Stuttering / Cutting out, petrol starvation

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Stuttering / Cutting out, petrol starvation

Post by Pommy » Wed Jun 14, 2017 3:39 pm

Just been out for a run 73 5a auto, trouble free for 25 miles, in light traffic its a hot day, temp shows 90. Suddenly in drive at 25-30 mph engine starts stuttering then cuts out, feather throttle, it fires up, then stutters then stops then starts, open road able to use a bit more throttle, OK until I slow down and it all starts again, finnaly having to start it on the key, limp home, fine at tickover, revs well in neutral. Gearbox overhauled early last year, done 500 miles in the cold weather no probs, engine gets a bit hotter and this starts, oil pressure good, new water pump, I haven't a clue, any suggestions welcome.. Pommy
Last edited by Pommy on Sun Jan 21, 2018 10:24 pm, edited 1 time in total.


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Re: Stuttering / Cutting out, haven't a clue

Post by philhoward » Wed Jun 14, 2017 3:58 pm

Sounds like an air leak - I had a similar sounding issue (on a 5a Auto) which was a hairline crack in the breather plate that sits under the carb. Only when it got really warm (i.e. in traffic) it started to open up and become an air leak. Would tick over all day long with the bonnet open as I had no build up of hot air under there. The additional load of it going into Drive and a slightly weakened mixture was just enough to stall it.


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Re: Stuttering / Cutting out, haven't a clue

Post by peter freeman » Wed Jun 14, 2017 4:18 pm

I would go for fuel vaporising - common problem. Additional info like where your fuel lines run - what sort of air filter do you have, what sort of fuel pump do you have - mechanical or electrical etc would help somewhat.



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Re: Stuttering / Cutting out, haven't a clue

Post by AJL Electronics » Wed Jun 14, 2017 5:34 pm

Blocked idle jets?


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Re: Stuttering / Cutting out, haven't a clue

Post by Pommy » Wed Jun 14, 2017 9:43 pm

Phil, Is there a way of testing for a air leak without taking the carb off.

Peter, I am running with a K&N oval, fuel pump is electric sited on the spare wheel plate away from they engine, coil is just next to it, fuel pipe runs low in the engine bay, then up by the cross member, then by flexible pipe to the pump.

AJL, would that effect the idle, which seems ok, if they were blocked and are they easy to check, dyslexic mechanic here.


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Re: Stuttering / Cutting out, haven't a clue

Post by AJL Electronics » Wed Jun 14, 2017 10:11 pm

For air leaks, you need to use brake cleaner or a similar volatile gas / fluid. Spray it at suspect areas. If the engine speed increases, you have found your problem leak.

I wrote my response in a rush and meant main jets! That having been said, the idle jets also handle progression, until the main jets come on stream.


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Re: Stuttering / Cutting out, haven't a clue

Post by peter freeman » Thu Jun 15, 2017 7:58 am

Pommy if you still have the original air filter I would try it - Unlike others I have had three different cars ( SS1 1600, 5A and Coupe ) with K&N filters which have caused vapour lock. The electric fuel pump will be better at preventing vapour lock though at low speed.



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Re: Stuttering / Cutting out, haven't a clue

Post by Pommy » Thu Jun 15, 2017 9:53 am

Thanks guys, a couple of things to start checking. Main jets though, full of trepidation messing about with the carb, and there are no specialists near me. Will post updates, thanks again.


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Re: Stuttering / Cutting out, haven't a clue

Post by Roger Pennington » Thu Jun 15, 2017 2:24 pm

I can only say that on Sunday I drove 25 miles each way, to a car show, in the K&N equipped Yellow Peril. The morning run included about 12 miles crawling behind a 250 tonne transformer transporter (as reported in the "What cars did you see" thread) and the evening return run, in blazing sunshine, was mostly 70-ish mph dual carriageway running. In neither case were there any symptoms of vapour locking. :)

The SS1 is my daily driver, is also K&N equipped, and also doesn't suffer vapour locking


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Re: Stuttering / Cutting out, haven't a clue

Post by Pommy » Sun Jun 18, 2017 3:56 pm

Hi all, tried the brake cleaner test today, engine didn't speed up, in fact it slowed down for a second, put this down to the cleaner lubricating the cable, pawls etc. Checked the timing, its OK, checked fuel delivery, that also looked OK, but don't know under running conditions. Next I will refit the electronic ignition, complete with new coil and maybe change the K&N back to original. Once done I will try a long hot run and cross my fingers. If its still being a Scimitar :) will move on to the carb (oh dear) jets etc. I keep thinking its fuel but then I 'know nothing' . thanks all Dave Pom


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Re: Stuttering / Cutting out, haven't a clue

Post by AJL Electronics » Sun Jun 18, 2017 3:59 pm

If it is running horribly rich, the brake cleaner would make it worse causing the slowing. What colour are your plugs after a run?


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Re: Stuttering / Cutting out, haven't a clue

Post by peter freeman » Sun Jun 18, 2017 4:07 pm

I don't think anyone has asked which carb you have fitted - we have a earlier 40 in the area and some of the passages are not getatable - so the specialist are having a go at drilling a new passage in the carb. Apparently once the passage "silts" up normally a new carb is the only answer. The owner does not want a new carb as the original has been set up for his stage 2 and a bit engine.



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Re: Stuttering / Cutting out, haven't a clue

Post by Pommy » Sun Jun 18, 2017 4:24 pm

AJL, plugs a light brown color.
Peter, the carb is a 38 Dgms less than 2years old, preferred a manual choke. Oh to have a carb specialist in the area.


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Re: Stuttering / Cutting out, haven't a clue

Post by halfpenny » Sun Jun 18, 2017 4:30 pm

Low tech test. Take 500ml water in a bottle, and dribble it over the fuel pump body . This will cool the pump and condense the fuel - and will help you decide if hot weather vapourisation is the problem. This always worked for me with fuel vapourisation on another type of Ford.



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Re: Stuttering / Cutting out, haven't a clue

Post by peter freeman » Sun Jun 18, 2017 5:47 pm

Hard to do when the car is running on the road - Pommy said it was ok on tick over.



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