True, there are several types of compression tests:
- Dry
- Wet
- Running
- Snap Throttle

Each have their own purpose. Dry and Wet would be good for your situation. As Speedy said, disconnect the fuel and I'd also neutralize the coil... there is no need for secondary ignition during the Dry and Wet tests.

 

Compression is the same on all cylinders. 135-145psi should be plenty to fire. This is really driving me crazzy here. I don`t think it`s anything internal. Again, the car ran fine, then it would go a week or two not starting, then it would start and run fine again for a week or two, then not start for a day or two. Then it would run but would backfire if you were quick with the throttle for a couple days, now it will not start again at all. Has spark but real weak pulse with a noid light. Now after cranking 5 or 6 times when you release the key it kinda pops and rolls over backwards a revolution or two, when it rolls over backwards the noid light seems to flash bright like it should. Is there any part of the security system that would shut down the injecter pulse width and cause the spark to be at the wrong time?

 

My dry compression is around 175-183. Are you sure your numbers are right? They seem pretty low.

How many miles are on this engine?

 

The car has 122,xxx miles on it. I`m not 100% sure the compression gauge I`m using is accurate( I could watch the pressure bleed off the dial) but all cylinders tested about the same. 90psi is all that`s needed to fire, is what I was always told anyway, this seems to at least have enough to be able to make it run. Again, this not starting problem has come and gone over the course of time, wouldn`t that alone rule out any mechanical problem like a broken cam or jumped timing chain?? It may jump out of time, but it could never jump back into time for a week or two, could it???

 

Sounds like your timing is off, way off.

 

???

 

bump

 

i would replace to entire opti with a brand new one, the opti sensors could be the poblem. it would run with less then 90 psi, it will run like crap but it'll still run. thats not your problem. its either fuel or ignition. sounds to me like ignition. but also test your fuel pressure and see if it changes at all when it starts.

 

Check the basics, vacuum, fuel pressure, compression check, like what was described here. Then go on to pulling the valve covers to check that all the valves are opening and closing, you can also see if the rocker arms are all in the proper place. The replacement of the opti like you did puzzles me, did you use previously discarded ignition components like the opti with out determining wether or not they are any good or not???

 

The original distributor broke a few of the cap screws and one of the rotor screws when we tried to do the tune-up(this is after it wouldn`t start). The housing was replaced with a used one and we reused the original optic sensor. When that didn`t work we tried the optic sensor that came with the used distributor, same results. Except for seeing spark and weak injector pulse I haven`t tested the opti, I thought if it was at fault I`d have neither spark or injector pulse. I have just ordered a replacement opti distributor from NAPA, hope you guys aren`t going to tell me they`re junk!

 

I installed the reman opti unit from NAPA, same no start condition.

 

I have the same condition right now. Except for the car turning over backwards. I have a brand new MSD opti in mines and it still not starting. Like others have said it might be timming related. Thats the first thing im gonna be checking today. You should do the same.

 

Looking at the wiring diagram for the ECM, there appears to be a "Theft Deterrent module" with a single wire, if it`s providing the wrong signal to the ECM could that cause this condition??

 

Sounds like a timing concern to me. Just got worse for some reason. Has timing been checked yet?

 

my no start condition is due to what appears to be spark at the wrong time and weak to no injector pulse. If the timing chain had jumped, it may spark at the wrong time, but the injection pulse would be strong. I believe this is a wiring/anti-theft/security issue. Something seems to be manipulating those signals. I don`t seem to be the only one with this problem, there must be an answer somewhere. The Haynes repair manual keeps mentioning about if the car has a Delco-Loc II or Theftlock, to disable those before removing the battery. I don`t know if the car has those or not, could they cause this no start condition??