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Old 11-14-2013, 10:01 PM
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Join Date: Apr 2008
Posts: 104
OM603 87 300SDL Injection pump leak at top.

I've been fighting leaks at the injection pump and have an interesting series of events to ask about.

I've had serial fuel leaks involving the injectors, high pressure fuel lines, fuel return lines, and injection pump. Have chased down various ones, fixed them, only to have new ones surface. About a year ago I replaced all the delivery o-rings in the injection pump, and for a while the top end of the injection pump was staying dry.

Now the leaks have started again and the problem goes like this: In response to a series of leaks between the nut and the delivery line at the injection pump, I've ended up replacing all of the metal fuel lines, one at at time, with lines that looked fine from a parts car. One at a time because starting with the line going to cylinder #3, a leak would start at the nut at the injection pump end; I would replace that metal line and the problem would be fixed for 50-100 miles. Then the line to the NEXT cylinder would spring a leak (#4), I replaced THAT line, same result: OK for 50 miles, then a leak springs up at the #5 line. Then #6, then BACK to #1, and finally #2, until all the lines were swapped out with ones from the parts car. At this point the top of the pump stayed dry for about 200 or 300 miles. Now today ALL 6 lines appear to be leaking again in the same spot, at the nut holding down the line at the injection pump.

From various posts, I would be looking at perhaps replacing ALL the lines again, but this strange sequence of leaks makes me wonder what else might be going on.


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Old 11-14-2013, 10:27 PM
jay_bob's Avatar
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Join Date: Oct 2011
Location: Columbia, SC
Posts: 3,693
Are your injection line clips in good condition?
The OM 642/722.9 powered family
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)
2008 ML320 CDI (Older sonís DD)
2008 E320 Bluetec (Younger son's DD)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech
gone but living on
1983 240D (body to greazzer, engine to t walgamuth)
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Old 11-14-2013, 10:34 PM
sixto's Avatar
smoke gets in your eyes
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You might be overtightening the injector lines. The line ends in a ball that fits into a cup at the delivery valve and injector. Overtightening deforms the ball.

87 300D
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Old 11-15-2013, 09:57 AM
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Join Date: Apr 2008
Posts: 104
Some of the clips are gone, but it also leaked when all the clips were there. Must replace them, though. I used to over-tighten, but I don't THINK I do any more. Maybe 1/16 of a turn with a wrench after they are hand-tight?
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Old 11-15-2013, 02:35 PM
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Location: Long Beach,CA
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Originally Posted by AUDIBLE View Post
Some of the clips are gone, but it also leaked when all the clips were there. Must replace them, though. I used to over-tighten, but I don't THINK I do any more. Maybe 1/16 of a turn with a wrench after they are hand-tight?
Over tightening can also damage the seating area in the Delivery Valve Holder although it rarely happens.

Where I worked we used to have a big box of new O-rings, Gaskets and Copper Washers left over because the Gasket Kits covered a range of IPs and not all were used in a rebuild.

When I just had to get something going and I had a leak at the Delivery Valve Holder or the Injectors between the Fuel Injection Hard Lines and those parts. I selected some tiny Copper Washers and inserted them between the leaking parts and tightened the Fuel Injection Hard Line Nuts down.

Not a permanent solution but if you did that and the leaks stop it would show you what the cause of the leaks is.

All of the line Clamps/Clips need to be in place or vibration will cause the lines to crack. Sometimes they crack anyway but it is odd for all of them to crack.
Normally only one at a time cracks.

84 300D, 82 Volvo 244Gl Diesel
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