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Holley Sniper EFI for BBD Carbs

ag4ever

Average Nut
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Lifetime Member
City
Richmond
State
TX
Just about wrapped up the fuel tank on the Overlander.

Started out with this:

73440067-5EF8-4862-8D22-A520B1542EE9.jpeg

D9D7D836-4B80-46CD-9562-A79E9BC2A2B3.jpeg

Now I have this:

C84BC265-9F1E-47F6-B65F-6729F13E792D.jpeg

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I just need to mount it in the Jeep and install the new fill hoses.
 

Chamba

Not obsessed: focused.
Member
SOA Member
City
Vero Beach
State
FL
So I think I missed it somewhere. Did you put the holley 15 gallon pump into a 20 gallon tank? This is exactly what I want to do. I've heard it's the same basic sender assembly only it uses the screw- down retainer rather than a snap ring.
 

ag4ever

Average Nut
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City
Richmond
State
TX
So I think I missed it somewhere. Did you put the holley 15 gallon pump into a 20 gallon tank? This is exactly what I want to do. I've heard it's the same basic sender assembly only it uses the screw- down retainer rather than a snap ring.

No, I am using the mechanical pump to feed a ‘surge’ tank mounted on the passenger (left) side of the engine. The surge tank has a submersible pump feeding the efi.

I was done with the install, all working great when the old varnished gas and rusted out sending unit decided to kill the fuel pump.

Learned my lesson, ALWAYS drop the tank and clean it when there is any sign of fuel issues.
 

ag4ever

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City
Richmond
State
TX
Still having issues with this one. I replaced the electric fuel pump after the debris took it out. Replaced the fuel filters, 100 micron pre pump, 10 micron post pump. And a new sock filter on the new pump. It all ran perfect, took it to the service station for the state safety inspection. Passed the inspection. On the way home it started starving for fuel, AFR spiked to 30+.

I replaced the electric pump again, and the mechanical pump. (I did not replace the mechanical pump after the tank was cleaned out and there was trash in it that made it to the 2nd pump’s sock.)

Now with the 3rd electric and a new mechanical, I am still having issues. Runs great for 2 +/- miles, then starves for fuel.

I installed 2 fuel pressure gauges, one after the electric pump 0-100 PSI and one after the pressure regulator 0-15 PSI.

Upon startup, I get 62 PSI after the pump. When it acts up, I get 10 PSI after the pump. After the regulator, I get 0 PSI (good reading showing no restrictions in the return line.)

So, now I need to find my cause for low fuel pressure. Bad mechanical pump? Bad electric pump? Also, for some reason, the surge tank is running really hot. I don’t remember it ever running that hot. I have been buying my replacement pumps from https://walbrofuelpumps.com/, so I assume they are quality pumps. :shrug:

I am thinking a bad electric pump, again. :shrug:
 

spankrjs

Scrambler Junkie
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City
Biloxi
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MS
Can the mechanical pump keep up with the volume of fuel the electric pump/return line are moving :shrug:
 

John N

Addicted....Ex-SOA VP
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Rockville
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VA
Pinhole leak in a fuel line causing the pump to starve, loosing suction? Just a thought.
 

FLCJ8

Legacy Registered User
City
Palm Bay
State
FL
How much fuel is in the tank?
I'm not clear on your setup so take this for what it's worth...
My buddies return line to the tank was clogged and he had the same systems as you're describing, the tank would get a vacuum in it after some run time (it was dependent on the amount of gas in the tank) you could hear a slight whoosh of air if you opened the cap immediately after the problem presented itself. It ran better with the cap loosened, which helped diagnose the problem.
Does the surge tank rely on fuel flow back to the tank also?

Just some random thoughts that may not apply to your situation. :shrug:
 

ag4ever

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City
Richmond
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TX
Mechanical pump fills the surge tank, excess fuel returns to the main tank via stock return line.

Electric pump is submerged in the surge tank, feeds fuel injectors. After the fuel rail it goes through the pressure regulator, excess fuel returns to the surge tank.

Theoretically, if the mechanical pump can keep up with a carb it should be fine with the efi. (Engine is not producing extra HP, at least not more than the mechanical pump can supply.) There should always be fuel flowing back to the main tank.

I have the main tank vented through the stock carbon canister, and all lines were tested as clear. I can alway remove the gas cap and test, won’t hurt anything.

I am wondering if I got a bad replacement pump (mechanical or electric, leaning towards electric).

I may try moving the 0-15 PSI gauge the the mechanical pump feed to see if I have any pressure there. Since that is an ‘open‘ system to the main tank, I don’t think I should see any significant pressure though.

And, ALL rubber fuel lines are new. Only the original steel lines from rear to front (supply, return, vent) and mechanical pump to above the engine remain.
 

Randyzzz

Blown Budget
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Redmond
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OR
Just a thought. If the pressure regulator on the return is calibrated for a system with a higher overall flow than your current system, might it be allowing too much bypass?

Maybe I’m saying it wrong. But if you have a mechanical pump that flows 80gph, feeding an electric pump that flows 255 gph, and a regulator designed to dump excess fuel from a 255gph pump- won’t the mechanical pump be overdrawn in short order? Have you thought of putting a calibrating orifice in the return line to minimize flow?

If my assumption here is wrong, please explain. I’m always wanting to learn. I have heard of several issues with systems that use regulators in the return line after the injectors. My experience is with GM fuel injection. They have the regulator in the pump, filter, or on the fuel rail. Not in the return line.
 

spankrjs

Scrambler Junkie
Lifetime Member
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City
Biloxi
State
MS
How does the return line plumb into/out of the surge tank? Is it just a gravity bleed off?

I had a GM TBI 350, sounds similar to the Holley set up. Pressure into the TB, pressure regulator, return line at pressure regulator. I remember that a bunch of fuel flows out the return line, even with the stock 15psi TBI pump.

I just wonder with the higher pressure pump, more fuel coming through return line, maybe causing cavitation/pressure/vacuum issue in the surge tank?
 

Chipster1990

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Birmingham
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AL
I recently installed the Holley Sniper EFI on my 4.2L. I installed the Holley in tank fuel pump, ran new high pressure fuel line, and have had ZERO issues. No return line is needed with this set up. Just a thought.
 

ag4ever

Average Nut
Silver Member
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City
Richmond
State
TX
It is plumbed exactly like this diagram (Except the low pressure filter is after the mechanical pump, not before it.) 40007, not the dual pump 40008.

71F849BF-0C2E-4543-A1F0-C9B74DB74604.png

I just replaced the mechanical pump with a Delphi unit and the electric with a really cheap Amazon unit.

D8271A20-F26D-4DC8-9117-9856928D0228.jpeg

I can’t say I recommend the Amazon pump. It had a nasty coat of an oil like substance on it, I assume to keep it from rusting while crossing the pacific. But it is MUCH quieter than the TI (walbro) pumps. I hate the fuel filter sock. The walbro units have a sock that will draw fuel if it touches it. The Evil pump will only draw fuel if the intake is fully submerged. But the Evil pump is producing 70 PSI where as the TI was producing 62 PSI.

So, after a test drive I can definitively say it is the supply from the mechanical pump. It ran great until the surge tank was almost dry. Then it would not restart at all. With the TI pump, it would at least restart and barely run. Not so with the Evil pump.

Now I need to find the restriction in the mechanical pump circuit. It might be the return line, or the filter after the mechanical pump. I will probably start at the filter and replace the Earl’s Vapor Guard 10 micron filter with a cheap parts store carb filter.
 

ag4ever

Average Nut
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City
Richmond
State
TX
I recently installed the Holley Sniper EFI on my 4.2L. I installed the Holley in tank fuel pump, ran new high pressure fuel line, and have had ZERO issues. No return line is needed with this set up. Just a thought.
I would have done that, but I was trying to keep the 20 gallon tank and wanted a system that could be removed and returned to stock with minimal effort. I have been thinking of putting the carb back on this one.
 

ag4ever

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Richmond
State
TX
Did the old school mouth test. Disconnected the supply line and blew through the supply line and the return line. No restriction on supply side, including the filter.

Tried the same, and burst a blood vessel trying to get air through it.

Isolated to the return line being clogged, now to find where. Probably above the fuel tank. And it has 15 gallons in it. Typical.
 

spankrjs

Scrambler Junkie
Lifetime Member
SOA Member
City
Biloxi
State
MS
Sometimes the rubber hoses on top of the tank will kink when you reinstall the tank. I usually secure them (now) to prevent this.

Had a similar problem on my old tan Scrambler. No fuel to TB, couldn't figure it out. Lowered tank, fuel supply line coming off the sending unit kinked. Secured the line (where it has to turn) to another line, never had another problem.

Good luck, hope this fixes your issue :thumbsup:
 

FLCJ8

Legacy Registered User
City
Palm Bay
State
FL
Isolated to the return line being clogged, now to find where. Probably above the fuel tank. And it has 15 gallons in it.
That was the same situation as my buddies clogged fuel line, full fuel tank equaled the vacuum problem he had on his set up.
His return line looked fine but was clogged with rust, I don't remember exactly what I did to locate the spot.
Hopefully correcting the return line issue will solve your problems.
 

ag4ever

Average Nut
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Lifetime Member
City
Richmond
State
TX
I bought the Holley 15 gallon pump / sending unit. Currently testing a mock-up to see what modifications are required.

D3E01D50-86CE-4D4E-BB8A-A4A62F215B4B.jpeg

The inlet sock is about 1.25” above the bottom of the tank, but the other end sags down near the bottom. This is Holley’s hydramat that is supposed to wick fuel to the pump as long as any of the sock touches fuel. I would rather have the sock firmly on the floor of the tank. This can easily be accomplished by lengthening the rubber hose.

The fuel level sending unit is in the middle of the tank. If the unit is dropped down one screw hole, it is about 2 gallons from the bottom of the tank when empty and about 4 gallons from the top when full.

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9CD6114B-B09D-4810-9C41-D385A668D5AA.jpeg
 

ag4ever

Average Nut
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Lifetime Member
City
Richmond
State
TX
The outlet is pointed in a different direction and would [edit] NOT require a loop of hose to reorient it towards the fuel lines.

4238A83D-7825-43EC-AE63-306CF3FE93B0.jpegF2D58CAD-704D-4679-8173-189756D8F1E5.jpeg
 
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