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fguillont

50lbs compression on all cylinders

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I have a 1986 hci turbo that will not start, it has spark, and fuel. the only thing i notice was when we did a compresion test was that all cylinders have 48-50 lbs only. To my understanding it should have at least 130 or more. What could be causing this. could the timing of the cams be so off that it would cause this problem. could puting the cam sprokets on the wrong cams cause this(intake on exhaust and exhaust on intake). the thing is the the compresion even though its way low its very even betwen cylinders.

I would realy apreciate if somebody can help me with this problem

thanks

Guillont

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Has it been running since the last time somebody did any major work on the cylinder head or cam belt?

If Yes, then we need to ask, when the compression test was performed, was the throttle (accelerator) held completely open (with somebody turning the butterfly sections by hand, not just pressing the foot pedal?

Yes the cams could be so far off as to allow the compressed gasses to escape during the initial stages of the compression stroke, either inlet or exhaust could achieve this, but re the first question, if the car has been running it would be a major timing belt slip to achieve this.

Has anybody done any work on the car recently?

Andy

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this is the first time that it has been started since the engine change, it was a used but its an original engine no work done to i before

what do you mean by bore washed ?

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In that case, take all plugs out (you probably have got them all out anyway), put a little bit 4-5 drops of oil down each plug hole, what does the compression test give then?

Andy

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Bore washing is where the engine is flooded with fuel and because of this it washes the oil off the cylinder walls leading to a loss of compression.

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the mecanicn told me he did this and the results where the same

i dont know mutch about bore washing but I dont think that would change the compresion numbers by about 90 lbs total fo all pistons

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In that case, I'd suggest a leak down test, that's where they put compressed gas in and measure the time it takes to loose that pressure.

It can also give indications of where the leaks are.

Andy

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Frank, to check the cams - rotate the engine to line up the dots on the back of the cam pulleys and the engine should be at TDC on the flywheel.

I agree - leak down test will identify the cause of low compression. Even-low compression on all four is most likely worn pistons / rings / pots.

Iain

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:thumbup: yes i found it the car has now 150 in all pistons my theory about to little overlap was rigth , wath hapend was that the mecanic change the cam sproket around so basically wath I did was rotate the sproket around and walla 150 on all pistons my engine seem to have the compresion of a new engine jejejeje. It was hard to make my mecanic understand about overlap but when i should him that both pulleys said intake on one side and exhauste on the other side he notice something was wrong , as you all know it has to say intake on the intake and exhaust on exhaust so basically it had about 4 thoot jumped thanks god it did not bend any valves. so the engine didnt have enoug time proces air adequatly.

thanks for you help

Frank

Guillont

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150 PSI compression ! - I would love to have that too

was that measured with engine hot or engine cold ?

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cold engine i guess when it gets worm it should get lower as the metals contract but should still be prety good

happy new year to everyone

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