Weber - gas coming out of 1 throat

[steve lyle]

I think it is most likely fuel level, I'd do the down the main jet depth test with engine running to confirm the level.

Other might disagree but I think its not uncommon for a very small amount of fuel to seep around the outside trumpets.It shouldn't be much and no pooling in the air box or leaking out the air box.

I've fitted o ring under my trumpets to ensure any fuel stays in the throat.

Keith Fankck recommended that I seal the base of the trumpets with EZ Turn Lube, so similar idea. But I agree - there shouldn't be fuel there at any significant quantity. The Weber warranty guys never heard of this sealing approach, nor have I seen it in any Weber book. But heh, I've got his recommended sealant on order...

[alan.barker]

Workshop manuel +2 fuel section "L" page 55 L22 weber carburetters Air Trumpets.
Commencing at engine n° C 22414 the Air Trumpets sealed with 'Hylomar SQ.32M'
Never done it myself but mybe it can help.
Alan

[ericbushby]

Hi Guys,
I have always sealed the Weber trumpets on my S3 due to leaks. I have had the car 13 years now and have done it many times.
Not knowing any better I used what I had available. Sometimes silicon sealer, the last time I think I used Wellseal.
And always a blob on the threads of the trumpet clamp screws to prevent the nuts coming off and being sucked into the engine.
Eric in Burnley
1967 S3SE DHC

[GLB]

I have used the EZ Turn fuel valve lubricant suggested by Keith Franck. I also used it on anything with threads on the Webers such as the mixture control needles and the covers for the transfer ports and it seemed to make everything better. I got mine in US from Aircraft Spruce and Specialty, No affiliation with either company

[h20hamelan]

I am only guessing here, but propane / gas ptfe type sealant is close.
Seems EZ Seal is not readily available.
I have used propane gas fitting in the past, just wondering if it is not correct?

Kind Regards

P.s sorry if this is not the correct place to ask

[steve lyle]

I went to O'Reily's and rented their fuel pressure kit. Pretty neat - it comes with lots of fittings, one of which fits the fuel inlet banjo on the Weber - so easily done. In any event, my replacement mechanical pump (no glass bowl) seems to be ok - the gauge goes to 200 psi or so, and the first tickmark is either 2 or 4, and that's where the needle stuck very solidly. So I don't think fuel pressure is the issue.

My EZ Turn Lubricant (the ONLY sealant that Keith recommends - all others will do HORRIBLE things to your jets or whatever - so you've been warned) is coming from SkySupplyUSA - all the vendors I could find for this were in the aircraft biz - no Amazon vendor even carried it. $20 for a 5 ounce tube, and $10 for shipping. So I hope it lasts a long time.

My current plan is to go ahead and pull the head and get the plug thread issue addressed, take that opportunity to inspect the carbs closely. If problems persist - i.e., the rough running - once the head goes back on, seek professional help.

Keith wants me to run much smalller air correctors. They're currently 200's, he wants me to try 120's. Every book I have, and the Weber/Redline warranty guy, says this will enrich the mixture at higher revs. Keith says it will lean the mixture. We'll see what my O2 sensor says.

Again, thank you everybody for your input.

[Andy8421]

I went to O'Reily's and rented their fuel pressure kit. Pretty neat - it comes with lots of fittings, one of which fits the fuel inlet banjo on the Weber - so easily done. In any event, my replacement mechanical pump (no glass bowl) seems to be ok - the gauge goes to 200 psi or so, and the first tickmark is either 2 or 4, and that's where the needle stuck very solidly. So I don't think fuel pressure is the issue.

Steve,

Don't dismiss fuel pressure issues quite yet. A bit more digging on the net suggests 2psi to 3psi fuel pressure is the optimum range for Weber DCOE carbs, and that they will start to flood at pressures over 4.5 psi.

The pressure gauge you borrowed is aimed at fuel injection systems which have much higher pressure than normally aspirated carbs like the DCOE. If you are lucky and the gauge you borrowed is of decent manufacture and hasn't been dropped too often, a 200 psi borden tube gauge should have an accuracy of somewhere between plus/minus 1% and 3% of full scale - so plus/minus 2psi to 6psi. Mechanical gauges are notoriously inaccurate as they come off the zero stop, it is common to pre-load the gauge slightly so that needle rests against the zero stop at rest. It takes a few % of full scale to get it moving. The chances of you getting an accurate enough reading from the gauge you are using of the fuel pressure and being able to distinguish between 2psi (fine) and 4.5psi (flooding) are very low.

Ideally, you want to choose a gauge so the pressure you are trying to measure is somewhere near the middle of the range, so a gauge with a full scale of between 5psi and 10psi would be ideal.

Andy.

[Frogelan]

I'll jump in here with just a few random ideas to consider (in addition to the good ideas above):

- are the Weber floats made from plastic (not compatible with modern fuel...) as some suppliers of "genuine" parts are proposing these?
- why not swap over some parts (chokes etc) from one carb to another to audit/see if there are undetected sizing issues (on either the parts or the carb bodies)

As mentioned above, it is best not to drive too far (perhaps bag up the distributor / coil if you must).

Andrew

[alan.barker]

What Fuel Pump have you and what pressure is it.
If you have an all metal Fuel Pump these deliver too much pressure
Alan

Stock mechanical.

Sorry Steve but the all metal Pump is not "stock". I had exactly the same problem on a +2S130 when someone sold me an all metal pump made in India.
I suggest you get a real "stock" pump with "glass bowl".
When i fitted the "all metal" pump there was fuel being pumped everywhere and a very big "fire risk" please be careful.
Alan

[steve lyle]

I went to O'Reily's and rented their fuel pressure kit. Pretty neat - it comes with lots of fittings, one of which fits the fuel inlet banjo on the Weber - so easily done. In any event, my replacement mechanical pump (no glass bowl) seems to be ok - the gauge goes to 200 psi or so, and the first tickmark is either 2 or 4, and that's where the needle stuck very solidly. So I don't think fuel pressure is the issue.

Steve,

Don't dismiss fuel pressure issues quite yet. A bit more digging on the net suggests 2psi to 3psi fuel pressure is the optimum range for Weber DCOE carbs, and that they will start to flood at pressures over 4.5 psi.

The pressure gauge you borrowed is aimed at fuel injection systems which have much higher pressure than normally aspirated carbs like the DCOE. If you are lucky and the gauge you borrowed is of decent manufacture and hasn't been dropped too often, a 200 psi borden tube gauge should have an accuracy of somewhere between plus/minus 1% and 3% of full scale - so plus/minus 2psi to 6psi. Mechanical gauges are notoriously inaccurate as they come off the zero stop, it is common to pre-load the gauge slightly so that needle rests against the zero stop at rest. It takes a few % of full scale to get it moving. The chances of you getting an accurate enough reading from the gauge you are using of the fuel pressure and being able to distinguish between 2psi (fine) and 4.5psi (flooding) are very low.

Ideally, you want to choose a gauge so the pressure you are trying to measure is somewhere near the middle of the range, so a gauge with a full scale of between 5psi and 10psi would be ideal.

Andy.

I went back and looked at the gauge - it's actually reads to 100 psi. But I get your point.

Instead of running around trying to find an appropriate gauge, and figuring out how to plumb it into the system, we instead look at the fuel level in the bowls. High pressure should mean high fuel level, right? Even if the fuel pressure is a bit high, adjusting the float higher should put more more pressure on the valve and shut off the flow sooner, right? Which should still give the correct fuel level of 25 mm below the mating surface of the cover plate.

Keith recommends an acrylic rod and nylon sleeve to measure that. After removing a main jet assembly, I took a dial micrometer and first measured the distance from the lip that that the jet cover sits on to the top cover mating surface. Then I cranked the engine about 5 revolutions to ensure the bowl was full, and dropped the depth rod of the micrometer down the jet well with a light shining on it, stopping when the tip of the rod disturbed the surface of the pool. Subtracting dist A from B and converting to mm gave me 26.21mm for one, 26.49 for the other. So my fuel level is actually a bit low - it can come up 1.21 mm on one carb, 1.49 on the other to get to the spec Keith, and presumably Weber, calls for. Which means when the mains are functioning, I'm a bit lean. Presumably the idles as well.

Make sense? I'll rerun the measurements, but I think this may clear the pump of any part of the problem. I'll run this by Keith and see if he concurs as well, and if it's worth it to tweak the floats to raise the level a bit.

[steve lyle]

What Fuel Pump have you and what pressure is it.
If you have an all metal Fuel Pump these deliver too much pressure
Alan

Stock mechanical.

Sorry Steve but the all metal Pump is not "stock". I had exactly the same problem on a +2S130 when someone sold me an all metal pump made in India.
I suggest you get a real "stock" pump with "glass bowl".
When i fitted the "all metal" pump there was fuel being pumped everywhere and a very big "fire risk" please be careful.
Alan

If you don't trust an aftermarket pump without a glass bowl, why would you trust one with a glass bowl? What's so significant about a glass bowl?

I appreciate the thought about the pump concern, but keep in mind that this pump worked great feeding a pair of Strombergs for the 15k miles or so I've put on the car, and who knows how many miles before that. Are Webers and Strombergs so different in their presssure tolerance?

In any event, the post just above this one has my initial results looking at the actual fuel depth in the bowl, which I think is the whole point of this area of concern.

[steve lyle]

I'll jump in here with just a few random ideas to consider (in addition to the good ideas above):

- are the Weber floats made from plastic (not compatible with modern fuel...) as some suppliers of "genuine" parts are proposing these?
- why not swap over some parts (chokes etc) from one carb to another to audit/see if there are undetected sizing issues (on either the parts or the carb bodies)

As mentioned above, it is best not to drive too far (perhaps bag up the distributor / coil if you must).

Andrew

Yes, they're plastic. Obviously, Weber thinks they can handle modern fuel. I've had them out multiple times setting and checking the float levels, and haven't noticed any degradation.

Interesting thought on the swaps. But since gas is coming out of the throats of both at times, I'm not sure what that will tell me. The gas is seeping out, not flowing out, so at this point I'm thinking the EZ Turn will likely take care of it. That will still leave me with the driveability issue.

No, I'm not driving far, if I drive it at all.

[alan.barker]

Hi Steve,
I've never had a "glass bowl" pump produce too much pressure in 50 years tinkering on Twinks.
But the only "all metal " pump i have bought was producing too much pressure.
Maybe if you prefer to keep an "all metal" pump you could fit a Pressure Regulator inline.
Alan

[steve lyle]

Hi Steve,
I've never had a "glass bowl" pump produce too much pressure in 50 years tinkering on Twinks.
But the only "all metal " pump i have bought was producing too much pressure.
Maybe if you prefer to keep an "all metal" pump you could fit a Pressure Regulator inline.
Alan

Lol, You just can’t accept the evidence that this pump is working fine, because you once had one pump that didn’t have a glass bowl that was faulty?

In any event, thank you for the suggestion, I do sincerely appreciate your concern.

[rgh0]

it appeas your later 40DCOE have the screw to clamp in the aux venturi rather than the spring clip used on the earlier ones. This clamps the opposite side of the venturi to seal the main jet fuel passage into the venturi. Leakage here is why you need some sort of seal on the trumpets. I have never needed it if the spring clamp or clamp screw is tight and the aux ventrui properly seated.

leakage due to high fuel level / high fuel pressure will occour at all revs but if itonly occurs when then engine is under load its due to a loose aux venturi

cheers
Rohan