As I started my 1959 3.4 litre Mark 1 today the engine started racing at about 2,000 rpm. I drove it around a bit and the idling revs went up to 3,000 rpm when I came off the gas pedal. I adjusted the idle down to 1,000 rpm with the idling screws on the carburetors but as soon as I pushed the gas pedal the engine started racing again. Is this a problem with the gas pedal linkage or is it in the carburetors? Any advice would be most welcome.

 

Are your 2 Throttle return springs in good order. The other thing that can happen is that the throttle lever has not been sufficiently tightened & slipped on the throttle butterfly shafts.

 

I would make sure the gas pedal itself is not hung up on something that keeps it from returning to its normal position. I would then check to see if possibly a return spring in the linkage has come off or broken, as Glyn gives good advice.
Schmitty

 

Thanks Glyn and Schmitty for your advice. I had neglected to reconnect the throttle return spring when I removed the air intake to change the spark plugs. Once reconnected, it runs very nicely. By the way, I found a complete 282 page shop manual for the car online at: https://jaguarrules.ru/wp-content/up...hop-Manual.pdf

 

Yeah, don't want to be a wet blanket, but that Haynes manual is incomplete in many areas.
There are links here on the forum to factory manuals.

 

Pleased you are sorted! Sorry ~ I keep forgetting it's a Mk1

3.4 only ~ remember there are 2 throttle return springs with SU carbs. 75 & 76. ~ 2.4 had Solex carbs until 240 arrived.

 

Thank you Schmitty

 

Thanks. I had only disconnected one. The car is running beautifully now.

 

Thanks Jeff. I'll look around the forum for a better manual.

 

Yes ~ they are very gentle springs ~ one would presume to prevent throttle/butterfly shaft wear.

 

Is the starting solenoid shutting off? Are dashpots full?

 

Quote "Thanks. I had only disconnected one. The car is running beautifully now."