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

nissan/datsan720

By nissan/datsan720
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nissan/datsan720 Newbie

nissan/datsan720

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Sorry for the long title... Ive had this idle problem that i havent been able to figure out.. Its a high idle thats erratic as fuck sometimes.. Idle adjust screw doing little if anything.. After dark... I was sittin in the quite and noticed I noticed faint, fast and erratic ticking sound .. Following the same erratic pulse as the idle tends too... ?.. the next day it died out on me.. Pretty sure i was out of gas.. But the odd thing is.. After refueling and just turning the key..(not the engine yet) i noticed the clicking sound was way louder.. Definitly from somewhere under the carb... Turned it off.. Tinkered with something else.. Came back and turned the ignition to electrical again and noticed a second.. Slightly quieter tick... Found that .. Fuel pump... So now im thinkin its more than the fuel air ratio seloniod.. Or another selonoid under the carb... Could it be a short? The. Computer? Could these run on the same line for some reason?

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Rhino13 Newbie

Rhino13

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Listen under the glove box towards the top of the kick panel on the passenger side. If the click comes from there it's a relay, don't remember if it's an ignition or fuel pump or both. Someone will chime in that can specify that.

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datzenmike Grand Master

datzenmike

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Ticking IN the carb will be the mixture ratio solenoid.

 

Clicking when ignition is turned on and off is the idle cut solenoid.

 

Fuel pump is on the frame just forward of the right rear wheel.

 

Choke heater relay is above the right kick panel. Only clicks when engine starts. My buzz if alternator not charging...

Fuel pump relay is just above it.

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nissan/datsan720 Newbie

nissan/datsan720

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Hmm Tickin in pump .. i'll check the relay first before i pull the pump..thnks.. And currently am replacing lines as i find bad ones.. .... the af ratio (mixure ratio) seloniod is what im thinkn as well. I have never pulled apart a carb... Honestly first carborated truck ive had and the car i had for a minute i just abused as a work car... (long gone) so pretty much what im askin is what i should keep an eye out for when i open it... For example plate pressurized springs anything that is not permanantly attached? Or is everything secured in sections(blocks)... One day i may know a bit of terming better... But well probably not... Been wrenchin my whole life and rarely use the right names for things unless im buyin a part. lol... Anyway i ramble too much... Is the blue one the fuel relay?... It looks like garbage so hopefully

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Octane Newbie

Octane

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Man am I glad to see this thread. This happened to me last week. I had just installed my new rear window and was headed out to check out the air flow with the slider, and before I left my driveway the truck stuttered twice then died. Wouldn't start up again. Loud ticking/clicking from the area of the carb, loud enough to drown out the sound of the fuel pump. Got a tractor and towed it back down to my shop, but then the truck started and has been fine since. Even been on a few short trips with it but I'm weary of it happening again.

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nissan/datsan720 Newbie

nissan/datsan720

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It would be normal for the pump to make a ticking sound when working. The are not silent.

 

Ahh thank you... Guess i just didnt notice it before.. Come to think of it i was on higher alert.. (listening for any sounds) so maybe my ears were just tuned in for it more..... Anyway gonna replace the water pump today wich has been needed it for a bit... (not terrible.. but has a slight play in it...) but the irratic idle is gone... Found some other bad vac lines... Still ixling high though.. And my idler screw doesnt do anything anymore.. Not even at a full turn...(done in 1/4 turn increments)... And gonna check the fuel lines while im out there... Hopefully this kid will let it be possible today hah.. ... Ill tryn keep the post updated

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nissan/datsan720 Newbie

nissan/datsan720

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85 z24 still lookin in book to find out how you can tell if its efi or el. feedback. Also checked fuel pump and filters.. lookin good so theres one check off the list.. Gonna replach this fan clutch/water pump now cause it arrived yesterday...and needed to be replaced anyway... Hmm. . any chance this could have anything to do with it? Say maybe a temp sensor or something went bad?

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datzenmike Grand Master

datzenmike

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Two possibilities for carb.

 

1/ Just a normal carb with two wires on the back

 

2/ Electronic feedback carb with round 6 wire connector on the back. Uses a solenoid primary jet to set the fuel mixture. A sensor driven ECU adjusts the mixture with an O2  sensor feedback in the exhaust to monitor fuel mixture.

 

 

 

 

 

Ahh thank you... Guess i just didnt notice it before.. Come to think of it i was on higher alert.. (listening for any sounds) so maybe my ears were just tuned in for it more..... Anyway gonna replace the water pump today wich has been needed it for a bit... (not terrible.. but has a slight play in it...) but the irratic idle is gone... Found some other bad vac lines... Still ixling high though.. And my idler screw doesnt do anything anymore.. Not even at a full turn...(done in 1/4 turn increments)... And gonna check the fuel lines while im out there... Hopefully this kid will let it be possible today hah.. ... Ill tryn keep the post updated

 

 

Fuel pump or filter will not affect idle. Idle uses the least amount of fuel. Only under a heavier load like driving, passing or climbing a grade will the carb float bowl possibly empty and the carb run out of gas and act up.

 

 

Warm up and that the top off the air filter. The choke should be fully off or open.  If not, the fast idle cam is likely engaged. Fix the choke... fixes the fast idle. Possibly the fast idle cam is simply dirty/stuck.

 

If fast idle cam is engaged no amount of idle adjusting will correct it.

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nissan/datsan720 Newbie

nissan/datsan720

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K changed some newly found bad vac lines. And.. Noticed a tare in the back of the air duct goin from exaust to the vac motor.... These took care of the erratic idle... The fuel thing i knew from the start was an empty tank... Just never heard the afr and pump sound like that ( also never ran dry on fuel before) so i thought there was a possibilty that it could piont me to a source for other issues ).. (at least the poor judgement that lead to me not filling it up before that drive lead me to the point im at now) checked the pump and filters anyway and theyre lookin good.. So at least i x'd one culprit... Idleing good while cold now.. And choke does kick in now when it hits that temp... (also good call mike.. Noticed it before i saw your comment.. But it was dead on....

it is still idling high again after a short tester drive this morning... So basically while its hot it still idles poorly... Damn it though the choke would solve that... Still way better than before... Gonna check on this fast idle cam... Once i find it....

 

Oh and for reference the engine is 84 which was thrown on an 85.. Wich now knowing that april 85 was when efi started it may. Explain all these disconected wire harnesses with nothing they could connect to... Shit was drivin me crazy the other day lol

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nissan/datsan720 Newbie

nissan/datsan720

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Also just by chance... How would i check the ecc control.. Incase the computer itself is bad... I mean it is 31 yrs old .. And i feel like everything ive been checkn runs back to this... And if ive gotta keep replacin parts (sensors/switches) that run back to this anyway... Theres a possiblity that it is bad... Figuring it out ... U mentioned the electronic feedback vs nil. Before and it brought me back to this old question after i realized they may be related... And yet another piece to the puzzle... Exaust smells a bit rich... I didnt notice this but neighbor (also a mech.) who happens to be younger than me and still has a sence of smell somehow (even though he smokes like a chimney) ( short story.. My sence of smell is rarely acute).. But yeah.. Puzzle peices.. Ahh and yeah guessin i coulda told you it was elctric feedback before just knowing that it has an ecc?

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