Hi, I have a 65 with a 289, so I'm posting here as members might have 302 which is essentially the same engine. Here is my plight...

The truck has always run well for the 5 years I have owned it.

About a week ago the engine started missing/sputtering at start and at low speed, but was fine as usual on the highway.

This led me to think is was gas-related so I rebuilt my 2100 carburetor. It had been five years since I did it so i thought something might have worn out. Everything inside looked fine during disassembly. I've successfully done this before so I have some idea what I'm doing. After install, the engine still stumbled/skipped/barely ran rough. Made sure the idle screws were 1 1/2 turn out from seated.

I then checked the vacuum advance because I suspected a vacuum leak and it seemed like the vacuum advance wouldn't hold vacuum. I pulled the cheap ready-to-run distributor I had in it. Figured now was the time to wire up a Duraspark, so I did that with a new distributor I had. I had an original wiring harness and double checked everything and read all the internet tutorials. Still would barely run/not start. Got a new control box, still wouldn't start.

Tried three different coils, same outcome - wouldn't start/run very roughly.

Picked up a brand new ready-to-run distributor, again, same outcome. Wouldn't start/engine would spit/cough. I made damn sure I was on #1 TDC compression stroke using a compression gauge. Ensured that the rotor was pointed towards the rear/number 1 tower. Double checked the firing order/wire locations. Wouldn't start.

I checked the positive power to the coil...in start (I tried both using the existing resistance wire and going direct to the switch for the start voltage) it was 12v with the direct wire. Also the run wire gave 12 v. The distributor tach/trigger wire is correctly wired to the (-) terminal and the positive (red) wire for the distributor is wired to the (+) terminal on the coil along with the voltage supply wires for start and run.

I checked continuity of the spark plus wires - they were all fine. I ordered a new set which will be in tonight just out of exasperation.

Replaced all the spark plugs. Started up slightly better but still spit and coughed. Would barely run, then die. I've rotated the distributor body to try different advances, to no avail.

I checked fuel pump output by pumping into a glass jar - got a good flow, got about 8 ounces with 3-4 seconds of spinning the engine over.

I've ensured that the rotor is turning by turning the engine over with the cap off.

When the engine does catch and sputter, I get good oil pressure so I know I'm connected to the oil pump.

Does anyone have any suggestions as to what might be going on? I am at my wit's end!! I really need some help!

Thank you

 

 

Battery is 13.5 volts. The alt appears to be charging when it runs as the light goes out.

 

Its always Fuel or Spark.

To eliminate the variable of Fuel/Air mix, I try to start with a can of aerosol starter (eg Nulon "Star Ya B@stard" )
https://www.nulon.com.au/products/ae...engine-starter

If it starts ok with this stuff, then you KNOW its a Spark problem...…

I'm guessing you have small vacuum leak - not enough to screw up the air/fuel ratio at a healthy rpm, but totally stuffs your fuel availability at low rpm/start.
Try a dribble of fuel down the throat, then start - if this works, it would also confirm the above - then go hunting for your vacuum leak with some brake cleaner, etc....

 

Check your brake booster hose and auto trans modulator vacuum feed hose as potential vacuum leaks....

 

I don't see any mention of a condenser change... the new dizzy include a new condenser?

 

OK, so this started to happen before any changes were made. based on your description I would check the following things;
1) Verify that compression is good on all cylinders.
2) Try pulling the fuel pump and look into the opening at the timing chain, is there excessive slop?
3) If both of those are fine then start looking at the grounds in your electrical system.

Good luck.