I have a very strange problem with a '78 351M motor with a 2 barrel carb. The motor itself is sound and very good as far as I can tell. But here is the problem. I can start the motor and get the motor up to normal running temp. shut it off and restart with no trouble. But if the motor sits idle for more than 1/2 hour it will not start again for 5 hours (or until cold). It is as if the motor floods itself while sitting for this period of time. I have tried a new carb on the motor, but still the same problem exists.
I am totally baffeled as to what the problem is. Can anybody shed some light unto this for me? I would like to keep this motor as it is in great shape for a '78 block
On Mon, 4 Aug 2003 10:09:28 -0600, "Bill Nobel"
Ford had a problem in that era with it's Duraspark electronic ignition boxes overheating. Have you checked to see if you are getting good spark at the proper time when this occurs?
I get spark, but I have no test equipment capable of measuring the quality. I did notice though that the coil gets rather warm. When I shake the coil I hear a liquid sound. Could this be the problem?
As you don,t have anything to test with the spark should be blue in color not yellow or orange.But your coil shouldn't sound as if it has water go to the auto parts and shake one of there coils:) If it sounds dry inside buy it.
I'ts the coil alright. I changed to a new one and all is fine. I never would of thought a coil could die when it gets warm.... oh well Thanks a bunch for the help
On Mon, 4 Aug 2003 14:49:11 -0600, "Bill Nobel"
It should be an oil-filled coil. If it has leaked, it may not be able to stay cool enough. A coil for that is fairly cheap and, coils frequently fail when hot. The coil should have a nice blue spark capable of jumping at least a 1/4" gap in open atmosphere.
I vote for the ignition module also, the next time it won't start, pour a pitcher of ice water on the module and/or beat it with a ball peen hammer. If it starts then, replace it. If it won't, replace it anyway and see if that cures the problem. Mine had a habit of just dying on the highway. Then you put it in neutral, turn the key and it would start right back up. ('76 460 same module)
I have a 400 in my '79 F-250 with a 600 holley double pumper and a Jacobs omni pak aftermarket ignition unit. The same motor with stock ignition and carb could be flooded and not start. With the above modification (Bosch platinum spark plugs also) I cannot flood this thing. It always starts even with several pumps on the pedal. The carb is tuned well so it starts immediately with out the extra gas, but I tried one day to see what it would do - even with the extra gas it started up just fine (with a healthy belch of dark exhaust). I don't know if Jacobs Electronics still makes a product like the OmniPak, but it's pretty slick since it bypasses the stock ignition but leaves it in place. If the Jacobs ignition bites the dust then you can bring the original ignition back online in less than a minute. Mine has been trouble free for about 7 years or so. The hotter spark also improves the engine's pickup - I can dump the holley with no bog, although that's partially due to the carb setup.