have a 53 239 cui ,new carb, fuel pump and fuel filter when it sits for a few hours or over night,cranks for a long time before it will fire off ,seems to start ok when engie is hot, shut off & restarted in a short periord of time..any ideas??? fuel pumps is a brand new napa <!-- / message --><!-- BEGIN TEMPLATE: ad_showthread_firstpost_sig --><!-- END TEMPLATE: ad_showthread_firstpost_sig -->

 

I think you're looking at the wrong side of things. It sounds like you've been focusing the fuel system, but I'm willing to bet that your trouble lies in the ignition system. Nothing really changes with temperature in the fuel system that would allow it to start easier when it's warm than when it's cold. If it starts and runs OK one way, then it should start and run OK the other way.

The ignition system, however, is a lot more sensitive. A warm engine will start much easier than a cold engine as the warm cylinders promote combustion. In addition, the battery voltage is higher when the engine has just been ran than it is after it's been sitting overnight. Are you still on 6 volts? If so, then it's imperative that everything be in tip-top shape. 6 volt systems can't compensate for weak or worn parts with higher voltage. Make sure the plugs, wires, cap, rotor, points, and coil are in good shape. Pay particular attention to your plug and point gaps. Double check your timing and make sure your advance mechanisms are operating properly. Check the voltage at the coil with a multimeter and compare it to the battery voltage. They should be the same. If the voltage at the coil is lower, then you've got a poor connection in the wiring somewhere. If everything checks out, suspect the coil. They can get weak over time. With a cold engine, you want to see a crisp, bright, blue spark at the plugs. Fat and snappy. A thin, dim, orange spark isn't going to light the mixture under compression.

 

i have a brand new coil on the bench,i will replace it this after noon!! points are less than a year old (about 1200 miles) wires are about a year old as well cap and rotor about 3 years old -I will replace them as well

 

I'm not sure I agree completely with the ignition system diagnosis. But as Big Blue pointed out it is always a good idea to ensure that those things are adjusted correctly and he is correct whith everything he said - I just don't think its the problem here - I could be wrong. Normally the only component of the ignition system that is affected by temperature is the coil, and then usually fails when hot, not cold.

Under normal circumstances, I would tell you to look at the fuel pump - that the gas is flowing back down to the tank as the truck sits and you are having to pump it back up after time to get it to start. Ok so it's new - just food for thought.

Next, I would look at how you are starting the truck - use of the throttle and choke when the engine is cold - and of course the ambient air temp when you are trying to start it. On the 239, you want to push the gas pedal lightly, pull the choke out half way then release the gas pedal. It should fire up without pumping the gas.

There is a possibility that the wear on the engine is such that it's needing oil circulation up to the cylinders to get enough compression to fire. When hot or warm the parts are expanded out enough to aid this. If the fuel pump is good, and you don't get any relief from adjusting your starting procedure, you might want to run a compression check on the engine to see if it's within spec.

Check for proper spark plug gap. Flatheads are sensative to that.

Lastly, there is a vacuum interaction between the carb and the distributor that can be a problem when not working correctly. Ross (Albuq F1) is the guy to listen to on this. I'm sure he will jump in here soon.

In the mean time, I invite you to review this thread we had some time back - there is a lot of usefull information and suggestions on another members problem starting - turned out to be fuel pump anyway. Here are the links to our previous discussions on Flathead starting problems:

https://www.ford-trucks.com/forums/8...t-running.html

https://www.ford-trucks.com/forums/7...do-matter.html

https://www.ford-trucks.com/forums/8...s-flattie.html

Good luck!

 

Holley 94's have a power valve that is prone to rupture of its diaphragm. When that happens, all the fuel drains from the carb's bowl, and needs to be refilled.

 

You said cranks for a long time but how long is that really? Your carb bowl may be emptying for several reasons overnight and the cranking fills it back up. Could try pumping the gas as your cranking and if it starts sooner than before then time to check out the carb. My flatty starts right off when warm but needs two or three good pumps on the pedal when cold.