Thought I could figure this ignition problem out.

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Feb 21, 2009 | 03:20 PM

Goader

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Thought I could figure this ignition problem out.

1978 2WD F-150

It ran when I parked it a couple of months ago. I go out to start it and it won't turn over with the ignition switch. Only when you short out the solenoid. I check and double check and everything I can think of is ok.

1) Truck turns over while shorting out solenoid. No spark to plugs.

I give up and come back a couple of weeks later. Now it will turn over when I use the ignition switch. I don't know what I touched but it's working. Still no spark to the plugs.

2)Truck turns over while using key. No spark to plugs.

What I have tested: Solenoid, Ignition switch, Harness plug going into ignition switch, Ignition module, Coil, Cap and rotor.

I replace the solenoid and coil with new parts because this is what I had on hand. I swapped out the ignition module and switch with parts I new were good.

I have tested wiring for current and everything looks good to the distributor cap.

I have noticed a couple of oddities. When I turn the dash lights on the turn signals stay lit. When I try to start the truck the brake indicator lights up.

So with this info can anyone narrow this problem down.

Feb 21, 2009 | 03:44 PM

427 fordman

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From: Plankinton, SD

check and clean any grounds you can find

Feb 21, 2009 | 03:51 PM

fmc400

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From: Austin, TX

The brake light coming on is normal; the warning lights are supposed to come on when you start the truck to let you know the bulbs are good. However, the problem with the dash lights and turn signals makes me want to agree with 427fordman. It sounds like a ground problem, especially since it's intermittent. Check that your negative battery cable is clean and properly secured to the engine block. Next, make sure you have a ground strap from the engine block to the sheetmetal, usually the firewall. This ground strap is very important because it's how your truck's electrical accessories ground - starter solenoid, voltage regulator, lighting system - pretty much everything except the starter and ignition.

Feb 21, 2009 | 03:56 PM

westtntrucker

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From: McNairy county, TN.

Another thing to check is the fuse box. Take all the fuses out and check for corrosion.

Feb 21, 2009 | 05:45 PM

Goader

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That sounds like it will fix my dash light problems, but what about the spark getting to my plugs? I have 12 volts at the ignition switch. I have 12 volts going to the coil. My analog meter shows about 8 volts coming out of the coil. If I put the coil wire on and test it than I have 8 volts at the end of the wire and the same goes for the distributor cap when I take it off and test the center post on the inside. When I put the cap on and try and start the truck than I don't get any spark to the wires. I pulled the wire from the plug on the right front of the motor to see if I could get a spark and it didn't have anything.

Feb 21, 2009 | 05:52 PM

kshaneh

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From: Rising Sun, IN

run a jumper from the battery to the + on the coil and see if it starts

Feb 21, 2009 | 05:58 PM

fmc400

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From: Austin, TX

Quote:

Originally Posted by kshaneh

run a jumper from the battery to the + on the coil and see if it starts

You shouldn't put 12 volts on a stock coil, as it's only rated for 7-9.

Goader - I recommended the ground strap check because of the starter solenoid problem. The starter solenoid grounds through the fenderwell, which grounds through the sheet metal ground strap.

Here is another check. Connect a test light from the TACH post of the coil (the negative side) and ground the test light on the engine block. The coil must remain connected to the harness. Use the key to crank the motor over, and the light should blink. If the light does blink while cranking, you know the rotor is turning, the magnetic pickup works, and the ignition module is trying to fire the coil. If it doesn't blink we will go from there.