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Generation 5 1967-1972 F100, F250, F350

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  #1  
Old 03-16-2015, 09:02 PM
69er 69er is offline
 
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Old truck is sputtering

69 F-250 390 auto with an Autolite 2bbl carb. I overhauled the motor last year and put on a factory reconditioned carburetor at the time. The carb never did adjust out quite right but in all fairness I didn't have the time to spend on it either. It was good enough to get by. Today I went back through it a little. I set the dwell and timing, checked for vacuum leaks etc. The motor idles great and does well out of gear but in drive in the lower rpm's it will sputter and hesitate. There was one other issue as well. Before when trying to start the motor when it was warm, if it had set for about 15 minutes it was like starting a flooded motor, consistently. Five or so minutes it was fine but after setting longer it acted as if it were flooded. Today I advanced the timing to about 12 and it smoothed things a bit. Not sure yet if it resolved anything though. I'm thinking the accelerator pump may need to be replaced although I don't recall any backfires or anything that may have blown it. Any suggestions would be much appreciated.
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  #2  
Old 03-17-2015, 06:59 AM
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Fellro Fellro is offline
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The accelerator pump is immune to backfire problems, you are thinking of the power valve. It also seems like it may be not doing its job. Easy way to check is simply look inside the carb with the choke open and move the throttle plates. It should squirt a bit of fuel into the carb. If not, then it isn't working. You need that little shot of gas to get the motor to quickly speed up, otherwise you get the lag you describe. The other thing to check is vacuum leaks.
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My trucks:
The workhorse, 86 F250 4x4 6.9 nat aspirated, 3.25 exhaust, custom intake, electric fuel pump, otherwise well used stock... not real pretty but just loves to work!

The other heavy hauler, 92 F350 2wd dually crew cab, flatbed/toolboxes, 92 Cummins VE 12V with intercooler, NV4500 manual

The beater: 88 F250 4x4, 5.8 5 speed
The project ... 1978 F150 4wd shortbed 351 auto

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Old 03-17-2015, 09:50 AM
69er 69er is offline
 
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Thanks for the reply Fellro. I will do as you suggested. I did look for vacuum leaks and all that seems tight from what I can see and what the gauge reads. I had someone else suggest moving the linkage to the inboard side to increase the gas flow. My specs show it should be outboard but I've noticed from some pics and videos that a few others had theirs inboard too. Make sense to you? Thanks again, much appreciated!
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Old 03-17-2015, 12:16 PM
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It does. You just increase the travel distance of the actuator lever, so it hits a little more gas into the carb.
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My trucks:
The workhorse, 86 F250 4x4 6.9 nat aspirated, 3.25 exhaust, custom intake, electric fuel pump, otherwise well used stock... not real pretty but just loves to work!

The other heavy hauler, 92 F350 2wd dually crew cab, flatbed/toolboxes, 92 Cummins VE 12V with intercooler, NV4500 manual

The beater: 88 F250 4x4, 5.8 5 speed
The project ... 1978 F150 4wd shortbed 351 auto

ASE certified parts specialist
I do most all of my own work so I know who to complain to..Roger
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  #5  
Old 03-17-2015, 01:06 PM
69er 69er is offline
 
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Thanks Roger. Tried all the above with no improvement. Got a good shot of gas when I did as you suggested. I may just get a kit or at least the accelerator pump. From my reading this seems to be a common problem
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  #6  
Old 03-17-2015, 10:39 PM
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Fellro Fellro is offline
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While it seems like a good shot, just kinda hard to tell if it is enough when you don't have a reference, but at least it is doing some. The accelerator pump is easy to change, as it is external, 4 screws and it is off. Commonly the diaphragm tears and makes for an external leak.

One other check, see if the carb drips after you shut it off. I have seen that happen as well, many times the float level is too high, and the carb drips when you shut it off, so you are in essence flooding it. I have also seen the fuel kind of boil as it was getting too much heat off the intake. That doesn't tend to be as much an issue generally on Fords though with the thick spacer between the carb and intake. Also, make sure the egr valve is not engaging too soon, as in having vacuum apply to it until higher rpm.
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My trucks:
The workhorse, 86 F250 4x4 6.9 nat aspirated, 3.25 exhaust, custom intake, electric fuel pump, otherwise well used stock... not real pretty but just loves to work!

The other heavy hauler, 92 F350 2wd dually crew cab, flatbed/toolboxes, 92 Cummins VE 12V with intercooler, NV4500 manual

The beater: 88 F250 4x4, 5.8 5 speed
The project ... 1978 F150 4wd shortbed 351 auto

ASE certified parts specialist
I do most all of my own work so I know who to complain to..Roger
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  #7  
Old 03-18-2015, 02:23 AM
69er 69er is offline
 
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No, it wasn't the accelerator pump. I'm going to check the float level again. It was good when I installed it but it doesn't take long to check again. I'm sure curious about what's going on with it. I have an old Model A IH tractor, had it for 35 years. About the time I think I know all it's quirks it will introduce me to a new one. Simple machinery but puzzling at times!
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  #8  
Old 03-18-2015, 06:57 AM
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They can get sticky, especially after sitting a while. I had one incident where I ended up with several gallons of gas in my motor from it sitting after having been run. Float stuck, and the tank was behind the seat, so it just kept a dripping. Made a hell of a mess when I did start it up. Had to change the oil where it sat, luckily it was at my parents house.
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My trucks:
The workhorse, 86 F250 4x4 6.9 nat aspirated, 3.25 exhaust, custom intake, electric fuel pump, otherwise well used stock... not real pretty but just loves to work!

The other heavy hauler, 92 F350 2wd dually crew cab, flatbed/toolboxes, 92 Cummins VE 12V with intercooler, NV4500 manual

The beater: 88 F250 4x4, 5.8 5 speed
The project ... 1978 F150 4wd shortbed 351 auto

ASE certified parts specialist
I do most all of my own work so I know who to complain to..Roger
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  #9  
Old 03-18-2015, 09:08 AM
69er 69er is offline
 
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I had this truck do the same thing Roger but not so bad as yours sounds. Still had to change the oil though. It more than likely is the fuel level as I've smelled some gas and had problems starting it when warm. I was in a hurry getting the truck together as it was January and the installation had to be done outside. Work got busy and I never got back to fine tuning it. Probably know more tomorrow. It's drizzling and cold here again today. Thanks for your input. I really appreciate it.
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Old 03-18-2015, 12:52 PM
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Fellro Fellro is offline
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That one actually caught me by surprise, as I was driving the truck fairly regular when that happened. I had about 1/4 tank in the oil pan...
__________________
My trucks:
The workhorse, 86 F250 4x4 6.9 nat aspirated, 3.25 exhaust, custom intake, electric fuel pump, otherwise well used stock... not real pretty but just loves to work!

The other heavy hauler, 92 F350 2wd dually crew cab, flatbed/toolboxes, 92 Cummins VE 12V with intercooler, NV4500 manual

The beater: 88 F250 4x4, 5.8 5 speed
The project ... 1978 F150 4wd shortbed 351 auto

ASE certified parts specialist
I do most all of my own work so I know who to complain to..Roger
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