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Old 06-18-2011, 01:05 AM
MrWendell MrWendell is offline
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Join Date: Jun 2011
Location: Colorado's High Country
Posts: 17
W115 240D Injection Pump Timing | Destroyer of Glow Plugs

Hey Everyone-

I have a 74 240D that has had a long a sordid history with the injection pump. I stupidly took it to a general diesel shop to get the diaphragm replaced--they then sold me on a full rebuild--which they boogered pretty good. A local MB shop then put in a used pump that was supposedly running fine in another W115 240D and:

* new timing chain
* injectors
* Removed and cleaned prechambers
* "Advanced the timing as far as they dared"
* Adjusted valves

Problems:
* incredibly difficult to start (even needs a glow when hot),
* way down on power (I know, it's a 240D at 7000', but I've driven it for years)
* Eats glow plugs with gusto. I have the new fast pencil plugs and I'm only glowing them for 10-15 seconds at a time--the ends seem to get blown off. I've chewed through 6 already--could detonation be doing this?
* Is incredibly loud (need ear protection working around the running engine--not sure if it's nailing??). It's never been this loud.

The MB shop then told me compression was too low (250s when cold and came up with oil) and that was the problem... I feel like I bought ocean front property in Arizona (and probably could have before the shop fee).

I really love the car and am hoping to get it back to normal. I'm thinking the timing is way too far advanced (in the shop's attempt to get more power). So, I have tried drip timing it. Here are the questions:

1) With crank at 24 BTDC (valve lobes up) and pump loose, it delivers about 1 drop/sec. With crank at 27 or 30 BTDC it delivers about 1 drop/sec at the same pump position. Is this normal? I would have expected a change.

2) If I move the pump away from the engine, the drips stop completely. Is this advancing or retarding the timing?

3) If I move the crank to about 40 BTDC and I prime the pump, no fuel comes out at all. Could I be timing the end of injection instead of the beginning? Could the shop have advanced it that far? I thought he mentioned having to move it a spline or so.

I'd greatly appreciate any advice and thoughts on this. I'm not sure where to go next.
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