Strange Fuel Pump Issue, Help please - FIXED! Options

[flat4tom]

Hello all,

Got my 914 back together today. Here's a list of what I've done since I brought it home...

Fixed front trunk release so it will open.
Pulled gas tank. Tank is clean, no rust, fuel sock there in good shape.
Replaced all fuel lines under tank.
Pulled injectors and sent them for servicing.
Replaced all vacuum hoses.
Tightened all intake runners down - they were loose.
Removed and cleaned the throttle body
Checked the TPS and adjusted
Replaced the throttle body, installed a new TB gasket.
Removed and fixed inoperative AAR.
Replaced the spark plugs with new NGK's
Reinstalled cleaned and serviced fuel injectors.
All new fuel hoses in the engine compartment.

She runs like a top now! No vacuum leaks. No missing. Idles smooth. Took her out for a spin and to get some gas. Has a strange issue now with the fuel pump.

The fuel pump has been relocated to the front under the gas tank - recommended relocation spot. I can now hear the pump running while the engine is running. Seemed like it was quieter before... anyway...

While driving down the road straight - all is good. If I make a turn to the left the fuel pump seems to cut out (the sound changes) and the engine starves for fuel.
Right turns, no problem. (IMG:style_emoticons/default/WTF.gif) If it's idling in the driveway and I turn the wheels, no problem - fuel pressure remains constant. I wish I could check my fuel pressure gauge while driving but it's mounted to a fuel rail.

Any thought why the pump would cut out on left turns?? Any suggestions on where to look for this?

I am so close to being able to drive her!!... (IMG:style_emoticons/default/driving.gif)

T.I.A.
Tom
'73 2.0

[Tom_T]

Check anything that could move in the direction of & under centrifugal force on a left turn - electrical connections, fuel lines/connectors, throttle body & FI tubes/runners, etc. Anything loose could open up under that force. If the EFI tubes were loose before, also check that the studs are stripped & pulling up under force. Same thing if something like the fuel tank is loose & shifting to pinch or squeeze a fuel supply line.

Centrif. force would be acting in the opposite direction of the turn - same direction as you get pushed in your seat when cornering fast! (IMG:style_emoticons/default/driving.gif)

It could also be the fuel pump itself, if not new or remanufactured recently.

[SUNAB914]

Pinched fuel line with weight shift?

[MecGen]

Hi
You know those little rubber lines on the bottom of the tank that you have to mess with to get the tank back in? if they are just a little too long they can get pinched, don't ask me how I know...don't know why only on right turns tho, hows the pump hooked up? wire extensions? maybe a loose connection.
Good luck
Frank

[TheCabinetmaker]

clogged fuel filter. Chashed that problem for a month before i got a new filter and all was good.

[Katmanken]

Noisy pump can mean there is a flow problem or a failing pump. Pinch the output hose on any pump or have a blocked filter, and the noise should go up. On the other hand, the pump relocation or new mounting system might make it seem noisier.

Definitely agree with the pinched line problem. Just fixed my son's Jetta yesterday by fixing a pinched section of plastic line. When he drove or cornered, the weight of the rubber line would fold a section in the high pressure plastic line and the engine would misfire. He was so happy when he called on his way home to tell me the misfire problem was gone

Per the noise, did you change the rubber mounts? A harder rubber will transmit more noise. One of the things I've been looking at is some VW cars mount the fuel pump in a foam container or box. The foam container holds the pump in place, the foam acts as a vibration damper, and absorbs noise.

[flat4tom]

Thx for the replies.

Some more info:

The fuel filter is new.
I did not relocate the fuel pump, it was already relocated to the front of the car.
No changes were made to the fuel pump or its mounting when I changed the lines.

It does seem to me to be either a fuel line is being pinched with weight shift, or the pump is going bad.

It did sit for 3 years without being run, so maybe something happened to the pump during that time...?

Thanks!
Tom

[Katmanken]

The problem might be the non-stock wiring added during the pump relocation. Start the engine and wiggle the wires at the pump and where they tie in to the factory wiring to see if it makes the problem come and go.

If that makes a change, there's your problem to fix.

Sitting for three years with old gas can cause varnish and crud to cake in your pump or rust to form in your tank. Did you drain your tank and get new gas?

[TheCabinetmaker]

sits for 3 years? Have you changed the filter? Or checked it? Rust forms in the tank. You drive, add gas, it sploshes around loosening the rust. First place rust goes? in the filter. The noise is (like kwales said) is caused by the pump starving for fuel. The fuel lubricates the pump, so it dies a premature death. The fact that it dies when you turn a corner means the fuel pump can't get enough fuel fast enough. You essentially "run out of gas".

[flat4tom]

The problem might be the non-stock wiring added during the pump relocation. Start the engine and wiggle the wires at the pump and where they tie in to the factory wiring to see if it makes the problem come and go.

If that makes a change, there's your problem to fix.

Sitting for three years with old gas can cause varnish and crud to cake in your pump or rust to form in your tank. Did you drain your tank and get new gas?

I did pull the tank to replace the lower fuel lines. They were all hard as rock and rotted. The tank is clean - no rust that I could see. The entire fuel system is new now with the exception of the pump. New filter, new lines under the tank, new lines in tunnel, new upper fuel lines in the engine compartment, cleaned and serviced fuel injectors. The car purrs now except when turning to the left when it chokes out.

I'm thinking either the pump is bad, or one of the replaced fuel lines is kinking, or almost fully kinked.

I'll be jacking up the front this weekend and take a look at the fuel lines looking for a kink in them. I'll also check the electrical connection to the pump.

After that...who knows. Probably replace the pump

Thx for the replies.
Tom

[Katmanken]

I think vgs914 is spot on

I guess one of the questions is: did you turn the tank upside down and shake it to look for rust?

Did you bang the sides of the tank to clean out the rust and crap?

If you didn't, the installation process might have knocked some crud loose that has filled up your new fuel filter.

I went through this with another vehicle. The symptoms were: Bosch pump got louder, the car bucked during corners or bumps , and the enormous downstream high pressure fuel filter got clogged. Replaced the $30 oil can sized filter, it ran better for awhile and the noise and symptoms started again. Then the pump died. I pulled the fuel inlet hose from the pump to drain the tank and to remove the pump, and rust flakes and crap came out with the gas into my milk jug.
Removed the broken pump and more than a cup of rust flakes and crap flowed out of my new downstream fuel filter... (IMG:style_emoticons/default/blink.gif)

Resorted to in car flushes of the tank with gas until the gas was clear, a new Pierburg pump, and a new high pressure downstream filter. After awhile, the new pump got noisy, the car bucked during corners or bumps, and I found rust flakes in the intake of the pump that were stopped by a small screen filter in the pump. Bosch and Pierburg pumps are OEM pumps used interchangeably by VW on their assembly lines, and the Bosch unit lacks the filter. I cleaned the screen in the pump, and added a low pressure upstream filter that had more area than the screen and the symptoms returned. That cheap 914 look alike low pressure filter was filled with crud and replaced. This happened repeatedly until I removed the tank and hosed out an enormous amount of crud at the car wash. Banging on the tank while washing flushed more crud.

All told, it was at least SIX fuel filters, a trip to the car wash to high pressure wash the tank, and a new pump until it ran right.

While an extreme case from a load of dirty fuel with clay and gas processor pump grindings in it, the symptoms seem awfully familiar.

I'd check the filter again. Even if it was just replaced.

Good luck.

[flat4tom]

Hello everyone,

Just to followup on my post and what I found this weekend.

All is well with my 914 now. As I suspected I found a pinched fuel line. The main supply line coming out of the tank was bent at too much of an angle and pinched the line.

I was able to pull the windshield washer tank and see the hose down there. I then reached down and pushed the hose down in under the tank more. Then from the bottom pulled the hose a bit more so it would open up.

I did look down into the tank and did not see any junk or rust in there.

Took it for a few test drives around the neighborhood (IMG:style_emoticons/default/driving.gif) It is running great after its 3 year sleep. Oh, and the fuel pump quieted back down.

Now, to get to the things I WANT to do to it!

Thanks for the replies.

Tom
'73 2.0