OM617 losing prime constantly - PeachParts Mercedes-Benz Forum

Crackstar · #1 02-15-2010, 01:17 PM

I had to do the timing chain so the hardlines from the IP to the Injectors came off. I had to replace the primer pump, the original one's O-ring was trashed. I replaced all my low pressure return lines, pre filter fuel filter and the 5/16 fuel lines to and from the tank.

What'd I do wrong, after sitting for 6-10 hours it seems to leak down to the point where it gives me a miserable time starting.

Replacing all the rubber lines helped, alittle, I double checked the seating of the fuel filter.

Did I not purge my injector lines correctly?

HOw many orings on the primer pump? SHould there be one in the bottom? Is it just a matter of not getting it screwed all the way in?

I'm getting confused

if you can offer any help, thanxs

crackstar

toomany MBZ · #2 02-15-2010, 02:22 PM

There is a crush washer (bottom) on the primer pump, that's all, at least externally.
How do you know if the fuel is leaking down?
Once the the lines that have been removed, re-installed and the car started, no more priming is necessary.

Crackstar · #3 02-15-2010, 02:33 PM

Over night the prefilter will develop a much larger bubble. Starting it can be accomplished with either constant cranking or by popping the hood and repriming. But I can't seem to find any diesel leaking any where. When I tried reusing my old low pressure return lines the leaked and it was obvious, fuel every where on the valve cover.

Tell me more about this crush washer. Should it have been included with my primer pump? Could an old one still be stuck in the IP housing?

My primer pump only had a little plastic dust cap on it, and at the the threads end it champhers 45 degrees to the pump body.

toomany MBZ · #4 02-15-2010, 04:14 PM

Seems there is a small leak, enough to introduce air, but not allow fuel to leak out. Inspect around the primer for wetness.
The crush washer fits over the threads on the bottom of the primer, should have come with it. Not all of the stock primers had one.

snookwhaler · #5 02-15-2010, 04:41 PM

You should pull the primer pump and be sure you did not install a new crush washer on top of the old one. There should have been a new crush washer under that "plastic cap" you speak of. I had to actually pry my old crush washer out with a screw driver when I replaced mine. It was really on there.

The air bubble in the primary filter means nothing unless the thing is empty. Your problem sounds like a glow issue. This is only when cold? Right? IE: "the first start of the day" Have you verified that the glow plugs are operating?

fruitcakesa · #6 02-15-2010, 05:31 PM

The crush washer on my new primer pump somehow got slightly offset when I screwed down the pump and allowed leakage.
I though the pump itself had failed and had bought another one and when I removed the first pump discovered the problem.

pawoSD · #7 02-15-2010, 06:11 PM

How are the rest of the fuel lines looking? Under the car? There is air getting into the system somewhere....

pselaphid · #8 02-15-2010, 07:36 PM

Perhaps you could disconnect and plug one side of the clear filter one night and the other side on the next night. That might allow you to isolate the air leak as either upstream or downstream from the filter. Then work from there. I'm fighting that battle on my 96 Cummins, which is a similar system but much more prone to cantankerous air leaks.

Edit: you could do it with pinch claps and not have to disconnect if the hoses are new and still supple. Check hose clamps to make sure they haven't slightly distorted one side of the hose. If they aren't exactly the right size they can do that, as I have discovered.

Crackstar · #9 02-16-2010, 10:22 AM

It has to be the missing crush washer. This morning right after I screwed the top back down after priming the system I noticed a few tiny bubbles rising into my prefilter. Getting new one today. thanks for the help, will double check all my lines from the tank to engine bay

MS Fowler · #10 02-16-2010, 10:28 AM

As another method of diagnosis...
Install ( temporarily, or even permanently) an electgric fuel pump between the tank and the fuel filter. It is far easier to see fuel leaking OUT than air leaking IN.
My Ford IDI diesel F250 has such a pump. I use it mostly for priming the system after it sits for long time ( tiny air leak somewhere), and for filling the fuel filter when I change it.

The Mercedes is bone stock.

vstech · #11 02-16-2010, 10:34 AM

another method for leak checking is to put a shop vac in blow mode, and pressurize the fuel tank... you will find every leak in the thing.

Crackstar · #12 02-17-2010, 09:17 AM

Installed a new style bosch primer pump with new crush gasket! No more bleeding down of the fuel in the pre filter.

Still a ***** to start, so I'm going to diagnose the glow plugs. Its the only other thing that was removed/changed/altered since i did the chain.

Here is a quick question. What would have to happen to have the glow light on the dash not work? I replaced the glow plugs 3 years ago with bosch units. I wouldn't think they were bad already. THe glow light on the dash lights up as it should, Could it be as simple as a loose connection at the plug?

snookwhaler · #13 02-17-2010, 09:32 AM

Quote:

Originally Posted by Crackstar

Installed a new style bosch primer pump with new crush gasket! No more bleeding down of the fuel in the pre filter.

Still a ***** to start, so I'm going to diagnose the glow plugs. Its the only other thing that was removed/changed/altered since i did the chain.

Here is a quick question. What would have to happen to have the glow light on the dash not work? I replaced the glow plugs 3 years ago with bosch units. I wouldn't think they were bad already. THe glow light on the dash lights up as it should, Could it be as simple as a loose connection at the plug?

See post #5.

If #1 glow plug is out the light will not come on. Or a couple with high resistance will not allow the light to come on. Or the light bulb in the dash is out.

More than likely you have a couple that have too much resistance. You can check all of this with a meter in about 5 minutes. Really easy to test.

But, first you need to verify that they are working at all. IE: GP relay clicking on and off, power to the plugs etc....

When tightening the little nuts on the plugs you need to be very careful not to over torque them. The shafts break loose pretty easily. Maybe check all the studs on the plugs first to be sure they do not spin?..

whunter · #14 02-17-2010, 11:04 AM

Quote:

Originally Posted by Crackstar

Installed a new style bosch primer pump with new crush gasket! No more bleeding down of the fuel in the pre filter.

Still a ***** to start, so I'm going to diagnose the glow plugs. Its the only other thing that was removed/changed/altered since i did the chain.

Here is a quick question. What would have to happen to have the glow light on the dash not work? I replaced the glow plugs 3 years ago with bosch units. I wouldn't think they were bad already. THe glow light on the dash lights up as it should, Could it be as simple as a loose connection at the plug?

Glow plugs link thread
http://www.peachparts.com/shopforum/diesel-discussion/137732-glow-plugs-link-thread.html#post1019018

Have a great day.