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JWray707

High Idle speed?

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If it's a new carb why are you fixing things on it?

 

 

Might be the idle cut solenoid. It's an electrical valve that allows fuel into the idle circuit. When the ignition it turned off the solenoid closes off the fuel to help stop the engine without run on or dieseling. A loose wire being shaken by the engine would do this. With the engine off and the key ON wiggle the red wire to the solenoid and see if it begins clicking. Yes? you have the problem.

 

Hold the throttle part open and close the choke. You should see a linkage move down allowing the fast idle cam to lift up and hold the idle speed screw open. Open the choke and the linkage releases the fast idle cam and it drops down out of the way allowing the throttle to close to it's proper idle position.

 

I have NEVER seen a vacuum leak cause a faster idle, ever. A vacuum leak allows more ai,r in leaning out the mixture and destabilizing the idle quality. NOW... if you were to be running excessively rich to begin with, then the added air might raise the idle speed BUT generally it everything is correct the idle would drop.

 

The same thing happens when you try to start a cold engine. Step on the gas once and the choke sets. At the same time the linkage pulls the cam up into place. Until you step on the gas the throttle is in the way.

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Yeah, there's always been missing parts or broken parts on all the "New" carbs I've gotten. They're obviously rebuilt but it seems poorly.

 

The last carb the BCDD valve was broken and had a leaking gasket on the fuel inlet.

 

This one is missing some retaining rings and clips, broken choke housing, missing some smaller plastic parts that the rods sit in and the brass tube that holds the float in was replaced with a retaining pin (luckily I have a spare) Have yet to get one that doesn't have missing or broken parts.

 

Should've re-read this thread and tried everything out. Searching the forums too for some clues as to what I can check.

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The cam doesn't seem to be resetting to normal with the choke. Maybe a loose spring or connection missing that I'm not seeing. Will be able to check tomorrow.

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Just went out and followed basic instructions for setting mixture and idle speed screw and got it to idle without dying but as soon as I tried to take it out of park, it died...one of the problems I was having with the previous carb. The idle speed was also climbing super high but this time I was able to drop it by turning the idle speed screw out. Need to dail it in better tomorrow and also check timing after. Will also re-read this thread in detail and check all the things I haven't yet.

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Adjust the idle speed only when the engine is warmed up. When cold the engine should idle higher

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Still no go...it's idling...but engine is running really rough and choppy. Not hearing the clicking on the idle cut solenoid. Can't figure out a way to get it off and inspect without taking the carb off again and removing the throttle linkage. May do that tomorrow.

Soon as I put it in drive or reverse it chugs out and dies.

Checked the plugs and they seem fine.

At my wits end...

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Where are you getting these carburetors???

 

 

Idle solenoid should click every time you turn the key on or off. If not working find out why. Without the solenoid working there is no gas for the idle circuit.

 

When warmed up, choke off, fast idle off.... turn the idle mixture screw in or out to get the fastest smooth idle you can. Then turn the idle down as low as it will go. Repeat. There should be about 1/2 turn either way before the idle worsens, so just guess at the middle. A good strong idle will not stall when you put in drive.

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Getting carbs from Autozone, which they order from UREMCO.

 

So if the truck is idling the solenoid should be in working order right? I will check better for the clicking...if I can get a second hand (or ear) over here to help.

 

Do you think the stalling has to do with the carb adjustments or just not a strong idle?

It would (when it was running fine) drop RPMS when I put it in reverse or drive...so I'm thinking it's just not idling high enough and when it's put in drive now it drops RPMS but maybe to much to keep it going.

 

My concern is that the smog guy originally couldnt test it because the idle speed was too high and wouldn't drop. Don't have a tachometer so I won't know how fast the RPMS really are. It needs to be under 900 (I think he said) in park to run the test...

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If the carb adjustments are not right and it is struggling, putting in gear is enough to stall it. Turning up the idle speed is not necessarily the answer. Too high an idle and putting into gear will shock the entire drive train. If idling between 600 and 800 you will barely notice it going into gear.

 

For a strong idle, the valve lash must be properly set. If valves and too tight they may not close properly and compression is lost. The timing must be set so that the maximum power is extracted from the fuel. The carb idle mixture and speed set to give the proper mixture and amount of gas and air..

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Buy a timing gun with a Rach or buy a tach. How are u going to diagnose if you don't know ur idle speed.

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OK, got a timing gun with a tach. The engine was peaking at about 3000 RPMS when warming up, then dropped as it warmed. Still couldnt get it to drop below 1000 RPMS at idle. Turned the distributor, didn't help...turned the idle speed screw out which dropped the speed but not under 1000 and it was not running smooth.

Just recently did the valve adjustment so I know those are OK. The cam is at 10 and 2 position at TDC and the distributor shaft is at the 11:25 position.

When turning the crank I noticed the the bright link wouldnt ever line up right on with the cam punch marks. It's usually off by 1 or 2 teeth. Is this a problem?

 

75tVXS.jpg

 

Going off that diagram the brite link has been on the next tooth to the right, usually.

 

Is there a way to adjust this without pulling the timing cover off? Do I need to adjust it?

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When u say cam punch mark, u talking about the "v" notch and indentation?

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Like in that picture above...the link wont ever match up with #2 (or any #) timing mark on the outside of the sprocket.

When the V and the notch are aligned on the #2 dowel mark the brite link is off a tooth from the #2 timing mark.

Make sense?

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Where is the v notch in relation to the indentation?

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The bright links are only for initial setup. Once the engine has been fired, you can no longer rely on the bright links for timing info. If the gear ratio were 1:1 then they would be in the same spot for every rotation.

 

Sounds to me like a vacuum leak. Cam timing being off isn't likely to make the engine idle higher than normal. Lower, yes, but higher, not likely.

 

Hanging up throttle linkage or bent throttle shaft also possible. Assuming the distributor is working ok...

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Where is the v notch in relation to the indentation?

V notch is to the right of the indentation.

 

The bright links are only for initial setup. Once the engine has been fired, you can no longer rely on the bright links for timing info. If the gear ratio were 1:1 then they would be in the same spot for every rotation.

 

Sounds to me like a vacuum leak. Cam timing being off isn't likely to make the engine idle higher than normal. Lower, yes, but higher, not likely.

 

Hanging up throttle linkage or bent throttle shaft also possible. Assuming the distributor is working ok...

Good to know. I won't worry about the bright link then and just set the cam where it's supposed to be.

Pretty sure theres no leaks, unless it's on the carb somewhere, but I sprayrd carb cleaner all around it checking for leaks and it seems tight.

The throttle linkage and shaft are all OK...and the throttle cable is not holding the throttle open.

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I thought he said awhile back that his vacuum was okay.

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From my experience, if its a vacuum leak, the idle is more intermittent, especially if u spray carb cleaner around area then rpm will go up

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Yeah, my vacuum has always been between 18-20hg. I'll hook up the gauge and check it again just to be sure.

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That's good vacuum. Is the reading steady or jumps around a lot?

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Just checked it and it was barely hitting 10hg and was jumping alot. Think there's a leak on the carb. I can see the gasket that's not properly fit. Time to delve into that...hopefully that will fix the problem.

Can i use regular gasket material on a carb (incase I need a new gasket)? I have a sheet I can make one from.

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Before doing that, let it run to operating temp. Then spray carb cleaner around base of carb and listen if rpm goes up. If it does, then vacuum leak. Do not gorrila tight...

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Checked around the base earlier and that was tight...no leak. There was definitely a gap in a part of the gasket on the carb. Spraying carb cleaner at that spot raised the rpm. I just made a new gasket and put it on the carb. Will reattach the carb tomorrow and try it out.

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So the engine definitely has symptoms of a vacuum leak. Won't go anywhere above 15hg and the needle jumps around, engine very shakey. Sprayed carb cleaner all around to no avail. So...I used the old cigar smoke test. The only smoke that came out was from the primary barrel of the carb. When I had the carb off last night I noticed the the throttle plate or butterfly of the primary barrel was slightly open and couldn't figure out how to close it...just figured it was meant to be a little open. Would that be causing the vacuum leak?

There's always been a fairly loud hissing from this carb aswell as the ones I've had in the past, but that's normal, right?

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Isn't this the second carb you put on? Seems like they are shitty supplier.

 

You should be able to adjust the carb almost closed in order to set the idle speed. I don't know what 'slightly open' means without a picture. Slightly open may be perfect. You sure it was the primary that was partly open??? Primary is the one closest the valve cover. Intake vacuum should be 15 -ish at idle. Much lower under full throttle load. And into the 20s when decelerating. 

 

If the gasket don't fix it, I think it's time for a compression test. 

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