Throttle stuck open

Technical queries or suggestions

Throttle stuck open

Postby Sean Horwood » Sat Oct 19, 2013 8:02 am

I think this is probably the best place to add this note as it appears to be a tech issue.

During the strip down of my Roadster, following my off at Snetterton, I have idendified the true cause of my stuck throttle.

I wanted to test my original theory that my extinguisher cables caught in the throttle return spring but found that I couldn't hold the throttle return gubbins open this way. I then pushed the accelerator peddle flat to the bulkhead, to see if the mechanism was faulty in some way, and the peddle failed to return - throttle almost wide open!

A closer look revealed that the linkage on the back of the peddle assembly, which holds the cable, had caught on the edge of the cable access hole in the bulkhead. Also, the cable itself was fraying badly where it has been rubbing against the edge of this access hole and is about to give out completely (shame it didn't do that first!).

I suggest, as a matter of urgency, everybody checks this aspect of the peddle assembly.

Anyway, back to the garage....
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Re: Throttle stuck open

Postby Philip Tisdall » Sat Oct 19, 2013 6:12 pm

Sean,
I had a similar issue a couple of years ago (also at Snetterton) when my throttle stuck open. Fortunately I was able to pull off and it sorted itself. I came to the conclusion that the most likely problem was the split pin at the back of the peddle catching. I have sorted that But it made me think and I subsequently fitted an aircraft stile ignition on- starter switch with a spring loaded red “kill” flap. It is in easy reach and almost instant if you need to kill everything. I like it as there are no keys to try and turn or fiddle with. Might be a thought You can get the switch kit from Demon Tweeks
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Re: Throttle stuck open

Postby Phill Thomas » Tue Oct 22, 2013 12:06 pm

Sean, is it an "Organ Pedal" type?

Good luck with the rebuild.
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Re: Throttle stuck open

Postby peter rafter » Tue Oct 22, 2013 10:16 pm

good queastion phil
i had a roller ball accelerator pedal adapted to organ pedal last year
at Assen last year i had severe throttle jamming open which was ultimately traced to the organ pedal slipping off the roller ball connection and slipping aside to the lever connection causing the throttle cable to stick widw open ( quite frightening when you are approaching a corner with engine racing)
clearly something to be ruled out
talk to Paul
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Re: Throttle stuck open

Postby Sean Horwood » Tue Oct 29, 2013 12:46 pm

The original 'roller' type peddle had been replaced with a standard flat peddle, not organ type, (for better heal/toeing I guess) but the arm and cable connectivity remained the same.

It's unfortunate that I didn't realise fully what had happened until I was on the grass as cutting the engine in time would have prevented the 'launch' from the tarmac - a cutout switch closer to hand may have saved a few split seconds as well, thanks for the input - one for the rebuild plan.

The front of the car is striped around the engine now, just waiting to start build onto replacement chassis etc.

See you at the dinner!
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Re: Throttle stuck open

Postby Andy Green » Tue Oct 29, 2013 1:02 pm

Sean

Does the damage/twist of the chassis extend back from the point of bulhead attachcment or not

If not then various experts are very good at straightening the legs and welding in a new gusset(this avoids a new chassis)
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Re: Throttle stuck open

Postby jack bellinger » Wed Oct 30, 2013 7:33 am

Dip the Clutch . Its instant

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Re: Throttle stuck open

Postby Sean Horwood » Fri Nov 01, 2013 12:24 pm

On the chassis it's difficult to tell at the moment how far the chassis has twisted beyond the bulkhead, there is certainly some twisting. If it looks salavagable then we'll give it a go - if only to have a spare!

On dipping the clutch, quite right Jack - I did this, unfortunately after I left the tarmac as I made the mistake of brake peddle first (on tarmac) then clutch (off tarmac) - another lesson learnt!.
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