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Tue Jun 27, 2023 12:54 pm

My VW stalls sometimes after running for 25-30 minutes and it will run fine again a 5-30 minutes after cooling down. It's especially bad when it's warm and I drive in the city (lots of stop-and-go traffic).

My fuel pump is pretty hot. You can touch it briefly, but putting your finger longer than 1s on top of it is no fun. The fuel pump hasn't been revised or detached from the engine the past 30 years. I thought that this spacer's main function is to prevent the fuel pump from heating up.

Heating up the fuel pump may cause vapor lock, but I suspect that the fuel rod that drives the fuel pump gets stuck. So I disconnected the fuel line at the carberator. When I turn off the ignition and start the engine, then normally it spits out some gasoline during every turn. When the engine stalled, then no gasoline came out of the fuel line. That's why I suspect the rod is stuck.

During my last oil change, I thought the oil had a little gasoline smell to it. I already plan to check the spacer and rod for damage, so I have to disconnect the fuel pump. I guess if it's leaking gasoline, then all grease should have disappeared from the underside of the pump?

Can I simply open up the fuel pump (6 screws) and check the rubber? I don't have a fuel pressure gauge, so I rather not tamper with it too much. Or do I already have to check the fuel pressure after replacing the spacer and gaskets?

Tue Jun 27, 2023 7:43 pm

hi rdk,
30 years is a long life for a fuel pump diaphram. a few years ago I was sent a fuel pump to rebuild that had the same symptoms as yours. I replaced the diaphram, set the preload and this was the result: "You rebuilt my '56 sedan fuel pump a couple years ago. I just wanted to say "THANKS" again. Whenever I take the car out for a drive it is a dream to drive. Like a new car. It was such a nightmare to drive when I would be going along and it would start cutting out. Scary in traffic! Now it just purrs along."
the smell of gasoline in the oil is another indication the diaphragm has a pin-hole that opens up with temperature increase.
yes, you can take the screws out of the pump cover, turn the engine by hand (generator) to verify the push rod is actuating (diaphragm going up and down). before securing the cover, the diaphram should be in a slightly concave position

Darryl

Wed Jun 28, 2023 9:20 am

But, like Darryl says, the diaphragm needs a preload. So, if all you do is take the six screws out and swap out the diaphragm, rotate the engine enough to get the pump pushrod to its highest point before you reassemble. This will give you the correct preload.

It is possible that the push rod is in fact sticking a bit so you would need to remove the entire pump and pull that out and make sure the block allows the rod to slide in and out with no binding. Pack the block with some good grease and reinstall.

Wed Jun 28, 2023 1:35 pm

You set the preload with this:
https://www.thesamba.com/vw/classifieds/detail.php?id=2586960

Wed Jun 28, 2023 2:43 pm

dmooresc wrote: yes, you can take the screws out of the pump cover, turn the engine by hand (generator) to verify the push rod is actuating (diaphragm going up and down). before securing the cover, the diaphram should be in a slightly concave position
I have removed the fuel-pump and the push rod looks fine and smooth. Also the flange came out easily and looks in perfect condition. I did sandpaper the rod a little to remove some stains.

The bottom chamber of the fuel pump had no grease at all. Also the mechanism seems to be rusty, so it's without grease for already a long time. After disassembling the fuel pump, I took out the diaphragm and it looks in good health, but the spring is rusty too. Everything does seem to work though.

I didn't get a new diaphragm and I don't have a fuel-pressure meter, so I put everything back together and installed it again. I put the bottom chamber of the fuel pump full of grease and also I put some grease in the left-side chamber of the flange. Then I put only a tiny bit of grease on the push rod and put it all back together.

I did use a very thin layer of silicone based sealant on both gaskets (both sides) before installing everything. I only bought a single gasket set (2 pieces), but I noticed there were two gaskets at the engine side. Not sure if the fuel pressure would be too high now.

I intend to drive the car for a few hundred miles and disassemble the fuel-pump again to check if the grease has disappeared. If it does, then it's time for a rebuild. I guess I will also need to flush the oil, because it would have dissolved quite a bit of fuel and grease.

I can buy a rebuild kit from Paruzzi, but I have heard mixed stories about it. The diaphragm looks completely different. The Paruzzi diaphragm seems just a single flag of rubber, whereas my diaphragm has a two layer rubber in the middle and is probably a lot more flexible. Also the rebuild kit misses the rocker-arm mechanism. I guess it's the rebranded rebuild kit of Wolfsburg West. I also found this rebuild kit, that does seem to have the rocker arm parts.

PS: I just read that I needed to set the preload. I didn't do that. I just inserted the diaphragm and screwed it all back together. I did run the car a few minutes (idling) and it all seems to work fine. What's the reason for applying a pre-load before putting on the top? Is it to prevent the diaphragm from being damaged (it may get between the two parts)?

Actual questions:
- Should I reassemble again and now use the proper preload or will the diaphragm already been damaged (I already ran the car for a few minutes)?
- Does anyone has experience with the mentioned rebuild kits?
- Can I run the car to test if the diaphragm is actually leaking or should I first do a full rebuild?

Wed Jun 28, 2023 2:49 pm

heimlich wrote: You set the preload with this:
https://www.thesamba.com/vw/classifieds/detail.php?id=2586960
I don't see such a tool in Europe, but I guess I can easily made using a piece of wood, 3 bolts and 2 nuts. I guess I'll be fine as long as the center bolt is 35mm outside the wood.

I guess, I'll first try to turn the engine so the rod is pointing outwards and then re-install the top plate.

Wed Jun 28, 2023 2:53 pm

rdk_1973 wrote: heimlich wrote: You set the preload with this:
https://www.thesamba.com/vw/classifieds/detail.php?id=2586960
I don't see such a tool in Europe, but I guess I can easily made using a piece of wood, 3 bolts and 2 nuts. I guess I'll be fine as long as the center bolt is 35mm outside the wood.

I guess, I'll first try to turn the engine so the rod is pointing outwards and then re-install the top plate.

I ship to Europe. It's around $20 for shipping. These are made from solid metal.

Wed Jun 28, 2023 7:57 pm

the pump I rebuilt (testamony above), I could not find a leak in the diaphram, but I replaced it and the problem disappeared. the preload process allows the diaphram to lay flat while being clamped by the cover and 6 screws
here is the factory explanation:

Thu Jun 29, 2023 1:24 am

dmooresc wrote: the pump I rebuilt (testamony above), I could not find a leak in the diaphram, but I replaced it and the problem disappeared. the preload process allows the diaphram to lay flat while being clamped by the cover and 6 screws
here is the factory explanation:

I do have the 1952-1957 workshop manual, but I just missed the part about bringing the diaphragm down before assembly. Thanks for pointing that out.

Which manual do you have? I noticed that it differs a little from your description. My manual is missing the part "Drain holes at the flange of earlier fuel pumps must be plugged up to avoid egress of the lubricant". I reinstalled my old flange, because it was in perfectly fine condition. It did have an open drain hole and I didn't close it, because it's not in my manual. I didn't take a picture, but it looks like I have an pretty old flange. This is what's in my manual (it misses the sentence in your manual, just before the second highlighted part):

Because the grease may become liquid during higher engine temperatures, it may also drained through the drain hole, but that's just speculating. After 30 years the rubber diaphragm may be shot and having a diaphragm that sustains modern gasoline is useful too. I always try to fill up with Ethanol-free gasoline, but in The Netherlands there can be up to 5% of Ethanol in there.

I will order a new rebuild set that includes both a new diaphragm and rocker arm and rebuild according to spec. Although the diaphragm looks fine, it may leak between the metal plates. I already have a new flange (without a draining hole) and will probably install that one and save this one. Nice to see that my car has plenty of original parts.

This is how my fuel-pump came out. No grease at all:

Thanks for your remarks. It's highly appreciated.