I have been working on my F100 religiously lately. I can get it to start and run fine some of the time. Even when its been running great for a few minutes it acts like it jumps time and runs like crap! Most times it barely runs. Anyone have a clue what may be going on? I have checked the timing on the gears and the entire ignition system is new. I don't know where to go from here. Help?

 

Next logical step (I'm laughing at the thought of me being logical) might be the carburetor. Could be something floating around in there that shouldn't be.

 

I just bought the holley 2300 and put it on there. It runs great for a minute then like crap. Lol, being logical hasn't been working. Its time for stupid luck to help. Do you think there maybe somethin with the new carb?

 

I'd say no. How's the inside of the gas tank? Could their be crud in there that's getting through? I mean, if you're getting fire, fuel is next in the order of things to look at. What does your compression look like?

 

A new carb--float level?

--fuel filter?

--fuel pump?

You checked your timing set, right, no slop and wandering timing, right?

 

If it's surging i'd check for vacuum leaks

 

I just another development. The coil popped last night. It isn't surging, it will just run great for a little bit and then act like its out of time. Like it aint getting any fuel. Or maybe spark I am not sure because it will not stay running long when it does this. I am pretty sure I don't have a vacuum leak. Not sure if the vacuum lines are hooked up right or not. What is this slipping timing you speak of? I know I probably sound like an idiot, but I have been turning wrenches on vehicles for over 15 years and I have another 390 in a '68 F250 that I have never had these problems with. Any advice would be awesome.

 

Hook a votmeter up to the + side of the coil and then start it up. Make sure that the voltage is not fluctuating espcially when it starts to run bad. Make sure your choke is locked in the open position and not hanging closed. Set the float level to the bottom of the sight gauge opening if there is one. Check for vacuum leaks. Make sure your vacuum advance is working and the diaphragm is not blown out. Replace the points and condenser.
Squido

 

Had problems like this twice first there was junk in the fuel bowl canister on fuel pump. Cleaned out bowl problem gone. Second time the black wire going from the coil to the dist was old and cracked, was grounding out on the engine. Would run for a few seconds then quite.

http://shop.advanceautoparts.com/web...RPTUNEAMS_____

 

Wrekerd, I must agree with sw on the voltage , you should have 8 to 9 volts at the coil when running. The only other thing I would check is with a dwell meter at the same time when running, make sure that the dwell is set at 30 to 32 degrees and not fluctuating, I once installed a set of points that would actually bind open after a few minutes, then restart like nothing was wrong, the dwell meter saved my sanity. I hope you are not using any of the big box parts store trash.I really miss the old style parts stores! Go to a NAPA store if you need new ignition parts. Or convert it to a Petronix system once that you are sure the electrical system is in good shape. Kenny Nunez

 

If the timing chain/set has never been replaced, it can be stretched/sloppy and unpredictable...but it wouldn't put itself back in time when it slips...it would stay out of time until you put it back. Sounds like a vagabond electrical problem if the carb has been cleaned or is new. As cheap as they are, I'd replace the points and condensor just for kicks...then check the coil and resistor wire to the coil from the ignition switch next time it acts up.

 

A sloppy timing chain will show up on pulley & pointer with a timing light while watching the timing marks. Also same goes for a warn dizzy bushing. With motor rpm between 600-550 rpm the timing marks will drift or float around not being able to stay at one set timing mark. The dizzy centrifugal advance can cause the timing to float around to if spring or other damaged to it. Carb air/fuel mix out of adjustment. float lever to high or low, Loose dizzy screws & wires & to coil. Bad Coil. Massive vacuum leak. Most guys don't check all the ideas as they thing this ok and not that. But rechecking they will find that there a bone head for not checking better. Trouble shooting is a slow thing to learn. Not ez like just R&R repair. All good thing to double check. Do a gas line flow test to see it pumping enough gas. Now how did this problem all come about for you to replace carb & ign stuff?? We need some background on your trucks big malfunction.. orich

 

Orich, I bought the truck two years ago. It was in pretty bad shape. I drove it for a little bit. Then I got deployed. The carb. Waz held together with bailing wire. The points were stripped and the vacuum advance was missing. Had a piece of wood holding the points in place. Exhaust manifolds were cracked all the way around and had rtv for gaskets. The wiring harness had trailer wiring kit spliced throughout it. After the deployment I started repairing and troubleshooting. I changed the manifolds out with hooker headers. Took the old carb off and was surprised to see the truck ran, one jet was missing and the other fell out. So I replaced it with a holley 2300 2bbl. Brand new. The distributor, cap, rotor, points, condensor, coil, plugs, plug wires, have all been replaced. The truck started burning up starter relays. Then started burning up coils. I changed out a bunch of the wiring so it back to the way it is supposed to be. Changed the ballast resistor out. It was still doing the same thing. I changed all the vacuum lines out and clamped them on. The voltage regulator, and the relays were replaced. The rotor looked like it was hitting on the cap so I put new ones on. The timing has all been checked and checked again. I can do that in my sleep now. How do you check for sure for vacuum leaks? I startex the truck up yesterday and it was running fine. I thought holy s#$%! Maybe its good, but as soon as my neighbor said somethin about it, it started running like crap again.

 

I say "Get rid of the neighbor"
Are all ground straps good and mounted to clean metal?

 

wrekerd, You said that you changed the resistor, did you check the voltage on the pink resistor wire from the ignition switch or has it been by-passed ? If not you may be reducing the voltage to a point that there is insufficent voltage feeding the ignition system. In other words you may have too many resistors. Thank you for your service. Kenny nunez