or uphill.

Did better on that account with the manual.

But with both, I have good performance whether at high or low speeds, and on any grade.

Better fuel mileage with both running.

And last, I don't worry about overnight bleed down. Turn the key on, wait a half a minute or so. Give it the GPs. And start right up. Plus, if I run out of fuel, I don't have to run the batteries down, or overheat the starter, trying to get the system bled again. Just turn the key to run, and let the electric pump prime the system again.

 

[hacked89]

My electric pump is in the doghouse. On the wheelwell.

It's pulling, not pushing. I believe this type was intended to push, not pull.

@Fort Ford will probably have even better luck than I, if he puts the electric pump down near where the selector valve was.

Was this in response to me?
Shouldn't matter for flow rate calculations and requirements.

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[IDIBRONCO]

And mine are truly parallel. They have the same source and the same destination.

This is why I said that yours aren't quite in parallel. He was talking about two pumps, each with a separate feed line from the tank both pushing into the same source (of course there's only one IP). This is a "true" parallel fuel supply system.

 

[Selahdoor]

I do understand what you are saying.

But do you understand...

There is one fuel tank. One fuel supply.

Whether you put two fuel lines into that tank, or you put in one fuel line, and 'wye' it off later...

It is still one source.