1997 Pontiac Firebird Low Compression - Due to Timing?

TWB2020

MEMBER
1997 PONTIAC FIREBIRD
6 CYL
2WD
AUTOMATIC
130,000 MILES

THIS CAR WILL NOT START. I HEAR SOME DETONATION BUT IT IS NOT ENOUGH TO ENABLE THE ENGINE TO RUN FOR EVEN A SECOND. I have been told by many others that even with low compression an engine will start if the only issue is compression.

I have checked the compression on cylinders 1 and 5 on Bank 1 and cylinder2 on Bank 2 of this V6 3.8L. My question is this: due to the fact that the readings for all three of the checked cylinders (the easiest to get to) are between 50 and 70 psi, is there a greater probability that either the timing chain has jumped/or it was assembled incorrectly OR that it has blown head gaskets/something else. I am about to head down the path of taking the timing chain cover off to check the timing mark alignment due to the fact that the low compression is on cylinders that are on both banks, but I thought I would get a Pro's input first.

History of this vehicle - supposedly the car ran, but when I got it thinking it was just a fuel pump, I found that there was a large amount of water in the tank and fuel rail. I have replaced the fuel pump, fuel injectors, fuel regulator, fuel rail and fuel filter. Additionally, I have checked that each cylinder is receiving spark.

1 Reply

MHPAUTOS

MECHANIC
31,938 POSTS

Hi there,

Thank you for the donation,

I would be doing a wet & dry comp test and a leak down test if you can get the equipment to do so, personally I feel that it will be worn rings or a valve problem, I would doubt it very much that it is a valve timing problem, a wet test is when you add about a tea spoon or two of oil to the cylinder and re test comps, this will seal up the rings for the test and if the comp are still low it will be a valve problem, I would try this first.

Mark (mhpautos)