81 f-250 400ci. The truck died. Changed coil. Started and ran about 10 sec. then died. Never fired again.

I have another truck that I pulled up and changed the coil, ignition module, wiring harness, and distributor. I also checked the 2 leads coming from the firewall and compared the 2 trucks. As far as I can tell everything is the same. Still no fire. Have tried 3 coils and 3 ignition modules and they work on the running truck but not the other.

Anybody got any ideas. I am about 1 day away from converting it to points ignition.

 

spray something combustible (starting fluid) down the carb, if it kicks the fuel filter is clogged. these old trucks anything is possible

 

It is getting plenty of fuel but there is no spark from the coil.

 

Coil wire?

 

The one that was on it was real rusty so I changed cap, rotor, and coil wire. Have had 3 coil wires on it. Have 6 volts at both sides of the coil.

 

With the key ON, not running, you should have fully battery voltage (12 volts) on both sides of the coil in a DS2 system. In a points dist, only when the points are open will you see 12v on both sides of the coil.

Try running a jumper wire from the battery POS to the coil POS.

Also have you done the "blinking light test" on the coil NEG.

Jim

 

My 84 only has 6 volts on both sides of the coil and it runs. IDK

What is the flashing light test you speak of?

 

Use a 12 volt test light, connect one lead to the coil neg, the other to GRD. The light should be ON the the KEY ON and flash on-off during cranking.
The coil NEG is also marked TACH TEST.

When you say... "6 volts on both sides of the coil" do you mean one test lead of the meter on the coil POS and the other on the coil NEG?

I would still try running a jumper wire, battery POS to Coil POS to see if it helps.

Jim

 

No, ground to coil neg. and then ground to coil pos.

I read about your flashy light test and dirt cheap ignition on another post. Wish I read that before I ordered the parts to switch it to points.

I am still gonna do some testing though. I hate letting these simple old trucks beat me. It just ain't right.

But I still just can't fathom how I put all the parts off my truck on it including the engine harness and it still won't work. I just can't believe it.

 

If you do end up with points, be sure to re-gap the plugs. Not sure what the correct gap is but it is smaller.

 

IS the rotor turning when you crank the engine?

 

Check the ballast resistor.

If it's burned out, you wont have power to the coil to make it fire.

 

my 1973 with points the gap was .35

 

Thanks I would not have thought about that.

Yes rotor is turning.

Don't think electronic has a ballast resistor does it?

I tried to check the coil with the blinking light test. I put the tester on the pos. side of the coil and the light lit. Dad turned the key from on to crank position. At a small point between run and crank the light got noticeably brighter. When it starts cranking it goes dim again. I put the tester on the negative side of the coil and the light neither lit in the run position or blinked in the crank position. I grabbed the coil off a running truck and put it on. The test results were the same.

Thanks for the help guys, I can tell from searching that you have been through this with other people, but I just can't seem to get it to go.

 

"I put the tester on the negative side of the coil and the light neither lit in the run position or blinked in the crank position."


It would seem the NEG side of the coil is being pulled to GROUND continually. It should be an open - close thing, like points opening and closing.

With the KEY ON put the test light on the coil NEG, then pull the 4 wire connector apart at the DS2 module to see if the light comes on. If it does the DS2 module is providing the constant ground.

If, after separating the connector, the test light is still not ON, check the green coil wire for a "short to ground" between the coil NEG and the DS2 module.

Do you have a round coil with the slide on connector?

Jim