Lift pump...If...and what if....

[burn_your_money]

I talked to Giles about it, we'll see what we can do.

[rodpaslow]

My question is I have a extremely hard time keeping the return line (to pump) from leaking with a 5 psi pump.  Is it possible for the pump pressure to have increased?

[burn_your_money]

Internal pump pressure does increase when you add a lift pump. It sounds like you have a restricted return though.

Something to note, if you add a lift pump you will want to be careful not to blow up your filter. The stock filter is built for vacuum, I'm not sure how much pressure it can handle.

[rabbitman]

Internal pump pressure does increase when you add a lift pump. It sounds like you have a restricted return though.

Something to note, if you add a lift pump you will want to be careful not to blow up your filter. The stock filter is built for vacuum, I'm not sure how much pressure it can handle.

Come to think of it, I saw an old diagram once of the vw diesel fuel system and it showed a mechanical fuel pump like the carbureted gassers have, running off the IM shaft lobe.

The diesel IM shaft gear is cut opposite of the gasser ones, hence it's a different piece so it shouldn't have the lobe either, yet it does.....my guess is vw decided the lift pump wasn't needed and ditched it.

I'll see if I can find the pic again.

[Rabbit on Roids]

if i had a carb'd rabbit fuel pump, i would try and use it as a lift pump. it cant make much pressure, maybe a couple psi max..

[Vanagoner]

That's a great idea (if it'd work).  I have one I could pull off of a '73 audi 1.5 gasser, 827 block like ours.  New ones are still available and cheap though-

http://frugalmechanic.com/auto-part/1144380-bosch-fuel-pump-mech-68802

[burn_your_money]

Is that one pictured to proper one?

One disadvantage of a mechanical lift pump is it won't help prime a system like an electric one will

[diffdude]

Carter makes the lift pump for the cummins in the dodges. Here's a one that is set to 6psi with 72gph that should be more than enough.
 http://www.summitracing.com/parts/CRT-P4070/

[truckinwagen]

the gas and diesel camshafts are the same casting, they just have a different gear pressed on the end.
I doubt the carburetor mechanical pump would flow enough for our engines, as it is designed for a non-return fuel system(which flows very little)

[truckinwagen]

whoops, you are right.
silly me, I did indeed mean IM shafts.

[truckinwagen]

thanks for catching it for me.
school just started, and my brain is all over the place.

[rabbitman]

I found that diagram of the lift pump, I tried blowing it up a bit but alas, I failed :


Appears to me that there's a pressure regulator built into the fuel filter mount, probably not as handy for filling the IP as an electric pump is.

I found that here: http://www.vwdiesel.net/forum/index.php?topic=12943.0

[darrenjlobb]

Where can that filter assembly be got from...could make it much easier just running that filter...would sort the pressure problem..

[rabbitman]

Where can that filter assembly be got from...could make it much easier just running that filter...would sort the pressure problem..

No idea, that looks like something vw changed there mind on really early.

[54321chris]

I saw it mentioned that the Digifant pump sits in fuel to keep it cool.  Could I use it without the in-tank lift pump to prime my fuel lines, or will it overheat?  Is it otherwise a good idea?  I'm tired of breaking out the vacuum pump every time I want to drive the car...