Fuel Pump - PeachParts Mercedes-Benz Forum

RC4U12 · #1 03-11-2009, 09:46 AM

after finding out my compression is actually good and changing chain, sent off injectors ect...i started my car again and re-tuned idle and seemed little rough,,checked fuel pressure and only 18psi..turn the regulator screw and nothing happens. I put the regulater from parts car on and 39psi,but it leaks down right away..i see on fastlane parts there is check valve..i didnt see this when i was installing the new filter nor last nite wehn i checked the hook-ups. where is it or is it optional?? Jeff

rowdie · #2 03-11-2009, 04:47 PM

[quote=RC4U12;2135807]after finding out my compression is actually good and changing chain, sent off injectors ect...i started my car again and re-tuned idle and seemed little rough,,checked fuel pressure and only 18psi..turn the regulator screw and nothing happens. I put the regulater from parts car on and 39psi,but it leaks down right away..i see on fastlane parts there is check valve..i didnt see this when i was installing the new filter nor last nite wehn i checked the hook-ups.

I checked the CD and all the other info I have and no check valve is listed. Having said that, maybe they started putting on in later models to fix a prolem. Niether my '72 or '73 have one that I know of.

JonL · #3 03-11-2009, 06:21 PM

There's a check valve in the pump. Is that what you are referring to? It may not have been a separate part in some years. Maybe not ever... I'm sure there are others here that know more than I do about this. It's been a looooong time since I dealt with those cars.

JonL · #4 03-11-2009, 06:22 PM

When you say it leaks down right away, I'm assuming you mean as soon as the car is turned off, is that correct?

RC4U12 · #5 03-11-2009, 11:33 PM

Jon thanks you are right its in the pump. and yes it leaked down after shut down...But most important when you are starting it and the pump primes it doesnt start agin till the engine is started so you have to crank more..........I took the one out of my parts car and tested pressure in the outlet and it held ...so after installing it works great..starts fast and holds 30 psi for 15 minutes..
After Tuning my Mega-Squirt again it idles so SMOOTH with the right fuel delivery... I am happy.. Jeff

meltedpanda · #6 03-12-2009, 11:29 AM

accumulator??
the accumulator is designed to hold pressure for some time after shut off, especially useful in hot starts,

Gurunutkins · #7 03-12-2009, 03:38 PM

djet doesn't have an accumulator Ron just the CIS cars

(you've been working on CIS too much). the djets just have the swirl can at the pump and a ball check valve in the long nose of the pump. between the check valve and the pressure regulator they should hold pressure for at least 5 or 6 hours minimum.
cheers
barri

meltedpanda · #8 03-12-2009, 03:51 PM

Ahh thanks for keeping me on track, yup too many engines , none the same

RC4U12 · #9 03-13-2009, 09:55 AM

here is a pic of the fuel pump and the fitting in the front is removed from the pump and is what is supposed to carry the check valve..mine was missing which leads me to believe this pump is from a different merecedes that had a better check valvle..i am mow in the market for an inline check valve as i want to replace the one from the other pump...the stock ones are just a spring and ball type inside that fitting..so if anybody has this problem you do not need to buy a whole new pump!! Jeff

PS the metal peices i just took out so you can see how it works..