Fuel Pump Not putting out much. Can it be adjusted?

[Jim Ed]

I have the fuel filter located between the fuel pump and the carb. I know it's a no no.
It is one of those clear filters.
It does not look like much gas is coming into it at idle speed.
Usually in the past they have been about at least 1/4 full of fuel at idle.

It is a Brocar for alternator style pump on a stock '73 Beetle.
Can this fuel pump be adjusted by removing the spring and stretching it a little or
should I buy a new fuel pump and try my luck with it?
Thanks In Advance!

I will check the fuel pump pressure at the next opportunity.
I ordered another fuel pump for a spare.

[Marc]

The fuel level in the inline filter is no indicator of the fuel pump performance. The outlet tube of the filter extends down inside the paper media towards the inlet end, so an air bubble will always be trapped in there.
Early fuel pumps were designed to be rebuildable but not so the modern ones...but even on a rebuildable pump it's not wise to go tampering with the spring pressure when you don't have a clue.

Do you have any actual symptoms of a fuel delivery problem?

More often than not if the pump isn't putting out as much as it should the problem is a restricted pickup screen in the bottom of the tank, or something's wrong with the vent system so the pump's trying to draw a vacuum on the tank. The latter problem's easy to confirm, after the engine's been running for a while there should NOT be a sucking sound when you open the gas cap.

Be aware that when generators were introduced in `73 the fuel pump design was changed for better clearance. These "low-pivot" pumps take an 8mm shorter pushrod than the "generator" pumps; use a short rod in a pump that takes a long one and you'll get low output, vise-versa will destroy the pump.

http://www.1800vw.bizhosting.com/fuelpumps.htm

[Steve C]

Hi

Good advice above, have a look underneath the car for other filters in line, they could be blocked if your having a fuelling issue.

Its best to fit the filter under the tank or between chassis and motor, its a pain to get to. We have to look after these cars, there not making any more of them.

Steve

[aussiebug]

Jim,

It's easy enough to look at the output of the pump - just remove the tube from the carb and place it in a clear bottle. Pull the black lead off the + terminal on the coil so the engine wont start. Get someone to crank the engine and watch the end of the tube inside the clear bottle. You should see a nice strong squirt-squirt and not a dribble-dribble. The pump works off the cam shaft so it pumps every second engine rotation - the individual squirts are quite visible.

The pump is designed to pump about twice the volume the engine needs at full throttle, so it's rare to find one which is not pumping enough for the engine to run normally.

As Marc says, the clear filters should not fill up when installed, because the outlet is down inside the filter paper. But as the filter does it's job and starts to clog, the fuel has to climb higher to find fresh filter paper, so the filter itself tells you when it needs changing.... it will be full - the fuel is climbing right to the top of the filter paper.

If the filter is lying on it's side this will still work, but when fresh it have more fuel in it than when standing upright - about 1/2 full to start with.

As you say, putting the filter between the pump and the carb is not the best location. Putting it before the pump means the pump gets nice clean fuel to work with, and the inlet in the top of the carby won't be subject to the extra weight of the filter jiggling about - many VW engine fires occur because that inlet pipe in the top of the carby is just a push fit into the carb metal. So move the filter please. Whilst you are at it - tug on the brass inlet pipe to see if it's still snug in the top of the carby. If it comes out, our web site below has is a simple procedure for securing.

[Jim Ed]

As you say, putting the filter between the pump and the carb is not the best location. Putting it before the pump means the pump gets nice clean fuel to work with, and the inlet in the top of the carby won't be subject to the extra weight of the filter jiggling about - many VW engine fires occur because that inlet pipe in the top of the carby is just a push fit into the carb metal. So move the filter please. Whilst you are at it - tug on the brass inlet pipe to see if it's still snug in the top of the carby. If it comes out, our web site below has is a simple procedure for securing.

Thanks Rob and thanks for keeping vw-resource.com online for us.

[Jim Ed]

I have the fuel filter located between the fuel pump and the carb. I know it's a no no.
It is one of those clear filters.
It does not look like much gas is coming into it at idle speed.
Usually in the past they have been about at least 1/4 full of fuel at idle.
It is a Brocar for alternator style pump on a stock '73 Beetle.
Thanks In Advance!
I will check the fuel pump pressure at the next opportunity.
I ordered another fuel pump for a spare.

Today I finally checked the fuel pump output pressure.
It measured close to 3.5 p.s.i. on my Actron vac/fuel pump tester.
So, I decided to keep using that fuel pump and keep the new one for a spare.

[surfbeetle]

Gene Berg did a write up on the stock VW bug fuel pump. The way to adjust the output of the fuel pump is with the rod in the block that pushes on the bottom of the pump. You get a longer or shorter rod to increase or decrease the pump's ability to supply fuel. Each pump is different, you could get a new one and still not have enough output if you did not match up the rod correctly. If you don't want to mess with all of this, just get an electric pump instead.

[aussiebug]

Well yes - you could mess about with the pushrod length to change the stroke of the pump - within the limits of the stroke on the pump's arm. There are two stock lengths - a longer one for the older upright pump design and a shorter rod for the squat canted pump used on the alternator equiped bugs (and can be retro fitted to the earlier bugs together with it's shorter pushrod). Those rods are not interchangeable for the different pumps - the shorter rod will not operate the older upright pump enough, and the longer pump rod is too long for the newer style squat pump.

A non standard fractionally longer pushrod would certainly change the max volume per stroke, but of course it won't change the pressure, since that is set by the return spring on the pump's operating arm. The pump rod only lifts the arm and sucks more fuel into the pump chamber - the spring pushing the pump arm back down provides the flow up to the carb. This makes the mecahnical pump self regulating - if the engine is using less fuel, the float in the carb does not drop much, so the pump arm does not descend much and it gets only a short push back up from the pushrod, but if the fuel flow increases (more power being used) the pump chamber empties more into the carb with each stroke and the pump arm descends more for a longer stroke from the pushrod. And since the pump should produce a max volume about twice that which the engine needs at full noise, it should not be necessary to alter the pump rod length at all.

If you fit an electric pump, it should operate at around 3 psi - similar to the stock pump. If the pressure is too high it will overpower the needle valve in the top of the carby and increase the height of the fuel in the float bowl, which will mess up the mixture settings.

[Jim Ed]

Well yes - you could mess about with the pushrod length to change the stroke of the pump - within the limits of the stroke on the pump's arm. There are two stock lengths - a longer one for the older upright pump design and a shorter rod for the squat canted pump used on the alternator equiped bugs

Thanks Rob.
It has the shorter of the two push rods with the shorty style fuel pump.
I tested it and it has about 3.5 p.s.i. fuel pressure. It runs fine.

[Jim Ed]

It has the shorty style fuel pump to fit under the alternator.

Instead of sanding down the bake light flange for extra pressure I suppose you could shorten one of the long push rods for the fuel pump for generator until it is just a little longer than a push rod for the shorty fuel pump.

[ched]

I have read two different recommendations on the max push rod height above the bakelite flange one recommendation is 13 mm another fro Dave is 4-5 mm. Which is correct I have the shorty pump with alternator

[aussiebug]

3-5 mm is correct.

[ainokea]

One method to the identity of the fuel pump's pushrod is to look at the fuel pumps pivot arm position. If the pivot arm is exposed and angled down it will need a 100mm pushrod. If the pivot arm is not exposed as above, it takes a 108mm pushrod.