My suspicion is Nikasil cylinder wash on a 1998 XJR. The engine rotates faster than normal with a no-start cranking starter. There is spark at the plugs, 12.56 volts in the battery, 46 lbs fuel pressure, but cannot read OBE II codes with my AutoEnginuity and AE's Jaguar module. AutoEnginuity does not recognize the connection; but that is a different issue, that I will take up with the AutoEnginuity folks.

To confirm the cylinder wash condition, I want to do a pre-oil compression test, or a compression test prior to adding a spoon-full of oil to each cylinder, then do a post-oil compression tests, and compare the two results.

My question is: Will a pre-compression test be harmful to the engine? Or should I be on the safe side and just add a spoon-full of oil to each cylinder and forgo the pre and post-compression test?

Thank you for in advance your comments.

 

If you want to take the scientific approach, then yes, you can do that.

If you just want to have the engine running, try to start the engine with the accelerator floored till the board, this will cut off the fuel supply.
Do it in burst of 10-20 sec. to save the starter.
The oil might seal the rings, and you might be able to start after some attempts.

If not, the spoon of oil is the way to go, remember to spread the oil before putting the spark plugs back in.
A rag on the holes will prevent spilling it all over.

 

Thank you Eric Jansen.

 

What is a "pre compression" test?

 

I think he means compression test before adding any oil. (Odd choice of term.)

No it won't cause harm.

 

A compression test done while in the bore washed state will simply confirm what you already know: not enough compression to start the engine.

 

It could very well just be "bore wash". There haven't been many Nikasil failures lately.

 

Thank you for responding to my query.

Sparkenzap, JagV8 expressed my thinking better than I did. In addition, yes JagV8, I did chose an odd term, but did not know a better one.

Mikey, yes exactly, “A compression test done while in the bore washed state will simply confirm what you already know”. I wanted to confirm not what I already know, but that I suspected cylinder wash. My question is will I do damage to the cylinders in a cylinder wash condition without the proper amount oil contacting the cylinder and rings?

JimmyL, yes you are right.

 

No.

The low compression observed will not help in any sort of diagnosis though. I'd just skip it, get the engine running then do a test.

 

Thank you Mikey, I'll do just what you suggest.