How do I tell if I have a points distributor on my '75 ford f100 4x4 with 300 straight-6? When I get the truck up to about 35 mph the engine about dies and sputters real bad. I took the fuel filter off to inspect it and brownish colored fuel with small particals came out so i thought my fuel was just bad but that doesn't explain why the truck runs pretty good untill you drive it and get it up around 35. My Auto Tech instructor says he thinks my points are fried. How do I check this and how does that explain my dirty looking fuel?

 

The fuel filter should be replaced, no doupt. And if any of the crap floating around got in the carb? Might need to rebuild it. Any crap that gets into the float bowl can block up the very small passageways within the carb, and can create fuel flow shortages.

As for the disty? Seeing if you have points or electronic ignition is easy. First off? If it's electronic you'll have an ignition control box/module mounted probably on the fender apron. Normally about 1 1/2 thick...maybe about 5 inches or so squarish size. Plus you'll have a wiring harness with a connector coming out of the base of the disty cap....And as a bonus? Perhaps the easist way to see if you have points, and to judge their condition if you do have 'em?

Just remove the disty cap. Look under the rotor button. You'll see either a pickup unit for the electronic ignition---or a set of "points"... (check out any auto parts store for your make and model..and look up ignition point set....good photos of what to expect)

Good news is? If the points are worn? Not to hard to replace, just have to take your time and ensure the contact is correct between the two point pads..and the 'dwell' timeing needs to be correct. (your auto tech instructor I hope would know what "Dwell" means.)

S-

 

You can take cap off distributor and look to see if you have points and you can look at them to see if bad. I had similiar problem but at 60mph with sputtering and my points were fried too.

 

interesting.. yeah the auto tech instructor is a genious. lol at least compared to me. thanks! so the sediment in the fuel is like ultra small, you can barely see it, the color is the worst part. i'm assuming i should dump the fuel tank and maybe flush it with something, too? or is that overkill?

 

ehhhh....older fuel tanks...you'll get some build up and crap. The fuel sock will catch the big stuff, and the fuel filter will keep (unless it's pretty well shot) the small stuff. Now fuel starvation "can" create problems keeping the fuel level in the bowl correct when running at speeds. If the filter is starting to clog up? With higher fuel demands, it might not have enough flow. That being said? It's cheap for a fuel filter. Any crud that gets into the carb? does have the chance of building up in the very small ports in the carb. Not saying it needs a full rebuild at this point? But I'd replace that filter just for peace of mind.

As for points? If you have points---There's also a chance they can start to stick up and also create issues. Inspect 'em, and change 'em out if needed.

Flushing the tank out might be a good idea....but I'd really start with the fuel filter and the disty.

S-

 

ok sound's good. i'll go from there. thank you!

 

As original = all 1973 and a few early 1974 F Series trucks have point dizzy's.

Most 1974's, and all the subsequent years have ignition modules.

A former owner could have installed a points type dizzy in your 1975, but it didn't come from the factory that way.

Dizzy ID number: On the curved portion of the base, just below where the cap rests. The number is STAMPED into the base and will be similar to: D5TF-12127-AA, or D5TF-12120-AA.

On the fuel sending unit (except in cab tanks) will be a plastic meshed filter screen (not a sock). The screen is approx. 1 1/2 inches long and 3/8" in diameter, and slides over the end of the pickup tube = still available from Ford, NAPA, other parts stores: D1AZ-9A011-A filter screen / sending unit gasket: C0AF-9276-A / sending unit float = C0AZ-9202-B = prolly leaking = replace this too.

 

well the easiest way to take care of the points that i have found is to get sometrhing like the crane cams xr-1 points to electronic ignition converter its simple 2 wire hookup no cutting very reliable and even has a built in rev limiter i belive i paid about 80 dollars for mine out of summit

 

I bought that one. Have yet to install it. Didn't feel like removing my distributor to put it in since that was step 1 in the instructions.

 

It sounds like the dirty fuel filter was causing the problem, and it does explaing why you can get to 35mph, and then it starts sputtering. Your dirty filter was flowing enough fuel to fill the carb bowl at idle, and extremely low loads. as you accelerate, the fuel pump (because of the cloged fuel filter) can't keep up with the fuel demand of the carb. But it will run great for a few seconds while the carb bowls are still full of fuel. If you think about it, at 35mph, the engine is doing way more work than it does at say 20 mph. work = fuel demand. Will the engine rev up in neutral at a stop? if that should disprove the ignition system causing the problem.

 

If you rev it up in neutral that may not disprove the points being bad. Mine revved up in neutral just fine when i had a points problem. Not much of a load on engine revving in neutral, IMO.

 

The duraspark ignition box has a low speed control and a high speed control. Mine failed on the low speed circuit and it would idle rough. You can have the box tested for free at any NAPA store. If not the box is 29.00 new.