SOURCE: NO COMPRESSION ON ALL CYLINDERS - TESTER GAUGE GOES UP THEN DOWN
The fault may very well be with the tester itself: The compression tester should have a check or "HOLD" valve which causes the needle on the gauge to REMAIN at it's highest recorded point. For example, my 1993 Isuzu Rodeo had a compression of 160 psi. The gauge "holds" the needle at the measurement UNTIL THE VALVE IS RELEASED-(mine had a button that needed to be pressed to release the pressure) then there will be a slight discharge of the pressure contained within, the needle should drop back to zero, and THEN you should be able to remove the tester. What I am getting at is if the pressure drops that fast, I think the "HOLD" valve on it may be defective, OR the tester is not properly sealing on the combustion chamber (stripped threads?). Might be worth buying another one for 20$ just to be sure.
A four cylinder engine, you say? Very rarely will you have ALL of your cylinders exhibit the same pressure loss symptoms. How did the other three cylinders test?
Here are the components required for a running engine to fire:
1-good spark (adequate voltage, good plugs/wires)
2-dedicated fuel supply (fuel pump with adequate pressure)
3-timing (slack in timing chain/belt?)
If the timing belt broke or maybe even jumped a tooth or two, it COULD cause DAMAGE to your engine-pistons hitting valves-if it IS what they call an "INTERFERENCE" engine.
Hope this helps.
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SOURCE: Toyota 1.4 ZZ-FE engine will not start.
How about some history.. like was it running OK and then was parked, and later would not start? or has it been sitting? or quit while driving down the road?? Mileage? Does it run good now? If so I would recommend using Chevron Techron Fuel additive to clean up the injectors and back of the intake valves. That could help if indeed the valves are a problem. Some repair shops have a Motorvac or BG Injector cleaning/ intake manifold cleaning that would possibly help that.
SOURCE: i have a 2000 gmc sierra 5.3 with a number 6
I would check the valves for number 6. If one or both are burned, stuck or out of adjustment it would cause your problem. If a cam lobe for that cylinder is burned or badly worn it could be the culprit.
SOURCE: 1968 beetle over heated and now it wont start,did
This sounds like a classic case of blown head gasket.
You seem to know some about cars, however I will attempt to give you my best answer.
You have a gasket that seals the engine to the head, when you over heat this gasket gets punished and in some cases the head can get warped and the seal between the engine and head is lost resulting in your loss of compression.
You need to remove the head for a better look, take the head to a machine shop and have them check it for warped condition, if so see if it can be machined flat, also look into a rebuilt head, it may just be cheaper to do that then the work to fix your original.
As well your going to have to find the reason the car over heated in the first place..
This might be a good time to see if the car is worth fixing?!
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