86 e350, 460, odd carb behavior.
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7th Gear
Joined: Dec 2024
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86 e350, 460, odd carb behavior.
Good morning, i drive a 1986 e350 rv with a 460. Other day, went out and started it up, all normal. Drove to the bank, i dont fot under the drive thru so i went in, came out maybe 30 minutes later. Tried to start it and all it did was crank. No signs of life. I tried several times, waiting a while between tries. Got a sorta catch once or twice, but no start. Called aaa, phone tree climbing for about 30 minutes. After, decidedto try once more. Battery was about shot by now, but, suddenly it roared to life, and i mean roared! It was idling fast, no tach. But faster than ive ever heard it run. Punched the gas a few times to see if it would idle down, but, it only went faster. I decided to high tail it home. Put it in drive, but had to ride the brake all the way to stay under the speed limit. I shut it off at home and it dieseled for several seconds, (think thats right term). Of curiousity, started it again, same roar to life. Tried it again several hours later, same roar to life. This all happened out of the blue. It had been running just fine prior. Id appreciate any input. Im not averse to a new carb, but if its something simple like a broken spring, secondaries stuck open? Im not a wrenchhead...lol...but i understand basic terminology and principles.
Thanks in advance,
Chuck Crawford
Thanks in advance,
Chuck Crawford
FTE Legend
Joined: Nov 2015
Posts: 30,981
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From: Angier, NC
Welcome to FTE
A 460 is bad enough on MPG and then make it a RV to do a bank run WOW
j/k
It could be anything why it would not re-start and the high RPM when it did.
I would pop the engine cover off and the air filter and give a look over everything looking close at the carb.
If you hit the throttle the choke should close if it was not, this should also kick the fast idle cam into the picture.
The fast idle cam is a thing that looks like stairs that the idle speed screw would hit when the choke is closed.
If you open the choke by hand the fast idle cam should move so the screw is now resting on the carb body.
It could be this cam is stuck you can try and move it with your finger.
If the cam is working as it should do you have a throttle return spring on the linkage to pull the throttle closed, maybe is fell off?
If it all looks good I would say start it and get it up to temp so the choke opens and the cam moves off the screw.
If the idle speed is still high more digging is needed.
Check is all the vacuum hoses are in place, not cracked. A vacuum leak can also cause a high idle but it would have to be pretty big if you had to ride the brakes home.
Dave ----
A 460 is bad enough on MPG and then make it a RV to do a bank run WOW
j/kIt could be anything why it would not re-start and the high RPM when it did.
I would pop the engine cover off and the air filter and give a look over everything looking close at the carb.
If you hit the throttle the choke should close if it was not, this should also kick the fast idle cam into the picture.
The fast idle cam is a thing that looks like stairs that the idle speed screw would hit when the choke is closed.
If you open the choke by hand the fast idle cam should move so the screw is now resting on the carb body.
It could be this cam is stuck you can try and move it with your finger.
If the cam is working as it should do you have a throttle return spring on the linkage to pull the throttle closed, maybe is fell off?
If it all looks good I would say start it and get it up to temp so the choke opens and the cam moves off the screw.
If the idle speed is still high more digging is needed.
Check is all the vacuum hoses are in place, not cracked. A vacuum leak can also cause a high idle but it would have to be pretty big if you had to ride the brakes home.
Dave ----
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7th Gear
Joined: Dec 2024
Posts: 7
Likes: 3
Welcome to FTE
A 460 is bad enough on MPG and then make it a RV to do a back run WOW j/k
It could be anything why it would not re-start and the high RPM when it did.
I would pop the engine cover off and the air filter and give a look over everything looking close at the carb.
If you hit the throttle the choke should close if it was not, this should also kick the fast idle cam into the picture.
The fast idle cam is a thing that looks like stairs that the idle speed screw would hit when the choke is closed.
If you open the choke by hand the fast idle cam should move so the screw is now resting on the carb body.
It could be this cam is stuck you can try and move it with your finger.
If the cam is working as it should do you have a throttle return spring on the linkage to pull the throttle closed, maybe is fell off?
If it all looks good I would say start it and get it up to temp so the choke opens and the cam moves off the screw.
If the idle speed is still high more digging is needed.
Check is all the vacuum hoses are in place, not cracked. A vacuum leak can also cause a high idle but it would have to be pretty big if you had to ride the brakes home.
Dave ----
A 460 is bad enough on MPG and then make it a RV to do a back run WOW
j/kIt could be anything why it would not re-start and the high RPM when it did.
I would pop the engine cover off and the air filter and give a look over everything looking close at the carb.
If you hit the throttle the choke should close if it was not, this should also kick the fast idle cam into the picture.
The fast idle cam is a thing that looks like stairs that the idle speed screw would hit when the choke is closed.
If you open the choke by hand the fast idle cam should move so the screw is now resting on the carb body.
It could be this cam is stuck you can try and move it with your finger.
If the cam is working as it should do you have a throttle return spring on the linkage to pull the throttle closed, maybe is fell off?
If it all looks good I would say start it and get it up to temp so the choke opens and the cam moves off the screw.
If the idle speed is still high more digging is needed.
Check is all the vacuum hoses are in place, not cracked. A vacuum leak can also cause a high idle but it would have to be pretty big if you had to ride the brakes home.
Dave ----
thanks again,
chuck
FTE Legend
Joined: Nov 2015
Posts: 30,981
Likes: 4,134
From: Angier, NC
Most of the time when the roll pin breaks the timing is off a whole lot and will back fire, carb or tail pipe, and not start / run.
I also dont think the timing being off enough to run would make the motor idle high. Loose dist. makes the timing retard and lower idle speed / no power that I have seen.
The hard start could have been a few things from motor being warm but the choke closed even a little and you giving it throttle flooded the motor and waiting cleared it enough to start?
Same could be fuel in the carb boiling when you ran in to the bank it is sitting over a hot intake manifold. Sitting it cooled and fired up?
The ICM could have heated from sitting, heat can make them fail. It cooled and motor started.
So we need to find whey it did not start, fuel or spark before we can look closer at that area why it gave you trouble.
Dave ----
I also dont think the timing being off enough to run would make the motor idle high. Loose dist. makes the timing retard and lower idle speed / no power that I have seen.
The hard start could have been a few things from motor being warm but the choke closed even a little and you giving it throttle flooded the motor and waiting cleared it enough to start?
Same could be fuel in the carb boiling when you ran in to the bank it is sitting over a hot intake manifold. Sitting it cooled and fired up?
The ICM could have heated from sitting, heat can make them fail. It cooled and motor started.
So we need to find whey it did not start, fuel or spark before we can look closer at that area why it gave you trouble.
Dave ----
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From: Virginia
If you hold it to the floor during one of these episodes, that will force the choke door open just a little bit and let it start. But it will still fast idle if the choke door is still mostly shut.
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Thread Starter
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7th Gear
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Ok, fits with what happened. i thought id flooded it and right or wrong, i was told to just hold the pedal to the metal in that case. Once it did start, it just roared and punching the pedal to throttle down, just made it go faster, then just back to a roar when i let up. I have no tach, so forgive the descriptive words...lol...
i put it in gear and off i went...(trying to get home to avoid a tow)... had to ride the brake to stay under the speed limit. Got a buddy coming to look at it. What would make the choke do that suddenly, out of the blue. Its never given me a lick of trouble before.
thanks for the help.....Chuck
i put it in gear and off i went...(trying to get home to avoid a tow)... had to ride the brake to stay under the speed limit. Got a buddy coming to look at it. What would make the choke do that suddenly, out of the blue. Its never given me a lick of trouble before.
thanks for the help.....Chuck
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Joined: Jan 2001
Posts: 57,025
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From: Virginia
Chokes are a complicated mechanical marvel with lots of places to fail. If it's fully electric, the heating element my have burned out. If it's a combination electric and hot air, your hot air line for the choke may have rusted off, a common problem on these since it goes to the exhaust manifold.
And they can simply get gummed up from dirt on the side of the carb where the linkage is located. A lot of people including myself eventually just convert to a manual choke. It makes the engine work much like a old lawnmower, you pull the cable **** to activate the choke, and push it in later when the engine is warmed up. I like a automatic choke, but I usually get frustrated trying to get it adjusted and working correctly and just go to a manual choke.
And they can simply get gummed up from dirt on the side of the carb where the linkage is located. A lot of people including myself eventually just convert to a manual choke. It makes the engine work much like a old lawnmower, you pull the cable **** to activate the choke, and push it in later when the engine is warmed up. I like a automatic choke, but I usually get frustrated trying to get it adjusted and working correctly and just go to a manual choke.
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