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GT6 mk3 intermittent idle/ engine stopping


lincolnsix

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It starts o.k. hot or cold on Strombergs,  but when on fast idle from cold the engine hesitates then settles down. If you run it up to temp on tickover sometimes it falters and then stops,  it will restart but needs a rev to get back to normal.

Normally the performance is spot on,  carbs are balanced ,  tickover around 900rpm.   I had my MOT this week,  the tester left it running for a long time and it was perfect,  but I had the same trouble when I first started it to leave for the test.

I guess that it is a fuel issue?   The filter is clean and the compensators are not sticking.

Thanks in advance for any help                                                                           John.

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John,

Sounds like it could be the dread rubber slivers blocking the fuel line. Tiny bits of rubber from the fuel line hose restricting the inlet valves. Other times they jam them open and the carb floods. Take off the reservoirs, undo the valves and have a close look. You can do this with the carbs still on the car, but a bit fiddly. There are a lot of threads on here about this! Do you have a fuel filter? Worthwhile! I had a blockage of orange sludge in the fuel line further back causing a similar problem, poked it out with strimmer cord.

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Compensators not sticking ??  Are they actually closed at cold and normal temperatures

This sound  its idle mixture is a bit out , slivers ,,, plague many ,,, well   worth checking

Also fuel pump,, is it sucking air from a poor connection, 

Loose condenser

Broken base plate earth lead   the  cotton covered one 

The list is endless onnthis sort of intermittent 

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Thanks chaps for suggestions.

I have a fuel filter the glass type,  no deposits in it.

Compensators closed at cold, they are not sticking. You can gently prise open with a tiny screwdriver and they return.

Will check fuel pump and electrics tomorrow.

I have been thinking when this problem first started,     I got caught in a stop/start crawl on the A1 Bank Holiday Monday it was stinking hot,  could this be related? 

Just out of interest I have ditched my electric fan today and fitted a mechanical one.

John

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  • 4 weeks later...

This problem is getting  worse.   After the struggle to get back home Saturday,  I 've taken the compensators off and set them up identical, four turns out from closed. They are nice and free to move in and out and have the two rubber washers in position.

I have checked the glass fuel filter and the pump filter, all the connections are tight.

It started easily and ran it up to temp,  it was idling perfect at 900rpm but this time it just stopped with no drop in the revs. It always restarts first turn of the key.

The really annoying thing is before this started the performance was spot on.

Once again any ideas?                Thanks John

 

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Personaly I would want the comps 4 turns closed not 4 turns open,  with them open at normal engine temp you cant set the mixture

Where ,/what is the position of the small delrin washer on the head of the needle ???  Proud, level or sunken

Can you put a small pea bulb on the coil feed so you know thencoilmis always getting a feed ?

Remind us are you on points or electronic ,  makemsure the coil 12v polarity is correct

Have you chased the slivers from the float needle zone ?..

Pete

 

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Pete,     I am points,    have checked the float bowls both clean      coil o.k.

The carbs were professionally rebuilt/set up by an 'Old School'  chap,  sadly now retired.

I am reluctant to alter the mixture as it's been running so well,  approx 2000 miles since the tune up.  

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I have a dreadful feeling of deja vu with this thread. All this advice is good stuff, but it all still failed for me until the mixture was set up properly, now no problems, however I did find excessive wear on the distributor cap carbon brush and replaced the rotor with a red one... thanks Pete!!

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Doug ,    If there was still any debris about would it not splutter a bit?     This morning it just cut right out from a steady 900rpm idle

Should I forget the fuel side and go to the electrics.    I do know the dizzy has no side to side play and the centre brush contacts the rotor.  I have another condenser to try.

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Rubber slivers are a dead certanty to drive you mad, they dont end up in the float chamber the merrily flat back and fprth in the fuel line to the carb and under demand the fuel, flow plants them in the needle valve port , leave it a while the pressure drops and they swim back into the feed pipe ready for next time 

If they were rebuilt ok you would not need not set the TCs or play with mixture ,   do pull a air piston out and show where the little washer is 

You need to at best remove the float valve and check its clear , and pump a cup ful of fuel out the supply pipes into a cup/jar and see if you catch a sliver of fuel hose.

Pete

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