sprfrkr

I started my car up after a few weeks and heard some clattering coming from the driver side cam cover. Crossing my fingers, I went for a gas run. I get 1/2 mile away and the car starts to die, like it is running out of gas. I turn around to make it home and it makes it 1/4mi before dying. It will restart, but sounds like it is running on 4 cylinders. I put new gas in, fuel pump, fuel pump relay, etc. Still the same.

What I didn't notice beforehand is that the driver side belt cover had been sawed through by the belt! The belt had tracked halfway off the cam gear (see pics).`Now, obviously I have to tackle the timing belt. I don't have a last date, the PO just stated "recently". The cam gears are marked in white paint, just slightly off to the left of the arrow marking in the casting. The arrow is pointing at the tooth of the gear, the paint mark is on the adjacent valley. This is at 0TDC.

Now, would this account for a rough running condition if it is barely off the timing mark?

Regardless, should I use the existing paint marks for my belt replacement? Do the cam gears have a mark on them that I can't see?

TIA.


Passenger Side




Driver Side




0TDC

Kevin in Atlanta

There are notches on the back side of the cam gears. Use them to verify timing when the balancer is @ TDC. If the white marks are on the notches then that is where you need to be.

worf928

As above but be mindful. When you do the belt you are supposed to have the crank at 45 degrees BTDC. The marks line up - if everything is well - at TDC. Check the alignment of the notches at TDC and note if they are off. If they are then mark the gears as aligned at the backing plate notch so that you know how far off they are.

Transfer the marks to the gears when you're at 45 BTDC before you remove the belt so that you can get proper alignment when you string the new belt. Once you have the belt restrung you can rotate to TDC to check alignment.

The cams like to jump when the belt is off, so it is vitally important that you have alignment marks at 45 BTDC.

sprfrkr

I believe the 45deg is for 32V, 16V doesn't need to be rotated AFAIK and can be done at 0TDC. Sorry for not stating 1984 928S previously.
Is that a misunderstanding on my part for the actual install process?

PorKen

Timing looks to be OK? The belt is in bad shape and has likely stretched to the point of retarding both cams, but both cams appear to be about even. 16V gears are non-adjustable and can be almost half a tooth off anyway.

Probably a lot of worn out tensioner parts there. Water pump (likely a rebuilt going by the pulley color) is suspect, too. (Forward belt tension can pull the impeller into the pump housing.)

Crossing fingers = not a generally accepted diagnostic technique. (See also: Kibort, Mark )

Imo000

You don't need to have the crank at 45 to change the timing belt on a 32V engine. If you are removing the camshafts then yes, otherwise no.

worf928

OP didn't specify model year; I defaulted to safest method: 45 BTDC.

dr bob

Dear sprfrkr:

Please consider Rennlist Membership, so you can add all your car's information (like model/year/gearbox options) to a permanent "signature line" that shows up at the bottom of every post. Absent that, please type in all your car's information (like model/year/gearbox options) to a "signature line" that shows up at the bottom of every post.

With that information, the group will be able to offer much more accurate/valid recommendations to the symptoms you share in your posts.

Thank you kindly,

The Support Desks

Imo000

Doesn't matter the year, the safest spot for belt change are the timing marks, otherwise you are counting from the mark. I've done it both ways and the leaving the engine at the marks is the easiest. Unless you are removing or rotating the cams, there is no reason to move away from the O/T. The 45 degree timing belt change location was invented by the internet.

docmirror

I may be the only one, but the driver side does not look correct to me. We need a better pic before making a determination. Coupled with the bad running, and dying, I'm going to say the driver side cam is not in time.

As for year model, I see a green wire.

As for moving the cams to 45deg, this has caused SO many threads, and questions, and issues, and worry that I'm of the opinion that none of the cars should be done at 45deg. Lock it at 0|T, use the ticks on the cam and the backing plate, do the belt and be done with it.

YMMV, pro driver close course, contents have settled, and may cause **** leakage.

PorKen

Which could be the reason for poor running, BTW.

(For those just tuning in: the green wire is the special distributor pickup sensor wire for 16V ignition boxes. Best to replace if original.)

sprfrkr

As mentioned in post #4, we are talking about an 84 928S US Auto.

The driver side mark is an equal amount off as on the passenger side. About 1/2 tooth. I am going to be locking the flywheel in the next day or so to finish the tear down and will report back here on the tensioner and various pulleys/water pump.

I'll keep the green wire in mind if the TB repair does not solve the rough running.

James Bailey

Do a compression check.....before opening it up. Helps narrow the potential issues.

docmirror

Please report back with your findings on the root cause of the mis-tracking of the belt. While it's no question you need a belt at min, we would also like to know why the belt went 'off the reservation'. A comp check is a very good idea before you start pulling stuff apart.

worf928

Try again.

It was "invented" on page 15-106 of the WSM.