Hello all, I have been lurking for at least 8 months or so since I bought my '84 60 series from a good friend of mine. I live in Albuquerque, NM and use the truck mostly for fun on and off-road. The truck has about 287k on the odometer. About 5 years ago my friend found it in backwoods New Mexico and bought it and started fixing it up. He put bigger wheels and tires on it, a full OME suspension kit with a 2" lift, had the original 2F rebuilt locally as well as rebuilt knuckles, new radiator, rebuilt carb, and other things. He also installed an ARB front bumper. I added the KC lights, the roof bars and roof box, and the stripes. It has been running great since I purchased it from him in January of 2019. However I just made this account so I could ask...
A couple weeks ago after filling up before a camping weekend suddenly the truck would start to have serious hesitation problems at speed, under load (i.e. trying to accelerate up an incline at normal speeds). It will start up and idle just fine, and I can drive around mostly normal but especially when in 3rd or 4th gear and trying to go up ANY kind of hill, it starts hesitating and chugging and feeling like it wants to die, but if I let off the gas and put the clutch in, it doesn't stall out. I first noticed this after a little stint on the highway, doing about 65 mph for maybe 30 minutes.
I feel like I've at least narrowed it down to "high engine load" and don't think it's anything to do with operating temperature, you can start it up first thing in the morning and go try to chug up a hill and it will produce the same issue. I thought the fuel pump was going bad so I put in a new mechanical fuel pump. It ran ok for a few days of light driving around town and then started doing it again. Meanwhile this is still on the same tank of fuel as when I filled it up before the camping trip as I mentioned previously. So I put a bottle of HEET in the tank along with some fresh premium from a different station. Again, it ran ok for a few days but then it started doing the exact same thing again. SO THEN still thinking it might be bad gas, I siphoned as much gas out of the tank as I could, and then ran the return line from the mechanical fuel pump out to another gas can and ran it till it was dry. Then I put a couple gallons of fresh gas (from a different station) in it, took it for a drive and it still does the same thing under load.
At this point I'd like to hear what your thoughts are. Carb? Vaccum? Electrical? Everything in the truck is basically "stock" except like I said it's been de-smogged by the previous owner. When I put a new pump on I did check the filter and it's good. I also inspected some of the gas I took out of the truck to make sure it dodn't have blobs of water in it. I don't know what to check next...it's hard to think of what I can bench test with it running in my driveway since it only does this when under heavy load.
Thanks in advance for your ideas!
A couple weeks ago after filling up before a camping weekend suddenly the truck would start to have serious hesitation problems at speed, under load (i.e. trying to accelerate up an incline at normal speeds). It will start up and idle just fine, and I can drive around mostly normal but especially when in 3rd or 4th gear and trying to go up ANY kind of hill, it starts hesitating and chugging and feeling like it wants to die, but if I let off the gas and put the clutch in, it doesn't stall out. I first noticed this after a little stint on the highway, doing about 65 mph for maybe 30 minutes.
I feel like I've at least narrowed it down to "high engine load" and don't think it's anything to do with operating temperature, you can start it up first thing in the morning and go try to chug up a hill and it will produce the same issue. I thought the fuel pump was going bad so I put in a new mechanical fuel pump. It ran ok for a few days of light driving around town and then started doing it again. Meanwhile this is still on the same tank of fuel as when I filled it up before the camping trip as I mentioned previously. So I put a bottle of HEET in the tank along with some fresh premium from a different station. Again, it ran ok for a few days but then it started doing the exact same thing again. SO THEN still thinking it might be bad gas, I siphoned as much gas out of the tank as I could, and then ran the return line from the mechanical fuel pump out to another gas can and ran it till it was dry. Then I put a couple gallons of fresh gas (from a different station) in it, took it for a drive and it still does the same thing under load.
At this point I'd like to hear what your thoughts are. Carb? Vaccum? Electrical? Everything in the truck is basically "stock" except like I said it's been de-smogged by the previous owner. When I put a new pump on I did check the filter and it's good. I also inspected some of the gas I took out of the truck to make sure it dodn't have blobs of water in it. I don't know what to check next...it's hard to think of what I can bench test with it running in my driveway since it only does this when under heavy load.
Thanks in advance for your ideas!
