Injector pump leaking after checking timing (drip method)
 

1983 300SD. I checked the IP timing (my first time) using the drip method. Worked fine--about 22 degrees BTDC--I'll set it to 24 later when I get a special wrench.

It is now leaking at the base of the pipe connection (slow leak, but after a 5 minute drive, the motor mount below is all wet). According to the Service Manual, I took it out and oiled the thread, then re-torqued. It still leaks.

If it leaks, the manual says to "exchange the pipe connection and exchange the copper sealing ring beneath the delivery valve holder" Hmmm...I guess that means buy a new pipe connection and a new copper seal?

When I checked the timing, all I took out was the spring and the delivery valve. How do I get the delivery valve holder out safely? Can't really even see it.


Any ideas Gents? Thanks. :confused:

I changed one on my daughters 240D and when I got everything out of the hole and looked down inside with a good light there was allot of crud. no wonded it didn,t want to seal. cleaned it out, installed sealing ring, no more leak:D

OK, I'll get a new washer and report back. Strange that a tapered pipe thread would not seal and that some sort of high-tech equivilent of teflon tape is not used.

Even stranger that the torqued distance a tapered pipe would move could be calculated so precisely to provide proper crush on a copper washer two parts below the pipe. Magnificent engineering.

:cool:

Get a new o-ring for the pressure valve holder, too, that's what is leaking if you have diesel on the outside of the pump.

The one on there is probably as hard as a rock, and you didn't even notice it!

Peter

Cuban8
Before you go any further be sure that it is not the injector pipe connection (at the swaging) that is leaking.

On the Bosch MW pump fitted to your model there are only two other possible sources of a leak.

1) The copper washer between the delivery valve and the metering element.
2) The lapped faces that “wring” together between the del. valve body and the pipe connector/spring housing (i.e. the long hex. sleeve)

Both of these must hold a pressure of <1800psi.

Sometimes you can be lucky if you do not disturb the del. valve body and it will not leak but if it does as in your case then the copper washer must be replaced and thoroughly cleaned out.

The del. valve body is best lifted out with a magnet, you can also use a thin wire and hook it out from under – Keep away from the chamfer where it seals, new D valves are expensive!

You will have to get a new copper washer from a Bosch agent – 15mm x 10mm x 0.5mm thick, don’t use a substitute.

The lapped faces of the del. valve and the valve spring housing (i.e the long hex sleeve) can be cleaned using a piece of plain paper on plate glass with silver polish. Don’t even THINK about using abrasive paper!

To re-assemble: Tighten to 30Nm and release. Again to 30Nm and release then finally to 48Nm. The purpose of this is to ensure the lapped faces are seated squarely and wrung together before final tightening. Always use two wrenches when tightening injector pipe sleeve nut.

BTW - The thread is parallel not tapered and there are no “O’ rings in the MW pump del. valve assy.

Before you go any further be sure that it is not the pipe connection that is leaking.



On the Bosch MW pump fitted to your model there are only two other possible sources of a leak.

1) The copper washer between the delivery valve and the metering element.
2) The lapped faces that “wring” together between the del. valve body and the pipe conn./spring housing.
Both of these must seal a pressure of <1800psi.

Sometimes you can be lucky if you do not disturb the del. valve body and it will not leak but if it does as in your case then the copper washer must be replaced and thoroughly cleaned out.

The del. valve body is best lifted out with a magnet, you can also use a thin wire and hook it out from under – Keep away from the chamfer where it seals, new D valves are expensive!

You will have to get a new copper washer from a Bosch agent – 15mm x 10mm x 0.5mm thick, don’t use a substitute.

The faces of the del. valve and the pipe conn. can be cleaned using a piece plain paper on plate glass with silver polish. Don’t even THINK about using abrasive paper!

To re-assemble: Tighten to 30Nm and release. Again to 30Nm and release then finally to 48Nm. The purpose of this is to ensure the lapped faces are seated squarely and wrung together before final tightening. Always use two wrenches when tightening inj. pipe nut.

BTW - The thread is parallel not tapered and there are no “O’ rings in the MW pump del. valve assy.


__________________
Beagle

The leak is at the base of the pipe where it screws into the metering element. I had previously thought that the pipe had to seal with the metering element, but from what you have said (if I understand), the high pressure fuel is sealed in the stack of parts in this order: injector pump body, copper seal, pressure valve carrier, pipe connection. There should be no fuel running around this stack and no need for a high pressure seal on the threads of the pipe. The only two places it could be leaking are the copper seal or the lapped faces of the pipe and the pressure valve carrier. Do I have it right?




I'll try my local Benz dealer for the copper seals. Anybody know a Bosch shop in south Atlanta or the best mail-order Bosch shop? Thanks.

This IP came with a factory rebuilt engine and has 100,000 miles on it. No dirt on it inside or out. Since the leak, it's running rough and nailing on number 1, so I guess it's not getting high enough pressure to actuate the injector properly.

Cuban8
I have edited my original post – please read it again and see if it makes more sense now.

“The leak is at the base of the pipe where it screws into the metering element.”
You mean the pipe joint at the swaging? If so you have no leak in the delivery valve assy. Fit the pipe to the pump first and nip up gently, then to the injector finger tight. Finally tighten at the pump followed by the injector. It is easier to fix a pipe leak at the injector than at the pump.

“the high pressure fuel is sealed in the stack of parts” That is correct


“There should be no fuel running around this stack and no need for a high pressure seal on the threads of the pipe?” That is correct.

Any Fuel Injection shop should have those washers, give them the sizes I quoted.

Thanks. I appreciate all the help.

If you have low power and #1 is nailing, the copper seal isn't sealing. I got a $2000 discount on my 300D because someone replaced the 0-rings on the pressure valve holders and didn't get the copper seals right. Easy fix (fortunately -- I'd planned on a head).

The o-rings in the pressure valve holders seal the filling chamber, not the high pressure part.

Peter