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Stromberg 150 CD flooding


antanol_1238
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The carbs in question are on a Vitesse 2 Ltr. Mk 2. Until recently I have not had any trouble with carburation other than it has been running rich so I decided to strip and rebuild the carbs. I have changed all the seals, gaskets, cleaned out the fuel lines, float chambers and needle valve.The carbs were rebuilt as per service manual with the correct float setting and on refitting fuel poured out of the carbs as soon as I started the pump working. I have stripped and checked everything at least 6 times and even when set up on the bench and gravity fed the fuel just floods up the needle jet. With the carb empty I have turned it upside down and tried to blow down the filler pipe and the float works perfectly, but it won't work when correctly set up. Anyone got any ideas other than increasing the float level height.  Tony Birkbeck  

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one of the best pictorial articles is on

 

http://www.buckeyetriumphs.org/technical/technical.htm

 

never mind its for TR the basics are the same

 

if the float has two needle arms its easy to fit the float upside down and the levels are never correct.

 

the flat base of the float is  at an angle  in the fuel.   fuel the contoured side it in air.

 

make sure no slivers of rubber are not flaotion in the supply network or jammed in the back of the  float needle, often occurs when refitting hose to bundy.

 

float height problems will overfill and surge out the vent in the outer face 

 

there are many gaskets for these , many small changes which leave unsealed joint faces on the float chamber,  double check its not an exterior leak .

 

if the jet seals are incorrect then it can leak out around the inner jet tube 

I would double check the O rings and seal washers are all the right way in.

 

Pete

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Thanks for that Pete the American article was very informative even though the jetting is totally different. the only thing it mentions different to the workshop manual is that you should keep the float tag at 90 degrees to the valve pin. This I have done to no avail. As stated all seals etc. have been renewed they are O rings and cannot go in the wrong way, but it is the fuel valve that is not shuting off, and this is on both carbs.It's got me baffled there is obviously something simple that I just can't see, I know use SU.'s

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have you checked the fuel pump pressure is not something excessive,  

 

  this is not a normal Stromberg problem so head scratching is in order.   rubber slivers are real rouges in the fuel line .

 

and I hate SU  and luckily you  cant do a straight swap. as all hole centres and even air box is very different.

 

  are they new float valves or old ones  ??

 

Pete

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Stag forum has a number of owners over time with similar problems, most seem to have been solved by fitting a pressure regulator to lower the fuel pressure and fitting new needle valves.  It could be linked to a cr*p parts problem so just because the valves have been changed doesnt mean they have been improved.

 

Running rich could be a clue to a higher than required fuel pressure.

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Thanks for all that Pete, but it does it with just gravity pressure.Yesterday I assembled the float chamber with about a 3mm gap and no gasket and introduced fuel watching through the gap with a very bright led light. when I saw the float rising I kept a check on fuel flow and eventually the needle valve closed without over flow, I then closed the gap and put 2 screws in it wouldn't take any more fuel and didn't flood. So then I reassembled the carb with a gasket and once more it flooded. I know it sounds crazy but I have ordered 2 new gaskets I don't know why it should work but watch this space. Tony

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just make sure the gasket does fit all round and is not bridging or enchroaching the float operation when assembled  there are 

a whole load of evolutions to the carbs over the years and the float chamber gasket changed in many small but significant ways

 

   if you have the brass tag number that should point it t the right gasket,  some repair kits supply all you need 

and there's up to 6 in the pack  all look the same but on close up there are wildly different in the corners 

 

Pete

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I had a similar problem with my GT6 with Strombergs (on this forum).

 

My problem was caused by the fuel pump being stuck open. As I tried to turn over the engine fuel poured out. The way we proved it was to put a fuel filter between the pump and carbs - the filter completely filled.

 

I eventually refurbed the fuel pump and fitted a pressure regulator.

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Thanks everyone for your input I tried everything to no avail and the system was set up to the book, I even spoke to Rimmer Bros and Zenith technical, who were unable to help. A little bit of thought (sat in the garage like the thinker) and it was obvious that the air in the carb float chamber wasn't able to be expelled when the petrol level was higher than the holes in the orifice adjusting screw.therefor pressurising the float chamber. It would normally get out via the top of the jet and the carb body but mine had become airtight, not a very good system! Making a very fine cut in the aluminium washer on the upper face worked.I now have another problem the engine won't start but it has nothing to do with the modification. Here we go again.

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actually the washer is too high and couldn't suck fuel in, however after lengthy discussion with Zenith/Stromberg I have reverted to the original settings and guess what yes it still floods.Everything is clean and as standard I can't believe I am the only person to have experienced this..Must try harder.

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Unfortunately Pete I am in France at the moment and specialist assistance out here is very limited, like I said I spent quite a while talking to a Mr Phil Whitlock at Zenith/ Stromberg and he couldn't help. I will willingly phone you to discuss the problem if that is OK with you, your number is in the Courier. The main problem as I see it is how does the float chamber vent when the fuel level is above the hole in the jet adjuster and the needle valve is still open. Regards Tony.

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  • 2 weeks later...

 Pete, is correct the problem was the interface gasket between the carb and K&N filter. Originaly there wasn't a gasket so the carb breathed between the carb and filter. I put in a home made cork gasket because No 2 carb has wider lugs where the mounting bolts to the filter go through the filter the heads hold it off the carb body, gaskets supplied are too thin. Unfortunately I made the gasket to match the filter back plate, it had the holes in the wrong place!!!!!! . Thanks Pete for your efforts all is now well. 

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  • 3 months later...

Hello! I have a problem with my Stromberg carbs on my Vitesse Mk I...  I know that these carbs generate a lot of questions and discussions here on the forum , so I did not make a new thread. Maybe it would be better to just have one thread “Strombergs” and collect everything in the same thread in order to avoid questions to being repeated?

 

Anyway… This winter I have finally replaced the old Lucas 25D distributor with a new one from 123 ignition, seems to be great quality. The problem is that the engine will not idle unless I pull the choke, too lean mixture I suppose. I suspected air leaks from the manifold, so I have replaced the manifold gasket. I assembled the carbs exactly by the book, and I can’t see any reason for this idling problem. The position of the float is set at 18 mm according to the manual, but I wonder if this kind of problem still can be due to low petrol levels in the carb? Would it help to reduce the level to 16 mm and thereby get a higher petrol level? Can it be the choke assembly itself, there are many tiny things, maybe I made a mistake there?

Some facts:

  • Petrol pump was replaced during the winter (low pressure suction pump max 0,1 bar)
  • Carbs where renovated about two years ago, very low milage since then
  • 123 ignition fitted this winter, so I feel that it is very unlikely that I have any problems with the ignition.
  • Can’t see (using oil) or hear any obvious air leaks
  • I have taken them apart, and re-assembled about a dozen times due to flooding. The good thing is that there is no more flooding… Hence, they have also been cleaned a dozen times, can’t see any debris inside.

Pete, you are a big fan of Strombergs, any suggestions?  :)  The only action I can think of now is Keihins…

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the initial pre set can be widely wrong and its not uncommon to richen them or weaken the jet  from the 3 or what ever turns down from Flush.

 

what needles are fitted ??  have you checked them to the manual ?/

 

make sure the two holes in air piston do actually face  engine side .

 

if the lifting pins are free raise it till you just toucky feel it meet the piston then raise about 2-3mm   what happens

 

idle  tends to drop a little  its weak

 

idle rises a little   rich

 

nothing ..about right  

 

youre only looking for a hint of idle change , like 50rpm   nothing dramatic for a few seconds only.

 

guess is yours a thames barrier choke and not a  starting valve on the side of the  front carb  ?? 

 

later models had a float height of 16mm but not vitesse  so 18 is correct to the highest point on the float as upside down viewed

 

what air cleaners are you using ??

 

is a air piston spring fitted inside ??

 

is the smiths breather if fitted working OK ??

 

just some  ramblings     

Pete

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I've had all this! But all fixed now (Thanks Pete!) Some one has already said it but are your floats the right way up?

 

Do they actually float?

 

Are they moving freely on the spindles? (I had one pop off on one side.)

 

You've had it on the bench gravity fed so it's not the pump.

 

If the float chamber was air tight you wouldn't get any fuel in there. I'd try taking off the sump and use your finger while gravity feeding, you'll make a mess but then you'll know!

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