'68 F100 Won't Start - Ignition? Solenoid?

[Wooley Booger]

'68 F-100
240 CID
3 spd
Basic Truck, No Frills

Greetings All - I am having problems with the ol' Ford and need some troubleshooting ideas. Here are the facts, which may or may not all be related to each other:

- Over the past year or so, I have had an issue where the solenoid just clicks when I turn the key... but no dead battery... if I rap on the solenoid a couple of times, then turn the key it starts. Sometimes the solenoid area would have a visible spark when turning over the engine.

- I don't drive it much (about 500 mi per year) but took it out a couple of weeks ago. After a couple of miles it started bucking and lurching, and I had to pull off to the side. It would not restart until about a half hour later, but the bucking persisted and I towed it home.

- Think it was an electrical problem, I sequentially replaced the coil and then the condenser. But the bucking persisted, so I put the original parts back in.

- Thinking it was a fuel problem, I took the hose off the carb... plenty of fuel comes through when the engine is cranked. So I ruled this out.

- Having run out of ideas, I researched some forums... could it be the starter switch is failing? How about the solenoid? Could either of these cause the no start and bucking/lurching?

Thanks for any insight or additional ideas to get things running again!

WB

[rjewkes]

it sounds like the selenoid is going or gone out.

as for the bucking it could be a bad ign. swtch. if it jiggles around it could cuase it to turn on and off real quick going down the road.

[fordman]

the solinoid is probably going bad for the no start thing. the bucking could be the ignition switch cutting in and out or it could be your sucking something up into the fuel line in the tank and when it sits long enough it unsucks itself.

[Wooley Booger]

Thanks for the advice.... but I have a new angle on the bucking and no start problem, but need a bit more direction. In logically working through all things electrical (there's not that many on this truck), I tried the basic spark test by unplugging the coil wire from the distributor and checking for spark to ground while it was being cranked.... no spark! So I replaced the ignition switch... still no start. Does this leave the coil wire to the ignition switch as the sole problem? If this wire was intermittent, maybe this caused the bucking and lurching and now it is just open so that it does not start at all... this is my current theory. Would testing the continuity of the coil wire to the ignition switch be next?

[fordman]

i could be the coil was going bad and now it has gone bad. the coil wire from the switch would be bured in two if its bad you should be able to find a burnt wire by looking for that. let us know what you find out.

[Thunderfoot]

You can just check the voltage with a meter... turn the key on and check the positive wire at the coil it should have around 6-9 volts... If it does then try this; put a test light on the positive wire at the coil and turn the motor over, the light should pulse... if it doesn't then you have a problem in the distributor... points, condenser, etc...

On the solenoid problem... on the fender be sure that it has good contact with the fender as this is how it grounds itself to work... loose mounting screws or rusty connection will give you grief...

[Wooley Booger]

Thunderfoot, let me check the methodology of your recommended test... I took my multitester and, with the ignition switch to on, had one probe on the + wire (pulled from the coil) and the other to ground. I measured 11.86 vdc. Should this have been the 6-9 volt reading?? In addition, instead of grounding the probe to the chassis, I held it to the + terminal on the coil and measured 9.88 vdc. What would that mean?? In either case, I am satisfied that I have a good wire between the ignition switch and the coil. However, still no start and I am still stumped. I will check other low tension wires and report back in later...

[fordman]

have you tried cranking while holding the coil wire up off the coil a little. if you dont get anythiing there its probably a bad coil.

[Banjo]

sometimes one bucks and dies and won't restart till it cools down good, it's vapor lock. Do you have a fuel line close to a heat source?

[Wooley Booger]

I am still leaning towards an electrical problem and not a fuel problem. I spent a few hours ths morning systematically checking the wiring with my multi-tester... here is my troubleshooting summary:
• Ignition switch on, one probe on ignition switch wire (from + terminal on the coil) and other to ground: 11.86 vdc... this means my ignition switch wire is good!
• Ignition switch on, one probe on ignition switch wire (from + terminal on the coil) and other to the + terminal on the coil: 9.88 vdc... not sure what this means.
• Resistance across the coil terminals: 1.6 ohms... not sure what it should be...anyone out there have this info?
• Voltage through the coil (ignition switch on, one probe in center of coil and other to ground): 11.86 vdc
• Voltage through the coil wire to distributor (ignition switch on, one probe in end of coil distributor wire and other to ground): 11.86 vdc
• Ignition switch on, voltage on the wire coming to the distributor from the coil: 11.86 vdc
• Ignition switch on, voltage at the points: 11.86 vdc
• No voltage drop across the points
• Good continuity on distributor plate ground wire

What I don't understand is how can I be getting 12v out of the coil and still I have no spark when I crank the engine and do a spark test with the coil wire grounded to the block? And,
When it first started acting up a couple weeks ago, a new coil was the first thing I replaced. But I put the old one back in when the bucking and lurching continued with the new one. I am beginning to think I have compound problems... I hate it when that happens!

Since there is no spark, maybe I should try putting in a known good coil and at least see if I can get it started, then work on the bucking and lurching troubleshooting (if it is still there). Still open for your input though...thanks!

[bluef250]

Check your battery ground. Check the battery under a load test.

[Thunderfoot]

• Voltage through the coil (ignition switch on, one probe in center of coil and other to ground): 11.86 vdc
What I don't understand is how can I be getting 12v out of the coil and still I have no spark when I crank the engine and do a spark test with the coil wire grounded to the block?

The way the coil works is that it steps up the voltage (like a transformer) from 12V to like 15,000 + volts on a stock coil... This is what makes the spark jump...

As this is a DC circuit it has to have an interruption in the incoming voltage to get it to make this transformation / voltage change... That is what the points opening and closing do...
If you have no pulse from the points then you will not get a spark out of the coil...

To test if you are getting this pulse from the dizzy do as I mentioned above... put a test light on the positive wire at the coil and turn the motor over with the key (just as you would to try to start it), the light should pulse... (you could do this with your volt meter, it should show the voltage going up and down)
If you have no pulse then try / check the points / condenser... If you do have a pulse then swap out the coil...

The condenser in the Dizzy helps take the arcing out of the points opening and closing wearing them out faster then they do... if it goes bad or there is a grounding in any of the wire in the dizzy then it will not alow the coil to fire / spark...

On your measurements on that wire from the ignition to the coil being 11.86 volts seems high, as that should be a resistive wire... not sure what's with that... When you hooked up the end of the probe to the coil instead of ground you added the resistance of the coil in there... even both together seem to high, so it is possible that the high voltage to the coil could have damaged it... or the condenser in the dizzy...

I would get it running again then see how the intermittent surge problem is... they could be related alright...

Hope this all makes some sense / helps...

[Wooley Booger]

OK... we're up and running again.. this is how it played out. The original coil was bad and even though that was the first thing I changed out, the replacement was bad too. I put in a second new coil and it fired right up... no more bucking which apparently was the coil failing.

[rjewkes]

i have often had to get a second replacement for everything electrical as they move the old dusty ones forward when they stock the shelves and sometimes your buying a part built 5-10 yrs before that has gone bad from sitting.

[Thunderfoot]

Glad you got it working... I hate it when the replacement parts are bad when your troubleshooting something, makes you want to pull your hair out