Club 80-90 Forums

Hello,
Have recently had carb overhauled by Bromyard and now have a couple of issues.
Cold start all fine but when choke valve fully open and engine hot the idle slowly decreases over 20 seconds or so until she cuts out. So far I have adjusted the idle screw in 2 turns and she ticks over ok there but then placed the breather hose back on and the revs dropped significantly again. Haven't touched mixture yet as I know it has been set to 0.75 by Bromyard.
Also looking inside the breather hose is some greyish oil sludge (emulsified?) that spits into the pancake/carb. I am sure the breather should only vent vapour and so concerned that this is excessive? The hose was off and open for a few weeks whilst the carb was away so could be condensation related? And obviously the pressure from the breather is upsetting the carb.
Any tips?
Thanks,
Charlie

Check ignition timing and for air leaks and then do a compression test.
I would not touch the carb it is almost certainly right its more likely something with your engine thats wrong.

Seconded. Bear in mind that with an air leak, choke will compensate for weaker mixture initially but as soon as choke comes off, there will be too much air to fuel as well as reduced vacuum at inlet so it'll die. Try removing your air cleaner too (if in place). I once had one so blocked with dust and pollen, the engine was sucking air through a straw

Take a step back, what's changed ?

Why did you have the carb refurbed?

Have you made any other changes or was it simply carb off, carb back on. If so then recheck what you have done. If you have made other changes then check what you have done there. Though not impossible, it's unlikely that something else has adjusted or failed while parked up.

Had the carb refurbed as the throttle actuator was damaged and John was the only guy with the expertise to keep this carb in service.
Trying to keep the old girl original.
I agree, defo not the carb.
OK, will check the timing and look for air leaks. Any thoughts on the breather oil? I suppose the extra intake of pressurised air on top of a weak mixture is enough for her to give up!
Thanks for your help, love that we are all keeping these vans going and sharing expertise along the way.
Cheers,
Charlie

I don't get it, if all you have done is remove & replace the carb then how could the timing be out ? (it is you that refitted it isn't it ?)

If it were me I would be looking to see what I had messed up, not potentially introducing new variables and problems. Of course, if it wasn't running properly before, then it won't run properly now unless the only issue was the carb.

Don't worry about the breather venting through the carb. It's what they are supposed to do, and extra air going through a carb gives extra fuel. Another way of saying that is forced induction or turbocharging.

On the other hand the removal / replacement of the breather hose is not something I would expect to affect idle, unless it's indirect through affecting timing through the vacuum advance mechanism on the dizzy. Take the vac advance off the dizzy and see how that affects idle and the removal / replacement of the breather hose. I don't have an engine with a Pierburg to check.

Excessive crankcase venting through the breather hose could indicate worn piston rings, but they haven't been changed so irrelevant for the moment.

You may have an air leak which means that the carb is not providing enough fuel to balance it and the engine cuts out. When the choke is on that provides the extra fuel. You need to check the vacuum pipes going to the distributor and the distributor diaphragm (suck on the pipe), air cleaner pipes. Check that there isn't an air leak on the brake servo pipe by blanking if off and seeing if the engine runs okay - don't drive the van in this condition!
There may be a leak between the manifold and the cylinder head - new gaskets?. Whilst the manifold is off check the manifold heater is sealed properly.
Or you could just richen the mixture screw a bit having first counted the number of turns in, from where Bromyard set it and see what happens?

Did you use three new gaskets when mounting the carb back on the manifold
Classic airleak for me

Thanks for all your tips.
Got her running OK now by adjusting mainly idle screw and little bit of mixture.
The difference in performance is amazing. Recommend Bromyard, they really know these carbs.

Still having trouble starting from hot where it takes a good 10 or so cranks and a bit of accelerator pumping.
Next step to change all the manifold gaskets. I have only installed one gasket and a spacer (what I removed) as I apparently do not have a channel heater.
How many should there be?

Charlie

Glad you got it sorted, it's always great to hear the end of the tale

charlie328 wrote:
Still having trouble starting from hot where it takes a good 10 or so cranks and a bit of accelerator pumping.
Next step to change all the manifold gaskets. I have only installed one gasket and a spacer (what I removed) as I apparently do not have a channel heater.
How many should there be?

Charlie

Two paper gaskets and a heat breaker.
What on earth is a channel heater?

Did you use a gas analyser to adjust the mixture? (which would have been set correctly at bromyard on a gas analyser.)
You are just compensating for an air leak.
Which is what's causing the issues