Engine Sputters

Maintenance/Repairs
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1

I am a 15 year old and rebuilt a 390 with a 2-barrel in a 1975 ford f150. I have put on about 500 miles on the motor after the rebuild (mainly around town and to my friends house 5 miles out of town.) here is my problem: the other day i almost ran it out of gas. It was very low but not completely dry. It was sputtering really bad, when i went to turn into my driveway it then ran fine. When i shut it off and restarted it and it started and ran fine. I put in 2 gallons of fresh gas from a gas can to get it to the gas station. When i went to drive it to the gas station it was still sputtering, but not as bad as before. After filling I drove it about 3 miles and it was still missing (although about the last 1/4 mile it was getting alot better.) It is still sputtering. Do you think i sucked up some gunk from the tank into the carberator? Should I change the Fuel filter? The filter is a inline see through one. If it got clogged would that cause it to sputter but lessen eventually? The filter is fairly old but still seemed to work good. the fuel pump is only 3 years old. this missing is driving me crazy! if anyone could help it would be greatly appreciated!!!

Thanks

2

Definitely find and replace the fuel filter, and if that doesn’t do anything for you (certainly can’t hurt, and is cheap) then you might have gotten something all the way up in to the carb.

3

390BigBlock,

If you rebuilt the engine, then what I’ll explain shouldn’t be a big deal…

  1. Check the fuel pump (Assuming its mechanical) with a fuel pressure guage. Look for a minimum of 7 PSI
  2. Check the float level of the carb (read the climber, chilton, or whatever manual you have for that…)
  3. Check the engagement and disengagement of the choke on the carb.
  4. After checking all this, read the plugs (one on each bank) to determine if the fuel mixture is good-- a nice carmel brown color is the “ideal”. A black color indicates rich conditions (suspect your float is bad) and a white color indicates lean. (Suspect jetting, or an intake leak.)

Has it always driven poorly? Did the “bad gas” you suspect start this condition? Is it a Holley 2BBL or Rochester?

Best,

Matt

4

Matt,
Thank you for your answer, I checked the fuel pump and it was running 8 psi, and the float on the carberator didnt seem to be sticking. The next day after I posted this question me and my dad took it out and drove it some, and it seemed to snap out of it, for the most part. It sputters a little now since it has snowed. I was wondering if the choke would cause that. Do you know which wire on the alternator to hook up an electric choke to? My old carb was an autolite 2 barrell with a hot air choke and was junk, so before we even started this motor I bought a motorcraft 2 barrell off of a ford 400 big block(it is supposedly rebuilt), which had a plug in for electric choke. I asked a local mechanic and he said to splice into a black and white colored wire on the alternator. I did, and when it was just cold outside it started up and ran perfect, but now when it is cold and snowy out the motor chugs a little bit and sputters untill it is warmed up. The choke only opens about half way, is that normal? It is a big improvement over the old carb and choke, but I was wondering if there is any way I could make it better.
Thanks for your help!
Aaron

5

Aaron,

Don’t put the electric choke lead on the alternator directly-- it should be on a fused lead.

Simply connect it to the fuse block on a “switched” connection that ties to your ignition. For example, the coil lead.

Yes, if this choke is not connected, it will run as you described.

Good luck.

Matt