Possible carb issue? Help or advice please

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Bub2006
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Possible carb issue? Help or advice please

Post by Bub2006 » 17 Dec 2017 06:33 pm

Hi folks. I have a 1989 1.4 vario. When its cold it starts fine but if turned off then started when hot it runs really lumpy. If i hold throttle on a bit it eventually rides it out then i can carry on. It also stalls a fair bit in traffic too. It does smell rich and i am getting around 23mpg local driving. Thanks in advance.

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bogbasic
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Re: Possible carb issue? Help or advice please

Post by bogbasic » 17 Dec 2017 07:28 pm

idle solenoid. Prob still available new from a carby place. You can check if it clicks with a test wire from the battery.
1988 340 1.4 GL, 218k, 5 door (Grey Bess). Gone to CBA.
1991 340 1.7 GL, 64k, 5 door, petrol blue (Deep Blue).
1988 360 2.0 GLE, 140k, 5 door, ocean blue metallic (Blue Bess).
1989 340 1.7 GL, 108k, 3 door (Red Ness).
More info here!

Bub2006
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Joined: 15 Dec 2017 11:32 pm

Re: Possible carb issue? Help or advice please

Post by Bub2006 » 17 Dec 2017 10:10 pm

Could that be causing lumpy running at low revs? I tested thecair filter wiggle test and its fine.

benji1985
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Re: Possible carb issue? Help or advice please

Post by benji1985 » 17 Dec 2017 10:39 pm

If you speak to mac on here he can guide you in all things carb related.

I'm glad we the de-clutching servo work and now going in to gear, only a few little things to go now.

Ben

Bub2006
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Re: Possible carb issue? Help or advice please

Post by Bub2006 » 17 Dec 2017 10:49 pm

Hi ben, thanks for your aid. Its a work in progress!

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mac
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Re: Possible carb issue? Help or advice please

Post by mac » 18 Dec 2017 10:32 pm

Hi there Bub2006, had a long chat with benji1985 last night and he's told me of your issues (he seems to think I know a little bit about carbs).

I'll make a few suggestions about what might be going on (as much from Bens description as well as your post).

There is well know situation that can arise with the Weber32DIR type109s which is popularly called"vapour lock" and this may be, in part, your problem.
In the mid 80s there was a move among most car manufacturers to raise the temperature of the engine bay (I won't bore everybody with the reasons unless anybody is particularly interested but enough to say that it was all about efficiency in the conversion of chemical to heat to kinetic energy and a reduction in thermal rejection from the engine block) during the same period there was a move by fuel suppliers to provide unleaded, higher volatility petrol.
If what I suspect is happening you will find that cold start and general running is OK but if when hot you stop and switch off for perhaps 10-20 mins hot start will be difficult, initial running will be very lumpy with a tendency to stall, to the extent of "kangarooing" and jerking. After running for a mile or so the engine smooths out and "normal" running resumes.

Under these circumstances, especially in warmer weather heat soak in the engine compartment (after stopping) can raise the temperature of the fuel in the carburettor float chamber to a level at which bubbles of fuel vapour will form, moreover vapour "gassing" from the f.c. will collect in the air cleaner housing and top of the choke tubes. When restarting this collected vapour gives a very rich initial mixture - just what is NOT needed for a hot start. When driving fuel including vapour bubbles will be drawn into the idle circuit and through the main jets into the primary and secondary wells. Whist all being fuel it nevertheless gives a rapidly changing mixture (due to the density differences of liquid as opposed to gaseous fuel). This rich, normal, weak, changing gives the poor running and kangerooing.
The 300 has a return to tank fuel system so cool fuel is continually circulating through the fuel pump, thus any fuel drawn from the float chamber is replaced with this cool fuel which rapidly reduces the carb temperature and any vapour bubbles condense back into liquid, mixtures return to normal and correct running resumes.

If this is your problem it will only occur in a time "window" - if you restart after a short while heat soak will not have had time to raise the fuel temperature high enough and restarting after a lengthy time will have allowed enough time for the system to loose enough temperature to drop below the vapour bubble formation point (my own research during the late 80s showed the "critical" period to last from about 11mins to 24mins - dependant upon ambient temp.

Not a great deal can be done except try to reduce under bonnet temperatures. Make sure the thermo fan is working correctly, avoid the "critical" time if possible, or try to introduce cool air into the engine bay.

The rich smell and stalling in traffic may or not be part of the same problem, but if the carb is incorrectly adjusted and running rich anyway it will only exacerbate the issued. The 23mpg in local driving is actually not toooo far out for a CVT - 25mpg is often given as normal with 30-34 overall considered realistic.

Usual checks should include adjustment of CO% screw (which affects idle circuit only) and float height (incorrect can give overall rich mix) and a punctured part load enrichment diaphragm could also give a rich fault.

If you think I can advise further do please ask.

Mac.
88 5door Redline 1.7 52k - 19 XC60 Momentum Pro D4 AWD 17k
1950 pair of legs that don't work very well.

Bub2006
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Re: Possible carb issue? Help or advice please

Post by Bub2006 » 18 Dec 2017 11:07 pm

Thank you. I was told you know your onions and certainly seems so! It doesnt make for happy motoring especially considering its an auto but ive a dab hand now at going to neutral,restarting and back to d in a very short time! Ben has gave me some tips on how to reduce under bonnet temperature which im going to try. Ive mentioned to ben another issue ive picked up on though,heaters drop cool if sat ticking over. Thermostat id guess as ive said also the temp gauge only goes to a quarter unless in traffic which it goes to half but on faster roads it drops down to just over c. I think its a great car overall. Certain feels a better car than my j reg 440!

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mac
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Re: Possible carb issue? Help or advice please

Post by mac » 19 Dec 2017 12:15 am

Sounds very much like the thermostat is stuck in the open position - or missing entirely.

.......

Or - there is very little flow through the heater matrix - check for heater valve operation, adjustment of temperature control lever, equal temperature of heater inlet and outlet hoses.

But - the temperature gauge suggest very strongly a thermostat issue.

Mac.
88 5door Redline 1.7 52k - 19 XC60 Momentum Pro D4 AWD 17k
1950 pair of legs that don't work very well.

Bub2006
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Joined: 15 Dec 2017 11:32 pm

Re: Possible carb issue? Help or advice please

Post by Bub2006 » 19 Dec 2017 12:23 am

Thanks mac. I know my way round an engine but like to be sure. Sadly not as able bodied as i once was so some things can be problematic. After new year ill contact you regards some prices on parts too if ok? I am trying to keep the old girl in fine standard fettle.

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mac
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Re: Possible carb issue? Help or advice please

Post by mac » 19 Dec 2017 12:56 am

Anything you think I can do to help please ask - it can sometimes help for another "head" just to confirm your own diagnosis is correct.
Given time most parts can be found and I can certainly supply any of the BBB range.

Mac.
88 5door Redline 1.7 52k - 19 XC60 Momentum Pro D4 AWD 17k
1950 pair of legs that don't work very well.

Bub2006
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Joined: 15 Dec 2017 11:32 pm

Re: Possible carb issue? Help or advice please

Post by Bub2006 » 19 Dec 2017 08:50 am

Thanks for the assistance. Ill see how this goes!

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bogbasic
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Re: Possible carb issue? Help or advice please

Post by bogbasic » 19 Dec 2017 12:50 pm

mate, mac is always right, but rig up a live wire from the battery red terminal and check the idle solenoid clicks on connection every time. If it doesn't click every time you will have the issues you described.
1988 340 1.4 GL, 218k, 5 door (Grey Bess). Gone to CBA.
1991 340 1.7 GL, 64k, 5 door, petrol blue (Deep Blue).
1988 360 2.0 GLE, 140k, 5 door, ocean blue metallic (Blue Bess).
1989 340 1.7 GL, 108k, 3 door (Red Ness).
More info here!

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mac
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Joined: 19 Apr 2006 11:02 am
Location: Needham Market U.K.

Re: Possible carb issue? Help or advice please

Post by mac » 19 Dec 2017 01:12 pm

Thanks for suggesting it Bog dweller but I'm NOT always right!

Good suggestion - a failing/failed idle shut off valve will certainly cause idling/stalling issues but is unlikely to do this only after a hot start, recovering after a short time. There also seems to be a stale fuel issue.

Keep those ideas coming though.

Mac.
88 5door Redline 1.7 52k - 19 XC60 Momentum Pro D4 AWD 17k
1950 pair of legs that don't work very well.

Bub2006
Posts: 20
Joined: 15 Dec 2017 11:32 pm

Re: Possible carb issue? Help or advice please

Post by Bub2006 » 19 Dec 2017 04:08 pm

Right,idle control clicks when disconnect /connect with ignition on engine off. The carb is still being a pain today. I wemt to sort dog out for the ex and she has speedbumps near hers. If i touch throttle then lift off completely like you do with speedbums like mountains it stalls. Ben has given me notes on adjusting carb but i feel uncomfortable doing that myself. I dod think maybe tickover too low but im unsure how quiet it should be enginr wise. And no rev counter yet.

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bogbasic
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Re: Possible carb issue? Help or advice please

Post by bogbasic » 19 Dec 2017 09:01 pm

Glad its not a solenoid issue. It could be the carb-to-inlet manifold gaskets - they perish but can be cut by hand easily if you have a spare cornflakes packet - ideally proper gasket material in the long term ;-0
1988 340 1.4 GL, 218k, 5 door (Grey Bess). Gone to CBA.
1991 340 1.7 GL, 64k, 5 door, petrol blue (Deep Blue).
1988 360 2.0 GLE, 140k, 5 door, ocean blue metallic (Blue Bess).
1989 340 1.7 GL, 108k, 3 door (Red Ness).
More info here!

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