Fixing stuck needle valves - Stromberg carbs

[James]

My car has been sitting for a year while I fiddled with the brakes. Now, first one, then both carbs began overflowing while turning over the engine. Question for you loti literati is - can you work on the float bowls/needle valves with the carbs on the engine or must the carbs be removed? OR...if anyone has a technique that will make the needle valves reset without tearing the carbs apart I would be glad to hear it.

James from B.C.
1970 Plus 2

[69S4]

Sadly I don't think you can. The usual first fix is to tap the float bowls with something like a wooden hammer handle to try and shock the valves into working. It has the secondary benefit of taking out some of your frustration as well

Taking the carbs off isn't that hard or time consuming - apart from the bottom nut on the rear carb which can take two minutes or two hours depending how lucky you are, and then each float bowl is only five screws. If you're careful you won't have a problem reusing the float bowl gasket.

Make sure you've got some replacement O rings first though - both the big ones where the carbs mount to the manifold and the smaller ones that seal the brass jet holder where it goes through the float bowl. I'm sure you probably know but I'll mention it anyway, that the Stromberg manifold O rings are bigger than the Weber ones. If the car hasn't been used for a while it's probably just dried fuel deposits sticking things in place and shouldn't take much time to clean up.

[James]

Stuart - I appreciate the opinions. Just spoke to a club buddy who restored a +2 (spent est. $20K and mega-hours); he says the aluminum bowls interact with the fuel and develop sticking problems. He's tried storing the car with fuel conditioner and it still didn't help significantly.
James.

[69S4]

Stuart - I appreciate the opinions. Just spoke to a club buddy who restored a +2 (spent est. $20K and mega-hours); he says the aluminum bowls interact with the fuel and develop sticking problems. He's tried storing the car with fuel conditioner and it still didn't help significantly.
James.

Most of the float bowls I've looked at (quite a few, car and motorcycle) over the years seem to survive unmarked as long as they're in contact with fuel vaguely similar to what came out of the pump but some sort of surface corrosion sets in when they're left for long periods with fuel slowly evaporating to solid residue.

Both my Stromberg float bowls look like they've been acid etched on the interior. My guess is that some of the additives that go into fuel are responsible. They're dilute enough when the fuel is fresh but as the volatiles vanish they concentrate and not only etch the aluminium but eventually gum up the various carb bits - floats, needle valves etc. Some of it does seem to redissolve when you add fresh fuel but I have found all sorts of gunk inside carbs that can only be got rid of by a stripdown and physically scraping it out.

On the other hand, as I know nothing about petroleum chemistry, this could be complete rubbish and whilst I'm reasonably ok in my ignorance I'd happily take on board input from someone who does know what they're talking about

[collins_dan]

I recently had Stromberg geysers. First time, tapping with a hammer near the needle valve or in my case grouse jet, helped initially, but the problem reoccurred, so I pulled the carbs off as a unit and it was a bad float. Good idea to have new orings... as mentioned as they often swell due to exposure to fuel and need to be replaced after disassembly. Dan

[James]

Took the rear carb apart today. To my novice eye the only obvious problem was the sediment which was substantial. The shafts appear tight; only tiny movement on 1-side but I'm told the vacuum created while running is significant and can bring in enough air to disturb the idle. This car has never idled very smoothly in the minimal time I've driven it. I got married about the same time I bought it; I'm sure you can fill in the gaps on that one.

A club buddy recommends soaking the castings in paint thinner to clean off gasket bits and loosen debris. Any other suggestions out there?

As for the carbs, a rebuild kit is about $55 Cdn. I'll go looking for those tomorrow.

James
70 Plus 2

[Jay-O]

James, could you please link the rebuild kit, if it`s online of course. My father is contacting Christopher Neil (I think) about it - but if there are other (cheaper) options out there, it would be nice to know. We`ve torn the carbs apart too many times now without the needle on the front carb doing it`s job (We think) - So we`re going for the full rebuild.

Also, when reading about residue in this thread, after been standing still for almost 3 years, we found our floatbowls to be coated in a thin green residue, much like oxydized copper. Any clue what might be the cause of that?

[69S4]

Best supplier for Stromberg bits is probably Burlen. I think they're the current owners of the Stromberg legacy and most other companies will be buying their bits from them. Web site is http://www.burlen.co.uk/ They've lumped them under S.U. and you'll have to search around a bit but just about all of bits you'll need are in there somewhere.

I've also seen quite a bit of the green residue stuff in dried out float bowls. No idea what it is chemically (other than guessing it's either just dried fuel or some chemical reaction between the aluminium and some fuel element) and never managed to find anything that will completely remove it. Hopefully someone will chip in with some practical advice soon.

[m750rider]

You should consider having the carbs rebuilt by Joe Curto (http://www.joecurto.com). They will be perfect when they return. I have no affiliation with Joe, just a satisfied customer.

[Jay-O]

Ok, I have one Stromberg geysir... Bought new needlevalves, but no improvement. Turned over the engine without the top on the front carb (the geysir), and it sprayed a nice little fountain. Now, if I'm not mistaken, this shouldn't happen, because the venturi effect is supposed to pull fuel up, right? And this is the source of misfires, bad idle and horrible RPM's and sputtering, right? Got good spark and timing, and the rear carb runs good...

Any clue? Maybe the floats? Can anyone link me guide on how to adjust them correctly, so that I might figure out what I do wrong?

[69S4]

OK, lets see if I've got this right. One carb is ok but the other is flooding. You've stripped the flooding one down and replaced the needle valve that controls fuel entry into the float chamber but when you've put the carb back on the car (without the top part containing the metering needle) and turned the engine over, fuel spurts out of the jet? Presumably you had to turn the engine over to get the mechanical fuel pump to work (or do you have an electric pump?)

When you replaced the needle valve did you check it was working correctly? You can do this simply by holding the carb the correct way up and blowing down the fuel pipe. You should be able to blow down it easily until you push the valve back up with a finger when it should block. Not a foolproof method but it'll give you an indication. Is the thread in the carb body where the valve screws in damaged so fuel could leak around the side? There should be an aluminium washer - is that damaged? Unless there is some sort of damage I've always found these valves to be pretty reliable. When you took the old one out was there any dirt in the pipe behind it that could be jamming the new one open?

You can check the float by removing it from the carb body (any visible damage?, any liquid inside the float (shake it)) and submerging it in a jar of fuel. Does it stay submerged or does it bob back to the surface? If the needle valve works and the float isn't damaged (check it's free to pivot on the mounting pin and isn't binding) then you'll need to check the float height. The book figure is 16-17mm from the highest point on the float to the face of the carb body. Measure it by assembling the float mechanism and then set the carb body upside down on the bench so the float is holding the valve shut. Then measure the distance.

If all of that checks out the carb shouldn't flood but it doesn't take much misalignment or wear for the system to stop working. I recently replaced a float and needle valve in a motorcycle carb that had been intermittently faulty for years and comparing the new parts with the old there was only the slightest of wear visible. If you've checked everything above and it's still not working properly I'd just order a new float as well. They're cheap enough not to break the bank.

Incidentally, even when you get both carbs working properly don't expect a nice even idle. Strombergs don't seem to give that.

[Jay-O]

I figured it out - took a while, because it didn`t make any sense at all.

I changed the needlevalve (Yes, the one that doses the fuel into the floatchamber), thinking it was defect. It wasn`t... So I changed it back to the old one.

I adjusted the floats according to Haynes Stromberg book, 13mm at the lowest point, and 17mm at the highest. Didn`t work. Frustrated, I overdid it with 20 and 23mm... that just shut the valve completely (of course), so at least I eliminated any suspicition about a faulty needlevalve...

The test method is as you descibed Stuart, put the front carb back, without the jet-needle and piston assembly on.

After three days now, and about 18 hours of troubleshooting, I reluctently resigned to the kitchen for a snack... While doing so, my father mentioned he had disassembled the carbs a few years back, WITH the crossover/EGR/Whatchawannacallit assembly and took said thingy off, blocking off the relevant holes and lines. Then it hit me... I ran out, took off the carb, took off the "converter" (please, if you know the real name for it, let me know), and there it was - the gasket was upside down, and blocking the ventilation channel for the floatchamber. With it blocked, the only way for the air to escape it through the jet-valve, pushing fuel in front of it! Hence the flooding...

Feeling relief, and joy over the fact that I may spend at least half the summer enjoying the Elan, I ave it a start...sort of... the starter wouldn`t turn the engine! Sighing, I took the starter off, and found out that the brushes where worn down. Luckily, I had an identical replacement (Yay, one point for foresight!) and now its running strong and good!

[rdssdi]

I use Jeff Palya at Paltech. He uses a vibratory micro polishing process that makes the inside and outside of the carbs better than new. He also had the linkages on a weber from a Cortina crossflow cad plated. Looks great.

I should be sending him my ZS carbs. Also a set of SU from a Jaguar 3.4.
http://www.paltech1.com/

Bob

[69S4]

I figured it out - took a while, because it didn`t make any sense at all.

After three days now, and about 18 hours of troubleshooting, I reluctently resigned to the kitchen for a snack... While doing so, my father mentioned he had disassembled the carbs a few years back, WITH the crossover/EGR/Whatchawannacallit assembly and took said thingy off, blocking off the relevant holes and lines. Then it hit me... I ran out, took off the carb, took off the "converter" (please, if you know the real name for it, let me know), and there it was - the gasket was upside down, and blocking the ventilation channel for the floatchamber. With it blocked, the only way for the air to escape it through the jet-valve, pushing fuel in front of it! Hence the flooding...

Feeling relief, and joy over the fact that I may spend at least half the summer enjoying the Elan, I ave it a start...sort of... the starter wouldn`t turn the engine! Sighing, I took the starter off, and found out that the brushes where worn down. Luckily, I had an identical replacement (Yay, one point for foresight!) and now its running strong and good!

One step forward, one step back ... Glad you've tracked down the carb problem but I'm not quite sure what bit had the gasket assembled upside down. The vent passage to the float chamber comes out on the front face of the carb - where the air box bolts on. If that was blocked it certainly would cause the symptoms you had. On Burlen's site their troubleshooting section has this passage:

Another cause of flooding, often mistaken for an over high fuel pump pressure, is caused by air trapped in the float chamber. When fuel is fed into the float chamber it rises and the float shuts off the needle valve. If, however, the chamber air vent is blocked, the fuel rising compresses the air in the chamber and fuel is forced out of the jet at pump pressure.

[Jay-O]

One step forward, one step back ... Glad you've tracked down the carb problem but I'm not quite sure what bit had the gasket assembled upside down. The vent passage to the float chamber comes out on the front face of the carb - where the air box bolts on. If that was blocked it certainly would cause the symptoms you had. On Burlen's site their troubleshooting section has this passage:

Another cause of flooding, often mistaken for an over high fuel pump pressure, is caused by air trapped in the float chamber. When fuel is fed into the float chamber it rises and the float shuts off the needle valve. If, however, the chamber air vent is blocked, the fuel rising compresses the air in the chamber and fuel is forced out of the jet at pump pressure.

Of course, I wasn`t thinking straight when I wrote the post There is an O-ring in the back, which I had to replace as well.

The whole purpose of my post was to inform that it isn`t allways the obvious, and perhaps needlevalves and fuelpumps have been changed in vain - but again, I should have checked the airvent first.