Stalling & misfiring when warm

Post by **asahartz** » 17 Sep 2008, 18:28

My bus (1.9DG with Solex carb) doesn't get used regularly - like a few others I guess. A couple of weeks ago I took it on a good run up to Manchester. About halfway back it misfired a few times, with a backfire at one point, but after that it was no trouble.

Since then, it stalls at junctions as soon as it gets warmed up, and misfires quite a bit. I cleaned out the carb - scraped some crud out of the float chamber and blew it through with compressed air, and it seemed to run fine - but of course it wasn't fully warm. Today I took it for a little three-mile local trip and it was hell to drive - stalling at every junction, misfiring, no hill-climbing power.

I'm not sure where to look next - any suggestions?

Post by **maxstu** » 18 Sep 2008, 00:03

coil, leads, dizzy cap, rotor, plugs, fuel filter, air filter, fuel tank, filler tube, water in fuel, crud still in carb?

But not necessarily in that order

My guess is the coil.

Post by **ermie571** » 18 Sep 2008, 07:43

I'm going for the cap and rotor arm - same symptons as mine..... misfiring, backfiring, stalling. Whipped dizzy cap off - full of grey dust where rotor arm had broken down....

Em
x

Post by **lambrettalee** » 18 Sep 2008, 12:14

ermie571 wrote:I'm going for the cap and rotor arm - same symptons as mine..... misfiring, backfiring, stalling. Whipped dizzy cap off - full of grey dust where rotor arm had broken down....

Em
x

thats favourite... start by cleaning off all that has grown inside the cap and on the end of the rotar arm...

Post by **asahartz** » 18 Sep 2008, 18:46

lambrettalee wrote:
ermie571 wrote:I'm going for the cap and rotor arm - same symptons as mine..... misfiring, backfiring, stalling. Whipped dizzy cap off - full of grey dust where rotor arm had broken down....

Em
x
thats favourite... start by cleaning off all that has grown inside the cap and on the end of the rotar arm...

Nope, pristine inside there (that's one bizarre rotor arm BTW!). If it were that it would do it cold too, which is why I turned my attention to the carb first.

Coil however is still a possibility as they can be affected by temperature. Is there anything special about it? I have a stash of coils in my shed, mostly from old A-series BMC engines...

Post by **maxstu** » 18 Sep 2008, 21:32

Got a local friend with a T25 or 80-90 club member that will swap coils to see what happens?

I think there is something in WIKI about testing a coil's too.

Someone will probably find the answer soon.

Post by **asahartz** » 20 Sep 2008, 11:52

I'm pretty sure this is a carb problem now, though I can't work out how to solve it.

Changed coil - old one had a damaged insulator under the HT lead cover, started up fine, idled sweetly, no problems. Until I drove it. 200 yards down the road, as soon as the temperature gauge lifted off the bottom, it began to misfire.

Further investigation shows that if I close the choke flap and start it, it runs fine. As soon as I touch the throttle and the choke flap opens, it stalls.

As I have a Solex carb on a DG, it looks like it may be a good time to source the correct carb...
Others have mentioned the manifold at the same time - is it completely different, or can I adapt the one I have?

Website · Post by **CovKid** » 20 Sep 2008, 12:01

Weak mixture through an air leak somewhere? Check all hoses are connected and not perished

Post by **asahartz** » 20 Sep 2008, 12:11

Air leak had occurred to me, but I can't find one other than the unconnected vaccuum pickup https://club8090.co.uk/forum/viewtopic.php?t=40536 that I've now blanked off.

Must look harder...

Website · Post by **CovKid** » 20 Sep 2008, 12:35

air leak (if it is that) could be anywhere from carb to inlet ports. Just check that throttle flap isn't worn out as that would do it although thats far more likely on bug carbs. See if spraying WD40 around suspect areas when its running suddenly makes the idle speed go up?

Post by **asahartz** » 20 Sep 2008, 18:20

Well I'm baffled. Had a good spray round, couldn't identify anything.

Went out to play hockey, came back to a cold engine. Started it up then sat & watched it. Perfect for about 5 minutes, then starts to misfire and won't idle without the choke flap being held onto to the second or third step of the cam. So it's clearly something that alters when it gets warm, but what? Help!

Post by **HarryMann** » 20 Sep 2008, 18:36

What?

Don't trust the WD40 test, it seems to running weak, so to eliminate that possibilty, re-clean carb and see if more muck has entered and partially blocked jets... if so you know to look upstream in fuel supply.

If it really is heat and not that the choke has finally come off then re-do WD40 test with something more volatile, like carb cleaner.

Did you spray it around ALL the abutment flanges of manifold to head and carb to manifold when it was running at a steady speed? Definitely no change in revs, rhythm?

Post by **VWCamperfan** » 20 Sep 2008, 18:54

Have you checked the operation of the cutoff valve at the base of the carb? Should click when ignition is turned on or off. Only operates on the idle circuit but if the choke is open then the idle circuit is bypassed and engine will run until the choke comes off... then stall!
Check for 12 volts at the terminal when ignition is on. If in doubt, take it out and connect to a 12 volt supply, should click and draw the plunger inwards. If not a replacement may have to be sourced.

Hope this helps.

Post by **asahartz** » 20 Sep 2008, 20:18

HarryMann wrote: If it really is heat and not that the choke has finally come off then re-do WD40 test with something more volatile, like carb cleaner.

Did you spray it around ALL the abutment flanges of manifold to head and carb to manifold when it was running at a steady speed? Definitely no change in revs, rhythm?

It definitely has to do with being warmed up. It runs absolutely perfectly from cold. After that, no chance.

Yes, I sprayed round the manifold to head joints as well - but steady speed? I can't get it to run at a steady speed!

VWCamperfan wrote:Have you checked the operation of the cutoff valve at the base of the carb? Should click when ignition is turned on or off. Only operates on the idle circuit but if the choke is open then the idle circuit is bypassed and engine will run until the choke comes off... then stall!
Check for 12 volts at the terminal when ignition is on. If in doubt, take it out and connect to a 12 volt supply, should click and draw the plunger inwards. If not a replacement may have to be sourced.

I'm sure this was working (had this issue on son's Capri the other week); there's definitely 12v on it because that's where I powered my strobe from. Will recheck it again in daylight.

Post by **Mocki** » 20 Sep 2008, 20:28

ummm, is this fault new?
im just wondering if the power to the perol cut off solenoid is at fault.

check it is getting 12v when the fault happens, coz its possible it being routed via the them switch for the carb heater (In the end of the metal pipe above the LHS head)

the mainifold for the DG is vastly different, but you need to see if you have Dg heads or Df heads, which will be apparent when you lift the manifold off and see if the inlet ports are the same shape and sizr as you manifold, or bigger, if they are DG?