webwe 34 ICH carb

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joe27979

joe27979

Well-Known Member
Posts
1,354
Location
west Norfolk
Hi guys,
I installed new plugs, leads, coil and electronic ignition, set timing to 6DBTDC and my 2.25petrol ran lovely.

I took it for MOT and it failed on CO2 so the tester turned out the mixture screw on my weber 34ICH a turn or two to lower the emissions and it passed the test.

Ever since though it has ran really lumpy and bunny hops all the time. I checked timing and it dies anywhere near 6DBTDC, its at about 15DBTDC at the moment and just about running.

The mixture screw doesn't do anything to the engine when I turn it in or out so I suspect some ****e may have dislodged in carb (it stood for a year until I purchased it last month)

I just fitted a new lift pump and bowl to see if that would help but it didn't, my inline fuel filter is new and in the correct direction.

I have just purchased a new weber 34ICH carb from paddocks and a 34ICH overhaul kit to rebuild my existing as a spare.

I cant find any decent tutorials to overhaul it, and no information on what gasket material to use when I bolt the new weber carb to the intake.

Can any of you shed any more light onto this for me pretty please?
 
Last edited:
OK - to be blunt if it is screwing up as you describe I'd have the cover off it first thing. Check the jets (brass screw things in the bottom of the bowl) for obstructions and check the fuel level in the bowl to make sure the float is set right.

Don't waste the rebuild kit just yet, or put on the new carb. Webers are pretty simple carbs (compared to the Zenith and the Solex!) and it may be you simply have a blocked jet.

As far as sealant for setting the new one I would just use a new gasket. You want to be able to put a carb off and on without having to replace the gasket or clear passages plugged by goop.

The other thing to check is other items that might have gotten messed up - coincidence is what it is. Check for vacuum leaks, ignition point dwell and other silliness - most diagnosed carb issues end up being electrical. :)

ajr
 
many thanks AJR,

if I try to set my timing again to 6dbtdc with a strobe on no.1 lead the engine won't start at all and seems as if it's getting stuck or held back, turn disi body clockwise a few degrees clockwise and it starts ok but runs like a lumpy bowl of mash potatoe.

only have one vac lead on engine from carb to disi dwell, if I pull off tube engine goes really lumpy and slows a little.

if I pull a plug lead on any cylinder it doesn't seem to make much difference to engine running which is very weird.

so I can separate carb and give it a good clean in situe without gaskets?
I've heard rumours of setting float gap?

I haven't got a taco so haven't even attempted to set any dwell angles on the disi-if I do rev her I see the timing mark going anticlockwise on the crank pulley so I'm guessing the vacuum from carb is adjusting disi some what?


cheers-I'm a carb noob but learning slowly :0)
 
If it ran lovely before you took it to the MOT just put it back to how it was, maybe the dude made a mistake and tried to make it run to the modern emission level of 3.5% instead of the 4.5% that would be correct for a series vehicles age?
 
leads are all correct, it's an electronic dissy too.
all he did was adjust mixture screw.

I took screw out and blasted carb cleaner in and polished needle, put screw back in and backed off 2 turns and revved it a bit and it's smoothed out again now :)
 
Fair play, when the tester was doing your MOT did he make sure the engine was fully up to temperature before cocking around with your carb? If it was cold he'd need to richen it up to make it pass the NOx test....
 
Are you sure the air cleaner is not blocked? I had a problem with the MoT a few years ago. He adjusted the mixture leaner to get it through. Later I noticed the air vents on the oil bath cleaner were half blocked with crud. When I had cleaned it, I had to richen (?) the mixture again to compensate for the extra air.
 
The 34ich is not easy to clean thoroughly as some of the passages and internal gubbins are not accessible. Compressed air os your best bet after a 24hr soak in a bucket (metal!) of carb cleaner.

When fitting the carb back onto the inlet manifold, always fit it dry and do not use any gasket seal or other sealant. Just use a paper gasket made from gasket paper or bought from Webcon or whoever.

I tried cleaning an old 34ich and failed to get it running properly. I pi$$ed around so much I just bought a brand new one from Webcon. yeah it was £100 but better than Zeniths which you can't buy new anymore (forget the Britpart ones they are Shiiiiiiiiiiiite beyond shiiite) and warp quite easily it must be said.

Just stick the new one on and follow the instructions. As for setting your timing I see you have an electronic dizzy. I don't believe you can static time those so I guess you are using a strobe? As such, you can only get an accurate reading by pulling the vac off the dizzy and idling her at 450RPM, no more. Above that, she will centrifugally advance and screw your reading. Any other method will give you an inaccurate advance reading.
 
so I go back to her today, check electronic ignition, rotor arm is pointing to no.1 plug at TDC-ok, started her from cold and she gated choke, would only run with no choke (mixture screw is out two full turns) if I press the throttle a little she bangs/back fires/pops out if the breather hose (I had air cleaner removed to get to dissy) if I floor throttle she builds up to a fast idle nicely, small amount if throttle and it pops like mad and cuts out.

once I've tried a few times and it's warmed up a little she likes small throttles! am I making sense?

out strobe on and she looks to be good at 6DBTDC

I've purchased a new Lucas gold coil that's designed for electronic ignitions-even though my existing coil is brand new.

am waiting for new carb to arrive, I take it I fit out of the box on dry gaskets, mixture 2 turns out and idle 1.5 turns in?

I don't have tacho so can't guess rpm unfortunately


thanks for all your input, this is a great thread
 
SOunds like a lean mix to me - if she won;t pick right up you also may have crap in the accelerator pump.

Don;t count on the initial settings being perfect. Expect to fiddle the idle and the idle mixture - they will inter-react a bit but when i play with petrol engines I'll set the idle speed, then back in the mixture screw slowly till it starts to stumble. Back out till it starts to run smooth, then a bit more. Reset idle speed and Bob's your uncle if all else is good.

One thing I might suggest is sticking in a fuel filter inline of you don't have one. i begin to wonder if you picked up a load of crap in fuel and all this carb problem is from crap in the fuel clogging things.

ajr
 
thanks for your input,
I forgot to mention there's a brand new filter inline just before carb, and I fitted a brand new lift pump just to be sure,

when I removed fuel line from carb I started engine and it ran for a few seconds until I turned her off, there was a cup full or so of fuel in my container and the carb bowl must have run on its own reserves?
 
Yes, that is actually a good test for the lift pump.It'll run for a bit on what is in the carb. The typical test is to watch the output of the pump into a jar and look for stream power and such.
 
Your webcon kit will have a weber filter, you must use it! Or your new carb will get gummed up as has been said. Set mixture last after setting timing, valve clearance and warming engine up. Instructions with the weber are good for setting the idle. I bet it will run good out of the box you'll see !
 
cheers guys, I'm not sure how to do valve clearances-I know
in principal what to do and it's in 9s...but is there an idiots guide anywhere? can valve clearance make a lot of difference?
 
joe27979 said:
cheers guys, I'm not sure how to do valve clearances-I know
in principal what to do and it's in 9s...but is there an idiots guide anywhere? can valve clearance make a lot of difference?
Click to expand...

Yes massive! Worth checking on any engine new to you.

Ignore the fact this guy thinks 300tdi engines came in series vehicles, the principle stands on any 4cyl engine.

https://www.youtube.com/watch?v=_kUxplaR3pI

Make sure your accurate and the feeler gauge just feels a bit of 'bite' in the gap. Fit a new rocker gasket while your at it.
 
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