Alton9

Hello all, new C3 owner here. Bought a '75 model that had been setting up for several years, got it cranked, fixed the brakes, all was good. Until one day last week it wouldn't start. Turns over, is getting gas, won't "hit". Have 12v to HEI dist., drops to about 9v while cranking. Replaced cap, rotor, module, condenser, and pickup coil to no avail. Even tried a new complete distributor to no avail. Grounding a plug/plug wire to the intake I get a yellow spark, the first is fairly large, tha subsequent sparks diminish noticeably. I think I should be getting a white or blue spark? Is the yellow spark not enough to ignite the fuel mix? I'm at a loss, it should run, it was running, but now it won't. Any advice or suggestions will be greatly appreciated.
Thanks Alton9

MelWff

If it drops to 9 while cranking you wont get a good spark, battery maybe weak.
How did you determine you are getting sufficient gasoline to the carburetor?
If you removed and reinstalled the distributor how did you get the timing close enough for starting?

Alton9

Battery is only about a month old, just had it checked minutes ago, tested ok. For the timing, I rolled the engine over until TDC was indicated on the timing marks and verified that the rotor was pointing at the #1 plug terminal on the distributor. Reinstalled to line up the same way. I don't expect the timing to be perfect, but it won't try to "hit" at all. I even double checked myself by pulling the valve cover and making sure #1 cylinder had both valves closed at TDC with the rotor pointing to #1.
As far as gas, you can thumb the carb linkage and plainly see the primaries squirting gas in. I'm at a loss....

Edit to add:
The car had cranked instantly every time I cranked it after initially getting it going. It cranked that way last Thursday morning, I let it run a few minutes showing it to a buddy of mine, and cut it off. Thursday evening it would not start. What changed? A marginal ground went away? But it still has 12v to the dist. and turns over?

69427

Nine volts is not a problem if you have a GM/Delco module in the distributor. These units are designed to work at 6 volts so that customers cars will still start in the winters with a half frozen battery.

The problem is if you aren't actually getting nine volts to the distributor. A voltmeter averages out the actual voltage levels, so you might be getting 12 volts at times but 4 volts at other times. The 4 volt level shuts the module off temporarily, preventing a startup. Are you sure the battery/ignition wire to the distributor has some good clean connections? Any corrosion in the connections will cause resistance, causing voltage drops. I'd make sure that the feed wire to the distributor is a clean, low resistance source.

Alton9

The module currently installed is a new one from Napa, an Echlin brand, I believe. The wire is the original wire, as best as I can tell. Does it come from the ign slot on the fuse box? I could run a new wire to check that...
Just tried with starting fluid, hit very weakly and intermittently.

Alton9

Maybe something? I checked my distributor feed wire (pink) for continuity with a pink wire on the small inside starter solenoid terminal. I have continuity with key off and battery negative post disconnected. But I also show continuity with the battery cable post, the hot alternator post, the alternator body and the engine block. So..... Do I have a short? If so where?


Edit to add: I just checked and found continuity from the yellow wiper lead to the same places ( hot wires and to ground ). Key off, battery disconnected. I'm no electrician, somebody please explain this to me����

blue427

I don't know about your electrical problem,but you're trying to start your car on 0 degrees,advance it to about 8 or 10 degrees btdc then try.

HeadsU.P.

The coil frame in the top of the distributor cap comes with a coating or paint to keep it from rusting. One wire off of that coil goes under one of the four mounting screws. Take a wire brush and remove the paint on one corner of that coil then reinstall the wire terminal and screw. You have to have a good ground. And while you're in there, how is the button spring under the coil?

Alton9

Sanded the paint off the frame on the new coil, made sure I had the little dogleg ground piece under the one corner, and also made sure to have good ground to the ground wire on the other corner. The button is new, installed under a new rubber washer. Also tried the old cap and coil that previously ran with the same result.

To summarize so far, weak or no fire with 3 different distributors, one a complete new unit. Also found continuity from the distributor BAT wire to the battery cable at the starter, to ground at the engine block and to the alternator (any place or wire on the alternator). I'm currently going to try a separate battery grounded to the engine and hot to the distributor?

Alton9

Update: I hooked a separate battery up to the distributor BAT terminal,
grounded to the engine, still just a tiny yellow spark, won't attempt to run, although the battery I used only shows 10v.... I'll charge it and try again. I'm starting to think I may have a short issue that's causing the not cranking/not firing problem? But the separate battery should overcome that, right? When I was a teenager working in a auto salvage yard, we'd crank these engines on the ground with just a battery to the starter and distributor....

Also pulled the battery, unhooked the cars battery cables, reconnected the battery with 2 shorter cables direct to the starter and grounded to the intake manifold, in an attempt to eliminate the battery cables as a possible problem. Still weak spark, no attempt to run, even on starter fluid.

Alton9

I have advanced and retarded to extreme amounts,and all points in between, can't make it try to run, I believe the weak spark is to blame? It won't even try to hit on starting fluid? There's got to be a reason why I'm not getting a good spark, I just can't figure it out. I'm questioning my power supply, but it shows 12v, down to 9 or 10 while turning over. I'm also questioning my plugs and wires, but it was running pretty good till it refused to start. I really think it's an ignition problem, seems to be getting plenty of gas. I have a brand new Edelbrock carb I could put on, but if it won't hit on starting fluid I figure "what's the use".

donaldb1

If you are using a digital VOM, you may have 12volts, but not enough amps. Try a test light and observe the light dim/bright change as you attempt to start the engine.

GunPowder

Just another thought, since I have a very similar problem (after shutting off and standing for one week she didnt want to start anymore): Spark/ignition is fine and fuel delivery to carb also. Seems my carb is the culprit, just waiting for some spare/rebuild parts to verify.

Alton9

I did notice the courtesy lights dimming some when trying to start it...... But still show 12v dropping to 9 or 10 while turning over. Could it be that the starter still functions, but has a short, or is drawing too many amps?

Alton9

SUCCESS!!!!!! Talked to a local mechanic this morning, went through the whole story with him. He listened, asked a few questions, and then said to put a new set of spark plugs in and try it. He said if that didn't work to call him. Well, I was pretty sure that wouldn't work, but I went ahead and took the advice I had asked for...... New plugs and it started instantly......
Thanks to all for your thoughts and suggestions