Why would I be getting zero compression in 3 cylinders? Is it the head gasket or is my timing way off?

Question

I have a 95 3000gt and it started backfiring and losing lots of power, if it did start up it would shake like all hell broke loose. So I check the plugs and all 6 are fouled(black) and smell like gas. So I do a quick tuneup and nothing changes so I pull the plugs and check it and once again all 6 are fouled and smell like gas. So at this time I take it to a garage and they run a compression test and the front three cylinders were perfect 166 but the rear three were at zero. I plan on doing a leak down test this weekend if i can find a shop that does it. I doubt it's piston rings or bent valves but of course I may be wrong. It's quite unusual for that to happen. Any help would be much appreciated..

I took it to my buddy and he said he thought the timing was off. So I need to set timing. What do you guys think about that

Answer 1

I suspect that 3 valves are not closing properly.. at all. If you have someone do a leakdown test, your cylinders will not hold compression to see the pressure slowly "leak down". Waste of time??

backfiring.... either the cylinder plug is firing when the exhaust valve is slightly open OR.. Your spark plug wires have become mistakenly replaced on the wrong plugs. When plugs fire at the wrong time, they compete with plugs firing at the RIGHT time, and your engine shakes like crazy.

Smells like gas? the gas is not being burned. A result of not enough compression. Fuel injection not spraying properly?
You sound like a guy who does his own mechanical work, when possible. If you have a lot of dark smoke, suspect a head gasket leak admitting oil into the cylinder. White smoke, water. Either one will cause a power loss. Mayonaise-looking oil cap? Water-to-oil. Try smelling the radiator water IF THE CAR CAN RUN for 10 minutes....smell like exhaust? Head gasket problem.

If your car turned over 20 times (coil unplugged to prevent starting) and you still had NO compression, then the valves aren't closing fully... ever! Even a small head gasket leak, recently occurring, would give you a little compression.

Answer 2

That sounds just like a typical episode of the timing chain or belt skipped a tooth or so. Thats why the valve operation charectoristics is off. Hence the sudden backfiring and almost total lack of power. When chevy and ford v-8 motors timing chain skips a tooth because of a streched and worn out timing chain they do the identical thing. Ihope this helps. good luck.

Answer 3

It would'nt be a head gasket with no compression you had to have bent some valves. Whatever caused the valves to bend is the ? Sounds like the timing chain jumped. Good Luck with that!Slick T

Answer 4

No compression could be at least three things, and likelyhood in this order:
1) Head gasket.
2) Valves remaining open.
3) Piston rings worn.

Answer 5

guy that around black under pressure strap at your 4.3's water neck stud,clean the two considered one of them damn good,the element of the made on bolt of that stud and the underneith of the nut and the few black wires loop that each physique this grounds jointly so which you PCM computing device can floor staggering and then your 4.3 will run and clean up after a minute or 2,this damn floor additionally blanks its shifting trend to your computerized,so attempt and carry the rpm's at 1500 until eventually ultimately the temp gets approximately general,then you definately ought to force it until eventually ultimately it shifts all gears which contains ODrive,pull over ,hit opposite, end after it backs up some ft ,kill your engine,commence it ,pass abode and write a Fu** You to GM for that shitty floor section for the damn computing device to artwork and inject properly..dude that comparable component bit numerous of my close GM proprietors,a damn floor that grow to be grimy and saved the friggin computing device from now and lower back even tossing up a hassle code while it ran like crap,thats a loose hassle-free attempt,guy i'm hoping this nailled it to your headache dude,i'm wally the above who had overkilled the respond,guy i meant no disrespect to ya bro,i hadnt study your profile to work out you knew your **** dude,i grow to be incorrect bro,appologiseing too dude,,good success bro, wally

Answer 6

it sounds like you lost the rear timing chain / belt