Home-made fuel pump rebuilding jig

[wcfvw69]

[Who.Me?]

[wcfvw69]

[Who.Me?]

[Who.Me?]

I got the diaphragm modified in the week. Reassembled it this afternoon.

It still seems very stiff. I can only just get the shaft to move if I actuate the pump foot by hand. It feels a lot stiffer than the one I've just taken off the truck.

I certainly wouldn't be able to get it to pump like Kdavid did in this thread...
https://www.thesamba.com/vw/forum/viewtopic.php?t=638589&start=160
His picture...

Should I be able to pump it that easily?

I've mounted it back up in the jig on the off-chance it'll stretch the diaphragm a little overnight.

It feels like if it takes that much force, the push rod will wear on the distributor shaft cam?
_________________
Andy


Looking for info on my truck's history. Are you from Campbell California or nearby. Do you recognise it? ... http://www.thesamba.com/vw/forum/viewtopic.php?t=636786

[kreemoweet]

Just a heads-up for anyone interested in this subject: recently there were links posted on thesamba to downloadable pdf's of
a large collection of VW Workshop Manuals. I've been looking through some of those, and noticed that everywhere the
setting of the fuel pump diaphragm preload was mentioned (for the 40-54 hp mechanical pumps), it was spec'd as 13 (thirteen) millimeters,
not the 14 (fourteen) mm that has been repeated numerous times since the beginning of this thread (and elsewhere too). So, it seems
that either the 14 mm figure is an error, or else there is a contradiction if there actually exists an authoritative source for that number (which I've
never seen).
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[wcfvw69]

I have this factory preload tool. I noticed it's pin is at least 14MM above the base. I need to measure it. I went to preload a pump I was rebuilding. It was clear that I couldn't tighten the pump base down fully on that tool as it put way too much pressure pulling the main diaphragm assembly down into the body of the pump.

I need to remove some material off the pin on this factory tool to get it down to 13mm. I've preset many pumps diaphragms with a pin in a vise sticking up 13mm. It works perfect at the height. 14MM is too much.
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Decades of VW and VW parts restoration experience.
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[McGuirk]

My blue Bentley 1200 61-65 manual says under Reconditioning Fuel Pump, Assembly:

"4. Place lower half of fuel pump in a vice with the Gauge VW 328d inserted. Thus the rocker arm is pressed in 14 mm (from flange jointing face), bringing the diaphragm to the required assembling position."

Which manuals say 13mm?

[kreemoweet]

[McGuirk]

Interesting. The VW pre-load tool is different too...I'm assuming VW 797/2 is 13mm and VW 328 d is 14mm.

I don't know enough about the different models of Pierburgs, but just looking through the galleries I found a picture of a 1500 fuel pump that looks like the one in that K manual. Do you know what year that was from? Maybe the preload was changed for later fuel pumps.

[wcfvw69]

[Who.Me?]

Update - I wasn't happy with the modified diaphragm. Everything felt too tight so I bit the bullet and imported one of WW's new diaphragms.

After shipping and import taxes to the UK, it was ridiculously expensive, but it fitted perfectly. After assembly, I could pump it by hand.

Checked the pressure today with one gasket above and below the pedestal. I'm only getting 2psi, according to my pressure tester. At W.O.T that comes down to just over 1.9psi. On shut down, the pressure drops immediately to 0.

I'm running a Solex 34-PICT-3 that was professionally rebuilt about 500-600 miles ago. From what I've found online I believe it needs 3 - 5psi.

The engine (1600 DP) ran fine at idle and W.O.T, but that's static in my driveway. Will I have starvation problems on the road, e.g. if I run at speed for a while, or under load?

I set preload at 13mm as per the above (square topped Pierburg). The generator push rod I have was 107mm long though. From reading online, I think it should be 108mm. It was a new part, not worn.

Would it be sensible to try rebuilding the pump with 12mm preload to account for the rod length, or just run it and see if the (relatively) fresh carb is happy with 2psi?

Thanks

Andy
_________________
Andy


Looking for info on my truck's history. Are you from Campbell California or nearby. Do you recognise it? ... http://www.thesamba.com/vw/forum/viewtopic.php?t=636786

[wcfvw69]

[Who.Me?]

[wcfvw69]

[kreemoweet]

The pump diaphragm preload has nothing to do with the output pressure. It's a safety measure to ensure the diaphragm is not ruptured by being pulled
on too hard. A ruptured diaphragm could quickly turn your vehicle into a big ball of fire.

The 3-5 psi output pressure given in the Bentley manuals is somewhat suspect, as many have reported no problems running with considerably less output pressure, on the same engines
with the same carbs.

As long as the pump volume output meets the specced 400 cc/min @ 3800-4000 rpm, which seems more than any stock engine would use, there should be no problem. If output
nevertheless seems insufficent, a thinner (or no) washer under the carb float valve could make things right.
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'67 bug: seized by the authorities
'68 bug: seized by the authorities
'71 kombi: not yet seized by the authorities

Stop dead photo links! Post your photos to The Samba Gallery!

[randydog]

whittle 14 mm piece of wood that fits the bottom of fuel pump,insert 14 mm wood chip, push pump down flush with flat surface, tighten screws. WA-la!

[wcfvw69]

[kreemoweet]

[Who.Me?]