Timing experts inside, please, I am lost

[mdregister]

Hi ALL,

I am having some difficulty with the timing on my non-aspirated 1985 6.2L diesel.

I will explain as clearly as I can.

With the pump flange marks aligned, my MT 480 reads approx. 4* BTDC at IDLE and approx. 1* ATDC at 1300 rpm.

By advancing the timing marks approx. 1/16 inch (the width of the mark), my IDLE advances to approx. 5* BTDC and 1.5-2** at 1300rpm.

That is about as high as I can get the timing at 1300 rpm. Even if I advance the pump as far as it will go (approx. 3/16 inch) I can not get the timing to the recommended 4* at 1300 rpm. What I do get with the pump advanced all the way is a TON of smoke at high rpms/hard acceleration and a slightly rougher idle.

Why can I not advance to the recommended timing?


I believe the meter is working fine due to its consistency and my ability to alter readings by adjusting the probe.

If I go the other way with the pump marks, the meter responds as it should with the timing becoming more retarded as the rpms increase.

:help:

mike

[britannic]

Is your timing chain worn?

[mdregister]

Thanks for the reply,

That is my best guess. I am the second owner and the truck has 122K miles on it. Not sure if the chain has been repllaced, but I do not think so.

Would a worn chain exhibit my problems?

When replacing the chain, how do you locate TDC?

[britannic]

If you plan to keep the truck, install timing gears and enjoy :D , otherwise, invest in the TDC article that describes timing chain replacement, available in the Reprints section on this website.