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16v TDC exhaust or intake - does it matter????

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Old 11-20-2010 | 10:01 PM
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Default 16v TDC exhaust or intake - does it matter????

The car was running although not well after I resolved my clutch issue.

I decided to pull all the belts, fan and check out the cam timing. With the harmonic balancer at TDC both cam marks were aligned but the rotor was 180 degress out from the index mark and #1 cyc on distributor cap per the WSM and Sharkskins write up. I pulled the distributor and rotated the stator to get the rotor aligned with the index mark and the #1 cyc as marked on the dist cap.

My external fuel pump was also making noise and was still under warranty so they sent me a new one.

Today I got everything back in and now the car turns over strong but does not even give a hint of starting. I have 1400+ ml fuel in 30 sec at the out port of the fuel filter. I even tried a spare pump and fuel pump relay, same result.

I have not pulled the return line off the fuel distributor but did pull one of the injector outlet lines seeing if I had fuel going to the injectors. I turned the engine over but no fuel. Makes me realize how little I know about this system.
How do I insure I have fuel going to the fuel distributor? Is it possible to have ample fuel flow out of the filter but not enough pressure to make the system work properly?

Could I have the rotor out 180 degress? Is it possible to be TDC with cam marks aligned and be on the wrong cycle, exhaust versus intake? Do I just rotate the stator 180 degrees back to the way it was?

Really makes me revisit the "if it aint broke don't fix it" theory.

Thanks

Last edited by jwillman; 11-20-2010 at 11:22 PM.
Old 11-20-2010 | 10:25 PM
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Sounds like you may have the distributor out-of-sync. Or some other change that boldly prevents starting.

Try a timing light on the cam sprocket. It should freeze the notch near the marks.
Old 11-20-2010 | 10:26 PM
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No assumptions.

Define what you are calling cam marks. Tic marks on back edge of gear?

Leading or trailing edge of rotor aligns with mark on distributor?

(good tests, above, also, just saw the reply)


This is where a few pictures can be real helpful to the armchair quarterbacks
Old 11-20-2010 | 10:58 PM
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It's also really easy to get the distributor off one tooth at the cam. It may look "OK" but not be on. A timing light can be most instructive on this one.
Old 11-20-2010 | 11:12 PM
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Originally Posted by Landseer
No assumptions.

Define what you are calling cam marks. Tic marks on back edge of gear?

Leading or trailing edge of rotor aligns with mark on distributor?

(good tests, above, also, just saw the reply)


This is where a few pictures can be real helpful to the armchair quarterbacks
The cam notches were aligned with the engine pointers when the harmonic balancer was TDC. My concern is that if I understand it correctly the harmonic balancer rotates past TDC twice for one cam gear rotation.

If the timing belt is off and the harmnic is TDC does aligning the cam marks mean everthing is good?
Old 11-20-2010 | 11:40 PM
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Yes, with a couple caveats.

1. Harmonic balancer is not flipped. (when standing in front of car, the numbers should read normally, not upside down)
2. Harmonic balancer periphery has not turned relative to its core (keyway) (the rubber degrades and the outer can move relative to the inner)

To recap, the pistons move up and down once per crank revolution, just like you thought.
Setting a properly installed, intact harmonic balancer to O/T is correct.
Cam gears (also keyed) are with the little divot marks on their backs aligned with arrows on back covers.
Timing belt is installed.
Then, as stated, install distributor and it must not be off a tooth.

IIRC its hard to get the distributor indexed just right without moving the passenger camgear a little (attached to everything else at that point).

Make sense?

(fortunately you are working with a non-interference motor, hopefully that doesn't have a shaved head and carbon buildup, which might cause contact internally if cams are rotated independently of crank without crank being in a certain place)
Old 11-21-2010 | 01:16 AM
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unfortunately I got to see 1st hand what a serious out of wack dist will do to a 16V 928......it varies from the car weezing like and asthmatic & not starting...to just running like crap....when we had the dist about 1 tooth off on the cam...I think it ended up around -5 degrees & it ran horrible....it also managed to dump enough fuel to turn the manifolds red hot!!! Once I set it correctly at 20' @ 3000rpm with no vac it ran great!!! We ended up setting it to 22' @ 3000rpm & it runs great!!!!
Old 11-21-2010 | 01:38 AM
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How about some pics of what you did?
Old 11-21-2010 | 01:41 AM
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There is one other thing to check on the distributor...

With crank at TDC, cams at the proper marks, and distributor rotor pointing at the mark on the body, the wire that the rotor is pointing at MUST go to cylinder #1, and the other wires must run to the cylinders in firing order.

If the engine was running with the distributor out 180 deg, and you turned the distributor rotor around, the WIRES are now 180 deg out.
Old 11-21-2010 | 10:42 AM
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Originally Posted by WallyP
There is one other thing to check on the distributor...

With crank at TDC, cams at the proper marks, and distributor rotor pointing at the mark on the body, the wire that the rotor is pointing at MUST go to cylinder #1, and the other wires must run to the cylinders in firing order.

If the engine was running with the distributor out 180 deg, and you turned the distributor rotor around, the WIRES are now 180 deg out.
I will recheck everything.

The outer distributor housing alignment mark is on the front side of the distributor case facing the radiator. The distributor cap was #1 cyc wire was also facing forward so I lifted the distributor until the teeth of the stator were free and rotated the stator to align the rotor notch to align the front (contact end) of the rotor with line on the distributor case.

The stator gear teeth are angled and what I found was that the stator rotates as the teeth engage during reinstallation.

The pic below shows the stator when I found it 180 deg out with the balancer at TDC (numbers facing me) and both cam marks aligned with the pointers on the engine housing.
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Old 11-21-2010 | 03:48 PM
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Passengers cam is aligned with TDC set on balancer. Rotor is pointing forward and aligns with the reference mark on the distributor housing. #1 cyc on distributor cap is forward and rotor points to #1 cyc. Plug wires and firing order verified.

Still no start. WSM has you pull the return line off the fuel distributor to check fuel flow with pins 30 and 87 jumpered. Seems I could also check at the return line connection to the flex line on the other side of the engine.

Guess it is time to start chasing spark and fuel
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Old 11-21-2010 | 05:21 PM
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Good belt tracking.

How about a shot of the alignment of r and l cam gears with respective marks at TDC?
Old 11-21-2010 | 05:25 PM
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They are both spot on. Car has not started since I reinstalled and only pulled the drivers side again to confirm TDC and cam position assuming that the other side is good as just done. Tensioner was rebuilt (tore apart, cleaned, fresh 90 wgt and new boot) and roller bushings replaced at the same time. Did not do water pump as it showed no issues.
Old 11-21-2010 | 05:30 PM
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Sorry, we had a guy aligning the porsche official parts logo triangle with the cam covers one day thinking that was the mark.

OK. Could you have disrupted the green wire on the distributor? It tells the spark box on the fender when to fire the plugs.
Old 11-21-2010 | 06:59 PM
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It's hard for me to follow but did you spin the distributor 180 during the timing belt job or is everything aligned as it was before taking anything apart?


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