(Another) Slant 6 No-Start Thread

[jfleming64dart]

Let me begin by saying that prior to this the car has always started easy and reliably. When I first got it it didn't run. I put new plugs in it and it's ran right ever since. Until recently. Here's the story, I had just finished welding on new frame rails (safetcaps actually) so I can finally daily the car and it won't start. Nothing is helping, it just won't. So I go back to college, and I come home a week or so later and before I decide to pull everything apart I give it a crank and it starts up! It sounds like it's on only a couple cylinders so let it warm up a tad and rev it some and after a minute it's purring along like it should be. Gas tank reinstalled, starts up, never even stalls from the air bubble, running great. We've turned it on and off like 5 times over the weekend and the no start is gone. So we take it for a test drive, and blow the metal fuel line. Fast forward to earlier this week, fuel like fixed, and the no start is back. The obvious culprit would be fuel but we have pressure, you can hear the idle (port?) spraying and you get a good shot when you pump the throttle. Here's the tests we've done: compression: decent. About 110 on all cylinders
Fuel: yep it's getting fuel
Electricals: it's been upgraded to an electronic ignition at some point before I owned it. We're getting 8 volts at the coil if I recall, 11.9 at one side of the ballast and 9 something at the other. We've tested if the coil wire will spark to metal and it does but it's not lightening. We pulled a plug connected it and cranked to see if it sparked and we got some minor fizzling around the base part and weak intermittent sparks to the ground strap. I'm guessing my problem lies here. The failure points I've identified from searches are bad grounds, why would that be intermittent? And bad wiring. Whoever installed the electronic control box just clipped one of it's wires on to the lowered voltage side of the ballast resistor along with the connector that belongs there. I've since swapped in a real wire but still just wrapped onto the post because I have no idea how it should be wired. I won't be home again until next Friday but I'd really appreciate some tips on what to check. It's so weird that it's such an intermittent issue!

 

[cdnEHbody]

11.9 is already way low on the high side of the ballast. The less voltage there the weaker the spark will be at the coil. Agood healthy battery voltage should be around 12.4 to 12.6 engine off. So if your battery at rest has that you need tto run through all the connections to the ballast resistor point and make sure they are clean and secure. good clean grounds are also very important. should be almost no voltage drop on all the + wires everywhere. Cleaning all of your bulkhead connector pins and die electric greasing them is also crucial.

I can't be much more specific with the ignition itself withoutseeing what kind and the wiring itself. Perhaps someone more knowledgeable on mopar e.i. than me might know. I'm only super familiar with my own home made t.f.i system.

edit. Is it points now then? And used to be e.i.? If that's the case. Clean clean clean. I would do a new condenser and a ballast resistor just to be sure. But like I said. 11.9 to the high part of the ballast is a big loss in spark energy down the road.

 

[nm9stheham]

No real spark across a spark plug gap in open is very bad! It should normally jump a 1/4" or greater gap in open air with a nice blue spark.

OP, what electronic ignition is this? What coil do you have?

And 11.9v at the ballast is not great, but it should run with that.

When you turn the key to START, then the voltage from the ignition switch should bypass the ballast (via the brown wire) and be applied directly to the coil + side. So try cranking the engine with the coil's spark wire connected disconnected from the distributor cap, and see what voltage appears on the coil + side when cranking. If it is within a volt of the battery voltage when cranking, then it is adequate. The battery voltage should not drop to less than around 10v while cranking.

Measure the ballast resistance with one connection removed; it should be around 0.6 ohms cold for a stock one. To get an accurate measurement of such a low resistance, first put the leads of your meter together and record the resistance of the test leads alone. Then measure the ballast resistance with one or both connections disconnected, and then subtract the lead resistance that you record.
If your ballast resistance is above 1 ohm cold, then a correct one is needed. There are many different ballast types, and most are wrong for the standard Mopar system, with points or electronic ignition.

If this is a Mopar system, check the gap between the reluctor and the 'pointy' tangs on the distributor shaft under the rotor. Check with a non-steel feeler gage. This gap should be .008".

Check the resistance of each spark plug wire to see if the are all below 10,000 ohms. Be sure to check the spark wire from the coil too.