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SU Fuel Pump

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Nunyas

Nunyas

Yoda
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I tried to reintegrate my SU pump into the Bs system today. I found it's leaking from the diaphragm area. So I disassembled the pump and found that the diaphragm has a plastic film on it. Is that normal?

I ordered a new diaphragm already. But now I'm kind of wondering if I can fix the leak without the new part, by maybe spreading a thin film of Permatex blue RTV. Opinions?
 
Hello Rob,

yes, from memory, I think that is normal and yes I believe a gasket sealer such as you mention would do the trick.
If you haven't unscrewed the diaphragm from the actuating spindle then I would go ahead and reassemble with the sealant.

There is a specific number of turns that the diaphragm has to be screwed onto the spindle to get the pump to work, so I hope that you have that information when you come to replace the diaphragm. I'm afraid that I don't have that information at this time.

Alec
 
ACK! I unscrewed the diaphragm from the actuator, and didn't count the turns... ugh...


time to search the forum for that thread on rebuilding SU Pumps.
 
Rob - "ACK! I unscrewed the diaphragm from the actuator, and didn't count the turns... ugh..." Naughty, naughty, for that the gods of SU will certainly punish you. All is not lost - e-mail me and I'll send you an assembly and adjustment procedure put out by said, same gods (AKA Burlen Fuel Systems), but only if you will promise to throw away your tube of RTV and never, ever consider using it anywhere in the presence of petroleum products. It has a nasty habit of swelling in the presence of gas and oil, oozing out from the joints and forming little balls that gum up everything. If you must use a joint sealer (and it really isn't necessary on the fuel pump), use something like Rectoseal or Permatex #2, but use it VERY sparingly.

There was a time when a plastic film was put over the main diaphragm material, but it is no longer used. I have found that it often interferes with the smooth operation of the pump and when it does so, I remove it with no detrimental effects. The new diaphragm that you get will not have the plastic film.

There is one gasket that will sometimes leak, making it look like the diaphragm is leaking, but most of the time, the leak is caused by loose screws attaching the coil housing to the pump body. When you put the pump back together, use some #10 lock washers under the screws to insure that they don't loosen again.
Cheers,
 
Thanks for all the help everyone! I got the pump back on and all seems well for now.

I reassembled the pump last night and applied a thin film of Blue Permatex to all the gasket surfaces. I also found that all I had to do to get the proper distance for the diaphragm was: screw the diaphragm in a good distance. Then unscrew the diaphragm a little, push the diaphragm down, and watch the linkage. Then repeated that step until the linkage moved through its full range of motion.

I let the Permatex set up over night, and installed the pump this morning. I then switched on the ignition, and listened to the pump. I was clicking away like there was no tomorrow. I figured that was because the pump wasn't "primed". So, with the iggy still on and the pump clicking away, I removed the gas cap and proceeded to give the fuel tank mouth to filler resuscitation. I was able to build up enough pressure in the tank to force the fuel up to the pump. At which point, the pump began to build up pressure and eventually stopped ticking. Once pressure in the fuel lines was built up, I checked for leaks and didn't find any.

I went for a drive around the mountain, and all seemed well on the drive. When I got back, I checked again for leaks and found none.
 
Now we will see if that blue permatex holds up in direct contact with the fuel.

Nice going.
 
erm... It just dawned on me that I was able to build up air pressure in the fuel tank. My B is a 1976 model, and has a "sealed" gas cap. I know it has a gas vapor separator and is plumbed all the way to the charcoal canister under the hood. So, in theory, building up air pressure in the fuel tank should not have been possible.... right?

The last time I checked I was able to blow air through the vapor system back towards the fuel tank.

After today, I am now wondering if my fuel tank is not connected to the vapor separator like it's supposed to be. And I think I can see why the gas pumps at gas stations never let me pump gas into the car at full tilt.

Any one familiar with connecting the vapor separator to the fuel tank?

Or suggestions on stealthily "ventilating" a gas cap?
 
Hehe, use an early model cap.
 
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