what would cause a instant compression loss?

[marsh63]

well i just did a cylinder head replacement last night. its a 1990 n/t eclipse 4g63 and i had the car running with about 180 lbs of compression across all the cylinders

now today i have 120 across 2 of them and 150 in the other 2 and it wont start. the timing is dead on and the valves are all seating fine. also when i added oil it went up to about 220 in each cylinder

so what is wrong with my car? could this be a headgasket? help me!!!!!!

i only ran it for like 20 minutes after i put the new head on it. im using a 3 layer cometic headgasket.

i have oil pressure so i dont think it killed my cylinder walls.

 

[matt98eclipse]

Im in the same exact problem you are. I had 150 across all 4 cylinders and after i put a new head gasket on i have 140,125,110,100. I made a mistake and right after i finished the head install i went out and started boosting right away witch caused my head gasket to leak around my oil jackets. Only signs i have are alot of crankcase pressure.

Do a leak down test to see were your losing compression.

 

[marsh63]

yeah i was scared that i did something really wrong. but what are the torgue specs for the cylinder head to motor? my chilton manual said 48 lbs and 2 1/4 turns over. is that right?

 

[matt98eclipse]

I have ARP head studs its completly different the the factory specs. I did 30,60,80ftlb. I just messed up and got on it to hard and didnt give the head gasket a chance to seal.

 

[crimsondragon]

Putting oil in cylinders during a leakdown test are to see if your rings are bad. If the compression increases, it means you got leaky rings.

 

[dsmdragon]

Putting oil in cylinders during a leakdown test are to see if your rings are bad. If the compression increases, it means you got leaky rings.

I second what he said... If you dn't let the gasket seal properly, (like 50-to-100 miles) then you are going to have problems. You might need a new gasket or you might need to check your bolt torque once again to see if something is loose.

 

[matt98eclipse]

Putting oil in cylinders during a leakdown test are to see if your rings are bad. If the compression increases, it means you got leaky rings.

This is not always true. I have hurd of poeple haveing a leaking head gasket and get the same results with the compression going up when adding a cap full of oil.

 

[crimsondragon]

Ok I stand corrected. To the OP, did you retorque them down? Usually when you do any head work, you torque them down to spec once, drive it for a bit, then retorque them again for heat compensation.

 

[rodent]

Stupid question but did you test both times when the engine was warm and the throttle open?

 

[marsh63]

im going to re torgue them again today when i wake up. ive been up all night tinkering with my talon.

ill see if that helps but i still dont know why it wont start. i have fuel, spark, crank and its dead on on the timing. it fires but wont turn over all the way.

would 120 lbs of compression make it so it wont start?

 

[marsh63]

Stupid question but did you test both times when the engine was warm and the throttle open?

i cant get it to run so that would be a no. i did the compression test when it was cool.

 

[rodent]

If your first compression test of 180 was when the engine was warm and your second test was cold, this can be the reason why its lower.

 

[matt98eclipse]

The car should still start with those compression numbers. The only way if wouldnt start is if you had a completely dead cylinder or if it was REALLY low.

Have you checked to make sure you installed your CAS right. I believe if it was installed incorrect it would cause it not to start. But i could be wrong.

 

[interex]

Maybe you have a terriable spark plug gap.

 

[marsh63]

the cas is dead on and it did run the other day but now it wont run. it ran right after i put the head on. and btw it hs new 92 octane fuel in it.

also when i compression tested it the first time it was at 180 cold so i lost 40-60 lbs when its cold compression.

the car has a new transitor and new coil pack which worksed good.

what should the gap be for a n/t?

 

[evileclipse909]

It should have no problem running with 12psi. Mine is only 125psi on all 4 and it runs great. make sure your plug wires arn't crossed. Check to make sure you have good fuel pressure at the rail. also make sure that none of your plug wires are broken.Notes Spark Plug Type Spark plug gap
NGK BPR5ES-11 .039 - .043 in
NIPPON DENSO W20EPR-11 .039 - .043 in
CHAMPION RN9YC4 .039 - .043 in

 

[marsh63]

It should have no problem running with 12psi. Mine is only 125psi on all 4 and it runs great. make sure your plug wires arn't crossed. Check to make sure you have good fuel pressure at the rail. also make sure that none of your plug wires are broken.Notes Spark Plug Type Spark plug gap
NGK BPR5ES-11 .039 - .043 in
NIPPON DENSO W20EPR-11 .039 - .043 in
CHAMPION RN9YC4 .039 - .043 in

remember this is for my 1990 N/T eclipse. i have 3 dsms. i have no turbo so i want to know why its not starting this car is a car im going to be giving to my mom as a daily driver so i need it to be reliable.

 

[matt98eclipse]

Have you checked the CAS to make sure its installed the correct way?

 

[marsh63]

Have you checked the CAS to make sure its installed the correct way?

yeah the cas is good and installed correctly.

 

[Sublime83]

Jumped timing?

 

[ontario AWD]

The head and block must be perfectly flat and smooth when using a steel gasket.I assume you also did the proper torque sequence?

 

[talon187]

sounds like you bent valuves if it ran and then now you went to start it again and wont. sounds like the timing jumped

 

[marsh63]

sounds like you bent valuves if it ran and then now you went to start it again and wont. sounds like the timing jumped

last time when i had bent valves the car would not make any compression. and timing is dead on. its a new belt and tensioner. i did everything to spec.

i didnt have the motor and head decked so could that be my problem? both surfaces were extremely clean though.

i did the torque setting that my chiltons manual said to do and the torque sequence too.

 

[matt98eclipse]

I think if you would have bent valves your compression would be lower. When using a metel head gasket you should always at least get the head resurfaced. I personally wouldnt use a MLS head gasket due to sealing promblems inless you get both head and block decked.

 

[marsh63]

I think if you would have bent valves your compression would be lower. When using a metel head gasket you should always at least get the head resurfaced. I personally wouldnt use a MLS head gasket due to sealing promblems inless you get both head and block decked.

last 2 dsms i had with bent vavles didnt make any compression. maybe the valves are not seating right. but i am thinking about switching to just a oem head gasket. its not a car that is going to run any amount of power due to its going to be a dd.