Can't set point of delivery

[Timmy]

My car is a 1978 240D that I drive daily. It has a 1982 engine that was installed in 2001.

The car runs well with no injector nailing, little vibration, and plenty of power at all rpms.

It does have some black smoke at idle and under load that has some fuel odor so I assume that it is running rich.

I have tried to set the point of delivery several times over the last few years, but have had no success. the problem has been that I don't get any fuel flow at 24btdc no matter how long I pump the hand pump.

Quite by accident with the system pressurized by the hand pump I got flow at 50btdc while turning the engine by hand to try it again at 24btdc.

I checked the marks on the camshaft sprocket and harmonic balancer at 0tdc and they both agree.

I am reluctant to change anything without more information because it runs so well.

Does anyone have any idea what's going on here?

[Rogviler]

First, are you sure it's on the compression stroke when you check and not 180 degrees off? Easiest way is to look in the oil fill hole and see that the first two cam lobes aren't pointing down AND it's at or around 24 BTDC.

It should basically be pouring fuel out of the #1 delivery valve holder (valve and spring removed of course) at where you said you got some flow (60 BTDC or so), and within just a few degrees approaching 24 BTDC it'll go from pouring to dripping (looking for the one drip per second) to stopped just after. If it's not, then you move on to setting the engine to 24 BTDC and move the injection pump to get it to the correct timing. However, before tackling that I would just verify where it goes from pouring to dripping to stopping. It has to do that if the engine runs at all.

If you're having trouble with the hand primer method (which is iffy at best), I highly recommend the constant pressure method. I can give you the steps of that if you want to try it.

-Rog

[Dan Stokes]

Another option is to find someone with an AVL or similar timing light system. They use a sensor that clamps onto #1 injection line and it reads the pulses of fuel going to #1 cylinder pretty much like a timing light works on an Otto cycle engine. Very accurate and extremely cool! I know Greazzer has one but there is almost certainly a shop near you that will have one. The setup is quick and easy so it shouldn't be too expensive to have a shop use it. One of these days I'll trailer Mutt down to SC and get Greazzer to check mine though I'm pretty sure it's OK as Goran set it up on the bench when he built the pump.

Dan

[jt20]

Agreed.

If you are doing drip timing, this is the best way to begin after you have set up your drip tube.

Start at 30-ish before top dead center on the compression stroke.

Spueeze the primer a bit

check for flow.

Advance the crank a degree or so.

repeat.

as you get closer to 25 or 26, don't move the crank much, just under a degree each time. Once it stops flowing, you have found your setting (pretty close).

If your engine is advance above 24, which is sounds like, then you are just fine. 27 to 28 is not 'too far'... it will run fine and might even be an ideal setting when considering internal wear.


injector maintenance may be a bigger concern for you considering what you have stated.

Originally Posted by Rogviler

First, are you sure it's on the compression stroke when you check and not 180 degrees off? Easiest way is to look in the oil fill hole and see that the first two cam lobes aren't pointing down AND it's at or around 24 BTDC.

It should basically be pouring fuel out of the #1 delivery valve holder (valve and spring removed of course) at where you said you got some flow (60 BTDC or so), and within just a few degrees approaching 24 BTDC it'll go from pouring to dripping (looking for the one drip per second) to stopped just after. If it's not, then you move on to setting the engine to 24 BTDC and move the injection pump to get it to the correct timing. However, before tackling that I would just verify where it goes from pouring to dripping to stopping. It has to do that if the engine runs at all.

If you're having trouble with the hand primer method (which is iffy at best), I highly recommend the constant pressure method. I can give you the steps of that if you want to try it.

-Rog

[leathermang]

Drip Timing Threads

[BillGrissom]

Nothing sounds wrong. You should get flow when pumping at 50 deg BTDC on compression stroke. You will continue to get flow until some point where the inlet valve in the IP piston closes and flow stops, rather abruptly. The 1 drip/sec is just to quantify that "start of cut-off" location. If your fuel timing is currently at 23 BTDC, you might measure no flow at 24 BTDC. Of course your cut-off point has likely shifted from as-new because of a worn timing chain. You want to rotate the IP until the cutoff point is exactly 24 BTDC, or whatever you want. Many here suggest that 27 BTDC will give better mileage and performance. I did so in my two OM617 turbo engines though didn't notice anything significant.

[Timmy]

Ok Bill, will try what you have suggested. I suppose I' m somewhere after 24 BTDC, but not sure where. It can't be that far off or it would not run this well. I'll try to find out. I' m not convinced that the timing chain is significantly worn though, as the camshaft and crank timing marks indicate the same position.