Strombergs - May need help?

[Ian F]

As one or two of you already know, I had troubles with my Stag on Sunday en route to Prescott. Symptoms were an initial misfire/hesitation which I then tried to clear by pulling the choke out, dipping the clutch and revving the engine.

This appeared to make matters worse, a petrol smell and a total misfire, feeling like 6 cylinders and not 8. Got to Prescott and with the help of John (KOY), Bob H and JPyke we checked the plugs and found No 2 loose (and wet/sooty) and 3, 5 & 8 (I think) sooty and wet. Bob tried to "flush" any dirt through by using the Inertia switch but the car still would not behave and eventually got home on half power - missed my hill runs entirely.

Ordered new needle valves/diaphragms etc. from LD, plus a new set of HT leads as a precaution. However now I have removed the carbs and started to strip them in readiness, but I cannot see anything amiss. Needle valves seem OK, floats OK and no major dirt/sediment. Have tried two more carb tops/diaphragms before stripping - no different. So I am now wondering if it is a carb? What else would affect 4 cylinders?

Can anyone explain what the Cold start enrichment device does? Could this cause it and how do I tell? How do I dismantle it to check and will I need to replace anything when I rebuild? Have Haynes manual but its not too detailed for that?

I don't want to take the Weber route (yet) as the car has been fine for the past 3 years, turned in close to 30 mpg on a run (MOD with 3.45 diff) so nothing major can be wrong? Any ideas/tips?

Ian F

[flying farmer]

These are the exact same symptoms I had on my stag powered estate, sometimes it was ok sometimes awful, when it was bad I needed to get above 60mph to make it run properly, I assume at this speed the float chamber needle valves were leaking more slowly than the fuel requirement for the engine.Changing the needle valves cured the problem, though I also changed the main jet and needle assembly as my fuel consumption figures never got past 23mpg. I could not see anything wrong with the needle valves either, but the important bit is inside (the needle and seat) and can't be got at
Neil

[martin]

Hi Ian, I agree with Neil, it's almost certainly those damned needle valves, you can't tell by looking what their like. The minutest bit of dirt and they pack up, over-filling the float chambers and each carb flooding 4 cylinders. While she's doing it, pull the overflow pipe off both carbs and see if petrol's coming out of either. Martin.

[John Wright]

The Strombergs are good carbs and are easily refurbished and set up if you have access to the information. Look at other recent posts and these will direct you to sources of information.

Your problem may not be the carbs and so it would be a good idea to look at the distributor. Points, rotor, cap, vacuum advance, mechanical advance, and timing. HT leads and coil also. If you don't have it, electronic ignition is an excellent option and can make more difference than carb replacement.

I have just refurbished my carbs and my old problems (similar to yours, but not so bad) have gone away.

John

[Bazstag]

I have now fitted those Moss Grose Jets and all is working fine, no smell of petrol/ no lumpy running when stood in traffic queues and most of all no hot starting problems. Time will till how long they last tho.
Baz

[Ian F]

All

Thanks for the tips, I am a little more re-assured now. New Diaphragms, needle valves, leads all ordered so will fit them along with new plugs and hope she's back to the rudest of health.

Have a wedding to go to Saturday and ESM at end of month so she'll need to be.

John - she has got Lumenition but suspicion that it's a carb is now re-inforced.

Thanks again - will post when I've tried it.

Ian F

[DJT]

Ian,
Almost the exact symptoms mine had recently. At first I thought it was fuel starvation, so changed the fuel pump. No joy, so changed the fuel filter. Still no joy, so changed the coil (getting desperate!). Eventually deduced it was not starvation, but flooding on one side - smell of petrol. Fitted new float valves (old ones only in for 3 years ) and re-set the float heights - they were a bit low at 15mm. Now 17mm. Problem has now gone away.

[Klaus Schlueter]

Hi Ian
I am a little late with an answer but I was out in the alps.

You mentioned your findings at Prescot: cyl. no 2,3,5 and 8. They are all linked to the same (LH) carb as the pic shows (sorry for the German text).
Misfiring indicates (to my knowledge) that there is unburned fuel in the exhaust. But why? If it is not the carb could it be that the ignition system has a fault e.g. fuel is drawn from the carb to the mentioned cylinders and flows via the exhaust valves into the exhaust and is partly burned there? I had once to renew the optical switch of the Luminition to solve the misfiring/hesitation problem. The German Luminition rep. also recommended to check the (red?) Luminition plug next to the distributor as it tends to corrode - giving ignition faults.

Abb. 10.jpg

You asked for a dicription of the function of the choke valve. Try www.buckeyetriumphs.org/technical/Carb part II. There you will find a good explanation.

Klaus

[Ian F]

All

Replying to my own thread - is that like talking to yourself??

Late Friday put carbs back on, new plugs, new leads (even if I did have 2 x No 6 leads and no No4!) and tried her before putting the air cleaner etc. back together - Cured!!!!!!! Finished off putting the air cleaner on and re-connecting chokes etc. and took her out for a blast - all seemed OK.

Left it until Saturday morning to check again, all appears to be back to normal so took the car to Stoke to a relatives wedding, 120 miles, a night-out in the cold and wet (yes it was and very wet) and she started first time and behaved impeccably. Ragley next weekend (more confidence mileage) and then the ESM the week after. Thanks to all for their help, tips and to Peter at LD for a prompt response and his advise as well.

Ian F

[KOY 23]

Great news Ian. Shame you missed Prescott but just as well you've sorted it before the ESM.

[Klaus Schlueter]

Hi Ian

and what is your verdict about the reason after all that? Carburettor(s), new plugs, new leads? Would be interesting to know the reason for your desaster!

Klaus