Ignition problems?, in an old dodge truck - PeachParts Mercedes-Benz Forum

JDmills · #1 11-21-2008, 11:40 AM

I've been working at an 46 Power Wagon, making some improvements, and trying to get it ready for snow plowing duty here at the house..

I put a dodge electronic ignition system in it out of a slant six van, and have had a little trouble getting it to run consistantly.

At first it would start and run right off, but stall easily unless it was nicely warmed up.. Now it will start and run for about a second and then stall, and this will happen a few times until it refuses to start at all..

Wondering about a balast resistor.. but dont really understand how they work.. I tested mine and it's resistance is slighly higher than the repair manual calls for.. on the primary side, and maybe the same on the secondary side..

so maybe i should replace that? is there also a good test to check the coil? or suggestions as to how to discover more about this ailment.

Thanks

Brian Carlton · #2 11-21-2008, 12:31 PM

Quote:

Originally Posted by JDmills

Wondering about a balast resistor.. but dont really understand how they work.. I tested mine and it's resistance is slighly higher than the repair manual calls for.. on the primary side, and maybe the same on the secondary side..

so maybe i should replace that? is there also a good test to check the coil? or suggestions as to how to discover more about this ailment.

Thanks

The ballast resistor is the usual culprit when the engine starts but immediately stalls when you release the key from the start position.

The resistor provides 6V to the coil during normal engine operation. However, when in the start position, it provides the full 12V. If the 6V side fails, the engine will start and run as long as you hold the key in "start". It stalls as soon as you let go of the key.

To confirm this as your issue, just run a wire from the battery to the coil. If the engine starts and runs, the problem is the resistor. Don't drive it that way for too long.........the system doesn't like to live on 12V indefinitely.

If it's not the ballast resistor, the choke calibration is quite sensitive on those vehicles. A very slight choke adjustment causes significant driveability changes. They have a vacuum dashpot to open the choke plate to a specified position upon start. If the dashpot has failed, the engine will run way too rich and stall. Post again if you want to get into it.

dlssmith · #3 11-21-2008, 05:23 PM

I guess the 46 is fully converted to 12 volts, but did you change the key switch too, or are you using the floor starter switch? Anyway, I'd consider looking at the switch if the earlier suggestion doesn't help.

JDmills · #4 11-23-2008, 11:25 AM

Quote:

Originally Posted by dlssmith

I guess the 46 is fully converted to 12 volts, but did you change the key switch too, or are you using the floor starter switch? Anyway, I'd consider looking at the switch if the earlier suggestion doesn't help.

It is the original key switch, with a push button to excite the starter circut. I am at present sending 12 volts to the "start" side of the balast resistor, by way of a jumper wire.. I will put a different key/starter switch on it once all the bugs are removed..

BUT I will try 12 volts to the coil to see if the balast resistor is the fault...

JDmills · #5 11-23-2008, 11:19 AM

Quote:

Originally Posted by Brian Carlton

To confirm this as your issue, just run a wire from the battery to the coil. If the engine starts and runs, the problem is the resistor. Don't drive it that way for too long.........the system doesn't like to live on 12V indefinitely.

Perfect. I will try that.

This system has never run to my complete satisfaction. Maybe the ballast resistor has been on it's way out for a while?

Will give this a try and if that does not work, look into the fuel side... although it does seems to stall more like a ignition problem than running too rich.

Thanks Brian, nicely put

Brian Carlton · #6 11-23-2008, 02:17 PM

Quote:

Originally Posted by JDmills

Will give this a try and if that does not work, look into the fuel side... although it does seems to stall more like a ignition problem than running too rich.

On the Chrysler products, you really cannot tell the difference if it stalls due to ignition problems or it stalls due to a lean condition.

However, usually, if they run for a few seconds after you release the key and then stall, ignition is usually not the culprit.

Also, if it runs fine when fully warm, ignition is definitely not the culprit.

JDmills · #7 11-25-2008, 05:51 PM

Ok fellas, what is going on now? NO spark but at the beginning and end of the cranking cycle? 12 volts from the (+) battery to the (+) coil lead..

nothing else is different...

and the starter motor is not controlled by the ignition switch, but a seprate push button... I may have to give up on this project for the winter.. but it would be nice if it would run, rather than need to be towed about the yard, in order to move it..

Brian Carlton · #8 11-25-2008, 08:42 PM

Quote:

Originally Posted by JDmills

Ok fellas, what is going on now? NO spark but at the beginning and end of the cranking cycle? 12 volts from the (+) battery to the (+) coil lead..

nothing else is different...

and the starter motor is not controlled by the ignition switch, but a seprate push button... I may have to give up on this project for the winter.. but it would be nice if it would run, rather than need to be towed about the yard, in order to move it..

What do you have for the ignition............the small electronic box from the sedan?

It's either the box or the coil...........and I'd bet against the coil.

Matt L · #9 11-21-2008, 06:04 PM

Is that ballast resistor for the original ignition system, or for the electronic system?

Electronic ignition systems often do not use ballast resistors.

JDmills · #10 11-23-2008, 11:29 AM

Quote:

Originally Posted by Matt L

Is that ballast resistor for the original ignition system, or for the electronic system?

Electronic ignition systems often do not use ballast resistors.

I believe it is from the dodge van which I snagged all the original parts from... I just read that the GM HEI does not use a ballast resistor, but the mopar ones do... I think.

YET this power wagon engine came from a military M-37, 24 volt system, so the original distributor did not have a balast resistor on it as best as I remember...

OMEGAMAN · #11 11-23-2008, 12:06 PM

You can use GM hei system with your distributor. Just build a small aluminum heatsink for the module to sit on> It's also the ground for the module. Ive used the HEI system in both old dodges and fords and have had many thousands of miles of trouble free driving.
What plugs are you using? Not Bosch platinum I hope they can give you all sorts of wierd drivability problems.
Also dont use premium fuel. If you have any fuel mixture problems when it's cold it'll run terrible.

The Clk Man · #12 11-21-2008, 06:20 PM

Quote:

Originally Posted by JDmills

I've been working at an 46 Power Wagon, making some improvements, and trying to get it ready for snow plowing duty here at the house..

I put a dodge electronic ignition system in it out of a slant six van, and have had a little trouble getting it to run consistantly.

At first it would start and run right off, but stall easily unless it was nicely warmed up.. Now it will start and run for about a second and then stall, and this will happen a few times until it refuses to start at all..

Wondering about a balast resistor.. but dont really understand how they work.. I tested mine and it's resistance is slighly higher than the repair manual calls for.. on the primary side, and maybe the same on the secondary side..

so maybe i should replace that? is there also a good test to check the coil? or suggestions as to how to discover more about this ailment.

Thanks

Hey man, do you have any pics of the old power wagon? I like those old Dodges.

OMEGAMAN · #13 11-25-2008, 09:46 PM

What is the voltage at the positive end of the coil during cranking.
What is the voltage at the blue wire on the ignition module during cranking

JDmills · #14 11-25-2008, 10:49 PM

Quote:

Originally Posted by OMEGAMAN

What is the voltage at the positive end of the coil during cranking.
What is the voltage at the blue wire on the ignition module during cranking

Good questions: I dont know as of yet.. will find out.

But I am pretty sure I dont have a 'blue' wire on the ICM.. green, white, red brown(?) and orange I think..

I did test all the 5 terminals with a voltage meter and found 12.6 volts on all of the approprate places..

starting to wonder if it could have something to do with the pick up (if it is not the coil as Brian is suggesting that such is unlikely)

yet the pick up tested "OK" by the Ohmm meter test, where as the coil, as well as the ballast resistor were both a little bit out of spec..

course my mulit-meter is a 12 volt setup, rather than the 1.5 volt that was asked for in the old manual.. maybe that would change the resistance readings?

Hey.. I do have another ICM.. maybe it is worth a switch out... but the present one is new and all but unused, despite being 2 months old on the truck... why didn't I think of that on my own??????????