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Hi, hope someone is able to help me with an issue I’ve been experiencing in my recently acquired Herald 948.

On the drive back from a recent long journey, after the car was sat in the heat most of the day, it struggled to start. After taking a few turns to start, it was idling very rough and would cut out after pressing the throttle which I usually play with to warm the engine up. Eventually it started idling somewhat fine and I was good to go.

On the journey back, I realised the car was struggling for power and ended up having to use the choke to make up for the sudden loss of power for some of the journey to prevent holding up traffic. 

Sidenote - I also noticed when stopping to fuel on the way back that the water in the radiator was boiling over after opening the cap (very carefully) and seeing the state of the water.

Anyway, since the journey back, the car still struggles to start and I have the same issue where the car idles very rough when started after being sat and stalls frequently after revving the throttle. Eventually after stalling enough times the problem seems to disappear and the car drives fine.

I’m planning to drain the radiator coolant this weekend and fill with suitable antifreeze to prevent boiling issue, but something tells me this will not solve the problem.

Any thoughts, ideas and recommendations would be much appreciated! I’m at a loss as I’m new to Triumph Herald ownership and after some googling don’t seem to see the issue on any other forums.

Thanks in advance,

Zee

 

 

 

 

 

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The water sounds ok, not saying that flushing and putting in new stuff isn't a good idea but it sounds unlikely to be your problem.

When starting the car or when it's running rough do you get a petrol smell from the exhaust?

I think you are looking at either fuel or timing for your problems

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I had similar problems with my Herald 1200 when I first got it on the road after 26 years laid up.  It was a combination of issues, I assume you have a single carburettor, probably a Solex situated immediately over the manifold, so this can lead to fuel evaporation,  also  I agree that timing may be  an issue, or it could be new points, condenser and spark plugs are required.  I actually had a fully electronic ignition system fitted so points and condenser no longer an issue.  Good luck in sorting it out and hope this helps with possible causes 

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If the rad water boiled AFTER removing the cap this is entirely normal as it quite often runs above boiling point but the pressure in the system stops it actually doing so. If it boiled over with cap in place then something is wrong which must be rectified first... 

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Sounds like your main problem is fuel vaporisation.  The rough running straight after hot start is the fuel boiling in the carb and loss of power on the move that can be  relieved with the choke is probably a combination of that and the fuel pump loosing efficiency because vaporisation is occurring in its inlet valve.  The latter has the potential to bring you to a complete halt.  Pouring cool water over the pump is the quickest fix for that.

 

As already suggested, a full service, including coolant flush, timing check and renewal of any fuel filters (highly recommended if none fitted) should help.  Modern fuel does have a higher vapour pressure though so you may need to go to an electric pump and re-routing fuel lines to completely eliminate it.  Eeven then the carb vaporising may persist.  Can't remember whether the Herald 948 & 1200s had (or were supposed to have) insulating spacers between carb and manifold?  That might help a bit.

Nick

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45 minutes ago, Nick Jones said:

Sounds like your main problem is fuel vaporisation.  The rough running straight after hot start is the fuel boiling in the carb and loss of power on the move that can be  relieved with the choke is probably a combination of that and the fuel pump loosing efficiency because vaporisation is occurring in its inlet valve.  The latter has the potential to bring you to a complete halt.  Pouring cool water over the pump is the quickest fix for that.

 

As already suggested, a full service, including coolant flush, timing check and renewal of any fuel filters (highly recommended if none fitted) should help.  Modern fuel does have a higher vapour pressure though so you may need to go to an electric pump and re-routing fuel lines to completely eliminate it.  Eeven then the carb vaporising may persist.  Can't remember whether the Herald 948 & 1200s had (or were supposed to have) insulating spacers between carb and manifold?  That might help a bit.

Nick

My 1200 does have an insulating spacer between manifold and carb but can still be prone to heat evaporation in hot weather 

it can be a real pain in the 😳

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4 minutes ago, Wendy Dawes said:

My 1200 does have an insulating spacer between manifold and carb but can still be prone to heat evaporation in hot weather 

it can be a real pain in the 😳

This is the type of carburettor spacer on mine available on eBay 

E21C33E6-133A-4D11-947C-648383FA35FB.png

Edited by Wendy Dawes
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One thing thats been suggested in the past is to remove, at least temporarily, the rubber seal between bonnet and bulkhead with the idea of increasing airflow in the engine bay. Its an easy thing to do and if theres an improvement points to the temperature being the problem....

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Thanks for the reply! Yeah I noticed a slightly ‘dirtier’ petrol smell than usual. Looks like the problem might be fuel vaporisation as mentioned below so will be having a play with some solutions.

On 21/07/2022 at 06:22, Piran2 said:

The water sounds ok, not saying that flushing and putting in new stuff isn't a good idea but it sounds unlikely to be your problem.

When starting the car or when it's running rough do you get a petrol smell from the exhaust?

I think you are looking at either fuel or timing for your problems

 

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On 21/07/2022 at 18:54, Wendy Dawes said:

This is the type of carburettor spacer on mine available on eBay 

E21C33E6-133A-4D11-947C-648383FA35FB.png

Thanks Wendy, I will purchase one of these as I’ve seen a simillar one on eBay. Think it might help with the fuel vaporisation issue as a heat shield doesn’t seem to be available for the 948.

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On 21/07/2022 at 19:56, glang said:

One thing thats been suggested in the past is to remove, at least temporarily, the rubber seal between bonnet and bulkhead with the idea of increasing airflow in the engine bay. Its an easy thing to do and if theres an improvement points to the temperature being the problem....

Will give this a go, cheers!

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On 21/07/2022 at 18:03, Nick Jones said:

Sounds like your main problem is fuel vaporisation.  The rough running straight after hot start is the fuel boiling in the carb and loss of power on the move that can be  relieved with the choke is probably a combination of that and the fuel pump loosing efficiency because vaporisation is occurring in its inlet valve.  The latter has the potential to bring you to a complete halt.  Pouring cool water over the pump is the quickest fix for that.

 

As already suggested, a full service, including coolant flush, timing check and renewal of any fuel filters (highly recommended if none fitted) should help.  Modern fuel does have a higher vapour pressure though so you may need to go to an electric pump and re-routing fuel lines to completely eliminate it.  Eeven then the carb vaporising may persist.  Can't remember whether the Herald 948 & 1200s had (or were supposed to have) insulating spacers between carb and manifold?  That might help a bit.

Nick

Thanks Nick, having looked into it the problem points more to fuel vaporisation as you’ve mentioned. Not sure if it makes a difference, but I notice the car struggles to start the first time when its been sat in this heat for a while but after getting started and getting warmed up it appears to behave fine.

Does that still sound like fuel vaporisation to you or does it point to something else?

Will do a full service as mentioned, may look into a fuel filter as the car doesn’t have one fitted.

Appreciate the help so far!

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4 minutes ago, 948Herald said:

I notice the car struggles to start the first time when its been sat in this heat for a while but after getting started and getting warmed up it appears to behave fine.

That's common even when you don't have problems, but it is due to fuel vaporisation, especially if you mean it's been driven, then parked in this heat. The whole engine bay gets really hot and the engine heat soaks through to the carb, where the fuel in the float chamber all boils off. Also, the fuel in the pump can boil and escape (the vapour is pushed through to the carb where it vents). When you come to start it, there's no fuel anywhere and it takes ages to prime first the pump then the carb, and as the carb fills the mixture gradually richens up, meaning it probably tries to start on too weak a mixture first, then gradually struggles into life.

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A further issue with the Solex carbs used on the 948 & 1200 is that when switched off after a long run, heat soak to the carb causes the fuel in the float chamber to warm up, expand and overflow through the main jet into the manifold.  Obviously the hotter the conditions the worse the problem, but if the float level is a bit high it makes matters worse too. 
 

The effect of this is to make a hot restart after 10 - 30 minutes (say) effectively a flooded start. Holding the throttle open while cranking helps with this and you’ll get a puff of black smoke and a fuelly whiff (probably). Triumph actually provided a manifold drain orifice with drain tube in the manifold to prevent/minimise flooding. These are often blocked.

Of course, for longer periods of standing, vaporisation/evaporative loss as Rob described above comes into play.  Modern ethanol-containing fuel is more prone to this than the brew in use in the 60s.

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