Author Topic: WTF timing! (Read 6179 times)

Greasecar · « **on:** October 12, 2007, 06:53:14 pm »

I had a reman injection pump in the shop that I decided to throw into my newly aquired Rabbit tonight. I used to be able to swap out a pump and have everything dialed back in within an hour but its been awhile.

I pulled the valve cover, turned the engine until I could use my cam and pump locks then loosened the cam pulley and tensioner swapped the pump and started tightening everything up when I remembered that I never checked the Flywheel mark which was not in the bellhousing window. I know that the crank didn't have a chance to move significantly and of course the cam didn't either. My concern is that the inj pump may be 180 degrees off so I turned the engine by hand to try and get a TDC on the crank and cam but after turning the engine over about 10 times I didn't once get the flywheel mark to line up at the same time as the cam slot is in its lock position!! I can't figure out what is going on! The engine turns and there is no valve interference. Due to the ratio difference between the timing belt pully on the crank compared to the cam and IP I expected a few turns before everything lined up but after at least 10 it didn't happen once. What am I missing here?

Right now my plan is to loosten the belt and cam caps to raise the valves out of the way, then turn the crank to TDC and start over unless someone can point out what I am over looking.

Greasecar · « **Reply #1 on:** October 12, 2007, 07:18:27 pm »

That's why I'm confused because the crank and cam are way off. I guess the crank must have turned by some fluke but I still don't understand why I'm not getting any interference. I guess I'll just have to go with the starting from scratch plan.

jolotter · « **Reply #2 on:** October 12, 2007, 08:51:06 pm »

The cam and IP gear have double the teeth of the crank gear. So for two turns of the crank gear you get one turn each of the IP and cam gears. If the IP and cam gears were both set 180 deg. off, (difficult as you can't lock them thast way,) then turning the crankshaft one revolution would line it all perfectly. But if the crank gear is 180 deg (or any other) off, there is a likelyhood of contact between the pistons and valves . You won't know where it is except that it's not right because you can only set in one place. That's where you see the flywheel mark.

Since you have no mechanical interference they must be close. If you turn the camshaft so the number one lobes are sticking up and lock it, then free the gear so it can spin on it's taper and turn the crankshaft forewards or backwards, whichever is closer to TDC, (you observed that before you loosened the cam gear,) then you'll be right on. Then you can set the pump with the locking pin or align the marks, put the belt on, tension it and time the pump.

You can't make contact with the valves if the camshaft is locked and you go less than half a rev to line up the flywheel mark.

Johann

jolotter · « **Reply #3 on:** October 12, 2007, 09:14:08 pm »

Over in Troubleshooting, I just read Burn Your Money saying that some IP gears have two indentical lock pin holes, 180 deg apart. Still wouldn't affect the cam and crank positions.

johann

Greasecar · « **Reply #4 on:** October 13, 2007, 05:47:03 am »

Just slept on it and I'm thinking more clearly. Of course, 4 stroke engine = 2 crank turns per 1 cam turn and the slightest mis turn of the crank in relation to cam will be doubled. The crank must have moved slightly under the weight of the pistons while I was banging away getting the IP pulley off.

Anyway, easy fix iunless I inadvertantly bent a valve in my hand turning (but don't think so).

jimfoo · « **Reply #5 on:** October 13, 2007, 08:08:07 am »

You could also turn the engine until a valve is fully open on #1, remove the timing belt, carefully turn the crank by hand in both directions, marking where it stops each time. Appx half way between the marks is TDC, which after you get the belt back on, you can compare with the flywheel mark. That would tell you if the flywheel is indeed 120 deg off or not.

Greasecar · « **Reply #6 on:** October 13, 2007, 10:31:28 am »

Looks like it must be 120 off. Came to the shop today, lifted the cam, set the flywheel mark to TDC and then set the cam up, now I have interference!! I should have left it where it was yesterday.

Now I have to figure out where 120 degrees from the mark is and in which direction. Anyone know how many teeth should be on this flywheel? it's a 1984 1.6 in a Rabbit.

Anyone else have any tricks to determining TDC without opening this thing up?

Vincent Waldon · « **Reply #7 on:** October 13, 2007, 10:50:16 am »

Quote from: "Greasecar"

Anyone else have any tricks to determining TDC without opening this thing up?

The common trick is to pull injector #1 or #4 and snake a stiff wire or long screwdriver into the cylinder (a bit tricky due to the pre-combustion chambers) Rotate the engine one way until the piston just touches the wire and mark the flywheel. Rotate the engine the other way until the piston again just touches the wire and mark the flywheel. TDC is exactly half way between both marks.... probably easiest to count flywheel teeth between the two marks and divide by two.

Vince

Black Smokin' Diesel · « **Reply #8 on:** October 13, 2007, 12:26:06 pm »

Quote from: "Vincent Waldon"

Quote from: "Greasecar"

Anyone else have any tricks to determining TDC without opening this thing up?

The common trick is to pull injector #1 or #4 and snake a stiff wire or long screwdriver into the cylinder (a bit tricky due to the pre-combustion chambers) Rotate the engine one way until the piston just touches the wire and mark the flywheel. Rotate the engine the other way until the piston again just touches the wire and mark the flywheel. TDC is exactly half way between both marks.... probably easiest to count flywheel teeth between the two marks and divide by two.

Vince

Good advice. If you stick a stiff wire into the cylinder are turn the crank until it starts to move up then down you should be able to find TDC.

Greasecar · « **Reply #9 on:** October 13, 2007, 01:15:46 pm »

Well, counting teeth is out since they aren't visible through the inspection hole. Whether it is the wire trick or some sort of valve interference trick I'll need to find the top of the pistons rather than count on the flywheel. This would be so much easier on a TDI where GP or injector holes go right into the piston face.

jolotter · « **Reply #10 on:** October 13, 2007, 03:04:03 pm »

If you loosen an injector a half turn then dribble a little oil around the threads, when you turn the engine by hand the oil will bubble on the compression stroke and it will suck down when you come over TDC. At least you can get a rough idea where it is and see if your flywheel is in fact 120 deg. out.

Johann

Greasecar · « **Reply #11 on:** October 13, 2007, 03:27:45 pm »

Okay, back in time. Good call on the wire.I stuck a welding filler rod into the injector hole and made a poor mans dial indicator. Now I have my new mark.

I still don't know what happened on the fly wheel though because the locator pins didn't appear to be damaged at the time of installation but I had one of my guys bolt it up so who knows.

Thanks to everyone for the tips.

bigblockchev · « **Reply #12 on:** October 14, 2007, 04:28:05 pm »

I see a lot of references to 120 degrees here, are we really talking 120 degrees or 180 degrees? The wire or coat hanger bit in the injector hole is a lifesaver to get you in the right ball park. Cheers Dan

jolotter · « **Reply #13 on:** October 14, 2007, 08:55:02 pm »

Quote

Libbybapa wrote:

There are three ways (one that is correct and two that aren't) that the flywheel can bolt onto the pressure plate and still have all bolts present. The locations are evenly spaced.

Figuring it out was like patting my head and rubbing my belly. Installing the crank 120 deg off off would cause interference with one of the either the intake or exhaust valves depending on which way it is off.

When I bolted the flywheel on my 1.6TD I'm sure that the bolt holes were spaced unevenly so I could only put it on one way. Is the 120 deg thing rabbit specific?

Johann

Edit: I bolted the flywheel directly to the crankshaft as it was for a Vanagon. I see how putting the pressure plate between those two parts makes it possible to incorrectly position the flyhweel.