Auto choke releasing too early

I don't just drive one car. And that manual's not much help as it doesn't cover normally aspirated engines by the look of it.

Oh - I almost forgot to say. It's a 1984 Bentley Mulsanne (non-turbo). Any the wiser now? No? Thought not!

Yet has identical photos in your link. Are you suggesting your photos weren't much help either?

Did you sort out the issue?

That's what I said earlier up the thread. But some folk here wanted to see 'em anyway.

Haven't had the chance yet.

Seems a bit drastic! I'd be quite happy with a manual pull-out choke, personally. And that would be a lot more do-able.

The issue was simply an automatic choke fitted to an SU is a very rare beast. Even Jags weren't fitted with them.

Good luck

Development work at Crewe was done using LPG.

Eh? See section K5-13.

Tim

Are the manual choke kits still available? Back in the 80s, I fitted my Ford Escort with one, as the new-fangled automatic choke was sometimes a bit 'iffy'. These days I think it would be rather difficult to find a path through the bulkhead to route the cable, and a place to mount the knob.

If you have a works workshop manual, they generally give very full overhaul details. My Bentley one did - and the one I've seen for a Shadow.

Eh? Classic XJ engines used from the 50s to 70s - before they went injection often had the SU extra starting carb system. My 58 3.4 MkI did, as did my 78 XJ6. Both gave problems and had to be replaced. Rover also used it too on some P5 and P6. They even made a kit to convert to manual choke.

Rolls tended to make their own version. Presumably because of the poor reliability of the SU one. (Although I'm not certain that starting carb was made by SU)

The pages I uploaded from the workshop manual are all they have to say on the subject. They do provide some details on rebuilding/resetting the mechanism to factory spec, but I was hoping for someone who might remember from back in the day what actually caused this issue and how they rectified it. They don't tell you in those manuals what the typical failure mode of any component is.

There was definitely a manual choke conversion kit for V-8 Rovers fitted SUs and their starting carb I remember fitting one to a pal's P5B.

The Rolls has bigger SUs, though. IIRC 2" rather than the Rover 1 3/4"

Late SUs (HIF) didn't move the main jet like earlier types - they had a cold start valve on the side. All to allow them to comply with emission laws.

I'd ask Burlen Fuel systems if cold start bits can be fitted to the 2" carb. As regards the linkage and knob. you'd be on your own, for such a low volume car.

The P5B conversion still comes up from time to time on Ebay, etc.

First warm it up with bonnet open and observe the cam and link. If that is moving too soon it may be the restrictor in the "stove pipe" elbow. The test is the very last bit in the manual, you won't have the required flow meter to test it.

Never seen a bi-metal auto choke heated by exhaust gas before. Usually electrical or coolant. Or they use a water heated wax capsule. But it does mean 2 less water hoses, 4 fewer leaky hose connections and no trapped air when filling the cooling system.

As I said, Rolls make their own, so you'd do better asking on a Rolls forum.

With the SU one, the common failure was the thermostat. Many replaced it with a switch inside the car - since any spare parts likely not easily available. Manual said to just fit a new or exchange unit.

Thanks for that, Peter. I might end up taping a thermistor to a coolant hose to bypass the bi-metal strip in that case - if I can't remedy the fault with the existing set-up, I mean.

Remembering back to the early days of automatic chokes, I seem to recall not all were as reliable / popular as they could have been.

Weren?t kits available to convert to manual chokes? (Not SU carbs of course.)

We had a couple of cars ( an Escort and a Panda) with a manual choke and they were fine.

They were for SU too. I fitted one for a pal to his P5B Rover.

Until someone unused to such things leaves it fully on.

Or hangs a handbag on it.