Intermitent Starting Problem

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jefflock

jefflock

69 Dart 408 10.08 best pass so far
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I don't drive my gold dart everyday so I always keep the battery hooked up to a battery tender. Not always but often if it doesn't hit right off the car won't start. I can crank it over but it doesn't seem to want to fire. Sometimes when I turn the ignition switch back off the engine seems to jump or maybe it fired then. It has done this since I've had it and I have changed out the entire ignition system to the FBO unit with a Mopar performance distributor. The only thing I haven't done is to check the wiring job that was done when it was converted to the electronic system. The engine is a built up 340. I'm running 18 degrees initial with 34 total. The carb is a 750 Quick Fuel.
This happened again yesterday so I put my large wheeled charger on it, set it on 40amps and it fired right up. I'm wondering now if the battery isn't big enough or bad. Any other suggestions??? Thanks.
 
Yep it sounds like a battery on the edge. I have noticed the same with a few of my small blocks also. They will crank until battery is dead but wont fire with out a little help from charger. Soon as that happens i replace battery and its cured. I put msd on the duster this 2 summers ago and it isnt picky about starting anymore. If it were a big block you could turn it over by hand and have it start. lol
 
The power of the spark is pretty low on the stockers and when you let go of the key and the starter isn't drawing that power the ignition has a little more to use and fires.
Thats what you are feeling when you let it off the start position and it fires a cylinder or two.
It's also why replacing with MSD fixes that because they have more spark power and even multispark.
 
If it spins over good but wont fire the problem is in the power supplied to the cars ignition. Th battery is fine. It probably did send one spark when the switch returned from start to run.
There are 2 wires supplying that power . One is hot only in start, the other is hot in run. Find them at the ballast resistor and check with a volt meter.

Year model and such would help. There was a electric choke assist mounted by the coil on 73 up models . That thing can short out internally and drink up your starting current.
 
RedFish said:
If it spins over good but wont fire the problem is in the power supplied to the cars ignition. Th battery is fine. It probably did send one spark when the switch returned from start to run.
There are 2 wires supplying that power . One is hot only in start, the other is hot in run. Find them at the ballast resistor and check with a volt meter.

Year model and such would help. There was a electric choke assist mounted by the coil on 73 up models . That thing can short out internally and drink up your starting current.
Click to expand...


^^^THIS^^^


I keep trying to tell people this. On my old Dart, there was a ONE VOLT drop through the deteriorating bulkhead.

Do TWO separate tests, which check the running ignition circuit (ign1, dark blue) or the bypass circuit (ign2, brown)

Turn the key to run, engine off. Put one meter probe right on the battery positive post, the other on the dark blue supply line to the ballast resistor, that is, the "key" side.

You are looking for a very low voltage (drop) the lower the better. If you have a "points" distributor make sure the points are closed Anything close to or more than 1/2 volt is too much, and shows a drop in the path from

battery--fuse link, through the bulkhead, the ammeter circuit, the connector at the ignition switch, through the switch and back out the connector, and back OUT the bulkhead connector on the dark blue line.

IF you show anything close to 1/2 volt or more, pull the connector apart, inspect, clean, fix

NOW check the ignition bypass, same way. One probe on the battery positive, other on the coil positive. You want 1/2 volt or less with engine cranking, USING THE KEY

NEXT hook the meter form the coil positive to ground and crank the engine USING THE KEY. You want a MINIMUM of 10V at the coil positive.
 
Sorry I should have posted it is the car in my atvater. A 68 Dodge Dart GTS that has been converted to electronic ignition. As I said in my original post that the only thing I haven't changed is the wiring that was adapted in when it was converted. The current system is a FBO unit with a Mopar Performance Distributor (Mallory). The system only uses a singe ballast resistor not the dual factory style. I also did the alternator bypass wiring conversion also. The carb is a 750 quick fuel with no choke.
 
It most boxes don't get 12 volts; no fire. If the ignition switch is going bad, no fire on start circuit, only run.
 
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