My truck wont stop staying at a high rpm

[mlo714]

A couple of weeks ago I was going down the interstate at about 70 mph. It then acted like it was about to shut off and after slowing down to about 55 it acted fine. Yesterday I got on it for a sec and it completely shut off and died for about 2 mins. This morning when I was getting ready to replace the fuel pump....I cranked it up and it stayed at a constant high rev. I replaced the fuel pump (mechanical) and its still staying at a high rev. Any ideas?

[Special-Ed]

what kind of motor, what kind of fuel system, kind of truck.... no details, cant help....

its like saying... i have a car it wont go 60! =)

[mlo714]

oh yeah...1972 C10. 307 motor, 2bbl Rochester, 350 trans, hei dist.

[Special-Ed]

i havent seen a carborated vehicle in over 20 years...so i'm a bit rusty...

but i would start with vaccuum leaks, check throttle linkage, not new enough for a 3c carb(or whatever they called it), check to make sure you dont have raw fuel getting in to intake with a vaccuum leak, check your choke. not new enough for an iac motor... possibly a float.

you have issues.... but they do not point to fuel pump.

rpm's comes from volume of air and fuel.... not one or the other.. it takes both

[mlo714]

ill go check all the lines and throttle cable.

[Special-Ed]

check the throttle spring as well... it should snap back and be firm... not soft and squisshy

with engine running spray carb cleaner on vaccuum hoses and items and at base of carb... if idle changes... you got your problem... idk... how do you explain to somebody how to check for vaccuum leaks when you dont have a baseline of their skill level...???

[mlo714]

ok It seems to be fine. When I had the carb rebuilt back in 1/2013 , they changed something on it to where I had no choke I guess. It used to idle fast for a min or two and then idle down. Its now doing that again. I have absolutely no experience when it comes to carbs. I can doing any and everything else except messing with carburetors. I just drove it and it seems ok.

[mlo714]

So this morning I start the truck and it wont start at all. after trying to start it for a while I was able to get it running. I then popped the hood and messed with some of the linkage on the right side of the carb and got it to idle perfect. any ideas?

[geezer#99]

Take a pic of your carb. Both sides and from the front with the Air cleaner off.

[LockDoc]

-
Did you check the throttle return spring as Ed suggested? You might also take the throttle cable loose from the carb and make sure the carb opens and closes easily by hand and the throttle cable moves easily by hand... spray everything down with a lubricant (not WD-40) and see if that helps.

Let us know exactly what you have tried and if it helped any...

LockDoc

[mlo714]

ok...these are the pics I took after I replaced the fuel filter and blew out the lines from the tank to fuel pump. ( I removed the seat and disconnected the lines from the tank and the fuel pump and blew out with compressed air) The truck started right up and idled low perfectly. I drove it down the street and the idle got higher, then eventually idled down. I made 4-5 passes down the street getting up to 60 mph at one point with no issue. we'll see in the morning. I am trying to upload pics of the carb now. I don't think the linkage is right with the choke/throttle?

[mlo714]

Everything is moving freely. Is the piece where that set screw rest on correct? the linkage came off one time and I think connected it back correctly put idk.

[jwinga]

Originally Posted by mlo714

So this morning I start the truck and it wont start at all. after trying to start it for a while I was able to get it running. I then popped the hood and messed with some of the linkage on the right side of the carb and got it to idle perfect. any ideas?

Sounds like your choke flap was closed.

[LockDoc]

Originally Posted by mlo714

Everything is moving freely. Is the piece where that set screw rest on correct? the linkage came off one time and I think connected it back correctly put idk.

The screw looks like the high idle screw for the choke. It controls the idle speed when the choke is closed. Really no way for me to tell if it is correct without being there to see what it does as the engine warms up.

LockDoc

[69Rumbler]

Mine was doing the same thing it was the idle .. But after pulling it out I seem that the carb shop didnt use the right gaskets so it was making my truck run like ish
Posted via Mobile Device

[geezer#99]

Originally Posted by mlo714

Everything is moving freely. Is the piece where that set screw rest on correct? the linkage came off one time and I think connected it back correctly put idk.

It looks correct. THat's your low idle and your high idle screw combined.
THe choke stove on the pass side controls your choke with that long rod.
It looks like your choke isn't open all the way. If you straighten that rod out a bit it will make your choke open completely.
Get some carb and choke spray cleaner and lube the linkages on both sides too.

[mlo714]

ok.. truck is finally running great. I have learned not to press the gas peddle before start up. (this would result in the truck not even wanting to start) If I just turn the key it starts up at a high rev until it warms up.

After 2 new fuel pumps and tinkering with the fuel lines I have gotten past the loss of power or fuel. I think it might of been vapor locking or just cheap fuel pumps. (mechanical pumps)

After taking it to someone I hardly knew to look at it for me I had to get the t350 transmission redone because all of a sudden I didn't have a high gear. hmmmm.

My next steps are to figure out why its burning so much oil and spitting out blue smoke out the tail pipes. it never ends.

And its my daily driver.

[GMCJOE]

Figure this would be an easier explanation for the blue smoke out your exhaust. Check out the link.

http://autoleak.com/Oil/Blue-Smoke-From-Exhaust.php

Blue smoke means your burning oil. Start with the PVC, and move on to the rest if it is still doing it.