Vanagon Fuel Pump Cavitation Noise

[ibulib]

I’m hoping the Vanagon family can help.

I own 1986 Vanagon Westfalia with factory 2.1L and 112,000 original miles. In preparation for 2025 summer adventures, I had an experienced Vanagon repair shop replace original fuel tank in May 2025. Parts were sourced from GoWesty which included fuel tank, re-seal kit & fuel sending unit. The moment after starting my Vanagon at repair shop, cavitation noise was immediate. It was late and I hoped noise was due to low fuel or maybe contaminants from new fuel tank getting caught in fuel pump. I have been driving with cavitation noise since tank replacement. Due to the noise, I did not drive Vanagon far. Over the weekend, I decided to replace fuel pump and filter to fix cavitation noise. Unfortunately, cavitation noise is still present and have no idea what to do next.

Here is a timeline:
08/24 - replaced failed factory fuel pump with Hella fuel pump and fuel filter. I also replaced rubber fuel line from gas tank to black hard line and included new fuel pump rubber bushings. Zero fuel pump noise.
05/25 - replaced factory fuel tank with re-seal kit and fuel level sending unit. Cavitation noise after tank replacement was immediate.
11/25 - replaced Hella fuel pump with Bosch fuel pump and fuel filter. Cavitation noise is still present.

I’m open to any suggestions as this noise is driving me crazy. Please know I searched Samba for troubleshooting this issue and spent hours reviewing threads =(

[Chootrain470]

I've had multiple fuel pumps and they all make some noise. I just carry a spare just in case, but I haven't had one go bad yet. How loud is it? I usually can hear it when idling, but road noise drowns it out.

[E1]

Is the filter fore or aft of the fuel pump?

Plastic cube or metal canister?

I also wonder if for some reason there’s a clog between tank and filter or pump, though seems unlikely…

Have you removed the fuel line from the rear of the pump, run a line to an empty gallon jug, and watched the flow with just a moment of running the starter?

Even though not very likely, it’d be worth swabbing the inlet screen on the front of the pump.

It’d also be worth dumping a jug or two of HEET in the red container in case there’s any water in there. It happens even with fresh fuel and a new tank.
_________________
If ever twice as rich, we’re gettin’ a double-wide
’84 “Westfailure”/2.1 Digijet/5.43 Ring & Pinion/Peloquin/D-rated BFG KO2s

AI has spoken to further illiteracy, to steal, to cheat, and to replace humans
The caveman’s first question to the headhunter: “Hey, you got any coffee?”

[ibulib]

[ibulib]

[MarkWard]

Get a Jerry can, some fuel, and some hose the same diameter of the pump inlet. Set the jug in the side door and run the van off the jug. Noise gone? Issue with the tank. Noise present it’s not the tank. Short of a rig, you could try pressurizing the tank through the filler with compressed air, blow gun, and a rag. Doesn’t take much. Also see if the pump quiets with the filler cap off. Could be a vent issue.

I’ve not done this, but some owners have added a resistor to the pump power to lower the voltage and slow the pump.

[whatwrenchwhere]

I recently changed out some fuel line and the fuel filter, and drained the tank for this. And right after that I heard the humming from fuel pump for first time ever. I had put about 1.5 gallon of 87 octane gas in there when done.

I was reading another post, and they said ethanol free gas fixed there issue, something due to the weight/viscosity/composition of it. I usually run ethanol free, and never heard fuel pump humming before. Anyway, filled up with ethanol free, and no more humming.YMMV.
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'85 Westfalia, 1.9L 2wd Manual

[jlrftype7]

I 2nd Mark Wards post. At the very least , with no tools needed, run the Vanagon with the gas cap off to rule out a venting issue as your 1st step.
The line from the Charcoal Canister to the tank for breathing/venting is not large at all in diameter.

Also make sure the side to side cross over vent hose is routed OVER your shifter rod ( manual) or shift cable( automatic). If it was routed UNDER these, it will need to be corrected.
_________________
'68 Westy- my first VW and vehicle/Bus- long gone.- sold it to a traveling Swiss couple....
'67 Type 3 Fastback, my 2nd car- gone
'69 Semi-Auto Stick Shift Beetle-gone
2017 MINI Coopers, our current DDs
‘84 Tin Top - Hilga....Auto

[sanchius]

[MarkWard]

[sanchius]

[SoquelDude]

Hi!

There's been talk of adding a resistor to the ground on the fuel pump to effectively slow the pump down to match the fuel flow. That trick seems to work and is described in may threads on Samba, such as this one:

https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0

Good luck!
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'90 Vanagon Westy GL, AT, EJ22E conversion (1993 2.2L Legacy Engine)

[E1]

[MarkWard]

Actually the cavitation is physics. The restriction causes vacuum to go up in the inlet to the point that the fuel vaporizes sort of like an ac vacuum pump. The fuel is boiling essentially. Those bubbles enter the inlet causing the noise.

It’s interesting the non alcohol fuel solved the noise. Assuming different vapor points.

[SoquelDude]

[E1]

It’s all in the Ear of the Beholder.

Related addendum… whenever I’ve heard serious pump noise — for sure a dozen times or more over the years — the pump has ALWAYS been hot.

When running normally, it’s been barely above air temperature.
_________________
If ever twice as rich, we’re gettin’ a double-wide
’84 “Westfailure”/2.1 Digijet/5.43 Ring & Pinion/Peloquin/D-rated BFG KO2s

AI has spoken to further illiteracy, to steal, to cheat, and to replace humans
The caveman’s first question to the headhunter: “Hey, you got any coffee?”

[SoquelDude]

[MarkWard]

Cavitation can destroy a water pump. I rebuilt lift station pumps as a side business many moons ago. These are impeller type pumps. The Vanagon pump is a roller design I believe. It does depend on fuel to cool and lubricate the pump, so probably not good for them.

[E1]

[SoquelDude]