Club 80-90 Forums

runs ok on choke but as soon as the choke disengages cuts out .seems like slight misfirehave checked coil with multimeter for resistance as per haynes instructions for the primary resistance ran the leads between neg and pos connections should have got a reading of 0.5-0.8 ohms.secondry resistance should be 2.4-3.5 k ohms(coil with green sticker)6.9-8.5k ohms(coil with grey sticker) got zero reading on primary ,secondry was within set values given (grey sticker)have just fitted motorquim coil (cheepy) same zero reading on primary and way low reading on secondry any ideas ?help! or have i tested it wrongly?

I'd check to see if the meter you are using is set to the right scale. The meter may default to a "zero" reading if the resistance is "off scale".

If the engine runs on the choke I'd be tempted to check for fuel / air faults before suspecting the ignition circuit.

gedbedhead wrote:runs ok on choke but as soon as the choke disengages cuts out .seems like slight misfirehave checked coil with multimeter for resistance as per haynes instructions for the primary resistance ran the leads between neg and pos connections should have got a reading of 0.5-0.8 ohms.secondry resistance should be 2.4-3.5 k ohms(coil with green sticker)6.9-8.5k ohms(coil with grey sticker) got zero reading on primary ,secondry was within set values given (grey sticker)have just fitted motorquim coil (cheepy) same zero reading on primary and way low reading on secondry any ideas ?help! or have i tested it wrongly?

If it runs ok of choke, then it can't be the coil...more likely some thing to do with carbs or carb. You need to tell more, engine size, water or air cooled..the list goes on..

its a 1.9 dg w/c pierberg carb.

The choke doesn't "disengage " it opens slowly.
What you describe is the fast idle stepping down as the engine warms

The misfire suggests you could have an air leak .. check ALL the vacuum pipes, carb gaskets, change them even.
once thats done have the mixture checked on a CO meter.

thanks for that. will order carb repair kit think gaskets are past there best.also thinking will bypass fuel tank in case fuel is contaminated been stood a while maybe sludge in tank contaminating fuel?

before you spend money, check the fuel cut-off solenoid is working, its a common fault that the feed to the FCoS is intermittent due to the wiring breaking down due to heat damage and chaffing (sp)

checked the fuel cut off supplied 12 volts and it clicked there is a slight mark on wire chaffing would this cause it not to idle when hot? gonna get a carb rebuild kit.have changed dizzy/rotor/plugs/leads/coil and carb gaskets.maybe the fuel pump diaphragm?

Don't suppose you've had the wiring apart and accidentally wired the fuel solenoid to the temp switch (normally made, goes open circuit when hot) in water pipe running front to back, left of the carb. This would make it run normally on choke, but would eventually cut out when warming up.

fuel cut off switch is wired to manifold heater is this right?its the only way it will go .gonna bypass fuel tank today try fresh juice,will kick myself if its that,let you know later if that has improved idle

gedbedhead wrote:fuel cut off switch is wired to manifold heater is this right?its the only way it will go .gonna bypass fuel tank today try fresh juice,will kick myself if its that,let you know later if that has improved idle

No, it shouldn't be wired to the manifold heater as this will switch off when the engine is warm enough.
It should be wired to the + side of the ignition coil.
No wonder it's cutting out when it gets warm!

yup i had a brain fart found wires hanging down thought they were off the tail lights (tail lights removed painting rear valance) you were spot on had the heater element wired up to the fuel cut off, the 4 wires are all switch live connected up BINGO thanks guys