lift pump - PeachParts Mercedes-Benz Forum

Mark in NJ · #1 11-28-2005, 04:57 PM

My lift pump seems to have stopped delivering fuel, and when I tried the primer pump, it would pump one stroke and then nothing else.

So, I replaced it with a cheap "facet-purelator" pump that I had. The car seems to run fine now. Same fuel lines and filters, getting about 4lbs of pressure before the IP regardless of engine speed or load.

Any suggestions or comments?

My original lift pump is now not connected to anything. Is this bad, to have it open to the atmosphere and elements?

Mark

#2 11-28-2005, 05:01 PM

Sounds like you need one of these:

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CQ0J3JZ41O710FF7G&year=1983&make=MB&model=300-CDT-001&category=All&part=Primer+Pump+Assembly

Ralph69220d · #3 11-28-2005, 05:43 PM

Probably best to wrap in plastic with some rubber bands to keep moisture out.

Mister Byrnzoil · #4 11-28-2005, 05:58 PM

my cheapie purolator has been pumping gas faithfully for over 4 years on my jeep. It'll probably last forever pumping oil. I think mine is rated @ 5-7psi.

Mark in NJ · #5 11-29-2005, 02:14 PM

Someone suggested: You may wish to use a higher pressure fuel pump than the 4-6 PSI Facet, as the IP return line pressure relief valve opens IIRC around 10 PSI. It would seem unlikely that the return line flow would occur if the lift pump pressure is less than 10PSI.

With a Mercedes, otherwise stock, is it true that there will be nothing going through the return line to the tank, if the pressure created by the lift pump is less than 10lbs?

Mark

boneheaddoctor · #6 11-29-2005, 02:16 PM

Quote:

Originally Posted by Mark in NJ

Someone suggested: You may wish to use a higher pressure fuel pump than the 4-6 PSI Facet, as the IP return line pressure relief valve opens IIRC around 10 PSI. It would seem unlikely that the return line flow would occur if the lift pump pressure is less than 10PSI.

With a Mercedes, otherwise stock, is it true that there will be nothing going through the return line to the tank, if the pressure created by the lift pump is less than 10lbs?

Mark

Trust me...there is plenty returning to the tank with a stock lift pump....

#7 11-29-2005, 02:16 PM

I guess I don't understand what you are trying to do

, it's easy and cheap to just throw in the correct pump. What's the point of trying to make something else work?

Mark in NJ · #8 11-29-2005, 02:30 PM

I already had the Facet-Purelator pump. I hooked it up in place of the stock lift pump, and it wored fine. I am considering keeping it because (it works fine) and can be electrically controlled. I have a 2 tank vegetable oil set-up. I would like to use seperate lift pumps for each tank. Having electric pumps can potentially simplify priming and switching fuels because the pump(s) can be run when the car is on or not.

But, will I be able to bleed off air to my tank with this electric pump if it only generates about 4-5 lbs of pressure?

Mark

#9 11-29-2005, 02:38 PM

Now I understand, I didn't know you were setting up a VWO system. Sorry, I don't know what the correct pump pressure is.

ostryjak · #10 12-05-2005, 03:44 PM

This is interesting. I have an '84 300D where the lift pump has started leaking. at first I thought I simply had an air leak somewhere but couldn't find it. (the car would die cos of no fuel). I noticed that when I was priming with the lift pump I had fuel squeazing out from under the plastic thang I was pumping up and down. So - I have decided I need to replace the lift pump. Now to the interesting observation. I am also running on WVO and switch from one to the other using a swap over unit but the lift pump still does the work. The question I am asking is whether it is could be fair to assume that pumping WVO (Way thicker than diesel) in 20+ year old pumps is causing lift pump failure ?. That is what I am guessing.