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Joined: Jan 2014
Posts: 2,343
J
'Bolter
Originally Posted by D B Cooper
Just a quick update.

The Holley Sniper is working great so far. I have not experienced carb icing. Mileage is consistent at 14 MPG.

I do have one issue, the Holley in tank fuel pump is loud. Fuel pressure is a solid 58 PSI as indicated on the fuel pressure gauge located at throttle body. I’ve reviewed the Holley fuel pump forum which blames a loud in tank fuel pump on pump cavitation. I don’t think that’s the case with my pump as I have a new 100 micron sock on the fuel pump, all new fuel lines and a new 10 micron filter before the throttle body. Fuel pressure is rock solid at 58 PSI and I have no performance issues. I did drop the tank and pulled the pump to inspect the sock and overall pump installation, which all looks good.

Any of you fuel injection guys experienced this issue and if so, whats the fix?

Is your fuel tank behind the seat?

Joined: Dec 2008
Posts: 1,785
P
'Bolter
The shared intake ports allow complete separation of A/F into cylinders 1-2, 3-4, and 5-6... with 3 throttles, not 2.
Moving the carburetors apart is probably an improvement, but the 3-4 port is still fed by both intakes.

As to ratios: it's nice to know what number you have, but without individual sensors it's just an average, and no way to tell whether the cylinder-to-cylinder deviation is 1% or 20%. Even with 13.8:1 on the display any cylinder may be borderline lean (16:1) and knock under high load. You have to adjust for what the engine tells you, not a number. If all cylinders had the same A/F 13.8 would be way too rich for high vacuum cruising, 15 and up will give better mileage.
Does the Sniper have vacuum input as part of the fuel control? Are you using vacuum advance at the distributor? Adding advance without leaning the mixture won't help mileage.

Most OEM EFI pressure is 43.5 psi.

Joined: Sep 2015
Posts: 174
D
'Bolter
JW51, I’ve moved the fuel tank from the cab to under bed aft of the differential.

Panic, The Sniper does not use vacuum input as part of the fuel control. I am using vacuum advance at the distributor. The Holley Sniper EFI Installation Manual calls out 58.5 PSI for operating pressure. The install manual also states that the AFRs displayed on the controller are averages.

My fuel tank is vented using a TANKS Inc roll over valve mounted above the tank. With the engine running I’ve removed the fuel cap which does not affect the noise the pump is making, so I’m pretty sure the tank is vented properly.


Dan

35 CC Case
38 Chevy Pickup
51 3100 AD
58 3100 Apache Fleetside
Joined: Jan 2019
Posts: 385
F
'Bolter
Does the volume change with the temperature or with the amount of fuel in the tank? The walbro I have in my truck is louder when it is hot outside, but not annoyingly loud.

What kind of sound is it? And how loud is it compared to the exhaust?


58 Apache, long bed fleetside, V8 w/SM420
Drivable but the rear axle needs work.
Joined: Sep 2015
Posts: 174
D
'Bolter
Fibonachu,

No change with temperature.

It’s annoyingly loud, whistle type noise that starts as soon as I turn the key on and prior to start. It then continues as long as the engine is running. My truck’s exhaust is pretty quiet and I can hear it in the cab while driving.

Fuel pressure is rock solid and engine performance is great.

I’m beginning to think I have some kind of vibration/harmonics happening in the steel fuel lines that run from the tank area and along the frame rail to the engine compartment. When feeling the steel pressure line it does have a slight pulse. I’m going to get under the truck today and see if I need to add some clamps to the lines and see if that helps.

I read somewhere (I think on the Holley Forum but can’t find it now) that having the in tank fuel pump internally regulated to 58 PSI and the Sniper unit itself internally regulated to 58 PSI can cause a noise as the two regulators are fighting each other. The fix is to remove the regulator from the in tank pump somehow. Have you heard of this?

Last edited by D B Cooper; Tue Oct 04 2022 10:51 AM.

Dan

35 CC Case
38 Chevy Pickup
51 3100 AD
58 3100 Apache Fleetside
Joined: Mar 2007
Posts: 1,910
Crusty Old Sarge
DB, I installed a 4 brl Sniper EFI on my BIL's 57'. The fuel pump on it was extremely loud(loader than the flowmaster mufflers) and had an issue with keeping up with the engine under load. I found that the return line was restricting the flow and causing the pump to cavitate. I relocated the return line to the top of the tank, actually in the filler neck and remounted the lines (the tank has no access point to attach a return line). Since that point I have had no issues and the pump is quieted down considerably.


Craig

Come, Bleed or Blister something has got to give!!!
'59 Apache 31, 327 V8 (0.030 over), Muncie M20 4 Speed, GM 10 Bolt Rear... long term project (30 years and counting)
Joined: Sep 2015
Posts: 174
D
'Bolter
Excellent info, thank you. I will give that some consideration. Did either your pressure or return line pulsate?

I’m checking the fuel line routing and security this morning. After that I’ll pull the return line at the tank, stick in a gas can and see what kind of flow I’m getting.

Thanks again!


Dan

35 CC Case
38 Chevy Pickup
51 3100 AD
58 3100 Apache Fleetside
Joined: Mar 2007
Posts: 1,910
Crusty Old Sarge
No, not that you could tell. I would think that the line pulsating would indicate the pump was cavitating. Running the return to a separate container for testing should show you something.


Craig

Come, Bleed or Blister something has got to give!!!
'59 Apache 31, 327 V8 (0.030 over), Muncie M20 4 Speed, GM 10 Bolt Rear... long term project (30 years and counting)
Joined: Sep 2015
Posts: 174
D
'Bolter
I think I’ve found and corrected my noisy fuel pump issue.

With the engine running I felt and tugged on the fuel lines with no change in the pump noise until I got to engine compartment. The AN 6, pressure fuel hose attached between the engine and the steel fuel line at the frame rail could be moved and the noise would stop. The line was attached in a horizontal position. I situated the hose in a more vertical position and the noise and pressure line pulsation are mostly gone. Much quieter, cant hear it driving and only faintly with the hood open.

Attached a picture of the hose in its new position.

Attached Images

Dan

35 CC Case
38 Chevy Pickup
51 3100 AD
58 3100 Apache Fleetside
Joined: Mar 2007
Posts: 1,910
Crusty Old Sarge
I found with this system any restriction is going to cause these symptoms. It's a good system, just requires a lot of pre planning.


Craig

Come, Bleed or Blister something has got to give!!!
'59 Apache 31, 327 V8 (0.030 over), Muncie M20 4 Speed, GM 10 Bolt Rear... long term project (30 years and counting)
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