Carburettor float vent solenoid issue

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PK68

Member
Posts
27
Location
North West
Good evening
I have a Land Rover 90 with a 2.25 petrol engine fitted with a Weber 32/34 Dmtl Carb.

I recently stripped the carb down to fit a new accelerator pump, needle valve and other bits and to give it a clean. I'd done the head gasket prior to that.
Long story short, since putting the carburettor back together I've had the following issue:
1. Starts fine, idles fine and runs ok while engine warms up.
2. Once engine is warm it loses power on acceleration and kangaroos while being driven. Still idles fine though.
3. Disconnect the float vent solenoid it runs fine if a little fast.
4. Reconnect, it suffers the same issues.

I've replaced the whole solenoid mechanism and fitted new connecters from the wiring loom. No change.

The float seems to be working fine and the fuel supply is fine as far as I can assess it.

Any ideas what might be going on? Most of the diagrams and workshop books I have don't show that part on them so it's difficult to diagnose the issue.

Thanks in anticipation.
 
Just to add to the above, the idle cut off solenoid works as it should so I don't think there is a wiring fault. Cheers
 
Ok. I hope this is the end of this thread.
Been looking at it again this morning and scratching my head as there was no change. However....
Whilst messing about with it last night when I uncoupled the spade connector I noticed it short out against the manifold. Hence why I changed the connectors as the wiring was in a poor state.
It looks like I'd not secured the new spade connector properly as it came off this morning when I was disconnecting it again. I've re-crimped it and, touch wood, so far so good. Going to take it out for a short spin locally and see how she goes
 
PK68 said:
Ok. I hope this is the end of this thread.
Been looking at it again this morning and scratching my head as there was no change. However....
Whilst messing about with it last night when I uncoupled the spade connector I noticed it short out against the manifold. Hence why I changed the connectors as the wiring was in a poor state.
It looks like I'd not secured the new spade connector properly as it came off this morning when I was disconnecting it again. I've re-crimped it and, touch wood, so far so good. Going to take it out for a short spin locally and see how she goes
Click to expand...
The simple things are easy to overlook
 
Spoke too soon. Set off ok but then had the ****test ride of my life! Had to keep revs up and it seemed to by surging when driving. Ended up having to stop and disconnect the solenoid again but even then it wasn't great but better.
The engine does seem to be getting quite hot so I was thinking possible fuel evaporation? But I'm really at a loss now!
 
There could be so many reasons for this.
I'd go back to the beginning, strip the carb on the bench and go from there. Good clean, set/check the float level, check for any inlet air leaks etc
 
I've stripped it down that many times over the past few days I can pretty much do it blindfold but I'll have another crack at it. Just seem to be heading around in circles now! Bloody thing!
 
Why did you think it needed a new pump and what else did you replace? Is it a genuine carb or a cheap copy?
What fuel pump do you have? Is it supplying a good volume of fuel?
Are you saying it runs on choke then struggles off choke?
 
Hi
The carb was leaking in places so I bought a kit and replaced some of the parts. Didn't strip it completely down, only replaced things that I thought needed it.

Got back to it before and had another good look under the bonnet. Low and behold the vacuum arm at the back of the carb had come off. Difficult to see without lifting the bonnet right back and getting right behind it. When I took it apart the arm was held in place by what looked like a bit of paper clip in the ridge that is in the stud that the arm pivots on. I don't know what is supposed to hold it in place so I'd done a similar botch to hold it for the time being.

I'm sure this carb hates me for disturbing it!!!!

Again, it "seems" to be running ok at the mo. Had a good drive back and did a few laps of the car park at work just to make sure.

So, fingers crossed it looks like a dodgey wire and a loose vacuum arm have held me back for the best part of a week!!!

Just hope that's the end of it????

Cheers for your advice and responses. Very much appreciated
 
Oh well. Success short lived!
Back to the original problem. Drove beautifully this morning until it got to temp then hesitated, dead spots and poor acceleration. Popped bonnet, vacuum arm still in place. Disconnected solenoid, drove ok but not quite as smoothly.
So I'll strip it back down again when I get the chance and clean everything again.

But what is that solenoid for and how does it affect things? I can't find a lot about it on this type of carb other than it either be the float chamber when the engine is off or cuts off fuel if the vehicle overturns? And how does disconnecting it affect the running of the engine? Could it be a bad coil causing the issue?

I'll strip the carb down again and give it another good clean but I'll end up staring at it blankly again, scratching my head!!! :)
 
Afternoon all
Managed to have another tinker today. Changed the coil but no change which I kind of expected to be fair. Just a wild shot in the dark!!!
Stripped the carb down again. Float height was fine but the float drop seemed excessive. So I adjusted the tab at the back so it didn't drop as far. Got the Landy up to temperature and drove her round a bit and it looks like it's done it. No dead spots, no lack of power, no surging, no hesitation. So I'm hoping that it's that and she'll be back on the road now.
Like Kermit said, simple things are easy to overlook. Especially when chasing an error that could be any number of things. In my case, when having the carb stripped I was so fixated on float height I hadn't noticed that the rear tab had bent out!
Fingers crossed that's the problem solved. :)
 
Damn it! I was so confident too!

Managed to take her out today. Got a bit further than before with no issues then.....lost power during acceleration and lumpy. It totally stalled at one point. I disconnected the solenoid again and it ran but I had to get passed the initial dead spot and keep the revs high and she ran but still lumpy/surging. I pulled the choke back out and continued to run but it was still lumpy.

So, I'm not much better off. Really thought I'd cracked it there but I'm almost at the point of throwing the towel in and getting a new carb but I could do without the cost!

Any assistance appreciated.
 
Hi, got the exact same issue with the same carb/setup.

reading this with anticipation, hanging on to every reply and follow up replies. Did you manage to fix it?

Thanks
 
Hi pal.
I stripped it back down again and checked the float gap. The gap seemed fine but it looked to me like the float might have been dropping too far allowing all the fuel to drain out before it had chance to refill. I adjusted the tab at the back of the float so it didn't drop as far. After I'd done that it ran better. I've tried adjusting it a couple of times since. It's never quite been completely right since. Currently, it's hard to cold start but when it gets going it runs fine.

I've no idea whether what I did fixed it or whether stripping it back down cleared a blockage or something. It was all a bit hit-and-miss.

I had a similar problem a few years ago and that time it was the float valve that had come loose. Worth a check.

Hope you get yours sorted. Let us know how you get on.

PS: By your sign-in name I take it you're military?
 
Hi again all
I'm just adding to this thread again as I'm encountering a similar issue again but nothing I've done so far has resolved it. As a reminder it is an early 90 with a 2.25 Petrol 5MB engine.

The Problem:
Engine dies or hesitates badly on initial acceleration and kangaroos in low revs when it does go with the Float Vent Solenoid connected. Helps a little if I pull the choke out or rev hard and keep the revs high. It idles fine but there is still hesitation when revving it, if it's not warmed up properly it'll die.
Disconnect the Float Vent Solenoid and it's close to normal operation, just idles faster but is drivable. It just has very slight resistance on acceleration, like driving headlong into a strong wind. A bit of popping at the exhaust in both cases.

What I've tried so far:
Checked the ignition system. I have an electronic dizzy and Accuspark ballast coil. I get good spark at the plugs and the vacuum advance is functioning.
Checked that the fuel pump is working and providing a good flow of fuel to the carb, which it is.
Cleaned all earthing connections at engine, fuel pump and battery.
Checked it without the air filter fitted and get the same symptoms so air filter isn't clogged.
Stripped the carb down. It's a Weber 32/34 DMTL for Land Rovers with the two solenoids wired in series: Coil > Float Vent > Fuel Cut Off.
Drained float bowl and blown all channels and jets with airline. Rechecked float level set to 7mm as per the manual. Checked that the Float Vent Plunger is secure. Accelerator pump working and pumping fuel fine. Had the diaphragm out and checked for splits but it's fairly new.
Set the mixture screw and fast idle screw to start state settings: 2 1/2 turns and 1 1/2 turns respectively.
Checked that the Fuel Cut Off is functioning properly by disconnecting it with engine running and it cuts it off. And I can here it click and engage when I reconnect it with power going to it.

None of the above have made any difference to the initial problem.

Specifically regarding the Float Vent Solenoid, finding out much about them isn't easy as they are a specific Land Rover requirement I believe. My Haynes Carburettor manual doesn't show it and my Land Rover original Parts Book doesn't either.
My understanding is that when the engine is off it opens a vent hole to allow the fuel bowl to vent when not in use. When engine is on it plugs the hole. I've tested that it is engaging as it should by removing the solenoid body and pulling the plunger by hand to plug the gap. This causes the issue I described at the beginning, engine slows right down and hesitation in revs.

I'm at a loss! I've had the carb stripped several times now. I've ordered new jets for it just to eliminate that as an issue. I can only think that it's either electrical or and air issue.

Could it be that as the two solenoids run in series that having the fuel vent solenoid fitted is affecting the cut off solenoid? One of them faulty in some way?
Or is it an air/fuel problem seeing as cutting off the air venting the fuel bowl kills it on acceleration?

Getting a bit desperate now as my daily driver (Freelander 2 TD4) has just died on me!!!! Think that's a fuel issue too!!!!

Any carb experts out there who might be able to help with this issue?
 
PK68 said:
Hi again all
I'm just adding to this thread again as I'm encountering a similar issue again but nothing I've done so far has resolved it. As a reminder it is an early 90 with a 2.25 Petrol 5MB engine.

The Problem:
Engine dies or hesitates badly on initial acceleration and kangaroos in low revs when it does go with the Float Vent Solenoid connected. Helps a little if I pull the choke out or rev hard and keep the revs high. It idles fine but there is still hesitation when revving it, if it's not warmed up properly it'll die.
Disconnect the Float Vent Solenoid and it's close to normal operation, just idles faster but is drivable. It just has very slight resistance on acceleration, like driving headlong into a strong wind. A bit of popping at the exhaust in both cases.

What I've tried so far:
Checked the ignition system. I have an electronic dizzy and Accuspark ballast coil. I get good spark at the plugs and the vacuum advance is functioning.
Checked that the fuel pump is working and providing a good flow of fuel to the carb, which it is.
Cleaned all earthing connections at engine, fuel pump and battery.
Checked it without the air filter fitted and get the same symptoms so air filter isn't clogged.
Stripped the carb down. It's a Weber 32/34 DMTL for Land Rovers with the two solenoids wired in series: Coil > Float Vent > Fuel Cut Off.
Drained float bowl and blown all channels and jets with airline. Rechecked float level set to 7mm as per the manual. Checked that the Float Vent Plunger is secure. Accelerator pump working and pumping fuel fine. Had the diaphragm out and checked for splits but it's fairly new.
Set the mixture screw and fast idle screw to start state settings: 2 1/2 turns and 1 1/2 turns respectively.
Checked that the Fuel Cut Off is functioning properly by disconnecting it with engine running and it cuts it off. And I can here it click and engage when I reconnect it with power going to it.

None of the above have made any difference to the initial problem.

Specifically regarding the Float Vent Solenoid, finding out much about them isn't easy as they are a specific Land Rover requirement I believe. My Haynes Carburettor manual doesn't show it and my Land Rover original Parts Book doesn't either.
My understanding is that when the engine is off it opens a vent hole to allow the fuel bowl to vent when not in use. When engine is on it plugs the hole. I've tested that it is engaging as it should by removing the solenoid body and pulling the plunger by hand to plug the gap. This causes the issue I described at the beginning, engine slows right down and hesitation in revs.

I'm at a loss! I've had the carb stripped several times now. I've ordered new jets for it just to eliminate that as an issue. I can only think that it's either electrical or and air issue.

Could it be that as the two solenoids run in series that having the fuel vent solenoid fitted is affecting the cut off solenoid? One of them faulty in some way?
Or is it an air/fuel problem seeing as cutting off the air venting the fuel bowl kills it on acceleration?

Getting a bit desperate now as my daily driver (Freelander 2 TD4) has just died on me!!!! Think that's a fuel issue too!!!!

Any carb experts out there who might be able to help with this issue?
Click to expand...
First off , hello from Canada. I have been struggling with a 32/34 DMTL carb issue for a long time. I recently spoke to my Land Rover parts supplier here in Canada who has been working on Land Rovers all his life. I explained all the similar symptoms as yourself and how no mechanic could seem to make any difference in performance by adjusting air fuel mixtures. This carb was new 5000 miles ago but it sat for years with the occasional start up and drive around the fields and fresh gas top ups. After I retired I put my Defender 90 into full time use. It drove ok but had some undesirable quirks . Poor gas mileage , black carbon exhaust and black smoke sometimes and even run on occasionally ( which should never happen with anti run on solenoid ). Paul Safari Components have helped me throughout my restoration and is always willing to spend time diagnosing over the phone. That said , he dug out a book from Weber on all their possible fault scenario's. We found the most relevant cause compared to symptoms was a diaphragm located at the front of the carb. which you will see has an aluminum cover with 3 screws holding it in place ( I believe he called it the fuel economy valve diaphragm which was a feature on my carb. but not on all 32/34's ). Anyway it said if it was punctured or defective it would suck fuel directly into the manifold bypassing any metering jets and cause a rich fuel condition and will even suck the fuel bowl dry after shut off causing run on. It also was hard to start when warm unless I fully opened the throttle . I don't know what all you have replaced but I suggest you try replacing this diaphragm and reset air/fuel mixture setting again. Good luck .
 
Last edited:
Hi Tom. Hope all is good across the pond in Canada?
Sorry for the late response. I ended up buying new jets which seems to have sorted that problem out. However, now it's started with other issues and is back off the road.
Thanks for the advice though. Ref the diaphragm, I did change that one recently as mine does indeed have one. Problem is, you can get bad replacement parts even for something as simple as that so it's no guarantee that the new part works properly.
Thanks again for your input. Off to post a thread about my latest issue!!!
 
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