BXProject

[charlie]

well here we go again

the bx seems to run ok until the hot weather comes

now the stupid friggin thing is over revving, again,

i noticed it at the end of last summer coming back through france, but it disappeared as the weather it got cooler

but the faults back again

is a 19trs

when it gets the weather gets hot, and it does seem to be weather related, and the engine has been running for a while, ie hot/fan on temperatures,

the engine idle speed begins to climb,

from the usual 800 odd it climbs and climbs. in france last year it rose to approx 3000 until i shut it down and yesterday it rose to about 1750 until i opened the bonnet to have a look.

the fan was on but nothing seems to be amiss and after a minute or so with the bonnet open the revs fell again

im puzzled by this so need some help in puttin this right

[Way2go]

It's got to be something silly hasn't it?

when it's hot and the fans running you say bonnet open and revs drop?
Check where your air inlet is situated, if the radiator fan is blowing into this then it may be opening the spring loaded throttle butterfly if you have one especially if the spring has become "tired" on this. Opening the bonnet gives a further clue as you are then "spoiling" the ducting effect.

[Vanny]

sticky throttle cable perhaps?

[Philhod]

Yes that's what I thought Vanny. Does the throttle cable run along the front like the diesel?? if so it just may need the outer fastening up with a cable tie

[Way2go]

Yes that's what I thought Vanny.

Surely a sticky throttle cable would not give rising revs? It would stick at certain revs in neutral and then slip back rather than up?

[docchevron132]

I'm having an epic blonde moment here but...
It has a carb right?
Not injected?
When t he revs climb does it smell petrolly under the bonnet or from the exhaust?

[charlie]

sticky throttle cable perhaps?

dont think its the throttle cable cause as way 2 go says the revs slowly rise

i can rev the engine freely enough but it will settle at...........

hmmm just thinkin about the symptoms

when the car comes to a stop

the revs fall to the idling speed

then after say 10/20 seconds its like someone is adjusting the idling speed

and its starts to rise

i can rev it quite freely but it will settle at the raised level once its started

and it never happens unless its hot weather outside

It has a carb right?
Not injected?
When t he revs climb does it smell petrolly under the bonnet or from the exhaust

its a 19tzs

with a carb and no injection

havent noticed any excess petrol smells but will be looking for this now that youve mentioned this

what you thinkin about doc ??????

me and the bandit thought about timing cause he reckoned that if the timing was out it would run hot

but we did the timing, and yes it was out

but i cant figure what would make the revs rise like it does

why would a hot day, ie the car at a high temperature have this effect ???????

is there some sort of air or even water temperature sensor anywhere?????

i even though about the choke but mines been converted to a manual one so i cant see this as being at fault

hmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm

[Philhod]

Autochoke ???Is that where your going Doc?

[Way2go]

Autochoke ???Is that where your going Doc?

That must be some beer your on Phil, or you're posting from the twilight zone!

Charlie has just previously posted:

i even though about the choke but mines been converted to a manual one so i cant see this as being at fault

[docchevron132]

I was actually venturing toward an autochoke issue TBH.
However, whilst it's been years since I've had owt to do with carb's, if the float needle / float itself is set wrong, and things are getting really hot under the bonnet, maybe it's causing some vaporisation of the fuel and upsetting things?
I duno..
Erm, what carb does the car have?
I'm assuming Solex? Single or twin downdraught?

[Fish_Botherer]

OK - a couple of half-baked thoughts/questions here. Charlie.

(1) Do you have a temp gauge fitted so you know whether the engine is running hotter overall than previously?

(2) Is it only happening when the fan is running?

(3) How about posting a pic? Even if you can't tell what carb it is, it might provide clues - I have a Haynes Book of Carburettor Lies bought for pennies which does at least show diagrams. It claims standard Weber and Solex for BX19 are both twin downdraught type . Solex carb appears to have a fixing bracket on r/h side of the lower carb body, viewing from the front of the car. Weber appears to have a wider lower body than the Solex, and no bracket.

[Philhod]

There is also another bit of a clue, one says Webber on it and the other Solex

Seriously though, if the heat is causing vaporisation it would be cutting out.
When I used to get anywhere mountainous with the tourer van, the Oxford would get v, hot
fuel vaporise then cut out. give it 30 mins all would be ok.


With the engine stopped, remove the air filter unit off the top of the carb. Get someone to pull operate the choke, while you watch it...err.... operate. start the engine and watch what happens.
Is the manual conversion a direct connection to the choke spindle?
If it connects via the autocchoke's round body with the bi metal valve inside it, heat could be making this operate.
When it does go pearshaped, another thing you could check this with, is to whip the top off quick to see if the choke is fully open or has closed a bit, coz that will operate the link that gives it a bit more fuel.
If the needle valve in the float chamber is sticking open, yes you will smell petrol under the bonnet but it shouldn't raise the revs.

[Bx Bandit]

When watching Charlie doing his clutch cable ( ) I remember the air inlet to the carb was a really awkward fit. No matter how hard you try and get the thing over the lip and secure with the jubilee, it always seemed to worm it's way off. Could this be letting in extra air and give the symptoms Charlie mentions?

BTW, Charlie's is a Solex carb and I know no more than that!

[charlie]

OK - a couple of half-baked thoughts/questions here. Charlie.

(1) Do you have a temp gauge fitted so you know whether the engine is running hotter overall than previously?

(2) Is it only happening when the fan is running?

(3) How about posting a pic? Even if you can't tell what carb it is, it might provide clues - I have a Haynes Book of Carburettor Lies bought for pennies which does at least show diagrams. It claims standard Weber and Solex for BX19 are both twin downdraught type . Solex carb appears to have a fixing bracket on r/h side of the lower carb body, viewing from the front of the car. Weber appears to have a wider lower body than the Solex, and no bracket.

no temp gauge fitted but fault kicks in when the cars been running a bit
first noticed it in france last year when after a run on the motorway and was queuing to pay the toll

not too sure about the fan running but i would assume so because of the heat
cant think of any link between the fan and revs but waht do i know

its a solex with twin down draughts

ill get some pics of the manual choke set up and of the carb itself

With the engine stopped, remove the air filter unit off the top of the carb. Get someone to pull operate the choke, while you watch it...err.... operate. start the engine and watch what happens.
Is the manual conversion a direct connection to the choke spindle?
If it connects via the autocchoke's round body with the bi metal valve inside it, heat could be making this operate.
When it does go pearshaped, another thing you could check this with, is to whip the top off quick to see if the choke is fully open or has closed a bit, coz that will operate the link that gives it a bit more fuel.
If the needle valve in the float chamber is sticking open, yes you will smell petrol under the bonnet but it shouldn't raise the revs.

and will play with the choke as suggested

ta

[David]

In my mind the first thing to find out is whether the throttle plate is closed properly when this is happening. If it's closed, then the problem has to be downstream of the carb, wheras if it's a simple case of something physically opening the throttle plate, the solution should be easier.

Charlie.. Next time it does this, whip the bonnet up and have a look to see if the throttle linkage is actually on it's stop, or is slightly off it. That will go a long way to working out what the cause is. If it is off it's stop, poke the mechanism back onto it's stop and see if the revs drop back again.

[Fish_Botherer]

There is also another bit of a clue, one says Webber on it and the other Solex

Well, if the labels/mouldings were visible, and it wasn't the Solex, I think it'd say Weber rather than Webber

Me? Pedant? Yes!!!!

[Vanny]

I have a webber in the garden, beastly little think, years old and still as good as the day i stole it off my dad. Mine is black but i understand these days you can get them in green!

[Philhod]

The names are cast on to the outside of the venturi.

It clearly say either Webbber or Soollex....did I mention my speecch impethimint