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compression test results?????

G

Gary Vinzant

New member
I have a 1983 johnson 90hp and just did a compression test and here is the results.
Cylinder 1----- 120lbs
Cylinder 2---- 120lbs
Cylinder 3---- 130lbs
Cylinder 4---- 119lbs.
My questions are this.... should I be worried about the 10lbs difference between the cylinders? What kind of problems could this cause in performance and with the way it runs in general?
 
Ok thanks. Thats kinda what I thought but I wanted to be sure. Also thinking I got a fuel problem then. The motor cranks fine it idles fines but boggs and stalls out when you try to accelerate. If you push the choke in while accelerating it does fine. So I was told to check the compression because the motor uses vacuum from the compression to draw fuel into the motor. I have checked all the cylinders and all 4 are firing so its not a ignition problem. I have recently rebuilt the ffuel pump and both carbs but I think the fuel pump is the problem because the cap that holds the fuel filter screen on will leak fuel when the primer bulb is pumped unless I put 2 gaskets behind it. Before I rebuilt it 1 gasket would seal it off. Even though its not leaking with 2 gaskets could it still be sucking a little air? Enough to cause this problem? I can pump the primer bulb until it gets hard and let it sit without cranking the engine or doing anything and it will lose pressure in a few minutes. So does this mean im sucking air and losing fuel pressure somewhere?
 
yes...you should be able to pump it hard and it should remain hard just sitting...your carb floats should have sealed off the carbs....the bulb it self has a anti-reverse flow valve in it to keep the gas from going back to the tank...
 
That is why I was thinking it was the fuel pump because now I have to have 2 gaskets behind the fuel filter cap instead of 1 to keep it from leaking gas. I do believe even though it is not leaking gas it is still sucking air causing it to lose fuel pressure. I ordered a new fuel pump from this site yesterday. I hope they ship soon.
 
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