560 Distributor Timing Q's - PeachParts Mercedes-Benz Forum

jcantor · #1 11-22-2002, 11:45 AM

Okay, I'm stumped. Well more likely very frustrated and therefore missing the obvious.

Background: I just completed timing chain and guide replacement along with cam oilers and valve stem seals on my '87 560SEL. On reassembly I double checked the cam timing several times, even removing the valve covers again to be sure while installing the distributor.

Everything went according to plan until I tried to restart the car. I've managed to get it to start a couple of times by moving the plug wires around on the distributor and have pulled and reinstalled the distributor several times in attempts to get it to start and run well. The best I've been able to get is a hard start, minimal ability to idle (usually at around 400 rpm), very little power, and a lot of overheating (I've driven the car about 5 miles).

According to what a couple of local indy techs have told me, the distributor can actually be installed one or two teeth off in either direction as the car has a means of auto correcting the timing. This makes at least a little sence to me as I've noticed that turning the distributor across the range allowed with the bolt makes little if any difference in the timing as observed with a light. As I mentioned above, I pulled the valve covers again just to make sure that I hadn't inadvertantly retarded one of the cams when replacing the chain (I hadn't) and reinstalled the distributor yet again.

Are there any tricks to distributor installation under these circumstances or some other thing I'm overlooking?

One suggestion that has been made is a vacuum leak, particularly at the brake booster. I've checked this line and it appears intact (brake performance was also normal during the brief drives I've been able to make thus far).

I'd really appreciate any advice or suggestions as the local techs are booked solid through early December and I really wanted to use the 560 for our pending trip with my folks to Boston for Thanksgiving.

Thanks to all in advance.
jlc

mbdoc · #2 11-22-2002, 11:52 AM

Timing of the distributor is PHYSICAL. Has no effect on timing of the engine. AT TDC on #1 cylinder compression stroke the center line of the rotor button must align with PUNCH mark on the outside of the distributor housing.

jcantor · #3 11-22-2002, 04:46 PM

M.B. Doc,

That's what I thought and that's what I've done. Any idea then on what I might have inadvertently disconnected or broken? Before starting this project the car ran nearly perfectly!!

jlc

#4 11-22-2002, 05:23 PM

If you suspect "a vacuum leak," replace the line with a new one, or at least put a known vacuum on it (e.g., via a Mityvac) and see if it leaks down or holds the vacuum.

The fact that " . . . it appears intact" doesn't say much from my experience - I rarely can find a small leak even once I know there is one.

M D "Doc" Nugent

mbdoc · #5 11-22-2002, 05:34 PM

Is the engine running on all eight cylinders?? It is easy to get the right camshaft 180deg out of time. The woodruf key must be aligned with the notched groove in the "washer" that goes on before the timing gear. Did you remove the engine to do the job? If so did you have the flywheel off? The flywheel MUST be aligned properly or the timing will be off by 40deg.

jcantor · #6 11-23-2002, 08:20 AM

M.B. Doc,

I did everything with the engine in the car so flywheel timing isn't the culprit. The suggestion of getting one cam 180 degrees off was made by one of the local indy techs I spoke with. That was what got me to pull the valve covers again, go to TDC on #1 and recheck the marks. Both lined up with the marks on the sprocket and cam tower.

One other suggestion that Mike Tangas made in a private email was that the distributor cap can be damaged by being too far out of time. I'm wondering if I damaged the cap then with all of my initial tinkering with the distributor as I do know that I had dropped it in out of time a couple of different ways before getting it in correctly.

jlc

#7 11-25-2002, 10:40 AM

Jeff - read slowly what MBDOC said "It is easy to get the right camshaft 180deg out of time. The woodruf key must be aligned with the notched groove in the "washer" that goes on BEFORE the timing gear." To check this, it sounds like you have to pull the timing gear off the right camshaft to check the alignment with the washer. Check this first. Many times I have screwed up because I couldn't remember how things went back together. Now, instead of throwing everything into little containers, I try to keep everything in order they came off and in the same position to each other as they are removed so three or four days later it is easier to remember how they went together. Check it out and let us know
Maurice

380SEGUY · #8 11-25-2002, 11:01 AM

Jeff,

Just to clarify what M.B. Doc and others have said.

The woodruff key must point to the timing mark on the cam tower on the left head.

The cam spacer washer will fit on two ways and if the timing mark on the washer points to the reference mark on the cam tower but the woodruff key is pointed down the cam will be 180 degrees out of time.

I don't know if the same rule applies to the right head but since that is where the #1 cylinder is you can check it by turning the engine to TDC and then checking the position of the cam lobes.

Since TDC of the engine is on the compression when the spark plug is firing the intake lobe should be closed and the exhaust lobe should be coming around to open the exhaust valve for the exhaust stroke.

After any changes in cam timing you should only rotate the engine BY HAND. If you feel any binding stop and fix the problem before you end up with a very costly valve job.

jcantor · #9 11-26-2002, 09:52 AM

Guys,

Thanks for all the input. Both cams were properly timed. The problem turned out to be something Mike Tangas suggested as a possibility -- a fried distributor due to my intial attempts to run the car with the distributor incorrectly timed. Once I ground off the burn marks created by the arching, it ran perfectly.

jlc

#10 11-26-2002, 11:26 AM

Curiousity question for MBDOC: If the cam was 180 degrees out because of the washer drift key scenario- and he tried to start it - would not the valves have hit the pistons since this is an interference engine?

mbdoc · #11 11-26-2002, 11:37 AM

NO! they are still in the same rotating phase. Only the FIRE comes at the wrong time in relation to the cam timing: only with the engine 180 out.

Glad to hear that you were successful!!