Problem with my Carburetor ( i think )

[kevoisevil]

So i have been periodically working on my 86' gmc k1500 and now when i hit the free way and get up to 55-60 it acts like its trying to go but pulls back and go and pulls back. i have asked a mechanic and he said its either the carb is bad or the carb needs to be rebuilt and last but not least the fuel lines filters and all that are shot... i can drive it on the street fine but i just dont know wha tto do at this point.

[njlimbaugh]

Check the easiest first. It sounds like a plugged fuel filter. Here's what happens: the filter will allow enough fuel to only reach a certain RPM. Then the engine momentarily starves which is the pull back. When the engine winds down enough to run on less fuel, the filter allows enough through for the engine to catch up, or go. This will continue until you drop the speed a few MPH at which time the filter can keep up with engine requirements and will smooth out.

[ramz]

I have that same issue Kevoisevil, I just bought a fuel filter today to see if that is the issue. 3.00 part so worth the try.

[terrylgreenjr]

Mine was perfect until I got to 55mph then it did the same thing. I changed the filter in the carb and fixed it

[ramz]

Well it didn't help me..... next on to the cap & rotor. It ran fine until a couple of week ago so I'm kinda of lost. My carb starts backfiring around 50-60mph while driving.

[njlimbaugh]

Does your truck have a computer? If so, all bets are off. I only have one car with a computer, that's my wife's car. I won't buy one for myself anymore unless it's pre-computer. Even the experts with all their fancy diagnostic crap can't figure the problem out a lot of times without reverting to trial and error. Nuts!

[ramz]

No computer here.

[piecesparts]

Check the rubber fuel lines on the truck (t the engine and above the tank. If one of them is collapsing or getting pinched, that could be your problem. Also do the fuel filter and if it still does it, then look at the carb bowls for debris or water in them.

[ramz]

Replaced the fuel filter yesterday. Haven't check the fuel lines ... don't think that is the issue but never know.
After some research it might be the cap/rotor .. maybefinally corroded thus the one day work next week not..
"If your car starts okay but acts up once you're on the road in the form of stalling and/or backfiring, this could be because your distributor cap has a fault. Since the cap contains the rotor that spins to help the voltage travel from the coil to the spark plugs, if it is cracked, clogged with oil or anything else that prevents it from spinning or slows the spinning down, it will only work part of the time."

[Your41Plague12]

Sounds like the advance weights in the distributor aren't working. Check to see if they're frozen up or rusted together or something.

[irishman999]

I just had the same problem, I changed the fuel filter and still had it.

Not sure what carb you are running but I would pull it apart and check it out. My current setup is a clear plastic filter into a Carter AFB carb, I took the hose loose and it was pressurized. The whole fuel passage way was packed full of what looked like black sand (deteriorated rubber from old hoses). Some of the crap even made it into the carb bowls.

Good luck dude!

[ramz]

Well took to my mechanic and it looks like the valve guide seals are leaking and the #8 plug had oil in it.
Replace it and runs good again....
Dont see white smoke when starting or while reving up so.....
Only 25k on jasper motor...
Any recommended Dallas Mechanics??

[kevoisevil]

sorry that it took so long but was out of town. i changed out the fuel filter and it seems to run fine for now... now on to the next project, rrebuilding the carb or buying a new one. if i buy one for my 305, what should i get?