96 Jimmy #3 misfire...STILL

[old_master]

Yup! You'll might just find a problem with excessive leakdown when you check fuel pressure. Look closely at the fuel pressure regulator when you've got the plenum off.

[Sheriff8524]

Is it safe to turn the key to on with the plenum off if I reconnect the fuel lines to see if anything is leaking?

[Sheriff8524]

disregard previous post.... I did a compression check on all cylinders today
all the cylinders are at 150 except for #3 it tops out at 90-100 so is it safe to say that cylinder is shot from my oil cooler line break and loosing most of my oil.If so what course of action should be taken to get to repair? Also the computer keeps alternating between a 300 and a 303 code what would cause this if just one cylinder is bad? Thanks

[old_master]

The most accurate way to check compression is remove all spark plugs, disable ignition and fuel pump, prop throttle wide open, crank starter and watch compression tester for four pulses. Mark down the highest reading for each cylinder and label them as "Dry test". Then add approximately 1 ounce of 10w30 motor oil to each cylinder and re-test compression on each cylinder and mark down the results. Label these as "Wet test". Doing the test both wet and dry will give an indication of piston ring condition also.
Post the results for each test.