IP Primer pump or lift pump concerns - PeachParts Mercedes-Benz Forum

lietuviai · #1 01-05-2011, 12:27 AM

I have a new style primer pump on my IP and noticed that it was hard to push down.

It gave quite a bit of resistance before I finally was able to push it down. Once I did get it to push down, it had no resistance at all but it didn't seem to pump at all.
The reason I was checking it was the car had stalled out on me and I couldn't get it to restart. It just lost power and sputtered out on me. I was thinking that it got fuel starved but the filters were full.
I was able to get it restart after putting a fresh charge on the battery. It seemed to run fine but I didn't want to drive it risking getting stranded again until I figure what could have caused it in the first place.
I'm thinking either the primer pump is going out or something in the lift pump is sticking. I leaning toward something in the lift pump is the issue since I don't think the primer pump would cause a loss of power and stalling.
What do you guys think?

Diesel911 · #2 01-05-2011, 01:18 AM

It is hard to say what is going on.

Some members have had problems with the Febi copy of the new style Bosch Hand Primers
.
One member had a problem with a Bosch Hand Primer, took it back and exchanged it for another and had a problem with that one. He took it back and got his money back.

He went to another store and bought another Bosch Hand Primer and that one worked fine. He concluded that the first Store must have received a batch of defective Bosch hand primers and that the one he purchased from the last different store must have come from another batch.

To see if your Fuel Supply/Lift Pump is working loosen some of the Hard Fuel Injection Line Nuts at the Injectors and crank the Engine to bleed the Air out. Tighten the Nuts and attempt to start. If it runs OK after that your Lift Pump is OK and you can concentrate on seeing if the Hand Primer is defective.

Stretch · #3 01-05-2011, 03:36 AM

My new Bosch one is a bit sticky too. I just give it a wiggle and it pops back up most of the time. It seems to get stuck when you are pumping a lot...

...I'm not impressed - but hey at least it doesn't leak like the old one...

yellit · #4 01-05-2011, 07:12 AM

I tee'd in a pressure gauge between spin on filter and IP fuel input ....I think 10-14 psi is normal if I remember correctly....lots of forum info on check valve issues connected to IP return regarding stuck or weak spring reducing fuel chamber pressure in fuel galley in IP....

lietuviai · #5 01-05-2011, 11:51 AM

My primer pump has been on the engine for about 16K miles and I pulled it off a junk engine I had that had a fairly new IP. I'm leaning toward a sticking check valve on the lift pump. I was looking for a diagram for the lift pump but none was to be found in the FSM.
I'll see if I have a spare lift pump somewhere and swap it out. Otherwise I'll see much of the current lift pump I can disassemble and clean.

tangofox007 · #6 01-05-2011, 02:14 PM

Quote:

Originally Posted by lietuviai

My primer pump has been on the engine for about 16K miles and I pulled it off a junk engine I had that had a fairly new IP. I'm leaning toward a sticking check valve on the lift pump. I was looking for a diagram for the lift pump but none was to be found in the FSM.
I'll see if I have a spare lift pump somewhere and swap it out. Otherwise I'll see much of the current lift pump I can disassemble and clean.

I had a similar problem to the one you describe. Installing a lift pump repair kit solved the problem. I have a spare kit if you need one.

Diesel911 · #7 01-05-2011, 03:28 PM

Some disassembled pics and stuff is here.
Lift Pump Rebuild...
The Fastlane Valve kit does not come with the little O-ring mentioned in the thread.

One Valve and Spring are under the Fuel Outlet Fitting.
The other Valve and Spring are located within the Bottom Plug opposite the side side of the Fuel Oultlet.

Thread with the kit info:
http://www.peachparts.com/shopforum/diesel-discussion/260325-anybody-know-good-fuel-pump-replacement-diy-page.html#post2284880

lietuviai · #8 01-05-2011, 10:44 PM

Thanks for the great links and offer guys. I'm not sure when I'll get a chance to work on the pump. I've been doing some major work on my truck lately which has taken about all of my free time.
I figure if I pull the pump apart, I might as well inspect / rebuild it at the same time. Tango, I'll PM you about the kit.

yellit · #9 01-07-2011, 01:32 AM

Still might want to check that little pressure regulator/check valve spring on the IP main return...if it gets stuck open....low pressure in fuel galley....
There was a thread on this a while back...with some thoughts on increasing galley pressure by stretching spring...mine was weak on the 240D....cleaned and replaced spring ....made a noticable difference....

About the lift pump>>>>>>
Found out the lift pump pushes fuel to filter by the L. pump piston main spring pressure instead of the IP cam like I thought at first...so the lift pump cannot over pressure the path....limited by spring strength...

lietuviai · #10 01-07-2011, 02:21 PM

I'll make that I check the valve on the return line. I've got a rebuild kit on the way from Tangofox so one way or another this problem will probably get solved.

lietuviai · #11 01-12-2011, 05:56 PM

I got my lift pump off today. It was quite a pita to get it off. The 10mm nuts at the bottom had very little room to access. There was barely enough room to get even the smallest 10mm wrench I had, which was one of my Mercedes wrenches. It didn't help that was raining as hard it could at the time either.
I got it in the garage and once I got it apart, I found what appeared to be the culprit. It was either the intake or output valves that were sticking. I thoroughly cleaned everything and I'm currently putting it together. I needed to figure out where those two little O-rings that are in the kit, need to go. No O-rings fell out when I took it apart. Looking at one of the threads relating to rebuilding the pump, it looks like it goes in the small bore that the main piston pin rides in. I'll get a good look where the recesses in the bore for the O-rings are so I can get finished.

Diesel911 · #12 01-12-2011, 09:19 PM

Quote:

Originally Posted by lietuviai

I got my lift pump off today. It was quite a pita to get it off. The 10mm nuts at the bottom had very little room to access. There was barely enough room to get even the smallest 10mm wrench I had, which was one of my Mercedes wrenches. It didn't help that was raining as hard it could at the time either.
I got it in the garage and once I got it apart, I found what appeared to be the culprit. It was either the intake or output valves that were sticking. I thoroughly cleaned everything and I'm currently putting it together. I needed to figure out where those two little O-rings that are in the kit, need to go. No O-rings fell out when I took it apart. Looking at one of the threads relating to rebuilding the pump, it looks like it goes in the small bore that the main piston pin rides in. I'll get a good look where the recesses in the bore for the O-rings are so I can get finished.

I am trying to post a pic. The Arrow points at the one O-ring that goes in the Pump. You will have to figure out wich one of the 2 in the kit is the right one.
To get at the O-ring you need to remove the parts in the Pic. Once the Pin is removed look inside and you will see that the O-ring fits into a groove in the Bore that the Pin rides in.

lietuviai · #13 01-12-2011, 10:21 PM

I actually used both O-rings. I stuffed the brown one inside the bore and put the black one on the outside of the bore on the piston side. I couldn't find anything more specific than what was in the previous links so that's what I did.
It's all re-assembled and installed now. I haven't tried starting it yet but I'm sure it should be fine.

Diesel911 · #14 01-13-2011, 11:01 AM

Quote:

Originally Posted by lietuviai

I actually used both O-rings. I stuffed the brown one inside the bore and put the black one on the outside of the bore on the piston side. I couldn't find anything more specific than what was in the previous links so that's what I did.
It's all re-assembled and installed now. I haven't tried starting it yet but I'm sure it should be fine.

If the Piston actually comes to rest on the O-ring it will limit your Piston Travel a little and eventually the O-ring getting squashed will have an effect on it.
If the Piston does not touch the O-ring it may never be a problem.

Were the 2 O-rings the same size?

The typical problem when there is an issue with that O-ring is Fuel gets into the Engine Oil.
However, 2 members have claimed the Engine Oil from inside of the IP mixed with the Fuel when that O-ring was no good.

lietuviai · #15 01-13-2011, 12:08 PM

No the black O-ring is slightly thinner in cross section. I don't think that the piston travel could be affected much if the piston touched the O-ring itself.
I guess I'll find out if it is an issue. I could remove it without removing the entire pump. All I'd have to do is take the 30mm cap off to get to it.

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