Holley Sniper With Powersurge (1 Viewer)

Dr. John

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I know several Sniper installers are going the RobbMc Powersurge route in order to NOT mess with the fuel tank. The conventional installation calls for blocking off the mechanical pump's return-to-tank line and having the unneeded fuel returned to the tank through the Powersurge return port. I see a potential problem with this setup. The Powersurge has a very restricted orifice in the inlet port (from mechanical pump) (pic). With it's return line blocked, the mechanical pump is trying to pump everything it has through that tiny hole......that can't be a good thing. The pump is rated (iirc) at 3.5-4.5 psi. What does that pressure rise to if the tank return line is closed? Wngrog had a mechanical pump failure that also took out his powersurge pump. Could this have contributed to that failure...dunno. I was considering reconnecting the mechanical pump to the tank return line but that could possibly force a back-flow to the Powersurge. Open to comments.

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wngrog

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I have two of them. I did have the one problem that time. I’m not sure what caused the cascade to be honest.

RobbieMac himself is great with answering questions. I would pose the question to him.

I ended up with an extra after converting my 80 to factory PS. I’m going to hang on to it in case it happens again but with all the miles between the two setups I have I’m not ready to ditch them over one issue that I don’t know how to pin down.

Let us know what Robbie says
 

Dr. John

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Here is Robb's reply:
The mechanical pump will produce no more pressure (in fact, usually slightly less) when used with a PS than without.
Test it if you want: Connect the mechanical pump directly to the carb and test the fuel pressure between the pump and the carb. Then install the PS (per the instructions; You must have a return line from the PS to the gas tank) and check the pressure between the mechanical pump and the PS. You will find that the pressure is the same or less.
So if anything, the mechanical pump is put under less stress than when used without the PS.

___________________________________________________________________________________

I will try to test the mechanical pump to PowerSurge pressure when the rain stops.
 

OSS

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the original mechanical pump is a diaphragm pump. It can only generate a small amount of pressure because the diaphragm motion is small. If the return line is blocked, the rapidly pulsating diaphragm that's now doing nothing could conceivably cavitate enough to create air in the fuel <guessing> or at worst, shorten the life of the pump <guessing>.
The mechanical fuel pump is very easy to replace on the side of the road. Just buy a spare and see what happens to the original
 

Dr. John

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I've been living with this truck for 34 years and 300k miles. It has never required a single "side of the road" repair. and I don't want to start now.:) The inlet to the Sniper is only 0.055" and while the pump may be making short strokes,... at 3000 rpm, 150 horsepower, and no pressure relief, who knows what's going on. I'm going to put a pressure gauge in-line between the mechanical pump (new) and the Sniper this weekend, and see. Will let you know.
 
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I've been living with this truck for 34 years and 300k miles. It has never required a single "side of the road" repair. and I don't want to start now.:) The inlet to the Sniper is only 0.055" and while the pump may be making short strokes,... at 3000 rpm, 150 horsepower, and no pressure relief, who knows what's going on. I'm going to put a pressure gauge in-line between the mechanical pump (new) and the Sniper this weekend, and see. Will let you know.
I would be interested in your test results. On my DIY surge tank, I have wide open 6AN fittings on the in and return lines. I often wondered if there is any pressure present on the input supply line.
I would expect very low pressures between the fuel pump and the surge tank. Let us know. TIA
SimS
 

Dr. John

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This is sort of a "bump" to let you know I'm still working on this. Unfortunately, on first "key-on" following setup, the Sniper was blowing fuel out the top like a volcano. Anyone out there running a Sniper with a D.U.I. or GM HEI distributor? I'll be back.
 

wngrog

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This is sort of a "bump" to let you know I'm still working on this. Unfortunately, on first "key-on" following setup, the Sniper was blowing fuel out the top like a volcano. Anyone out there running a Sniper with a D.U.I. or GM HEI distributor? I'll be back.

Sounds like something is stuck. I’ve never seen that.
All mine have DUI.
 

Dr. John

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Well, that's good news (sorta). Do you guys have both the Sniper yellow tach wire AND the OEM tach pickup connected together at the dizzy ( - ) terminal?...OR...are you using the Sniper's 10 pin connector's brown wire tach output for the OEM tach.
 

Dr. John

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I'd estimate about 8-10 oz of fuel escaped before I shut it off. The whole scenario was: The actual 1st key- on... the surge pump ran about 5 sec and shut off... pressure gauge showed 58 psi (all good). Had a fuel weep at the Power surge out port so, key off and 2 days later replaced the leaky fitting with a better one. This next key-on, I get the gush and no pressure showing on gauge. The Holley gurus suggested the Sniper was getting a false RPM signal from the D.U.I., like a tach sweep.. hence my original question. But that should only apply (maybe) if had set up for Sniper timing control (I didn't). Maybe some crud is holding an injector open? Will hit it again tomorrow. Keep the ideas coming🤔
 

Dr. John

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While I won't have an answer to my original question until I actually get a Sniper installed, I wanted to give a:

SHOUT OUT TO HOLLEY!

Even though my Sniper had been sitting in its box for 2 years prior to first installation, they are going to ship me a new (hopefully not a re-furb) Sniper.
 

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