240D Drip Tube Conundrum

The idea is to rotate the motor so one sees when the IP's flow to the #1 cylinder begins and ends. Some owners remove the #1 IP valve and spring (as you did) and very slowly turn the motor until they see fuel welling up in that #1 cavity. Then they stop turning the motor and note the crankshaft reading. Others submerge the drip tube's end in some fuel and proceed to turn the motor until air bubbles STOP marking the end of injection.

-->> T.G. Lambach proceed to turn the motor until air bubbles STOP marking the end of

Thank you T.G.

I made another attempt and did get drips.

I moved the crankshaft a tiny bit to the left of the 24 degrees BDC and the drips began. As I rotated clockwise they continued off the scale and at some undetermined point stopped. I continued around and the drips started again at close to 60. The measurements all started with the first-cylinder cams in the right place.

This info would be more useful if the scale continued around but you may be able to see a reason why there is no need for it.

A few days of research brought up a few sets of instructions and not one suggested moving the crankshaft. I guess they assumed that staying at

24 degrees BDC was enough.

Next Q: What settings should I have for the one second drip rate?

Many thanks :-)

I know that I need to swivel the IP until the drip rate reaches 1/sec and to raise the roughly 20 deg start position to about 24. Does that call for some magic? Fingers crossed :-)

The post above was theory only. Swiveling the pump from extreme to extreme appears to have no effect on the starting BDC value for the drips. At 24 down to 20 deg there is no drip at all. They start under 20 deg but the crankshaft always slips at this point to about 15 deg where the fuel drips profusely.

Ok, the point is to see at what crankshaft angle the fuel begins to flow for that's the mark, so to speak. The target is 24 degrees BTDC. The amount of fuel is not important - that's controlled by the throttle. Turn the motor right handedly veerrryy slowly from 30 degrees BTDC until the FIRST drip occurs, then STOP turning for that's the reading that's produced by the IP's current setting. Read it from the crank.

If fuel drip occurs at say 26 degrees BTDC then the injection is 2 degrees early or advanced and the explosion inside the cylinder will occur before the piston is quite at the top of its stroke so the motor will be working against itself.

A bit late, say 22 degrees BTDC (retarded) will cost a bit of power but is a more forgiving error than the motor being too far advanced.

Turning the top of the IP towards the engine advances the injection timing; turning it away from the motor retards the timing.

If you cannot achieve 24 +/-2 degrees then I suggest you set the crankshaft angle to 24 degrees BTDC, remove the IP and turn its gear so that its missing tooth is aligned with the mark cut into the collar behind that gear and reinstall the pump without turning anything. Then you will be certain that the pump is approximately correct and can set it to 24 degrees BTDC using the drip tube

-->> T.G. Lambach for that's the mark, so to speak. The target is 24 degrees BTDC. The

The best I could do is no drips at 20 and drips at

1. Even with a 10" wrench on the power steering pump I could not stop it popping at intervals of about 5 degrees. Maybe the engine was telling me how good the compression and valve springs are :-)

Thanks for the info. I got fed up of the messy MBZ manuals and scanned the parts for my 123.616 into a JPEG file in my computer. I dumped all the irrelevant material. It does tell about swiveling the IP.

Thank you for a great idea. That's my task for tomorrrow. Will be in touch. I will have a close look to see how a gear tooth could have been skipped. I didn't try to rotate the camshaft with the gear, in fact all I did to it was to slide off the collar to check on the condition of the o-ring and then slid it back on. This time I'll see what size of torque it takes to rotate it. Is it possible that the mating gear in the engine could have moved a little? The crankshaft certainly was never touched while the IP was off.

Take care and have a great night :-)

The task is to coordinate the IP with the crankshaft. Turn the motor to

24 degrees BTDC then remove the IP.

The IP's drive gear has an intentionally missing tooth - that's a position marker when aligned against a mark on the collar (on the IP) behind that gear. Use your fingers to turn the IP drive gear to be aligned. It will then be correctly set for the motor, now at 24 degrees BTDC. Reinstall the IP. Go on to checking the injection timing with the drip tube and adjust the IP accordingly by turning the pump if necessary.

On Aug 14, 2:12=A0am, "-->> T.G. Lambach

-->> T.G. Lambach 24 degrees BTDC then remove the IP.

First I set the 24 degrees BTDC on the crankshaft.

When I removed the IP, the missing tooth was about

2 teeth around from the mark on the collar*. I aligned them and replaced the IP. I had to swivel the pump hard towards the engine to slow down the drip rate. I hadn't tried this before and noticed that, when I pumped 5-6 times, the drips went quite fast at first and then slowed down to a steady pace. Small adjustments to the IP position brought the rate down to 1 per sec. That's where I tightened the anchor nuts on the IP.

I haven't restored the IP tubes yet and should be able to do it tomorrow and hopefully get some smoke-free exhaust.

• I have not been able to find a crosssection of the IP in the MBZ manuals, so I don't know if the IP has a camshaft working on tiny pistons that force the fuel along the lines to the injectors. If they do, then it's possible that these may cause the IP gear to rotate a bit when removed from the engine. It would explain what happened to me when I replaced the gasket between the IP and the engine. I never touched the gear at that time yet it was not in the correct place.

Thanks again for your help :-)

Success to report :-)

Bad planning forced me to wait for the copper washer for the IP. However, it was worth it. Now the car is completely smokeless, at least when revving it up as much as I dared in the garage.

Thanks again T.G. Lambach. You are a walking encyclopedia :-)

I am now convinced that the IPs are powered by cams and springs which knock the IP shaft out of sync as soon as it is pulled out of the engine block. If I have ever to remove it again, I will make sure it is aligned before re-installation.

I didn't fork out $25 for a drip tube - just made one myself for less than $1. It is a plastic tube connector that is typically used with

1/4" plastic lines in small water filters, for example. It has 1/4" internal pipe thread at one end and a nut on the other. This nut can be unscrewed and a short piece (5"-6") of 1/4" of plastic tube pushed in. Then the nut is slid onto the tubing and screwed back on - it clamps the tubing. The threads inside the connector are 1/4" pipe threads and the top of the injector unit has a slightly different metric thread. However, I found that the Permatex filled the gap sufficiently to prevent leaks. Afterwards I thought that teflon tape might have been less messy but I'm not sure what the fuel would do to it. A piece of wire holds the tubing in the loop, and that's all folks!

One thing I missed was the star socket to tighten the injector units. It's on my shopping list. I had to do a lot of improvising to get the unit out and back into place. Apart from the star socket, only a pipe wrench is usable but I also tapped around the clamping plate which helped a lot. Not sure what the ultimate torque was though. :-( Oppss!! Forgot to mention my torque wrench has a minimum of 40 NM. Any recommendations for one with a range below that?

Now I can go for a celebration drink :-)