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lo"85 erratic high idle followed by under carb tick coupling with a tick at the fuel pump


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Damn wish ida waited to do this.. Didnt plan it well.. In terms of when id need my truck.. Nor in terms of marking things or counting turns by exact measuments.... A note to anyone with kids and a bad attention span such as myself... Wait till theyre not right next to you askin a million questions before attempting this . K gonna get back out there and tryn get it closer to where it was

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Unlikely the ECC as they seldome fail. Lets look at the external inputs to it that can. First the mechanical parts of the carb....

 

When running.. wiggle the wires on the connector at the back of the carb. If the idle changes, you may have a loose or bad connection.
 

 

This is the fast idle cam. It has steps on it to give faster or slower fast idle depending on how much the choke is on. Only when the choke is ON does the linkage pull the cam into place against the throttle and hold it open. Normally when the choke warms and opens the cam is free to drop down out of the way by it's own weight. Doesn't take much to gum it up so it sticks. WD-40 or carb spray and move the cam and linkage usually loosens it.

carbZ24idlestepLg.jpg

 

The screw with the spring on it is the idle speed screw. It may just need to be turned down.

 

Can you loosen and set the throttle cable if it is too tight to allow the carb to close properly?

 

With the engine off, use a flashlight and look down the secondary to see it it is fully closed. I had a fast idle once that turned out to be the secondary was stuck open a crack.

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Nice thank you so much for all of the recomends. Ima get my friend who has a carb exp to help me... I may need to replace(or hopefully reset) my dashpot... I fucked up and turned the wrong screw... I.e. the one on the dashpot... So basically... Asked my good friend if he can help me with it... So fuck yeah i can still watch and learn and dont have to have someone under my hood doin things i dont know about ( im a bit over protective of my machines.. And if its something im new to.. Id rather learn about it) ill be sure to share more once we start gettn somewhere... Rather than goin in cicles as i have been somewhat doin the past few days.. Also please refrain from telln me how much i coulda fucked it up with that dashpot thing... I know... Hence why im passin the wrench..

 

 

Dont trust a mechanic with bullhorns.. Its cool... We all fuck up sometimes

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So carbs functioning well.. Basically got it narrowed down now and is only idling high when hot... And not as high now... One thing i also noticed is that the dash temp gauge is reading at low temps even on hot days after running for a bit... (only threw this in here cause im wondering if a sensor related to the temp.. could be linked into the trottle speed..I slowly am learning how some of this trucks electrical stuff is programed in ways that.. In my opinion.. Make no sence) (if its got nothing to do with it its got nothing to do with it... But figured id give it a shot)

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Yes the temp is important. The ECU needs to know if the engine is warmed up or not. The ECU is in open loop if the temp sender signals the engine is not warmed up.

 

Replace the thermostat.

 

Also check that the choke is fully open when warmed up. Locate and check that the fast idle cam is not engaged or stuck on on the carb.

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Oh and by well .. I ment better.. We still may end up doin a rebuild.. But at least we fixed what i fucked up... Also side note the idle screw isnt doin anything in terms of reducing the idle but it will raise it and reduce it back to the spot its runnin at now.. Still pretty high though.. One thing i noticed is if i push on the accelerating lever (or any of the other levers attached) it will drop the idle... My buddy did try loosening the cable and it didnt make any difference... I may check this out again though come to think of it... By then it was gettn late and my memory is a bit foggy as to what we actually got to

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Faster than normal idle..

 

Cable not adjusted

Throttle shaft worn

BCDD adjusted too sensitive not shutting off. Turn adjustment counter clockwise.

Secondary stuck slightly open.

Fast idle cam stuck on or choke on holding the fast idle on.

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Choke is definitly opening fully.. Fast idle cam is moving freely.... It could still be the fast idle cam we just got to skim a bit and havent gotten a chance to focus on it a ton yet. Since we had to get it closer to were it was was running before the dashpot thing..(reminder dont start adjusting things until you can actually pay attention to what your doing..lol)... Noticed however that both seem to depend on an electrical component.. So it lead me the last question... The temp gauge is working however.. Just seems like it would be running hotter than the gauge is tellin me.. Sorry just shat my thoughts on that one.. But it will be the next place i look if i do end up ruling out the fast idle

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Feeling like the title of this thread should be changed but i dont know how... Or maybe a new thread should be started with the other info but i may never understand this information box enough organize one lol

 

 

Go to your first post and find the EDIT along the bottom. Click it and then the find and click on the Use Full Editor. This will give you access to the title so you can make corrections or changes. When done don't forget to hit the Save Changes along the bottom.

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  • 2 weeks later...

Anyone know if the carb kits differ between 84 and 85? And if so how would i find out which mine is? Also at the end of this i will tryn load my pictures and consolidate threads or link them?... Gonna do a carb rebuild. Since my adjustments from outside seem to do very little if anything good... Basically have brought most back to there origional places... Gotta open it to get to some of these things.. And ill keep yaw updated.. Mike... Thank you a million times for sharing

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  • 2 weeks later...

Oh and by well .. I ment better.. We still may end up doin a rebuild.. But at least we fixed what i fucked up... Also side note the idle screw isnt doin anything in terms of reducing the idle but it will raise it and reduce it back to the spot its runnin at now.. Still pretty high though.. One thing i noticed is if i push on the accelerating lever (or any of the other levers attached) it will drop the idle... My buddy did try loosening the cable and it didnt make any difference... I may check this out again though come to think of it... By then it was gettn late and my memory is a bit foggy as to what we actually got to

 

I believe this is indicative of a vacuum leak at the shaft that connects the throttle linkage to the butterfly.  I had this on my feedback carb as well, and I didn't find it until I took it to a Datsun specialty shop; they smoked it and it was apparently clear as day.

 

In my case, I disassembled the bottom section of the carb and found some O-rings that fit snugly around the throttle shaft, and inside of the little counterbore that's at the linkage side of the throttle shaft bore.  Super hacky solution, but it worked.  It's lasted me 2.5 years, but is showing signs that it needs some attention again.

 

A more permanent solution might be to find a brass washer or two that fits snugly in the same spot — between the throttle shaft and the throttle shaft bore's counterbore.  Maybe couple that with the O-ring.

 

The legitimate solution is to have the carburetor re-bushed — there's a brass bushing in that bore that wears out over time, and that wear is what causes the vacuum leak. 

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  • 5 weeks later...

Turns out the majority of screws on my carb are stuck as hell.. So far i ended up re adjusting the fast idle cam... Pretty sure i adjusted it wrong the first time.. And tryed flushing the carb while it was off with cleaner.... Seems to have done its job temporarily... Got a feeling ima be pullin this carb off pretty consistantly untill i can get those screws loose.. Once i do... Puttin allen heads in.... Not sure why anyone woulda ever thought philips head bolts would ever make sence on aluminum that is constantly exposed to heat and chemicals.. ??

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