High idle on 340

  • Thread starter Thread starter C.M.F.
  • Start date Start date
C

C.M.F.

Only when engine is hot, idle up to almost 1000 rpm (very hot) since 400
when is cold. Why could it is?, Engine is 1.7 with solex carb. Trothle is
adjust at min.

How can I adjust mixture?

thanks
 
C.M.F. said:
Only when engine is hot, idle up to almost 1000 rpm (very hot) since 400
when is cold. Why could it is?, Engine is 1.7 with solex carb. Trothle is
adjust at min.

How can I adjust mixture?

thanks
Click to expand...

Warped base of carb. I'll put money (and lots of it) on that being your
problem.

Tim..
 
I have just tighened screws of the carb to base and it improves. So you are
right. Thanks.

What about adjust mixture?
 
Do NOT overtighten because all you will do is warp the carb base even more
than it is.

This is a very common issue with the Solex and Weber carbs, cost cutting by
Renault is my guess. At the base of the carb is a 1/2 inch thick (or
thereabouts) gasket that was supposedly designed to get around the carb base
bowing, it was never particularly successful. This gasket costs something
stupid like £80 and must be replaced each time the carb is removed.

If the problem returns (and I hate to be the forbearer of bad tidings) but
it could well do so then retightening the bolts is likely to make the matter
worse. You may get away with a replacement gasket, it depends on how badly
warped the carb base is.

The carb base is already on the thin side which does not help the bowing
issue so having the bottom of the base milled is also likely only to be a
temporary fix (and you will still need a new base gasket.

Unless someone knows of a fix (PLEASE LET ME KNOW) you mare heading for a
replacement carb.

A possible alternative is to get a carb AND inlet manifold TOGETHER from a
breakers like CP Motors 01827 331 402, NorthWest Motor TRading 01942 322 880
or Braydon Motors 0208 985 2266, there are probably others but these guys
specialise in breaking up Volvos (CP Motors I found out recently also do
servicing). Cricial that the carb and manifold are NOT seperated and then
all you will need is a manifold to block gasket which will set you back
around a tenner.

If you try and seal the carb base with some sort of gunge I was told by a
Volvo techie that this should be an absolute last resort only job as the
petrol vapoyr usually breaks down whatever sealer you yse and bits of the
sealer end up inside the carbs jets.

We went down the replacement manifold/carb route and with a manifold and
carb from NWMotor Trading for about £80 all up. It came of a good running
1.7 but even that is after 4 years presenting the same problem. We have
come to live with it.

Andy
 
Andy said:
Do NOT overtighten because all you will do is warp the carb base even more
than it is.

This is a very common issue with the Solex and Weber carbs, cost cutting
by Renault is my guess. At the base of the carb is a 1/2 inch thick (or
thereabouts) gasket that was supposedly designed to get around the carb
base bowing, it was never particularly successful. This gasket costs
something stupid like £80 and must be replaced each time the carb is
removed.

If the problem returns (and I hate to be the forbearer of bad tidings) but
it could well do so then retightening the bolts is likely to make the
matter worse. You may get away with a replacement gasket, it depends on
how badly warped the carb base is.

The carb base is already on the thin side which does not help the bowing
issue so having the bottom of the base milled is also likely only to be a
temporary fix (and you will still need a new base gasket.

Unless someone knows of a fix (PLEASE LET ME KNOW) you mare heading for a
replacement carb.

A possible alternative is to get a carb AND inlet manifold TOGETHER from a
breakers like CP Motors 01827 331 402, NorthWest Motor TRading 01942 322
880 or Braydon Motors 0208 985 2266, there are probably others but these
guys specialise in breaking up Volvos (CP Motors I found out recently also
do servicing). Cricial that the carb and manifold are NOT seperated and
then all you will need is a manifold to block gasket which will set you
back around a tenner.
Click to expand...

Hi all,

Further to my previous post, and Andy's lengthy reply, it is possible to use
the carb and manifold from a Renault 1.7 from either the R19 or 21 with some
modication. You need the 1.7 energy engine though, which has a much better
twin barrel Weber carb.

It will need re-routing of vacuum pipes, and some blanking off for it to
work though, but once fitted and working is warpy-base free.

Tim..
 
Andy said:
Do NOT overtighten because all you will do is warp the carb base even more
than it is.

This is a very common issue with the Solex and Weber carbs, cost cutting
by Renault is my guess. At the base of the carb is a 1/2 inch thick (or
thereabouts) gasket that was supposedly designed to get around the carb
base bowing, it was never particularly successful. This gasket costs
something stupid like £80 and must be replaced each time the carb is
removed.

If the problem returns (and I hate to be the forbearer of bad tidings) but
it could well do so then retightening the bolts is likely to make the
matter worse. You may get away with a replacement gasket, it depends on
how badly warped the carb base is.

The carb base is already on the thin side which does not help the bowing
issue so having the bottom of the base milled is also likely only to be a
temporary fix (and you will still need a new base gasket.

Unless someone knows of a fix (PLEASE LET ME KNOW) you mare heading for a
replacement carb.

A possible alternative is to get a carb AND inlet manifold TOGETHER from a
breakers like CP Motors 01827 331 402, NorthWest Motor TRading 01942 322
880 or Braydon Motors 0208 985 2266, there are probably others but these
guys specialise in breaking up Volvos (CP Motors I found out recently also
do servicing). Cricial that the carb and manifold are NOT seperated and
then all you will need is a manifold to block gasket which will set you
back around a tenner.

If you try and seal the carb base with some sort of gunge I was told by a
Volvo techie that this should be an absolute last resort only job as the
petrol vapoyr usually breaks down whatever sealer you yse and bits of the
sealer end up inside the carbs jets.

We went down the replacement manifold/carb route and with a manifold and
carb from NWMotor Trading for about £80 all up. It came of a good running
1.7 but even that is after 4 years presenting the same problem. We have
come to live with it.

Andy
Click to expand...

Hi all,

Further to my previous post, and Andy's lengthy reply, it is possible to use
the carb and manifold from a Renault 1.7 from either the R19 or 21 with some
modication. You need the 1.7 energy engine though, which has a much better
twin barrel Weber carb.

It will need re-routing of vacuum pipes, and some blanking off for it to
work though, but once fitted and working is warpy-base free.

Tim..
 
We have the Weber carb. Usually Weber are a good name in carbs. The ones
fitted to the 1.7 volvo/Renaylt engine has this weakness. Pity cos the
engine (107k miles) goes like a steam train.

Andy
 
Thanks at all for yours advices, they are very interestings and useful.
 
mind you, I have not worked on these specific carbs but do have some
Solex experience.

Is it actually a gasket, or is it a hard, lastic spacer. usually the
"thick" gaskets are a heat speacer made to insulate the carbh from teh
heat of the intake manifold when the car is turned off after a hot
drive. If that is the case, I would find some gasket material to make
gaskets for both sides.

Another alternative- thoroughly clean the carb base and manifold. Wrap
the bottom of the carb in some stretchy plastic or shrink wrap and do
the same on the intake manifold. Use some JB Weld, put a thin coat on
the gasket and assemble with the least amount of torque possible. Wait
until it hardens, then disassemble, remove the plastic wrap, and
reassemble.

Are there no gas-resistant sealnts? I seem to rmember some epoxy made
to seal gas tanks and such, or even use something like Kreem or other
tank liner material to build up a gasket to form fit the warpage.

Just brainstorming... maybe more the later than the former....


__ __
Randy & \ \/ /alerie's
\__/olvos
'90 245 Estate - '93 965 Estate
"Shelby" & "Kate"
 
Warped base of carb. I'll put money (and lots of it) on that being your
problem.
Tim..
Click to expand...

I had an opel kadett long time ago. Wasn't running well. I wanted to
look in the carb, lifted the airfilter and the whole carb came with
it! Was standing completely loose!

Pi
 
Storming Brains are good.

You are probably right about it being a heat insulant (as well) but Volvo
told me it was there because of the bowing carb base issues. I do not
actually remember there being a paper thin gasket on each side of the thick
thingy, there may have been it is just that I can not remember.

I do remember putting a straight edge across the carb base and noticing it
bow upwards in the centre. The carb base has 4 fixing bolts (studs/nuts)
one on each corner and either the base of the carb needed to be thicker ot
it needed another 2 fixing studs in the middle to help stop the bowing.. It
seems that the more the 4 corner bolts are tightened the greater the chance
of the carb base bowing.

I like the idea of making and trying a thicker paper/thin card gasket and
fit this between the thick spacer and the carb base, it could just work.
WHAT DO YOU HAVE TO LOOSE.

I spoke at length with people about using some form of liquid gasket
including a techi who builds F1 racing engines and to a core they were NOT
in favour for bits being effected by the petrol vapour and getting stuck
somewhere inside the carb/jet etc.

We also discussed having the carb base skimmed but keeping swarf out of the
carb was close to an impossibility so would have needed a complete carm
strip and clean, and for what, at best a temporily flat but even weaker carb
base.

Andy
 
Andy Coles said:
Storming Brains are good.

I spoke at length with people about using some form of liquid gasket
including a techi who builds F1 racing engines and to a core they were NOT
in favour for bits being effected by the petrol vapour and getting stuck
somewhere inside the carb/jet etc.
Click to expand...
How about this: make a thin metal gasket to match the outside
perimeter of the carb. Run a thin bead of JB Weld along the base of
the carb- mostly near the center where it is bowed up, then place the
carb on the gasket on a sheet of glass so that the JB Weld fills the
gap between the metal gasket and the base of the carb. In essence, you
are making a new carb base a few tenths thick, but not making the carb
any taller than it has to be.
We also discussed having the carb base skimmed but keeping swarf out of the
carb was close to an impossibility so would have needed a complete carm
strip and clean, and for what, at best a temporily flat but even weaker carb
base.
Click to expand...
I agree.



__ __
Randy & \ \/ /alerie's
\__/olvos
'90 245 Estate - '93 965 Estate
"Shelby" & "Kate"
 
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