BearKiller

This question came up around the dinner-table, yesterday.

The standard as-issued diaphragm lift-pump can leak fuel into the crank-case, either extremely slowly, or by the gallon, depending on the size of the rupture.

As it has no diaphragm, can a piston lift-pump leak fuel into the crank-case??

I would assume that it would be possible for a piston-pump to leak; but, I also assume that it would be highly unlikely.

Please enlighten me on this.

Thanks.
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Question #2.

I need the Cummins part-number for the 3936320/4944714 piston-pump rebuild kit.

I will be at a Cummins distributor, tomorrow, and would like to go armed with a correct part-number.

Thanks.

Ace

I suppose it is theoretically possible. But the seals would have to be so bad it would have stopped pumping a long time before any appreciable amount of fuel could seep through.

I think one of the root issues behind alot of fuel realted problems on these fuel systems is that the VE will pull enough fuel on it's own to keep running. This can mask a bad diaphragm pump, and is one reason a fuel pressure gauge is nice to have. But a bad piston pump would prevent it from getting any fuel at all, or at least slow it down enough to make it quit or run really bad. The piston pump basically won't flow unless it it is pumping, whereas the diaphragm pump will allow flow when it's inop.

BearKiller

That is about like I was thinking.


Another question, while we're talking lift-pumps.

Is there something that can be smeared/sprayed on the pump gaskets (or any gasket, for that matter) to permit them to come away un-harmed, should the pump need be removed for any reason, even years later??

Thanks.

BearKiller

I asked the parts man at the Cummins shop about a rebuild kit for the piston pumps, or a replacement pressure spring, and he informed me that Cummins did not supply pump rebuild kits or springs.

The pump is a CARTER; so, maybe I need to check with CARTER and see what they have to say about it.

It is no biggie; but, if a kit can be had that will convert a piston pump not meant for a Bosch VE to the correct pressure, at a bargain, it would be worth looking into.

wannadiesel

He's full of it. I'd give you the part number but I lent out the book that has it and the guy is still using it.

BearKiller

YEAH, or just afraid it might take a couple minutes of his time to look it up.

wannadiesel

Probably the second one.