The problem: I have a 68 F100. It starts fine cold, and runs fine for a while (say 30 minutes.) It begins to sputter a little in 3rd gear. When I stop and start it up 30 minutes later or so, it is nearly impossible to get it to start. The only way I've found is no choke and lots of gas. Then it runs like crap, sputtering in every gear. If I accelerate too fast in each gear it's worse. If I accelerate slowly it's ok. Hills will make it cut out completely depending how steep the hill is.

I thought it was the inline fuel filter, so I got one. The problem is, I don't see an inline fuel filter anywhere. Is this piece necessary? Is it possible someone took it off, and I don't need it?

Does anyone think it's something else other than the inline filter? I thought it might be the fuel pump (or the fuel filter on the fuel pump,) but I just change it last year. Not to say that isn't it, just feel like it's maybe not so likely.

Thanks

 

I believe these trucks only came stock with the fuel pump canister filter. I added one under the truck between the line from the fuel tank to the hard line that runs along the frame to the fuel pump.
I dont think that is your headache. I would look for vacuum leaks. It really sounds like a carb rebuild kind of weekend.

 

You're not giving us a whole lot of information but...
Check your carb. There's a small filter there that looks like an in line filter. Depending on what engine and carb.
Your issue sounds more like a distributor, condensor, points or coil issue. A lot of times things will run normal cold and then with heat these areas go on the fritz

 

2x.. On a P3 Orion I worked on the radar system would go haywire after it heated up. We found a small crack on a hardwired circuit board that would erratically cycle a voltage signal on and off depending on how warm it got. .. took us a week to find it.

 

Could be a partly broken wire, or maybe vapor lock from a fuel line that is too hot.

 

My truck was doing the very same thing last week. It had nothing to do with fuel. It was a bad (intermittent) condenser in the points distributor.

That condenser was only 5 months old when it went bad.

 

There is no inline fuel filter as original. The ONLY fuel filter is C4AZ-9365-B .. Cartridge Fuel Filter (Motorcraft FG-1A), fits inside a canister that threads onto the fuel pump.

 

I initially thought my engine's stammering and cutting out problems was fuel related. It has a canister filter on top of the fuel pump (inline 240 engine) and a filter at the carburetor like this. (Motorcraft part listed for a '69 F100 W/240 and Carter 1 bbl).

Motorcraft FG14C - Fuel Filter | O'Reilly Auto Parts

As it turned out though, the problem was not fuel related. It was spark related. The engine would run fine when cool but as soon as it warmed up, it began cutting out and missing with an occasional backfire. I took the condenser off and shook it. I could hear the guts flopping around inside. I replaced it with a new condenser and it's back running like it should.

 

Thanks for all the advice. So, there is a definite change in power when I go up a steep hill. Do you think that would still be the points distributor? I mean, I can get it running, even with a lot of sputtering, until I try a steep hill and it's like all the power is gone. If I've given it enough power on the flat ground to overcome the loss of power on the hill, it will sputter, slow to a snail's pace, but eventually make it up. If I haven't given it enough power, it stalls out completely.

Sorry if that's still not enough info. I can't think of anything else.

 

I really does sound like timing. Have you checked anything?

 

My engine's problem acted just like a clogged fuel line, pump or trash in the carburetor. After the engine was up to operating temperature, it would start missing. Going up an incline on the road or any additional load on the engine --like stepping on the gas pedal, would make it miss and cut out more.

I found the problem by putting my timing light on the engine. I started the truck and just watched the light until the engine got up to operating temperature. Up to that point, the light would steadily blink.

Once the engine got up to operating temperature, the light started skipping (not steadily blinking). If I tried to give the engine gas, the spark would drop out more or, it would make the engine go dead.

The internals of the condenser were loose. I could twist the lead around that was sticking out of the condenser (it shouldn't do this). I suspect the ground connection inside to the case was broken loose. As long as the condenser was cool, the ground lead inside the case would make contact and the engine would run. As the engine warmed up, the case expanded and vibration was making the internals bounce around --sometimes making contact to the case, sometimes not.

The cure for my engine problems was a new condenser.

 

Hey ultraranger,

That sounds exactly like what's happening. I'll check that out and see. A lot of people seem to be pointing to the condenser. I'll give that a shot.

 

Should I just switch to an electronic ignition system?

 

The electronic drop-in modules are outstanding. But.

Points and condenser work OK, but the modern manufactured exemplars are usually of poor quality and are impossible to use.

NOS points from the 50s and 60s are cheap and plentiful, these are the type to use, if you're gonna run points. Usually they would last 8-10k miles but they did need adjustment now and then, a little cam grease for the rubbing block, etc. i only installed a Pertronix because on a Y block the distributor is at the back of the motor and it's super awkward to work on.

 

This sounds exactly like the problem I was having with the condenser in my truck. (loose innards and poor case contact).

Condenser Failure in Conventional Ignition Systems