Engine crank during compression test?

best would be to have 2 more hands
so ask a friend if he/she can help
and disconnect the ignition ECU for safety

 

Make sure the throttle is wide open during the test.

 

You would connect the remote starter switch between the "+12V" battery cable on the large post at the back of the solenoid and terminal 50 on the starter solenoid (terminal 50 is the terminal with the white wire) -- but it needs to be a high-current capable switch as the solenoid current is something like ~10A.

Also remove the two fuel pump relays (in addition to unplugging the MicroPlex ignition ECU over the LH rear wheel as romano suggested).

 

This is common on a carb'd car - but is it applicable to a FI engine?

Rgds,
Vincenzo

 

I just did this yesteray. I didn't open the throttle though. Basically it builds pressure more slowly. I'm sure my reading were off a bit because of it. I also did it on a warm engine. My readings weren't as "tight" as those in the link, but they seem fine.

 

It makes a big difference on some motors and none on others. It is a good rule of thumb unless it is known for sure what the effect is.

 

Are you selling the car? Does it run poorly? If the answer is 'no' to both of those questions, you may get an answer you don't want to a question that shouldn't have been asked. I've let curiosity get the better of me on more than one occasion.

 

Vicenzo: Any engine that ingests air must have the throttles open (no restriction) to get an accurate compression test. Closed throttles will give you inaccurate readings from cylinder to cylinder.

 

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