I have a 1979 F150 pickup with 400 engine. It used to start just
fine. A few weeks ago, it did not want to start at times and other
times started right up. Lately it has gotten worse. Most of the time
it starts when it's cold, but once it's warm, it's a gamble whether it
will start again. Eve nshutting it off for a few seconds and it may
not restart. The starter spins and is engaging the flywheel, but it
just cranks and cranks and will not start. However, here's the odd
part. It pops when I release the key from the START position. In
other words, it appears it is not getting ignition voltage during
cranking, but as soon as put the key to the RUN position, it pops. If
I am real lucky, it will start within that moment, but 99% of the time
it will not start. So, I have to just keep flipping the key and
hoping I can catch a spark as the key is withdrawn.
I replaced the solenoid, thinking there was a fault in it. However,
that did not solve the problem.
This is driving me nuts. WTF is causing this?
I should note, it IS getting gas. I can see it squirt into the carb,
and have flooded it a few times while trying to start it. The timing
chain was replaced one year ago, so that is ok. The carb was rebuilt
not too long ago either, and the plugs and wires and cap replaced last
spring. I am 99.9% sure it is just not getting a spark. This makes
me think of the coil, electronic ignition module, or distributor
problem. However, the problem is intermittent, and once started, it
runs just fine and has lots of power.
Here's an example. Yesterday I started it 4 times on my driveway, It
started fine, so I drove it about 20 miles, stopped for gas, stopped
at 3 stores, visited a friend, loaded some hay, and came home. By
this time I had started it, and shut it off at least 15 times without
any problem. I unloaded the hay, and moved the truck up to my gate.
The gate was loose so I had to shut off the truck to get my toolbox
key. 5 minutes later, I tried to start the truck and it would not
start. After cranking it about 30 times, I finally got it to start
upon releasing the key. I drove it to the lower part of the farm to
load some lumber that I needed to move. left the engine running, but
when I stepped on the gas, the tires slipped on wet grass so I got out
and turned the wheels to 4WD. When I got back in, I gunned it, and
the engine died. It took me 15 minutes to get it to start again. I
took the lumber to the shed and left the engine running while I
unloaded the wood. It idled fine for 10 minutes, then suddenly just
quit running for no reason. Now I can not get it to start at all, but
still get a pop when I release the key. Maybe when it gets totally
cold, it will start again, but the problem seems to be getting worse.
Any idea what is causing this?
Are there any tests I can do using a 12V test light?
This really is driving me nuts.
PS, I did take the coil plug off and cleaned the contacts (low voltage