ok here goes: my '77 f250, 300 I6 is having some trouble... ill be cruising along at 60mph or so and after about 5 minutes(ish) the truck will start to hesitate, and if i push the accelerator down it wont do anything, wont rev or anything, if i push the clutch in and hit the gas, sometimes it will rev somtimes it wont really do anything. ive heard, and my friend has saw it backfire when this is going on. whatta ya guys think? carb? well thanks for any help!

 

Hey, how's it goin'? Yes, it sounds like a carburetor/fuel problem to me. Here's my take on the problem. Does your truck resume running normal after letting off the gas for a little bit? Does it run ok at slow speeds? It sounds like your engine is starving for fuel. When you get up to speed like 60 mph or so your engine needs more fuel that what is being provided. Kinda like running out of gas, which is why it's stumbling and why pushing down on the gas pedal doesn't do anything. It's outta gas. At least the carburetor is. It could be a cloged fuel filter, bad fuel pump or dirt in the carbureator. Check the filter first. If dirty, replace. Check the weep holes in the fuel pump to see if there is a sign of fuel leaking from the holes. Check when running. If there is, this is a sure sign of a bad pump and needs to be replaced. Check fuel pump to see if it's putting out enough supply. If you don't have a fuel pressure guage to check this, perhaps you can take it to a shop and they can do this for you. If you can't you can disconnect the fuel line at the carburetor and place the end in a coffee can. Crank the engine over a FEW times and watch to make sure you have a good strong flow. If it is weak, replace the fuel pump. Just be careful and wear safty glasses. Do you have a fire extinguisher? Check fuel lines and fittings to make sure your not loosing gas or sucking air just to be sure, although you didn't mention any gas smell. You could have a kinked fuel line. If all else fails, pull the carburetor and check for dirt. A cloged fuel filter will give you a good indication of whether you might have dirt in the carb. If you have a lot, or even a little dirt sitting in the bottom of the float bowl, chances are your jets might be cloged as well. This will give it the symptoms your discribing. Give it a good cleaning or put a rebuild kit in it and try again. Good luck.

 

Try a drive with the gas cap off. Vent line for gas tank could be
stopped up, or if you have a Calif. emmissions canister it may be
stopped up too.

 

hey thanks a lot for the replies. right now my truck is sitting on the side of the road :< i had been cruising on the highway for about 15 minutes, and had a little trouble. but then it started hesitating really bad, so i pulled over, got her going again for like 30 seconds, then had to pull over again and now it wont stay running. i would rev it up and it would back fire like crazy... when it would let me rev.
i replaced my fuel filter about a 2-3 weeks ago. and i ran some STP carb cleaner last night. but ill look into your other suggestions. thanks again
aaron

 

sloth,
It's not your fuel. The key clue is the backfire. Fuel problems don't cause a backfire. I would guess the duraspark module or the coil or the stator pickup in the distibutor. These items are temperature sensitive and can fail intermittemtly with respect to temperature.
My guess is the stator pickup.
My Way is the Highway,
KingFisher

 

[updated:LAST EDITED ON 02-Aug-02 AT 07:13&nbsp;PM (EST)]sounds like a spark problem to me...The whole after 5-10 minutes thing....just sound like some electronics are heating up and not functioning properly...We all know electronics are tempiture sensitive and will do VERY odd things to say the least. Good luck!

 

Hey,

This is exactly how my old truck behaved when the condenser popped out of the little bracket that holds it. At highway speed I would lose spark momentarily and the motor wouuld start to spin down, pumping unburnt fuel into the exhaust system. Then it would get a ground, start running again, and KaBOOM. Blew out my mufflers.

Mark
--
74 F-100 Ranger XLT 4x4

 

Sounds like a spark problem to me too.Check the simple stuff first.Look for a plug wire touching metal(anything that gets hot),or touching another wire.It only takes 1 small pinhole in 1 wire and they could start arcing.Start it at night,and look for a light show!If you see sparks you found your problem.Hopefully this is all it is.One thing I learned about these trucks is not to jump to conclusions and start changing parts right away,its usually something very minor.Always use the K.I.S.S. theory:keep it simple stupid!
Good Luck!

 

thanks for the replies... ok, the other day, when my truck got stranded: i went back out to it like half an hour later and it started up, it did this again like 2 days later, i came back a few hours later and it started right up. so i finally got some new parts... my dad put on a new fuel pump, 6 new spark plugs (the old 3 and 6 ones where roasted!), a new coil wire, a new rotor, and a new spacer for the dist. cap. i havent taken her out on the highway yet... so i dont knwo if it worked yet... but i guess ill see later today!

 

well all that stuff didnt help... :<
one of you guys said somthing about a "stator" something or other... what is that and how much does it cost?

 

ok guys, ive tried about everything mentioned above! and well of course none of it worked! but yesterday we took off my gas tank to put a new gasket on it... and realized the tank sending unit was all messed up. the little filter thing on it was destroyed, and some of the fibers were floating around in the tank. ya guys think this could be the cause of all my prblems?
thanks

 

I have a duraspark distributor in my 71. A couple weeks ago It would'nt start when hot. Finally got it started and drove it 10 miles to my next stop. Would'nt start at all. The pick-up in the distributor had opened up. $16 fix. When it won't start try using an ohm meter to check the pick-up coil in the distributor, I don't remember what the new one read, but the old one was completely open.
Also have seen coils overheat and open-up, will cause some of the same symptoms.Goodluck
Clint

 

try the coil. also time the thing to about 10 BTDC. that's what i did when mine hasd a simliar problem. also try a tune up

 

well my dad tested the pick up coil, but he didnt do it after it wouldnt start and stuff, he tested it cold. it checked out ok. are you saying that it can change when hot? thanks

 

Sounds like you missed the module. Go to the junkyard and tear out a used module to see if it cuts out on you like it is now...if not you found your problem. Where are you? I have a perfectly functional one I swapped out when I went to a MSD setup. I'd be more than happy to let you try it out. I found the same thing with my sending unit too. I called Ford looking for a replacement "sock." The parts guy suggested that I tear off what was left of the sock and install an inline filter before the fuel pump in addition to the filter that threads into the carb inlet. I doubt the fibers would be small enough to pass through a filter - but migh create a bloackage in the fuel line. My gut feeling is the module or some ign short going on somewhere.