Assistance with Ignition Issue

[SoCal_C-10]

So, my son and I were replacing the cap and rotor on our 1970 C/10 250 and we incorrectly reconnected the plug wires and started the engine with the sparkplug wires crossed. It ran rough and smoke came out of the air cleaner nozzle.

I shut it down and we connected the plug wires in the correct firing order and it now won't run right at all. It stumbles as though its running on two or three cylinders and will not increase RPMs above idle.

I inspected the points, which were pitted and also noticed that the wire from the coil to the point had lost most of its insulation, so I also replaced that, along with condenser.

So here is where we are today:
New cap
New rotor
New points
New condenser
New wire to points from coil

Here is what I know:
There is spark
There is fuel going to the carb
It starts, but won't run
Timing was correct before this issue started

I am wondering if I damaged something in the carb when it backfired?
I am also wondering if the timing is now off for some reason?

Any assistance is appreciated.

[Wrenchbender Ret]

You are probably out of time. First make sure you are going in the right direction putting the wires in the cap. Turn the engine till the timing marks line up. Raise the cap & the rotor should be pointing to #1 or #6 wires. If so check all the wires in order in a clockwise direction looking down at the cap. It couldn't be 180 off or it would not run at all.

[jjzepplin]

I would also look inside cap and rotor to double check. Sometimes we get in a hurry and miss the small things. Like the rotor actually making good contact with the cap and plug terminals. I always make sure to buy cap and rotor from the same manufacturer. Set points first to get running then set the dwell. Or just get an hei and relax.

[dflarsen77]

The first time I ever replaced a points and condenser, I gapped it wrong, car ran terribly. You said it has spark, so I assume it's good, but double check.

[davepl]

Make sure your points are set correctly. I struggled for 3 days trying to cold-start a car in -40F only to find out the points weren't set correctly. Fired right up when I fixed that. So you can have spark but weak or at the wrong time due the points.

Also very possible you've got the distributor out of time (you'll need a timing light to check) or even a couple of other wires crossed.

[RodnRudy]

Try putting in a new set of plugs. You could've fouled a couple when the wiring was incorrect. Worth a try.

[snipescastle2]

Make sure your wires are in the firing order going clockwise, 1-8-4-3-6-5-7-2 easy way to tell the direction of rotation is to look at the vacuum advance canister,it pulls opposite of the distributer rotation, or you can just bump the engine over with the cap off. Sounds like it's just out of time.
Good luck,
Ben

[Wrenchbender Ret]

Originally Posted by snipescastle2

Make sure your wires are in the firing order going clockwise, 1-8-4-3-6-5-7-2 easy way to tell the direction of rotation is to look at the vacuum advance canister,it pulls opposite of the distributer rotation, or you can just bump the engine over with the cap off. Sounds like it's just out of time.
Good luck,
Ben

Good advise, but it is a 250 so evidently a 6 cyl. Firing order 153624.

[snipescastle2]

Geez I didn't catch that about the six cylinder, my bad, but the vacuum advance
Still pulls against the direction of rotation
Ben

[mike16]

similar thing happened to me. blew out a few carb gaskets. maybe check that too.

[SoCal_C-10]

Just wanted to update this thread.

The C/10 is back in running condition and after checking everything mentioned in this thread, I finally realized that the engine is still running as if plugs were wired in the wrong firing order.

I decided to rotate all spark plug wire connections on the distributor by 1 hole counter-clockwise.

The 250 fired right up! Apparently, the distributor is not indexed correctly, so even though I had the plugs in the correct firing order per the shop manual diagrams, they were will each off by one cylinder. That is, plug #1 was connected to the distributor where plug #4 should have been.

The engine is a rebuild installed about 30 years ago, so I'm guessing the shop that did the installation never caught the error.

My mistake was to not number the plug wires to indicate where they were connected to the old cap when I removed it to begin with.

At any rate, timing, dwell, points and idle are now all set correctly and it runs like a top.

So, at some point I will replace the distributor and get it properly aligned.

Thank you all for input. It helped rule everything else out and return to look at the firing order one more time.