JDM for Lyfe

Did some starter circuit tests on my car and i didn't disable fuel. I started the car and it started fine when i finished and was letting it warm up to do a compression test and the car started running bad and died. I tried to start it again and it would not start. I tested the ignition and fuel. both were working good. fuel injectors were all at 11.7 ohms and fuel was pumping out of the relief valve. grounded plugs and all fired. let it sit for a bit and tried cranking the engine with no plugs with wot and tried again but nothing fired. plugs were dry when pulled back out. put the torch to them for several seconds and threw them back in and nothing. did a compression test while engine was cold and got 170 psi in cylinder 4, 140 in cylinder 3, 135 in cylinder 2, and 140 in cylinder 1. nominal spec is 184 psi, minimum is 135, and variation is 28 psi. has bad knock sensor too. im letting the car sit for the night with plugs out to dry up whatever is in the chamber. if it doesnt start tomorrow what should i do? could it be the knock sensor? is the compression too far apart to even start?

ezone

What was the original problem? Was there a real problem, or were you just playing? LOL

So it died while it was running.....

Were the plugs wet or dry when you pulled them out?


Check for spark:
Just seeing sparks fire across a spark plug gap isn't enough. If you can only get 1/8 inch of spark, that ain't enough to run the engine.

See how big of a lightning bolt the ignition can make.

You should be able to get sparks to jump across at least 1/2 inch gap or more at the end of the plug wires. 3/4 inch is better.

If you can't get that much spark, you have a problem there. Weak coil is common.


Checking compression on a flooded engine does not give an accurate indication of the internals, all it does is confirm lost cylinder sealing.

Put about a teaspoon of oil in each plug hole. Then crank it over without any plugs in it, this distributes oil around the cylinder and rings, and can blow excess out of the plug holes.
Your compression check should be a bit higher now.

JDM for Lyfe

i was doing some tests to practice for a shop test at school on the starter circuit. the last time i pulled the plugs they were all dry. i did a spark plug gap test and didnt read anything at 3/8 but got spark at 1/8. lets just say there is weak spark. what do i do now? i just replaced plugs wires cap and rotor 800 miles ago.

ezone

I would repeat the gap test directly at the coil tower. Take the dist cap off, use a grounded wire or a screwdriver that is attached to ground, use that to create a spark gap.

If the spark is still weak there right out of the coil, put a new coil in it. A good coil should throw lightning bolts 3/4" to an inch long.

If the spark is great there, then it is getting lost somewhere between the coil and the plug wires. Proceed with troubleshooting.

HTH

JDM for Lyfe

retested the spark gap and it was bad. #4 didnt have any spark. tested the coil and the a - b terminals gave out 1 ohm resistance which spec is .63-.77 ohm so gonna buy a new coil tomorrow and should do the trick

ezone

Does that mean the other three plugs got spark?

JDM for Lyfe

yes but very little. i know the day before all the plugs fired when tested. i just layed them on the valve cover and they all sparked. when gap testing today cylinder 1 2 3 had about 10,000 kv spark and 4 didnt reach 10,000