Series 3 Weber 32/34 DTML on 2.25 petrol vapour lock woes

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olriley said:
Would you mind expanding on this? Issue how so? As in spilling over the float bowl?
Click to expand...
I'm no engineer, but trying to think logically.. the fuel line to the carb is cut off by the float.
Fuel in the float chamber expands due to hear from the engine and some of it turns to vapour we can only go into the manifold, making a fuel saturated environment which makes the car impossible to start and you end up fouling the plugs
Maybe.
 
Aye, that’s what one of the solenoids is for - when it doesn’t get 12v it opens and vents the bowl… (haven’t tested it yet as I’m away)

however that problem shouldn’t arise while the engine’s running as it’s constantly drawing fresh fuel into the bowl and through?
 
olriley said:
Aye, that’s what one of the solenoids is for - when it doesn’t get 12v it opens and vents the bowl… (haven’t tested it yet as I’m away)

however that problem shouldn’t arise while the engine’s running as it’s constantly drawing fresh fuel into the bowl and through?
Click to expand...
The float bowl will always be full, because the lift pump can deliver much more fuel than the engine can use.
So it is quite possible that a bubble of vapour in the top of the float bowl could sit there undisturbed with the engine running.
The carburettor must be very badly designed if this can happen, though, I have never even heard of this issue before you posted about it.
 
Few questions.

So it stalls and wont start for 30mins +/-, But when it does there is still fuel at the little filter going to the carb?

Does it only do it when you are in slow traffic or stopped? does it do it if you are travelling? Can you get it to do it sat on the drive, so you could be armed and ready for when it did it again to check stuff.

Next time it does it give it a squirt of easy start it should run, If not you are in a flooded state cos of too much fuel or an electrical problem something breaking down with heat.
If it starts then one would assume you do have a fuel, or lack of problem.

Do you know how much fuel pressure you are getting at the carb with your setup?

J
 
NRC9772 Swirl Pot.jpg


Those that use their rectal-passage for speech are telling you to remove the above. Don't.

It's, in LR language, a vapour separator. We'll assume your pump is sited near the tank. Vapour-lock, if indeed that's what we have here won't be anything to do with a correctly installed vapour separator. Historically Series LR have always suffered vapour-lock issues in hotter climes. Land rover finally sorted it, that'd be what the swirl-pot NRC9772 Vapour separator/ Swirl Pot is there to do.

Only... if it's plumbed ' in muppetry,' - vapour-lock is guaranteed.

I know for fact, the 2.5 petrol got them, and I think Stage One V8s?

I run a 2.5 17H in my Series, and it gained a NRC9772 Swirl Pot as a result. Hence I confirm, found on 17H coilers.

Check it's in right.
 
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I haven’t had much time for tinkering of late, but my next tasks are to fit an exhaust heat shield … of course it looks like the series 2.25 part, which I have, won’t fit the 2.5 manifolds with which mine is fitted … interestingly they came with a carb spacer from the factory to insulate against heat!

Heat shield part no ERC8712 appears to be unobtanium … so I suppose I’ll have to make something.

90531FEC-1293-4924-8F11-2EA3CC920684.png
90531FEC-1293-4924-8F11-2EA3CC920684.png
 
That this problem is anything to do with fuel vapour could just be an idee fixe. I haven't seen any evidence of the engine being checked to verify that it is really a fuelling problem - the thread is all surmise.

One approach is when the problem manifests itself, to check both the fuel delivery AND the spark. While cranking, if the engine isn't starting,a CO/ HC meter should go off the scale if the engine is actually getting fuel, and checking for a spark at the same time can help in diagnosing the problem.

I wouldn't be at all surprised that the spark is the real issue.
 
Tall Ratbag said:
That this problem is anything to do with fuel vapour could just be an idee fixe. I haven't seen any evidence of the engine being checked to verify that it is really a fuelling problem - the thread is all surmise.

One approach is when the problem manifests itself, to check both the fuel delivery AND the spark. While cranking, if the engine isn't starting,a CO/ HC meter should go off the scale if the engine is actually getting fuel, and checking for a spark at the same time can help in diagnosing the problem.

I wouldn't be at all surprised that the spark is the real issue.
Click to expand...

very good point, thank you. I don’t have such a meter but I can get it hot and test the spark.
 
17H with ACR SU 04.jpg



Agreed, as my last post - at the start of this thread the knuckle-draggers had their finger pointed at the one thing - assuming correct install - it won't be; that Vapour separator NRC9772 . I only raised the issue in case there IS an install issue. Seems there isn't. This may be a fuel-starvation issue, this is NOT a vapour-lock problem.

The header reads vapour-lock, and then I saw why it isn't. Carb insulated, had I read the text, headline nullified, I'd look at coil/condenser. If tired, they get temparature dependent.

I'd shove a new coil / condenser on, because it won't hurt. Cheap, quick and easy to do. I'd be surprised if that's not it sorted.

You say you've rebuilt the carb? Then there's nothing left.Else...

£50 says your tank is rusty beyond help.
Thus, if you've covered everything else in logical order,coil /condenser breaking-down etc et, there's less to finger. More likely....

I run a 17H. It came with its Weber 32/34 DMTL. NOT to be confused with Weber 34ICH replacements famously bad on Series.... it's the best carb ever fitted to an LR and (along with better cam, head and manifold) responsible for the improvement in economy and low down grunt you get out of a 17H. It took decades, and a proper kicking from the Japanese, LR finally , finally sorted the issues with godawful Solex/ Zenith etc. You've all read those 'carb' threads arguing for Zenith or Solex that go on and on and on... and on.

And [stands back....] there's some in this thread telling you to put a Zenith / Solex on? If either was good there would be a clear winner and those threads could not exist.

Some 32/34 have a 12V feed to them, yours does... I see a spade going in - we're assuming this has 12V? It'll idle 'ruff' without. Pull it off at idle and hear the note change. No change? Check 12V and/or solenoid.

But... the Weber 32/34 DMTL is prone to being fussy about clean fuel, the 32/34 DMTL Weber needs kid-gloves, hence be filtered up to the gunnels. Else they WILL clog - ths after a rebuild. Next to impossible to clean. Normally an upgrade to be rid of your more usual s&*t Zenith/Solex, in this case shoving an ACR SU HS6 on there, is actually no better, and might truly be worse. When it's right, the Weber 32/34 DMTL is very good. Unlike a Solex/Zenith, no good reason to replace with an SU. But if I'm right, SU it is.

An SU is easier to use, and less fussy. And I suspect (if clogged) you'll struggle to find properly jetted new examples of a 32/34 anyway? The 2.25 is jetted differently to the 2.5. Hence see pic above. An SU becomes the easy way out of the mess.


Ask me how I know...

Coil / condenser first.

17H in pic. Can I ask if 2.25 of this vintage got a starting-handle and starter-dog? I had to put a dog on my 17H. Metric thread, pricey and rare,
 
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neikeel said:
........and the result was?
How much is a suitable SU and manifold?
Click to expand...
Ongoing. I picked up an adaptor elbow from HNJ engineering. Got an HIF44 carb although throttle mechanical looks to be reversed. Broke a stud in my exhaust manifold so need to extract that… then we’ll see!
 
olriley said:
Ongoing. I picked up an adaptor elbow from HNJ engineering. Got an HIF44 carb although throttle mechanical looks to be reversed. Broke a stud in my exhaust manifold so need to extract that… then we’ll see!
Click to expand...
Ah the snapped manifold stud chestnut! Lat couple I drilled out and retapped from scratch as my stud extractors were not up to the job.
I've got a 2.5petrol in my Series 3 with the original Weber that I stripped and cleaned, rebuilt with a kit from Fast Road Cars. I have a Facet lift pump under the floor and two filters but no anti-swirl pot. I had a misfire and poor running when hot before the rebuild so I am pretty sure it was muck in the fuel. I also put on electronic ignition and new coil.
I am pretty used to SUs in my MG but the Weber seems to be doing its job well.
 
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