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Mk2 Digifant 1 Timing gurus...need help

Want to check my timing, failed smog miserably. Car is a '91 GTI 8V, totally stock engine. Got questions. Bentley #1: On cars with manual transmission, use a 27mm hex wrench to remove the plastic plug from the timing check hole at the top of the transaxle bellhousing.

I say: OK did that.

Bentley #2: With the ignition off, connect a tachometer and timing light to the battery + and to the coil negative terminal 1.

I ask: Ummm...ok I can identify the coil negative terminal 1 just fine using the Bentley's drawing but how the heck do I attach my timing light to it? My timing light has a big ol' clamp type terminal designed for connecting to the battery neg. terminal. Can't I just do that? (I did.) I also connected my + to battery + and connected the other thing (whatever it's called) around #1 spark plug wire.

Bentley #3: Disconnect the harness connector to the coolant temperature sensor as shown.

I say: OK did that.

Bentley #4: Start the engine and allow it to fully warm up. Oil temperature should be at least 176F. Radiator fan shoudl cycle on and off at least once indicating that the engine is up to normal operating temperature.

I say: Waited until fan cycled on and off once.

Bentley #5: Briefly raise the engine speed to about 2100rpm and let it return to idle. Repeat 3 or 4 times.

I say: OK did that (3x).

Bentley #6: With the engine running between 2000 and 2500rpm, aim the timing light at the timing check hole in the transaxle bellhousing. The timing mark on the flywheel should appear adjacent to the pointer in the hole as shown.

I say: Had someone sit in the car and hold at about 2250rpm according to the tach on the dash, checked timing...ummm...what mark on the flywheel? I don't see it.

I put everything back the way it was and just for fun checked the timing at idle with the coolant temperature sensor connected. I see the mark now but I'm at idle and with the CTS connected, not 2000-2500rpm.

So if Digifant is supposed to be set at 2000-2500rpm with the CTS disconnected, then my timing's off, right? Last time it was set someone else did it (dealer actually). Did they do it wrong and set it at idle instead?

Since I physically can't connect my timing light to the coil's terminal 1 negative wire, was connecting it to the negative terminal on the battery ok? or did that invalidate everything?

Argh.

Reply to
Matt B.
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Reply to
vwtopdown

thanks but yeah i've seen that page. doesn't really tell me the importance of connecting the '-' of my timing light to the coil power stage vs. '-' on the battery. and I think he's referencing a different set of timing marks than in the bentley b/c the ones in the bentley are not marked in degrees BTDC (at least it doesn't appear to be).

Reply to
Matt B.

Just connect the timing light to the battery + and -. The clamp is hooked up cyl.#1, that is the one on the cambelt side. Don't pull any connectors just point it at the flywheel. If the mark on the flywheel is unclear use some paint or tipp ex. to highlight. Top dead center is indicated by a "0" the v shaped notch is not far from it.

SFC

"Matt B." schreef in bericht news:tDygf.1158$1x.711@fed1read06...

Reply to
SFC

OK cool...thanks...that was pretty much my #1 question (battery '-' vs. the negative coil power stage wire).

Reply to
Matt B.

I hope you took off the entire green plastic plug not just the little clear plastic thing in the center. You can't see the timing marks unless the entire green plastic "bolt" is removed.

Not sure what the point of all this is. If you have an inductive timing light you just put the clamp around the #1 plug wire (closest to the timing belt).

Shouldn't this be done right before you start setting the timing, after the engine has warmed up?

I don't know if you've ever timed a VW before. There is a distinctive diamond shaped mark at 6 degrees BTDC on the flywheel and a smaller dimple at 0 degrees. The threaded area has a small pointer on it. The two should line up when you are looking straight down at it. Unfortunately, virtually everyone I've met (including myself) misidentify the mark the first time they try this, and unless you are familiar with it, or someone points it out to you, this is a problem. One thing you might try doing is having someone crank the crankshaft by hand while you observe the flywheel looking for the mark. Some people put a dab of paint on it.

It's always possible, that is the correct way to do it for CIS/CIS-E. Maybe they didnt realize Digifant has to be set differently. Does the car drive badly? Why did you suspect bad timing? What were the readings and limits?

dan

Reply to
notme

Yep did that.

That's eventually what I did (I have an inductive timing light)..

Engine was warm already (I guess I didn't state that). However I think this is where the "gotcha" is. The Bentley seems to indicate (or at least this was how I read it the first 6 times) you disconnect the CTS and then start the engine. Nope. Eventually at some point I instead started the engine first, *then* disconnected the CTS, and *then* went about setting the timing. This made all the difference in the world (disconnecting the CTS after starting the engine, not before). Somehow that put the ECU into the correct mode for adjustments and when set at 6-degrees BTDC and everything then was reconnected, the car ran great.

No. Last car I timed was I helped my dad time a Pinto in the mid 80s. :) I was like 14 at the time.

I found a pic of this (rather than a bentley drawing) on the 'net and identified it OK. My main issue was disconnecting the CTS before vs. after starting the car. That seemed to make all the difference in the world in the results of setting the timing.

My readings were very high on HC and NOx. After I got the timing right I took it back and NOx improved a little bit (not enough to pass though) but HC got worse.

I then gave up on the DIY and took it to a smog repair place for gross polluters. they replaced the cat and decarboned the engine. Tested awesome after that.

I think all the DIY I did (pretty much a tune up) and new O2 sensor didn't hurt 'cause they were all old and it was time for all that but it wasn't the worse cause of failing smog.

Reply to
Matt B.

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