Re: Bad news from my compression test I think....how can car STILL refuse to start?

Posted by Jim McDermaid On 2012/9/11 19:11:55

A couple of thoughts,

I have had trouble with those low cost compression testers in that if you crank it with the starter it may trap a reading but if you try by hand you won't trap a reading. (I worked with model T Fords and they have a crank in front). The Schrader valves always leak and the rubber thing you stick in the sparkplug hole always leak.

I admittedly haven't had a Packard motor apart but I would think the piston is probably centered below the sparkplug. You should be able to shine a flashlight down through the hole and see the piston move or at least the side of the bore. The soda straw should get to the top of the piston and you should be able to feel around with it. I don't stick screwdrivers in a sparkplug holes just in case it gets jammed.

I don't know how heavy the valve springs are on Packard motors but I have had them stick many a time on older motors. If the car has been parked for a long tome there can be a little surface rust on a valve stem or gummy dried up oil. It can run but a valve can stick in an open position. I use a little spray oil which may be blown in through the spark plug hole or if you have the manifolds off or through the valve cover. Valves don't get a lot of oil but once you get things moving they will usually loosen up.

With the plugs out get some to crank the starter and try the compression tester a hole at a time, I don't use my finger however. If you have a stuck open intake it will blow back through the carburetor and you won't get it to start.

Jim