Technical pre i.e. FIRE carb anti stall valve

[a73uk]

I`ve had a hot idling issue start recently & I suspect its the anti stall solonoid.

Has anyone had one go & what were the symptoms when it did.

Ta!

 

[alexGS]

I can't actually say that I've ever had one fail, except on the fuel saving versions with cutoff-control unit (those sometimes fail and then the fuel cutoff plunger tip gets cut off with pliers A less-brutal solution is to wire it to the ignition coil positive terminal which I think is what your Uno has).

Take the top off the carburettor and remove the jets, blow everything out with compressed air - and refit the top without gasket sealant, as that tends to end up blocking the jets, don't ask how I know this You know this anyway but I think an intermittently-blocked idle jet is rather more likely than an intermittent solenoid. Still, all things are possible. Clean the solenoid connections/solder any crimped connectors that you find?

Another likely possibility is an overheating ignition module (bad ground in distributor?) but that would be hard to get going again and wouldn't respond to a couple of accelerator pumps like a fuel cutoff-valve problem would.

-Alex

 

[a73uk]

I`m pretty sure its a carb issue, not ignition. I`ll explain what its started doing..

Cold starting is fine, perfect in fact. I rarely have to use the choke & after a couple of minutes its comfortably & smoothly idling at 700rpm.

You drive for 10 minutes, turn off, go & do what your doing, come back & get in... starts instantaniously & usually runs fine.

Drive for another 20 minutes, stop, get out & leave it for 1/2 an hour.

Get back in, start (instantaniously again), BUT, it will not idle, you try to use the throttle to keep an even 7-800rpm, but even with the accelerator a few mm down, the idle is very erratic, like its flooding.

It`ll then cut out everytime you take your foot off the accelerator, even when changing gear, so you have to do alot of foot work when coming to a halt or when in traffic (splitting your right foot between the brake & accelerator). Its very distracting & makes people think your trying to race them or get their attention!

It still starts perfectly every time, but then dies constantly.

I`m pretty sure its using more petrol when it does it too.

I`ve turned the idle up a couple of times to compensate when it does it, it does stop it cutting out, but the idle is very erratic & it then runs on when you turn it off, again pointing to the solonoid.

The idle jet is the small one & I keep meaning to get a bigger one or take mine out a bit, but, its all perfectly clean & the fact its not a constant issue makes me think its the cut off solonoid.

I know you can chop the end off, but I dont want to do any bodges!

I`ve been trying to get on ePER for over as week to see if its still available but as-PER usual, I cant get on!

I can't actually say that I've ever had one fail, except on the fuel saving versions with cutoff-control unit (those sometimes fail and then the fuel cutoff plunger tip gets cut off with pliers A less-brutal solution is to wire it to the ignition coil positive terminal which I think is what your Uno has).

Take the top off the carburettor and remove the jets, blow everything out with compressed air - and refit the top without gasket sealant, as that tends to end up blocking the jets, don't ask how I know this You know this anyway but I think an intermittently-blocked idle jet is rather more likely than an intermittent solenoid. Still, all things are possible. Clean the solenoid connections/solder any crimped connectors that you find?

Another likely possibility is an overheating ignition module (bad ground in distributor?) but that would be hard to get going again and wouldn't respond to a couple of accelerator pumps like a fuel cutoff-valve problem would.

-Alex

 

[alexGS]

I hope you get some better answers from other people, but in the meantime, based on the additional info, I think your diagnosis is spot-on.

Maybe check/clean the float needle valve just in case it really IS flooding? I had some similar symptoms when I saw one of these 32TLF carbs literally overflowing with petrol once (could see fuel gurgling into the venturi).

Another similar problem I had was difficult hot starting/no idling caused again by flooding but that time due to a missing heat shield, BUT that was on the 1116cc engine where the carb is over the exhaust manifold, so that won't be the problem this time. I only mention it in case someone finds this thread in the future and has a 1116cc or 1301cc model

Incidentally - don't want to be petty, but re: the thread subject, I think the purpose of the solenoid on the Uno 45 FIRE is not as an 'anti stall valve' but rather as an 'anti run-on device', to alleviate the running-on effects - caused by high compression (pre-ignition/dieseling), poor quality fuel, and potentially high idle speed if the choke is in use - when the key is switched off. I could be wrong.

As I mentioned before, the same valve is used on some Uno carb versions post-'86 (60, 60S, 70SL) as a fuel-cutoff-on-the-overrun device. You can spot these by the small black control unit mounted on the strut tower and the spring-loaded wire contact on the idle speed screw (that signals when the throttle is closed). The control unit has a connection to the ignition coil as well, so it knows how fast the engine is running. According to Haynes manual trivia, the later Weber control unit acts on rate-of-change of engine speed, rather than merely cutting or restoring fuel flow at fixed RPM points.

-Alex

 

[Chas Uno]

Eratic idle can also be symptomatic of an intake air leak. Check the vacuum pipe from the carburettor to the dizzy mounted diaphragm, though I would have though this would be give permanent rather than intermittent symptoms. As it is intermittent and more likely to occur after the engine has been running I suspect that the ignition module may be at fault. If you still think it is running rich then do a plug chop - that will show straight away if the problem is fuel related (black sooty electrodes indicate on over rich mixture though ignition failure can also cause this).

And Alex, the 32TLF carburettor does have an anti-stall device! It's a small diaphragm that is connected to inlet manifold vacuum, and if vacuum decreases (as in the engine about to stall) it opens the throttle butterfly thus preventing stalling. The other diaphragm in the 32TLF is the accelerator pump though that only works off the throttle itself.

 

[a73uk]

There may be some crap in the float chamber as well, but the fact it only does it when hot & under certain circumstances leads me to believe its a faulty component issue rather than dirt.

I still havent got round to getting a carb repair kit, I dont think they include the anti stall diaphram & definately wont include the run on solonoid, so I may just get a whole new carb.

For other peoples reference, the anti stall device is a diaphram (I think white plastic?)on the bulkhead side of the carb (near the base) & the anti run on solonoid is the silvery gold tube with a spade connector on the end, just behind the rocker cover.

I hope you get some better answers from other people, but in the meantime, based on the additional info, I think your diagnosis is spot-on.

Maybe check/clean the float needle valve just in case it really IS flooding? I had some similar symptoms when I saw one of these 32TLF carbs literally overflowing with petrol once (could see fuel gurgling into the venturi).

Incidentally - don't want to be petty, but re: the thread subject, I think the purpose of the solenoid on the Uno 45 FIRE is not as an 'anti stall valve' but rather as an 'anti run-on device', to alleviate the running-on effects - caused by high compression (pre-ignition/dieseling), poor quality fuel, and potentially high idle speed if the choke is in use - when the key is switched off. I could be wrong.

-Alex

 

[a73uk]

It would be perminant if it was the vaccum tube, although it could still be a manifold to head or carb to manifold leak, as it might be affected by slight heat movement.

Having said that, you`d also expect it to suddenly happen during a long run when the critical temperature is reached, & it doesnt, so again, I think a faulty component.

Its not running perminantly rich, the plugs are fine, its only when its showing these symptoms that it seems to use more fuel.

Most of my driving is 1 run, leave for a few hours, then run back. Its fine like that, but if I have to stop off to say get shopping, thats when it happens.

Have you got a spares carb Chas? I`m sure I had a couple of spares somewhere but I cant bloody find them now.:bang:

Also, I got some NGK BCP7ET plugs a while back, these are fundimentally the same as the standard ones but with 4 earth electrodes instead of the usual 1.

Has anyone tried them before?

Eratic idle can also be symptomatic of an intake air leak. Check the vacuum pipe from the carburettor to the dizzy mounted diaphragm, though I would have though this would be give permanent rather than intermittent symptoms. As it is intermittent and more likely to occur after the engine has been running I suspect that the ignition module may be at fault. If you still think it is running rich then do a plug chop - that will show straight away if the problem is fuel related (black sooty electrodes indicate on over rich mixture though ignition failure can also cause this).