Author Topic: More Injection Timing Questions  (Read 3727 times)

June 05, 2004, 10:02:10 am

Mikeyworks

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More Injection Timing Questions
« on: June 05, 2004, 10:02:10 am »
For the sake of discussion, if I remove the timing belt to do a head gasket job, and don't move the injection pump in doing so, will I have to adjust the injection pump timing with a dial indicator to get the timing right when I button it all back up ? If so, why?

Thanks,

Mikey



Reply #1June 05, 2004, 12:09:59 pm

VWRacer

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« Reply #1 on: June 05, 2004, 12:09:59 pm »
Maybe with practice it isn't difficult, but I still remember trying this for the first time. In 1985 I blew the head gasket on our '80 N/A Diesel Rabbit, and changed it myself without having the right tools to time the pump. The engine turned over by hand and with the starter motor without interference, but try as I might, I could not get the timing right and it would not start.

I took it to a mechanic recommended by a friend, but he lacked the right tools as well, and when I got it back it would only do about 40 mph (what...10 hp?). Only by taking it to a shop with the right tools would it run right.

This is not to say it can't be done, but I am a fair mechanic and couldn't get it to run when I tried it for the first time. YMMV...  :wink:
Stan
C-Sports Racer

Reply #2June 05, 2004, 05:50:51 pm

Mikeyworks

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More Injection Timing Questions
« Reply #2 on: June 05, 2004, 05:50:51 pm »
Ok, another sake of argument question.

If the cam sprocket was off by one tooth, how bad would the damage be?

I'm not saying that it is, yet, but I thought I would ask.

That's the first thing I am checking in the morning.  Damn this rain...a full day with nothing on my plate...and it poured all day!!!!!

Mikey

Reply #3June 07, 2004, 09:29:58 am

BlackTieTD

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« Reply #3 on: June 07, 2004, 09:29:58 am »
one tooth off on the cam is bent valves  :cry:

engine should still run one tooth off though.. just not properly.

Reply #4June 08, 2004, 12:49:04 pm

racer_x

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« Reply #4 on: June 08, 2004, 12:49:04 pm »
Quote from: "Mikeyworks"
Ok, another sake of argument question.

If the cam sprocket was off by one tooth, how bad would the damage be?

I'm not saying that it is, yet, but I thought I would ask.

That's the first thing I am checking in the morning.  Damn this rain...a full day with nothing on my plate...and it poured all day!!!!!

Mikey

Cam timing is absolutely critical on the IDI diesels. With everything exactly to spec, there's 0.020" (0.5mm) clearance between the pistons and the valves. That's why the diesel cams are the only ones that work. Even the mildest gas engine cam will put the valves and the pistons in the same place at the same time (and bend the valves or damage the pistons).  

The main reason there's no key on the camshaft is that you can't be off with the camshaft timing. Even half a tooth off can cause damage to valves and pistons. It's also best to turn the engine over 3 or 4 complete revolutions after doing anything that involves reseting cam timing (anything you have to remove the timing belt for). You can tell by feel if the valves are touching the pistons. It's even better to do the test turns of the engine with the glow plugs or injectors removed so there's no compression fighting you as you turn the engine. That way, any resistance you feel from valves colliding with pistons is more obvious.

Reply #5June 09, 2004, 07:50:34 am

Mikeyworks

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« Reply #5 on: June 09, 2004, 07:50:34 am »
Well,  I checked and rechecked the timing. It seems everything there is right. Now it's on to other things.

I will recheck the injectors. I will remove the fitting and lines one at a time to see if I can get the noise to go away.

Next step is to drop the oil pan and see if there's something awry down there that's transmitting the sound to the top of the engine.

I'll keep you updated.

Mikey