Jump to content


Photo
- - - - -

High Idle speed?


  • Please log in to reply
64 replies to this topic

#21 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 71,700 posts
  • Location:Vancouver Island
  • Cars:'74 710 sedan, '76 710. prevoius... '78 620, '71 521, '68 510 new '76 B-210

Posted 16 November 2017 - 11:34 AM

I would rebuild the original before I would pay for a piece of crap. I trust myself.


Posted Image

#22 JWray707

JWray707

    Advanced Member

  • Members
  • PipPipPip
  • 103 posts
  • Location:Lake County CA
  • Cars:1978 Datsun 620

Posted 22 November 2017 - 04:31 PM

Still waiting on the carb to come in. They could only get ahold of a Federal emissions carb (not entirely sure the difference from the Cali?) Figure I have the warranty, so it doesn't cost me any extra to exchange it for a possible better rebuilt one. Seems like it's been very hit and miss when it comes to all the parts being there and working. May rebuild it in the future...but after it passes smog will probably just convert it over to a different carburetor.

#23 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 71,700 posts
  • Location:Vancouver Island
  • Cars:'74 710 sedan, '76 710. prevoius... '78 620, '71 521, '68 510 new '76 B-210

Posted 22 November 2017 - 07:31 PM

California emissions generally have smaller jets and run leaner. The choke may be riveted on and not adjustable by the owner. The idle mixture screw may have a limiter cap on it to prevent the owner messing with it too much. I believe the two venturies are staked in and also not removable where federal ones have set screws holding them on.


Posted Image

#24 JWray707

JWray707

    Advanced Member

  • Members
  • PipPipPip
  • 103 posts
  • Location:Lake County CA
  • Cars:1978 Datsun 620

Posted 22 November 2017 - 10:05 PM

Good to know...

#25 JWray707

JWray707

    Advanced Member

  • Members
  • PipPipPip
  • 103 posts
  • Location:Lake County CA
  • Cars:1978 Datsun 620

Posted 25 November 2017 - 05:42 PM

Not sure if this should be in this thread, let me know if not.

Got the new carb and there were a few little things that needed fixing after inspecting it...but I got it on there.
So now, the engine won't run or idle.
It WILL turn over and start with a push of the gas and then I have to continue to have my foot on the gas or it will die, slowly. It's really chugging when it does run and lots of shaking going on.
One thing is that the choke housing is cracked away in a few spots. Would that affect anything?
The fast idle cam wasnt set the right way so it could catch on the steps and that's one of the things I fixed. Not seeing how the cam is supposed to get back to the first step when choke closes again. If that makes sense? There's no tension on the cam to bring it back to its starting position.
Anyways...just wondering if someone has ideas of why its not running?
Fuel/Air? Haven't touched the adjustment screws yet.
Timing? Haven't checked with a light yet.
Pretty sure theres no vacuum leaks, but will check better tomorrow.
Float is perfect level.
Suggestions?

#26 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 71,700 posts
  • Location:Vancouver Island
  • Cars:'74 710 sedan, '76 710. prevoius... '78 620, '71 521, '68 510 new '76 B-210

Posted 25 November 2017 - 06:42 PM


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.
Posted Image

#27 JWray707

JWray707

    Advanced Member

  • Members
  • PipPipPip
  • 103 posts
  • Location:Lake County CA
  • Cars:1978 Datsun 620

Posted 25 November 2017 - 07:42 PM

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.

#28 JWray707

JWray707

    Advanced Member

  • Members
  • PipPipPip
  • 103 posts
  • Location:Lake County CA
  • Cars:1978 Datsun 620

Posted 25 November 2017 - 07:44 PM

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.

#29 JWray707

JWray707

    Advanced Member

  • Members
  • PipPipPip
  • 103 posts
  • Location:Lake County CA
  • Cars:1978 Datsun 620

Posted 25 November 2017 - 09:02 PM

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.

#30 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 71,700 posts
  • Location:Vancouver Island
  • Cars:'74 710 sedan, '76 710. prevoius... '78 620, '71 521, '68 510 new '76 B-210

Posted 25 November 2017 - 09:14 PM

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

#31 JWray707

JWray707

    Advanced Member

  • Members
  • PipPipPip
  • 103 posts
  • Location:Lake County CA
  • Cars:1978 Datsun 620

Posted 26 November 2017 - 03:34 PM

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...

#32 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 71,700 posts
  • Location:Vancouver Island
  • Cars:'74 710 sedan, '76 710. prevoius... '78 620, '71 521, '68 510 new '76 B-210

Posted 26 November 2017 - 04:46 PM

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.


Posted Image

#33 JWray707

JWray707

    Advanced Member

  • Members
  • PipPipPip
  • 103 posts
  • Location:Lake County CA
  • Cars:1978 Datsun 620

Posted 26 November 2017 - 05:20 PM

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...

#34 datzenmike

datzenmike

    KING RAT

  • User Administrator
  • 71,700 posts
  • Location:Vancouver Island
  • Cars:'74 710 sedan, '76 710. prevoius... '78 620, '71 521, '68 510 new '76 B-210

Posted 26 November 2017 - 05:30 PM

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..


Posted Image

#35 racerx

racerx

    Senior Member

  • Senior Member
  • PipPipPipPipPip
  • 5,016 posts
  • Location:NorCal
  • Cars:71 Datsun 510 and 65 Mustang Fastback

Posted 27 November 2017 - 12:29 PM

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.

#36 JWray707

JWray707

    Advanced Member

  • Members
  • PipPipPip
  • 103 posts
  • Location:Lake County CA
  • Cars:1978 Datsun 620

Posted 05 December 2017 - 01:44 PM

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?

#37 racerx

racerx

    Senior Member

  • Senior Member
  • PipPipPipPipPip
  • 5,016 posts
  • Location:NorCal
  • Cars:71 Datsun 510 and 65 Mustang Fastback

Posted 05 December 2017 - 01:47 PM

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

#38 JWray707

JWray707

    Advanced Member

  • Members
  • PipPipPip
  • 103 posts
  • Location:Lake County CA
  • Cars:1978 Datsun 620

Posted 05 December 2017 - 01:54 PM

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?

#39 racerx

racerx

    Senior Member

  • Senior Member
  • PipPipPipPipPip
  • 5,016 posts
  • Location:NorCal
  • Cars:71 Datsun 510 and 65 Mustang Fastback

Posted 05 December 2017 - 02:00 PM

Where is the v notch in relation to the indentation?

#40 Stoffregen Motorsports

Stoffregen Motorsports

    Datsun Mechanic

  • Senior Member
  • PipPipPipPipPip
  • 4,117 posts
  • Location:Cool, CA
  • Cars:http://www.4wdandsportutility.com/features/rover/0611_4wd_1957_range_rover/viewall.html

Posted 05 December 2017 - 02:01 PM

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...