77 f250 bogging under load HELP

[gingerbreadman]

my new ride just got a new non leaking carb


77 f250 4x4 351m
holley truck avenger 670cfm



It was doing this before the new carb aswell, it will bog down and hesitate and damn near stall under load in any gear at lower rpms.


where do I start?


-gbm-

 

[Gud T.B. Blown]

i'd start with the float bowl adjustment being that it is a new carb.

 

[a.vannoy]

I had the same problem and tried everything fuel related (including flushing the gas tanks) it was the electronic control box

 

[ForceFed70]

Since it was doing it before the carb swap, I wouldn't bother looking at the new carb.

My guess would also be that it's a problem with the ignition system. There's no electronic control module in a 77, so I would look closely at your coil. There's no easy way to test a coil for this sort of problem, so the easiest thing to do would be to borrow a coil from another vehicle.

I saw in another thread that your trying to pull the distributor. Is this related to your problems? Cause my other suggestion was that if it isn't the coil, there is a good chance it's the dist.

 

[krash kendall]

Fuel filter?

 

[gingerbreadman]

Since it was doing it before the carb swap, I wouldn't bother looking at the new carb.

My guess would also be that it's a problem with the ignition system. There's no electronic control module in a 77, so I would look closely at your coil. There's no easy way to test a coil for this sort of problem, so the easiest thing to do would be to borrow a coil from another vehicle.

I saw in another thread that your trying to pull the distributor. Is this related to your problems? Cause my other suggestion was that if it isn't the coil, there is a good chance it's the dist.

I got the distributer out, i was just wanted to move the timing a couple degree advanced and retarded and see what it did, it didnt change anything.

It isnt a points system it is a duraspark system.

I have a spare coil kicking around which iv used in my 85 with no problems, i tried that allready and it still did the same thing.

I took another look at the cap and rotor and decided to buy a new set. This helped it but its still got a slight bog but a definate difference. I have a new set of plugs to put in im just waiting for it to cool down, it was running really rich with the old carb so there fouled up pretty good and show some slight signs of wear.

If that doesnt solve it i will buy a new set of wires.

I know throwing parts at it isnt the best diagnoses tool but on a used vehicle and with high wear items like plugs,wires,cap and rotor I guess its not gonna hurt to just replace them, no big deal if i do it now or 10,000 miles from now.


-gbm-

 

[gingerbreadman]

Fuel filter?

replaced that with the air filter a hundred miles or so ago.


-gbm-

 

[ForceFed70]

Always a good idea to give it a tune up. Then you know the parts are good.

Well, letse how the rest of the tune up helps.

1 more reccomendation.. if the truck was running really rich, it's probably a good idea to change the oil now that the new carb is on. In extremely rich conditions, fuel can wash past the piston rings into the crankcase.

 

[gingerbreadman]

1 more reccomendation.. if the truck was running really rich, it's probably a good idea to change the oil now that the new carb is on. In extremely rich conditions, fuel can wash past the piston rings into the crankcase.

Good idea, it seemed to get dirty rather quickly...

-gbm-

 

[gingerbreadman]

Well the new plugs didnt help. I think i might want to take back what i said about the cap and rotor helping things out.


heres what it does.

I start from a dead stop, if i take off with lots of rpms and shift at high rpm its fine. if I try and take off slowly and smoothly and shift gears at a reasonbley normal rpm if i give it too much throttle it will literaly die, if i feather the throttle its fine, i can literaly shift from 2nd to 3rd start to accelerate fine hit it good and will stop and roll to a dead stall, i can do this again get it to almost stall back off on the throttle and it will catch and go.


Holley web sight seems to be saying its the accalerator either shooting too much fuel or not enough fuel.

How is the accalerator pump ajusted??? is it that nut and bolt with the spring?


-gbm-