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Thread: Fuel Pump Noise

  1. #1

    Default Fuel Pump Noise

    I'm in the process of installing the Sniper system into my TR8 and I just finished plumbing the external fuel accumulator and the Holley fuel pump for it in the rear near the fuel tank. I tested it using just a loop back line and the fuel pump is really loud. Easily audible inside the car. Will it get quiet when the system is at 70 psi or have people had to do other things to suppress the noise?

    I have a manual fuel pump override button to prime the fuel accumulator should I ever run out of gas. A fuel accumulator is required to prevent low fuel tank level starvation around corners for tanks that were not FI to begin with and hence have no internal swirl pot. Holley does not even mention this problem in their installation documentation, but it is very real.
    Last edited by Floobydust; 07-27-2021 at 01:50 PM.

  2. #2
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    Default

    This is just a copy & paste of one of my other posts:
    Originally Posted by Danny Cabral
    A loud fuel pump is usually an indication of fuel pump cavitation or maybe a clogged filter(s). Inspect/troubleshoot/service the fuel system (fuel pump, cavitation, plumbing, voltage, filters, pickup tube, tank venting, etc.). A datalog will just verify a problem with the fuel pressure, injector duty cycle, pulse width, etc.

    An EFI fuel system needs two filters:
    Before fuel pump - 100 micron pre-filter. (Or the OEM in-tank sock filter.)
    After fuel pump - 10 micron post-filter. (40 micron is for carburetion.)
    The 40 micron (carburetor) fuel filter has no place on an EFI fuel system. (I know you're not using it.)
    It's too "fine" of a filter to be used before the pump, causing fuel pump cavitation.
    FYI: The sock filter (HydraMat or OEM) of an in-tank fuel pump, is the pre-filter. Don't add another one.
    http://documents.holley.com/holleyfu...ems_chart1.pdf (Fuel System Selection Chart)
    http://documents.holley.com/flyer_ho...el_systems.pdf (Holley Fuel Systems Brochure)
    https://forums.holley.com/showthread...395#post223395 (Related Forum Thread - NAPA 20 Micron Pre-Filter)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Holley Dominator MPFI & DIS, 36-1 crank trigger, 1x cam sync, 200A 3G alternator, Optima Red battery, R134a A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans, Frostbite 3-core aluminum radiator, Pypes dual 2.5" exhaust, off-road X-pipe, shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, BMR upper & lower torque box reinforcements, LenTech Strip Terminator wide-ratio AOD, 3000 RPM converter, B&M Hammer shifter, Stifflers trans crossmember & driveshaft safety loop, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

  3. #3
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    Default

    Yeah, people put the pump in the tank. The DB will come down when under psi. You could test it with an external fuel pressure regulator.

  4. #4

    Default

    Thank you all. The filters are all new and as they should be. The in-tank pump fills the accumulator via its sock. Fuel circulates from the tank to the accumulator and back through a return line to the tank. The Holley pump has the Wix 100 micron filter on the input and the 10 micron filter on the output. The Sniper fuel circulates from the accumulator, to the Sniper, and then back to the accumulator. This system worked silently and perfectly with the TBI setup for 15 years.

    The TR8 has the tank above the rear axle between the trunk and the rear of the passenger compartment in the usual European safety minded fashion. This means the pump is much closer to the passenger's compartment than with the typical tank location under the trunk by the rear bumper. I'm going to mount the Sniper and just connect the fuel lines. I'll then use the manual fuel button to pressurize the system and see how loud it is. I'll report back.

    Well, I mounted the Sniper body, connected the fuel lines and used my manual fuel pump relay button to pressurize the system and and only got to about 25 psi before the pump started to make some really ugly noises. I did not let it go all the way to 60 psi because it's late tonight and I don't want to risk a leak. Tomorrow I'll take it all the way up and measure the voltage at the pump terminals, but in the mean time I have two questions. Is the Holley pump a positive displacement pump and/or does it have an internal check valve? The pressure that I did achieve has not bled down, so it has to be one or the other or both. BTW, the in-tank pump is a low pressure turbine pump. Thanks!

  5. #5
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    It sounds to me like you have a plumbing issue. There's no check valve in the pump. Where is your fuel pressure regulator? The basic Sniper has an internal regulator. You could draw your system (post your drawing here) and take pics to post here and we'll take a look.

  6. #6
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    The fuel accumulator is probably what's causing the problem.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Holley Dominator MPFI & DIS, 36-1 crank trigger, 1x cam sync, 200A 3G alternator, Optima Red battery, R134a A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans, Frostbite 3-core aluminum radiator, Pypes dual 2.5" exhaust, off-road X-pipe, shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, BMR upper & lower torque box reinforcements, LenTech Strip Terminator wide-ratio AOD, 3000 RPM converter, B&M Hammer shifter, Stifflers trans crossmember & driveshaft safety loop, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

  7. #7

    Default

    I've attached a fuel flow diagram and a picture of the accumulator itself for you to look at. This same setup worked perfectly for 15 years with my GM TBI system. All I did to prepare it for the Sniper is to upgrade the under-chassis steel fuel line to 3/8" instead of 5/16" and replace the filters and pump with the Holley pump and filters. The Holley pump replaced the GM FI pump.

    I suspect that the Holley pump may be drawing significantly more current that the GM pump (Holley tech support couldn't tell me how much it draws), so I'll measure the terminal voltage at the Holley pump under load.
    Click image for larger version. 

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  8. #8
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    Check free flow from the Sniper by disconnecting your connection at the accumulator. If it's flowing fine there, your problem is most likely the accumulator. What are the dimensions of that accumulator? The Holley pump very well could be sucking it dry and trying to pull fuel through the in tank pump.

  9. #9

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    @a b c: I think you're correct. During the priming process with a totally dry system, the Holley pump was sucking air for a while. I ran the system for a while using the manual override and the pump began making a "normal" pump noise and the pressure stabilized at 60 psi. The pump noise level, however, is still unacceptably loud, so I'm going to have to mitigate this somehow. Maybe sound deadening wrapping or maybe change to a German made Bosch pump (my G-Wagen has two external pumps that are totally silent).

    I did note that the pump voltage was only about 8 volts at pressure. The Holley harness assumes battery in front and pump in the rear. I have the battery in the back and the pump in the back, so there is a big wiring loop that's contributing to the voltage drop.

    I'm going to modify the harness to move the pump relay to the rear by extending the relay control lead. This will allow the pump to feed almost directly from the battery, so the voltage should be acceptable. I'll also include an interface to the factory harness to power the in-tank pump as well. This will also eliminate any voltage drop to the ECU.

    I'm also going to add a Kaehler Over Voltage Relay (yes, an MB part) to protect the Sniper ECU from voltage spikes and VR failure over voltage. The Kaehler will also provide a super clean "run/start" +12V signal for the ECU and any other loads (like a HyperSpark distributor) that will require it.

    On my original TBI install, I used GM Weather-Pack connectors for all connections between the FI system harness and the chassis and engine harnesses. I still have the mating connectors which I'll fit to the Holley harness so it'll literally be plug and play to hook up. I have also designed a transistor inverter circuit that will fit in the harness to deal with the asinine Holley ground start A/C input (e.g. no relay required).

    I'll get all of this done and then go back and revisit the pump noise since the Holley pump is providing correct, but noisy, fuel flow now.
    Last edited by Floobydust; 07-31-2021 at 07:29 AM.

  10. #10
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    It may be as simple as remembering noise is a vibration. Solve and or isolate the vibration and you change or isolate the noise.

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