95 Grand Am Quad 4 questions

[GreaseDog]

a few months back i purchased a 1995 Grand Am with a 2.3 Quad 4 in it. i purchased it knowing that it did not run. the shop who it was taken to for diagnosis said that it needs a timing chain. they also said that it had 150psi on all 4 cylinders on a compression test, which leads me to believe that the timing chain is not the problem. could this actually be the problem? also, i pulled the ignition housing off of it, and had the ignition module check (i have had problems with modules on previous "non-running" cars before) it tested fine. due to the coil tower design, i cannot check for spark like i normally would with a distributor. how can i check for spark on this system? any help you can provide is greatly appreciated.

[Slade901]

No spark? check the ckps (crankshaft position sensor). It provides reference signal to the computer and in turn the computer relay it to the ICM and tell the coils when to fire.

You can test for sparks by lifting the whole coil housing enough where you can still have the plug to the ICM still connected. You can then use a known good (used) spark plug wires between the spark plugs and the ignition coil housing. Use an adjustable spark tester with a clip on it so you can clip the spark tester on a ground where you can see it from the driver seat when you crank the engine.

[GreaseDog]

am i correct in thinking that the 150psi on all 4 cylinders is not consistent with a timing chain in need of replacement?

[GreaseDog]

anybody?

[GTP Dad]

Not necessarily, good compression only means that all the valves are closed. They can be closed by rotating the engine even though the timing chain may be bad. There was a thread about a Quad 4 on this forum about 3 months ago where the engine had similar problems, search the forum and see if you can find the correct one as it may help you with your problems. Slade901 makes a good point about checking the CPS as it may be the entire problem. The CPS is located just above the oil filter.

[GreaseDog]

Originally Posted by GTP Dad

Not necessarily, good compression only means that all the valves are closed. They can be closed by rotating the engine even though the timing chain may be bad. There was a thread about a Quad 4 on this forum about 3 months ago where the engine had similar problems, search the forum and see if you can find the correct one as it may help you with your problems. Slade901 makes a good point about checking the CPS as it may be the entire problem. The CPS is located just above the oil filter.

not to totally blow your post apart or insult your intelligence, but if im reading this correctly, your idea of how a 4 cycle gasoline engine works is a bit flawed. if the timing chain was broken, the valves would not move if the crankshaft was turned. if it is bad, or skipped a tooth or two, the compression reading would vary, either up or down. you are correct, that having "good" compression means the valves are all closed. however, if the chain is stretched, or skipped a tooth, the compression may be too low to properly ignite the air-fuel mixture. i guess what i meant to ask was if my 150psi was within the operating range of this engine. the post 3 months ago very well mayb have been mine, since i picked this car up about 3 months ago and have been sitting on it ever since, without time to work on it.

[GTP Dad]

You are correct Greasedog if the chain was broken the valves would not move and if it skipped a tooth the valves probably would not operate properly.
But if the chain was only slightly stretched and the person doing the compression check watched the valves while rotating the engine manually you could get proper compression. 150 psi across 4 cylinders is very good compression for a stock engine. That is why I don't think the problem is with the timing chain and that the problem is in the ignition or fuel system on the engine which may include the computer.