Help!!

I'm selling the engine out of my 88NA, and a couple of people have asked me to do a compression test. The engine is out of the car and sitting in my garage. The tranny is still attached.

Is there any way to hook a set of jumper cables on to the starter and turn the engine over to get a quick compression test?

Also a note - turning the engine over manually with the throttle body closed resulted in:

Front Rotor - 30 - 30 - 31
Rear Rotor - 29-30-30

After opening the TB, I got almost a 70 on one quick turn by hand. Not opening the TB causes that much of a pressure diff??

 

Yes, your supposed to keep the throttle open when testing, or theres no way for the engine to suck in the air it needs to compress.Your best way to do it, would be to get an air ratchet, and spin it over using the bolt in the main pulley.

 

Ground the jumper cables to the engine somewhere, and jump the positve between both the solenoid and the stud. It will spin over that way, but watching the gauge will be kinda hard.

It should be noted that a test is supposed to be done on a warm engine, but its somewhat impossible in your case.

 

Figured it out. Negative to block, Positive to the outside terminal. Take wire and hook to spade terminal on top of starter. Touch wire to positive to get engine to turn over.

Comp results:
Front Rotor - three bounces over 115.
Rear Rotor - three bounces over 110.

Thanks Guys!!

 

Compression test results depend on engine rpm, so you should really turn the engine with the starter motor so you know it’s turning at the right speed. It shouldn’t be too difficult to connect a battery to the starter motor using jumper cables.

 

Oops, too slow!