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#1
03-30-2004, 12:05 PM
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I've become a pretty good troubleshooter, but this one has me baffled. '78 T/A runs pretty good except for a few carb tuning issues. However, one morning I go out and the car won't start. Fuel spits out of the carb...interesting. I do a compression test and #1 cylinder is at 90 psi, all others are around 150 psi. So I pull the valve cover and inspect the valvetrain. Everything looks OK. I crank the engine and watch the valves and everything looks ok. Pushrods don't bind or anything. Anyone have any suggestions or ideas??
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#2
03-30-2004, 12:05 PM
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I've become a pretty good troubleshooter, but this one has me baffled. '78 T/A runs pretty good except for a few carb tuning issues. However, one morning I go out and the car won't start. Fuel spits out of the carb...interesting. I do a compression test and #1 cylinder is at 90 psi, all others are around 150 psi. So I pull the valve cover and inspect the valvetrain. Everything looks OK. I crank the engine and watch the valves and everything looks ok. Pushrods don't bind or anything. Anyone have any suggestions or ideas??
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#3
03-30-2004, 01:42 PM
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I helped by brother change heads on his GTO and we ran into a similar problem. When we did a compression test, all cylinders except 1 and 7 were at 120 psi, one and seven were at 160. What we found was the head gaskets were leaking. Your problem is very different because if it were a head gasket leaking the lack of compression on the #1 shouldn't cause it not to run. With the gas spitting out of the carb it sounds like the timing is off, would it be possible for the timing chain to have jumped? I hope that this may have helped. Good luck
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#4
03-30-2004, 02:48 PM
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It's funny you mention the timing chain jumping. At first, since I was having problems with the carb, I got a different carb. Also, the timing cover was leaking coolant so I decided to replace the gasket. Since I had the cover off, I replaced the timing chain, which had some slack, but not too much to worry. When I put the new timing chain on, I made sure it was at tdc and the marks on the cam gear and crank gear lined up. I'm pretty sure the cam timing is right. Especially since it's pretty much doing the same thing it did before I started all the crap listed above. BTW, there's plenty of spark and fuel.
Suppose the chain had jumped? Would that cause cylinder #1 to have low compression? |
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#5
03-30-2004, 05:14 PM
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a valve that is bent or stuck will cause the spitting out of the carb. my guess would be bent as it appears to still move . as long as you have the valve cover off , check for a bent pushrod. i just went through the same problem with the same symptoms. even if this is the case it should still run , it will just miss on that cylinder.
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#6
03-30-2004, 05:50 PM
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You could put a dial indicator on the #1 valves to see if they are travelling exactly same distance as a good cylinder. If not they are bent or sticking.
I think a leak-down checker may help, but they cost a few bucks and need air. Turn #1 to top dead centre, and pressurize with checker through spark plug hole. Listen with hose through carb and oil filler hole. If hissing is louder through carb than than good cylinder, intake valve is leaking. If louder through oil filler hole, rings are leaking. I am not sure how well you can here leaking exhaust valve back at tailpipe. No, I don't for a tool company but maybe I should  Malcolm |
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