Compression question

[hooken203]

SER# 1E 053049
300XS
When checking compression how will the air injectors affect your readings? Should they be disconnected when you check it?

[Savage]

1. The air injectors will be closed so its a non-issue (kill switch activated). Motors not running, so the compressor is not pumping much air.
2. No

[hooken203]

Ok thanks. That’s what I thought. I was told different by a Facebook expert.

[EuropeanAM]

Facebook Expert must be using key switch, too.

[hooken203]

So if you don’t use the key switch but instead jump the solenoid then you don’t have the compression loss through the air injector’s. Is that correct?

[JOE54]

correct , and key in off position

[hooken203]

Thanks for the response Joe. I have always used a remote start switch to jump the solenoid if it’s easy to get at. I like to know what that first compression jump is. But every time I learn one of these things that I should do when I checking compression I have back up try it the other way just to see how much difference it makes. As near as I can tell if you were to ask 10 mechanics how to check compression you would get 8 different answers.

[JOE54]

and probly 6 are wrong

[EuropeanAM]

Thanks for the response Joe. I have always used a remote start switch to jump the solenoid if it’s easy to get at. I like to know what that first compression jump is. But every time I learn one of these things that I should do when I checking compression I have back up try it the other way just to see how much difference it makes. As near as I can tell if you were to ask 10 mechanics how to check compression you would get 8 different answers.

It's outlined quite clearly in most service manuals, as well as in the FAQ Section at the top of the Forum.