I was in the process of replacing my delivery valve seals and I thought this would be a convenient time to check my timing. I know there is a method that involves some fancy factory tool and the timing is checked at 15 deg ATDC, but as a home mechanic I'm trying to do it the old-school way using the bubble method just like it would be done on a W123 diesel.

I removed the #1 pump element, the valve and spring, reinstalled the element, reinstalled the injector pipe as shown, put a brick on the throttle pedal and disconnected the vacuum hoses that connect to the side of the IP as shown. Then I tried submerging the end of the pipe in the bowl of diesel fuel and watching for bubbles while blowing into the hose that's connected to the input line on the main fuel filter as shown. The trouble is I can't get any more than a few initial bubbles to come out regardless of the position of the crank. I tried 30, 25, 24, 22, 18, 16, 10 and even 5 degrees BTDC and all gave me the same result despite very hard blowing. In fact I was blowing so hard that I could hear bubbling in the fuel tank. Can anyone tell me what I'm doing wrong here? Is this method simply not usable on the 603 engine?

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

I've never felt comfortable with either the drip or bubble methods. Much easier in your case would be to simply remove the 17mm hex plug (just above the white text box in your photo), set the crank to either 14 or 15 degrees ATDC, then use a mirror and flashlight to see if the raised vee [see pg.7] on the internal flywheel is aligned in the center of the plug hole. Incidentally, the lock tool to manually check this position is only ~$30, so any DIY OM603 owner should really have one of these on hand [# 601 589 05 21 00]

Thanks for the reply. I've heard of the locking tool being used for checking the timing but I also heard it's easy to damage the IP by using it this way so I was kind of put off by that. From your comment I'm not clear on whether I actually need this tool to check the timing. Are you saying I can just look for the "raised vee" in the plug hole at 15 deg ATDC? I looked at that pdf file and I'm still not sure what this vee is supposed to look like, but I guess I'll know when I see it.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

You turn the crank clockwise until reaching 14 or 15 degrees ATDC, then look in the hole to see if the vee is centered. If not, you loosen the IP nuts [four I think, don't forget the one at the back of the pump], then use the handy built in adjuster to rotate the pump until the vee is centered in the window and voila! Pump timing the easy (and less accurate) way. The locking tool just confirms whether you're exactly centered. I think the only way you can bugger things up with the tool is if you forget it's in there and try to turn the engine over--for Pete's sake, please don't do that !!!

Keep in mind that I'm offering this advice to get you out of a pinch, but you really should either get the lock pin or the RIV tool at some point for more accurate timing. That vee can be difficult to see, so use a high powered flashlight and a clean mirror. To avoid parallax perspective you need to view the hole directly above the vee, not at an angle.

H202 offers good advice here...

I have the RIV and lock-pin tools, In my experience the lock-pin tool will get you close enough for the engine to run OK but it can still be 3-4 degrees off the published 15 ATDC spec. I have not tried the "center the raised mark in the hole" approach to see how accurately that works. My guess is that it would not be as accurate as the lock-pin approach.

Several very knowledgable people here have said the bubble method will work on the OM603 engine, even though that method is not described as a valid timing procedure in the OM603 book. Hopefully they will see this post and offer a bit of guidance.

I had my IP out to install a new IP seal. I cut a slot into the end of a 3/8 or 1/2, cant remember, wood dowel and put it in the 17mm hole and with the bar, or you can call it a vee, don't know why, the bar, or vee, looks like the business end of a medium sized slotted screw driver that can be seen through the hole on the governor body. The slotted wood dowel slips right into the hole and slides into the slot locking the IP. I set the flywheel to 15 degrees and reinstalled the IP.

Worked fine for me, and my 0 to 60 was better, showing 12 seconds from 12.78 before! BB

Am I the only one getting an image of a bong hit here???

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)

Not if you're like that certain someone who "didn't inhale". Word has it that you're supposed to suck, rather than blow on a bong. I'll have to ask a "friend" for independent confirmation, cuz I surely wouldn't [cough] know anything about such matters.

Hehe, I was actually thinking while I was doing this last night that if somebody saw me they might think I'm getting high on gasoline (surely they wouldn't know it's diesel and that I'm not sucking on the hose ). Well tonight I tried the easy timing method and I'm pleased with the results. Just from eyeballing the mark in the IP I can see that my timing is 14-16 ATDC, which is within specs. I could tell that 13 and 17 degrees are a tiny bit off so this method is accurate to +- 2 degrees or a little less which is good enough for me. I was just trying to make sure nobody has monkeyed with the timing. Now on with the delivery valve seals...

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

I figured out why I wasn't getting any bubbles. Since this was my first time doing the delivery valves, I didn't know that the valve seats (the bottom most part of the pump elements) are supposed to be oriented in a certain way. Each hole in the IP has a pin that slides into the notch on each valve seat and it's possible to install the valve seat at a wrong angle and push the pin out which will lead to blockage of fuel flow. That's what happened to me while I was doing the bubbling. The pin being pushed out really scared me, but then I found out I could take the side cover off on the IP and gently hammer it back in. I'm glad I caught this mistake before I reinstalled the delivery valves with the new seals.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

Thanks for the heads up. You didn't happen to take any pics did ya? I'll be replacing a full set of delivery valve seals when I install the intercooler manifold in the next week or so. I'd love to avoid any further delays.

No I didn't take any more pics. I know from my search that there was one person on this board who seemed to have the same problem and he was getting all kinds of diagnosis from his mechanic. I wonder if he ever figured out the problem.

Now about the timing, I noticed my W123 diesels have similar plugs on their IP's, not quite the same but in a similar location. Does anyone know if these are timing holes and if so what degree of the crank they're supposed to be checked at? I guess for the W123's the drip method is the only official method.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

gsxr can confirm this, but I believe OM617 pumps starting sometime in '83 began showing up with those same plugs. I believe the timing is the same as the OM60x engines as well. That's how I'll be timing my recently acquired '84 300D--I hate the drip method.