intermittent spark

[bentpushrod]

I have a 75 Powerwagon with a 440 and ignition troubles. I've replaced the cap, rotor, plugs, plug wires, coil, ballast resistor, starter relay, and the ECU(5 pin).

The truck would run great sometimes, than start running rough. Sometimes it would come out of it, sometimes not. I've eliminated the fuel system as a culprit.

Today I went out to start it and it would not start, not even fire.

I'm getting spark intermittently. And when I get spark it's weak. I've checked the resistance off the pick-up coil and it falls within range. I'm getting the correct battery voltage to my ECU connector. I replaced the ECU, and ballast resistor and coil. What I did happen to find is I'm only getting 7 volts to the positive terminal on my coil. Book says I should be getting battery voltage there within 1 volt.

I traced the wire from the positive terminal of my coil back to the ballast resistor, then it goes to the ignition switch.

I didn't see any breaks in the insulation of the wire from coil to ballast resistor. Could the problem be as simple as that wire being bad? I'm stumped! Please help before I pour gas on the truck and light a match.

I replaced the wire from ballast resistor to coil, and now am getting 8 volts. Still not enough voltage.

'72 Commando. 360 TH400 SOA 33" Swampers
'78 F250 SuperCab 460 C6 NP205 Dana 60's 33's
'75 Dodge Powerwagon 440 NP435 NP203 Dana 44&60 33's, Western plow

[bentpushrod]

Finally got it fired up. Ran great for about 5 miles, than the intermittent rough running began. Came out of it 5 miles later, than started again. Think I'm going to take it in to a place with a scope tomorrow.

'72 Commando. 360 TH400 SOA 33" Swampers
'78 F250 SuperCab 460 C6 NP205 Dana 60's 33's
'75 Dodge Powerwagon 440 NP435 NP203 Dana 44&60 33's, Western plow

You should only get battery voltage at the coil when the key is in the START position (for ease of starting)

In the RUN position the ballast resister drops the voltage to about 6-8 volts to prevent the coil from overheating and burning out. so 8 volts is normal (maybe even a bit high).

Check your ground between engine block and frame. If you aren't getting a good ground it'll do all kinds of crazy stuff. I had a ground strap rot off on one of my older dodges years ago and had all kinds of intermittent electrical phenomena going on - it was grounding itself thru the manual choke cable I had installed. I discovered it when I went to push the choke in one day and about burnt my fingertips.

Mudbooger

'84 W250... 360... 727... 5" of lift and a rear locker

[ronknott32]

I went through the SAME thing about 2 mos ago. I have a '77 RC w/ 440/727. I tried everything too, so I thought....
!!!I replaced the following to no avail: plugs, wires, grnd strap & wire, ecu, cap-rotor, then the 5 pin plug, still had some intermittent problems..!!!
Then I checked the voltage @ the coil, ballast etc. according to Chilton's, found a voltage drop that always changed, according to temp, etc.
To make along story short, I REWIRED the ignition system, completely, from coil to ecu, never has died due to an electrical problem since.
The wires were melted under the electrical tape that was wrapped on them.
Just what fixed mine.....

RonK.



Why run with the BIG DOGS? When U can play like PIGS in the MUD!!!
http://ronknott.net new homepage http://ronaldknott.com 4X4 homepage