1969 cranks but won't start

[William S.]

I started up my 1969 350/300 a couple of weeks ago. It started and ran fine. I drove it around the neighborhood and about a half mile from the house it started to buck and seemed to want to stall. I nursed it home and it died in the driveway. I went out today and it won't start. It's getting fuel so I tested the coil. Resistance on the secondary circuit is within range, but the primary circuit tested at around 2 ohms. It's supposed to be between 0.35 and 0.55. It is a little cool out, but not real cold, about 65 degrees, maybe a couple of degrees cooler in the garage. Manual says to test resistance at 72 degrees. The difference doesn't seem big enough to matter.

Would this much excess resistance keep it from starting? I seem to remember that when it started to stall it ran better when I accelerated but can't be sure. Thanks very much.

[Mark E.]

Re: 1969 cranks but won't start

William,

Where did you get this spec? I haven't checked all applications, but the primary coil resistance spec is typically about 2 ohms. For example, the spec for my 1970 LS-5 is 1.77 - 2.05 ohms. Is the '69 300hp really that different?

What's weird is that most replacement coils don't meet this spec. They're typically rated anywhere from 0.6 (Accel 8140) to 1.5 (Echlin IC12).

More frustrating is most replacement coils do not physically fit into the original coil bracket. They're just a bit too large in diameter for the bracket screw to fit. I've read on this forum that even the expensive "reproduction" coils are too fat.

Besides the original, the only other coil I know about which physically fits is the Accel 8140 (there's probably others). It's physically about the right size but the tower for the secondary cable is deeper, so a 90 degree boot won't fully seat. This is the coil I currently use, and it seems to work fine despite the out of spec primary resistance. (It's close to your spec, so if it's correct maybe this coil is a winner for you.)

I never felt confident a coil is really ok by just checking primary and secondary resistance. I usually just swap in a known good test coil to eliminate it as the problem.

To troubleshoot an ignition, I like to start at the spark plugs and work "upstream": Spark to plug? If yes, then spark to high tension coil lead? If yes, then proper primary voltage to coil? If yes, then coil test ok? If yes, then primary circuitry ok (points, cond., related connections)?

Let us know what you find.

[William S.]

Re: 1969 cranks but won't start

Thanks Mark. That spec came from the 1969 Chevrolet chassis service manual. I'll probably go ahead and replace it as you suggest to eliminate it. I've never replaced it so it's been around for a while.

[Terry D.]

Re: 1969 cranks but won't start

I agree with Mark, sort of. Check spark at plug, if you have good spark at plug the coil, points etc are working enough to start the car. A bad condenser will keep the car from starting. You don't say how many miles are on the car. With the timing mark up is your rotor pointing at number one plug wire? How did you check that you were getting fuel? Did you check distributor cap for cracks? Is the rotor tip clean? Are the contacts inside the cap clean? Lots of things to check but very easy to and not much time involved. Engines need fuel, spark and air to run. Start with the basics and go from there.

[Kenneth B.]

Re: 1969 cranks but won't start

If you have the shielding on the distributor make sure that the coil wire is NOT touching it. My 67 390HP did that & I had to put a piece of rubber under the lid.

[William S.]

Re: 1969 cranks but won't start

About a hundred thousand miles on the car. Condenser, rotor, cap, wires and plugs are pretty new, I tuned it up a couple of months ago. Timing and dwell were also fine at that point. I drove it for a while after the tune up and it ran fine so I don't think it's related. I checked that it is getting fuel to the carburetor when the accelerator is pumped and tried starting fluid. I've driven it at least once since the last time I filled the tank so I think the gas is good. I've got the battery out charging right now but will check for spark when I put it back in.

[William S.]

Re: 1969 cranks but won't start

No shielding on the distributor. Coil wire not touching anything.

[Gary B.]

Re: 1969 cranks but won't start

I had a similar problem with a 427-390hp 69. It was getting spark and fuel. A whole lot of fuel! It was flooding the engine out while cranking it, blowing past the needle and seat in the carb. After having the carb apart three time, new needle, seat, float each time, I was convinced it was not the carb. I sent the carb in and had it tested on flow-bench. He said it was perfect. Ran the fuel pressure up to 9-lbs and said everything was good. Then, what is it?

Looked up fuel pressure in an old 1972 Motor's manual. It listed 427-390hp motors to be 7 to 9 lbs of pressure. So, I bought a 25psi pressure gage, some rubber tubing, brass fittings and made a setup to crank the engine and see fuel pressure. 19-lbs was what I was seeing. So I sent the "original" fuel pump out for rebuild. Yes, they do rebuild crimp type fuel pumps.

I bought a reproduction fuel pump for the car, just to see what it would pump. It was pumping 17-pound of pressure! Now, two pumps being almost identical pressure? Doesn't make sense.

Normally I don't like to make a whole bunch of changes at a time, I like to do changes one at a time to see what fixed the problem. This time, I guess out of time and frustration, I broke my cardinal rule. Ugh...

I blew out the fuel return line back to the tank with about 15-pound of air pressure. (Take the cap off the fuel tank first) I put a new (NOS) fuel filter on. I also re-installed the fresh rebuild "original" fuel pump. Tested the fuel pump pressure, 7-pound. (HMM, wonder what fixed it?)

Reinstalled the carb, fuel line, straightened everything up I un-did, started right up and ran fine. What fixed the problem? I do not know. But... I think it was either the fuel return line being plugged or the fuel filter was plugged, not allowing fuel to return.

Trivia. Not always electrical problems.

Gary Bosselman

[Bob W.]

Re: 1969 cranks but won't start

Gary So who rebuilt you'r original fuel pump?

Thanks Bob

[Gary B.]

Re: 1969 cranks but won't start

I send them to Brian at Volunteer Vettes. He has somebody do them. I have never pressed him who. They have always worked good when I get them back.
Gary B

[Bob W.]

Re: 1969 cranks but won't start

Gary Thanks for the info.

Bob

[Edward J.]

Re: 1969 cranks but won't start

Bill, I had a situation this summer after installing a new set of uni-points, drove to the gas station for fuel, ran fine there and then while I was fueling the car (while its running) it begin to stutter and run rough and then finally stalled, had to have towed. it ended up the condenser failed. Some parts made today are not lasting as we expect. just food for thought.

[Richard G.]

Re: 1969 cranks but won't start

Remove the wire off of the coil (The one that goes to the distributor). Then get a short piece of wire and connect it to the coil at the same terminal you pulled the coil ground wire from. Pull the high voltage wire from the distributor end and put the end 1/4 from a good ground. Now touch the other end of the short piece of wire to ground and pull it off. When you remove the wire from the ground the coil should spark to ground on the high tension side. If this works it is likely something in the distributor. If it's new doesn't mean it's good. Been burnt too many times on that assumption.
Rick

[William S.]

Re: 1969 cranks but won't start

I went ahead and ordered a condenser when I ordered the coil. I seem to recall years ago when I had my first corvette the same thing happened to me. I pulled the battery out to charge it and won't be able to put it back in until Sunday. I'll check the spark then. Thanks for all the suggestions.

[Guest]

Re: 1969 cranks but won't start

If your getting spark at the plug , cap and points ,coil , dwell, wires are good to start car , check fuel to carburetor if there 5 to 7 psi pressure your good then you jump the timing chain and timing is off , check timing Marks