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Rough Idle/cutting Out Cold/warm


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#1 andylep

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Posted 05 February 2020 - 05:48 PM

Hi All,

Now i have been through all the threads and tried most of what i can think of before starting a new thread so here it goes.

1992 MAYFAIR 1275 (1296) , HIF44 CARB, KENT 266 CAM, STAGE 1, NEW ENGINE BUILD (1300 miles on it)

 

Ok so i have had the engine rebuilt and carb tuned by a well known mini garage, driving back the car cuts out at junctions lights so on.

Like an idiot i didnt turn around but i need the car for work and thought i might be able to trouble shoot myself.

 

now i have replaced the coil checked voltage, wiring. changed leads. I have timed the car with strobe light at 2000rpm and checked the specs (8-12 degree advanced). set idle at 1000rpm.

 

but the car struggles to start and the idle is bouncing slightly.

 

Only thing i havent done is change the ele dizzy which i believe is original as it has 1992 on it, its a lucas 65d.

I noticed the vac breather had a carb needle jammed in so i have removed that now the car starts better. 

 

on both cold and wrm if the car is left to idle it will start too die slowly, this is starting to do my head in because i cant think of anything else that i may have forgotton bar changing the dizzy which i will but an aldon yellow which is more suited to my set up and i have also heard that a worn carb spindle that the throttle disk is on may cause a rough idle. any ideas ?

 

Andy



#2 blacktulip

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Posted 05 February 2020 - 08:44 PM

Have you tried checking the piston in the carb raises and drops smoothly? Also I would try using a thinner dashpot oil like 3 in 1 oil. Also check that the breathers to the carb are in good condition.

#3 andylep

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Posted 05 February 2020 - 09:30 PM

Yeah ive checked and it moves freely, using 3-1 oil its topped up. 

breathers im still checking them, few are blanked off but have been since ive owned the car. and this problem has only occurred after the carb was tuned onto the new engine.



#4 blacktulip

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Posted 05 February 2020 - 09:51 PM

Did they reprofile the needle to suit the engine?

#5 andylep

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Posted 05 February 2020 - 10:15 PM

Did they reprofile the needle to suit the engine?

I got a needle to suit off them when they did the engine work.



#6 postve

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Posted 17 February 2020 - 10:47 AM

Andy, for what it is worth a buddy had similar issue and after a month of fiddling with the engine turned out the fuel pump was faulty quite strange as fired up but started to cause problems after running for a while.

#7 andylep

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Posted 21 February 2020 - 06:41 PM

Andy, for what it is worth a buddy had similar issue and after a month of fiddling with the engine turned out the fuel pump was faulty quite strange as fired up but started to cause problems after running for a while.


Was this with an original mechanical pump mate ?

#8 postve

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Posted 21 February 2020 - 07:02 PM

Yep, turns out he just needed the "points" replaced as learned they go after centuries of use:)

 

All well now he had it refurbished as wanted to keep original SU.

 

Would have just put in a facet but his decision.

 

Hope this helps..


Edited by postve, 21 February 2020 - 07:11 PM.


#9 andylep

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Posted 22 February 2020 - 08:53 PM

Andy, for what it is worth a buddy had similar issue and after a month of fiddling with the engine turned out the fuel pump was faulty quite strange as fired up but started to cause problems after running for a while.

 

So im feeling daft but i reckon fuel pump is the cause. After walking through everything, im sitting in the pub with a mate explaining my problems and symptoms with the car and the penny drops. i remembered while i was at work my dad took 3 pints of 'oil' out of the car and i had put the correct amount in when replacing the oil. 

I was explaining to my mate about how old mechanical pumps work and thought about the diaphragm. 

I reckon its gone dry while i had the engine overhauled and i hadnt realised.  so went out and smelt the oil, stinks of fuel  :goaway:.

 

So looks like its that will be the cause, thanks all.

I will update when ive fitted the new pump.

 

 






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