Won't start

[Dan Robertson]

I have a problem that has me baffled. I will try to be brief. I have a 63 GMC truck with the 351 V-6. I decided to replace the points and spark plugs as I use it in the winter to plow snow. I installed the points and set them at .016 and the spark plugs at .030. When I got done, it would not start as it had no fire at all. The new points looked exactly like the old ones. For whatever reason, I got a spark back after I put the old points back in but it still wouldn’t start. It would cough and sputter a little but wouldn’t go. I did not take the plug wires off the distributor and changed the plugs one at a time so I do not believe that I crossed any wires. Just to be sure that I hadn’t, I took all the plug wires off the distributor and started over, being very careful to get them as shown in the diagram that I found at <http://www.6066gmcguy.com/EngineData.html.
> Now it pops back through the carb and still won’t start. The truck was running before I changed out the points and plugs so it is obviously something that I have done. This truck is “old school” and shouldn’t be that hard to figure out. Can anyone steer me as to what I have done wrong?

[AZKen]

Possibles:

1. You did not say condenser. They can be bad right out of the box. Points can be too.
2. You left off the rotor?
3. Points are not really .016. Recheck. Follower must be on tip of lobe on distributor shaft when checking points.
4. I'm sure you have the correct firing order but maybe not starting at actual no. 1 on distributor. Can't go by a picture, must verify TDC on the compression stroke of No. 1. You didn't remove distributor, did you?
5. Do you or do you not have good strong spark now?
6. You must have 12V to coil during cranking and after cranking.
7. Some folks buy the wrong spark plugs.
8. Check to see that the Chinese points have their "contact pads" concentric and parallel.
9. Make sure you see the rotor turning with cap off.
10. Make sure you didn't forget that you did something else innocently and forgot. Like leave a hot wire off...or a ground wire off.
11. Choke stuck on.
12. You are out of gas.

[Dan Robertson]

I did not mention the condenser because I did not change it, nor did I replace the distributor cap, mainly because the parts store did not have them on stock. I did replace the rotor button. I am very familiar with setting points as I am old enough to remember when that's all there was. (I predate electronic ignition by about 2 decades) I set the points at 16 thousandths as that was what the website that I went to (and also a down loaded PDF manual that I paid money for) indicated was correct for both the 305 and the 351. If that is not correct, please enlighten me on what the proper point setting actually is. The new spark plugs are AC Delco R44XL, which was also what was in it. It has a strong spark now and, as posted above, I put the original points back in as the new ones didn't seem to be working. The new ones looked good with proper alignment and appeared to be an exact duplicate of the original ones, they just don't seem to work. (which was why I took them back out. I am very familiar with defective new in the box parts) I have 12 volts at the coil (both sides) with the key on and while cranking and is is definitely not out of gas. It has a manual choke, so that is not an issue either. I will find top dead center of #1 and with the cap off see which distributor cap tower the rotor button is is pointing at and start the firing order from there. Again, if .016 on the points is not correct, what is? While were here, is 5 degrees BTDC the correct timing for these engines?

[AZKen]

Yes .016 and 5 BTDC. Plug gap .030. Don't take the comments personal. Just going over everything I think of. You asked for help and I don't know your expertise or what you have done. We all can make mistakes no matter how much experience. You said correctly is must be something you did. I say maybe you or defective parts. Don't see a way that timing could be off.
Strong spark? That is great. Squirt some gas in carb throat. It HAS to start... if all those things you said have been checked. A condenser would be nice but if you have "strong" spark, then you have strong spark.

It is very strange that it does not even fire with 12V at coil and good spark. That does indicate timing or fuel. Especially if you did not take wires off dizzy. Can you describe exactly what it does? No fire at all? Starts for a few RPM's? Runs then dies? Starter spins faster than normal?

You said "Can anyone steer me as to what I have done wrong?"..........that is what I am trying to do. If you have missed something or messed something up, you don't know it. So start down the list slowly, no ego, no guilt...and you will find it. You know what you are doing. We have all done things, stared right at it, and don't see it until we wake up in the middle of the night.

I am assuming you did not take distributor out. But you did not confirm yet. These questions are not meant to disrespect but someone has to ask them. Asking questions/brainstorming/troubleshooting brings out the answer.

[Dan Robertson]

With the old points back in, the engine would fire on what sounded like one cylinder but would not catch. Excessive cranking has flooded it. (gas smell very strong and carb is weeping at the seams.) I have to leave it sit for several hours and stay away from the choke. I am assuming that I initially must have had some wires crossed and didn't realize it. After I took them all off the cap and started over, it was worse than before as it would then only pop thru the carb and do nothing else. That is telling me that I have one (or more) cylinders firing when the intake valve is open. I believe that you have hit the nail on the head about not trusting the photo. I will take your advice and find #1 top dead center by feeling for compression at the spark plug hole, line up the timing marks and then see where the rotor is pointing. Dimes for dollars it wont be the 5 o'clock tower as indicated in the diagram. Hopefully I will be able to get back to this project tomorrow. I seem to have a whole lot more to do now that I'm retired. I'm very glad that this is only August and my old truck is only a snowplow.

[AZKen]

I think you will find it. Just be careful not to cause more trouble. That seems to happen to me when I don't take my time.

[Dan Robertson]

It's running!!!! Not completely sure what the major malfunction was but I'm leaning towards either the condenser wire or the wire to the coil possibly touching ground as to why the new points would not fire. (Nothing else seems to make and sense) Still not sure why it wouldn't run with the old points after I got a spark back. After the second time of finding #1 TDC and wiring the plug wires in the proper sequence, it fired and ran like a champ, with the new points too I might add. Checked the timing and found it dead on at 5 degrees BTDC. I like plowing snow with my GMC rather than my Farmall because it has a heater.