GT6 Mk3

[euan douglas]

Hopefully someone can help me in my ignorance!  What type of Stromberg CD150s are on my GT6? They have the temperature compensators on the side but I'm not sure if they are CDS, CDSE or what!  Also is it normal to have the choke on only the front carb?  Have had the car for years but would like to be educated further.

Thanks

Euan

[Paul H]

1 minute ago, euan douglas said:

Hopefully someone can help me in my ignorance!  What type of Stromberg CD150s are on my GT6? They have the temperature compensators on the side but I'm not sure if they are CDS, CDSE or what!  Also is it normal to have the choke on only the front carb?  Have had the car for years but would like to be educated further.

Thanks

Euan

look like CDSE’s which have temp compensators which should be screwed down and choke on the front carb . 
Paul 

[Pete Lewis]

yes temp compensators go off should not be open at normal temps and are best closed off completely if the small plunger is open you have air bleed past the throttles at normal temperatures and you cant set the mixture 

remove the two screws  lift the assy out then take the plastic cover off    screw the small nut to fully close the plastic plunger 

remove the air piston and with allen key adjust to get the small delrin washer on the needle top to be level with the air piston  is the basic mixture setting 

if the diaphragm is all baggy   wash it in petrol to return it to size

Pete.

 

[chrishawley]

14 hours ago, Paul H said:

What type of Stromberg CD150s are on my GT6

I'll comment cautiously since I'm not 100% sure of the details off the top of my head and happy to be corrected by other members if need be.

If the carbs have managed to retain their original brass identification plates (small squares attached under one of the four screws of the top cover) then that can provide identification: 3092 would be CD150, 3507 would be 150CDSEV. Some numbers for CDSE are 3432, 3426, 3335, 3384, 3369, 3172. However, the brass tabs may be missing or sometimes incorrect if they've been jumbled up when previous repairs were made. So not 100%, but a clue.

150CD are distinguished by - hexagonal brass adjuster for jet under the float chamber and 'Thames Barrier' type choke (cold start) mechanism acting on both carbs by lifting pistons.

CDS/CD2S - in the most these retain the hexagonal brass adjuster, have the external disc-type choke on the front unit (only)  but do not have the tempature compensators.

CDSE/CDSEV: Hex adjuster not present, just a plastic blanking plug in bottom of float chamber, have the external disc-type choke on the front unit (only) and mixture adjustment is from above using a special tool. Temperature compensators present on both front and rear units.

I think that the CDSEV had an additional valve relieving the float chamber but since I've never owned any 'SEVs I can't back that up with direct experience.

I suppose it's possible (???) that a GT6 could acquire 150CD3 carbs transplanted from another vehicle but I've no direct experience of that either.

Maybe worth reffering to

to see if that corroborates what I've said above.

 

 

[Nigel Clark]

You should have a pair of Stromberg !50 CDSE carbs on a Mk3 GT6.

Nigel

[dougbgt6]

Hi Euan,

Long time no speak!

If your car is a 72 it should have CDSE, but as said anything may have been replaced. Temperature compensators are best left alone, once opened up and tinkered with they are buggerd and the best you can then do is close them right off. You can take the whole unit off and replace the washers underneath and put them back. I've done this and no further problems.

However, can I ask why your asking? Is there a problem?

Doug

[euan douglas]

Thanks Paul, Pete, Chris and Nigel.  I'm now confident I have the right set-up on the car and all is as it is supposed to be.

Doug:

Thanks for your input also.  Yes there is a problem, basically the car will no longer start!  I had it in the garage getting some rot removed and a bit of a re-spray, so far so good.  Went to collect the car, started fine from cold with the choke and drove home.  The car went very well but the next day was difficult to start from cold and now won't start at all.

I have checked there is a good spark and that petrol (new fuel- I keep it well supplied) is flowing freely into the carbs.  Checked this by removing the float bowls and seeing the fuel coming out of the needle valves.

What appears to not be happening is that when the choke is pulled fully out the piston on the front carb does not lift at all so effectively the car is trying to start with no choke - well actually it doesn't even try to start, turns over well but doesn't fire at all.  I think that the choke is not moving the cam lever enough to move the air valve lifting pin and the piston.

I can't understand how this could suddenly happen having worked fine for years, never had any trouble with cold starting up till now.  I guess I should be able to see the front piston lifted when I pull the choke out?

I've been back in touch with my friendly mechanic and he'll look at it in a few days but in the meantime I'm trying to figure out if there is anything I can do.  Nothing appears to be loose or have moved, I wondering if moving the outer cable in its clip is the way forward?

All thoughts very gratefully received!

Euan

[Pete Lewis]

on cds/e  operating the choke does not have any effect on the air piston ( that only gets raised on the early CD (thames barrier device.

do you have the smiths emmision valve     is yes does the diaphragm fit/not failed ???

when you pull the choke you will only see the throttles fast idle cam open the throttles a bit 

check the coil 12 v polarity  the neg should go to the dizzy  the pos to the ign feed 

lift the dizzy cap is the centre brush intact  etc

peter

[chrishawley]

A couple of thoughts of a 'first aid' nature.

• With air filters removed crank engine and observe for fuel swimming about in throat of carb(s) or leaking from face of carb. If so, implies needle valves failing to close.

• Breather as mentioned above by PL. Or, if you have breathers directly from rocker cover to carbs then inspect closely for splits which may be be obvious on casual observation.

• With choke knob pulled well out crank engine and observe for droplets of fuel passing from the cold start mechanism (front carb) to the rear carb down the transparent transfer pipe. If transparent pipe has been replaced with opaque rubber then do the same but promptly remopve the pipe and see if moist with petrol inside. If no transfer of fuel then implies failed cold start unit. Usually repairable but don't disassemble unless replacement gaskets are to hand.

• . Remove dampers. Lift air pistons with finger. Confirm free movement upward and when released a free fall with a definite 'dunkk' as it hits the bridge. Replace dampers confirming that there is sufficient oil.

• Blank off the air feeds to temperature compensators (upper right hole on face of carbs). Masking tape will do. If then starts implies markedly deteriorated TCs.

• If you want to go a bit further then remove the dash pot covers (4 set screws). Then lift out the piston to which the rubber diaphragm is attached. ***But note precisely the orientation of the assembly - it has to go back exactly where it came out**). Hole units up to light an observe for decay or holes in the rubber.

And for your situation it's perfectly reasonable to try starting the engine after a liberal dose of EasyStart (halfords have it) directly into the carbs. Not a fix of course but can get a non-movable car at least...err...moving.

Obviously a comprehensive diagnostic is more involved than the above but maybe a 'first aid' step will be informative.

Here's hopin' it's simple!

 

[Pete Lewis]

if you are on points and condenser its worth getting anew condenser from the distributor doctor

have the points closed up ???

there are some really poor condensers on sale    have a read of this 

Delco condenser: RD7774, CD369, 829111,829107,1861709,1866049,18655972, 1869704,1882239, Lucas Condenser 484249, 400308, 407044, 54411935 / DCB105, 54413006, 23D4 22D 23D DM2 25D DM6 DM4 lucas distributor, Lucas condenser number 423871, GDC101. Condensor 405833 for Ford 8 and Ford 10, Lucas condensers from Distributor Doctor

[euan douglas]

Hi Pete and Chris

Thanks for the advice.

Car is using Accuspark ignition and I have a good spark so presume all is well there. It has been fitted for a couple of years and having been running well so I am assuming the ignition side of things is OK.

No don't have the emission valve. Now that I understand better how the choke works maybe I'll have a look at some of the things Chris mentioned.  I'll keep fiddling about and see what I can do.  The only other thing that is different is that the garage had the tank out to do the bodywork but it was running fine even after that, no slivers in the fuel feed and the carb bowls are filling well.  Any chance of the choke plate being bunged up I wonder?  What is the purpose of the balance pipe between front and rear carbs and should I see fuel transfer (as Chris suggested)?

Chris;  where and what is the cold start unit?  Is this the disc with the 4 holes in it to give extra fuel when choke pulled out?  Sorry for all the daft questions but all help greatly appreciated.

As I said my mechanic will get here to have a look but before that I want to be as clued up as possible.

Euan

[dougbgt6]

28 minutes ago, euan douglas said:

What is the purpose of the balance pipe between front and rear carbs and should I see fuel transfer (as Chris suggested)?

There is only one choke mechanism, it's on the rear carb and connects to the front carb via the tube. So with the choke on you should see some fuel transfer.

But even if the choke was only working on one carb I would expect the engine to try 

Doug

[Paul H]

52 minutes ago, dougbgt6 said:

There is only one choke mechanism, it's on the rear carb and connects to the front carb via the tube. So with the choke on you should see some fuel transfer.

But even if the choke was only working on one carb I would expect the engine to try 

Doug

The choke on my CDSE’s is on the front carb . Is this wrong ? 
Paul 

[euan douglas]

On mine too Paul.

Euan

[Pete Lewis]

starting valve   Yes,  it allows enrichment via a rotating disc which has a number of metering holes 

called a start valve   as it does not restrict the airflow as that would as the word says makes a choke 

a early base CD has a device like the thames barier this does block the air flow so thats a Choke 

most dowdrafts like hearalds have a choking flap but some early solex have a starting valve 

and they make a destinct noise   ford 100E comes to mind  and many others of the era

if that helps ???? 

Pete

[Peter Truman]

4 hours ago, Paul H said:

The choke on my CDSE’s is on the front carb . Is this wrong ? 
Paul 

On my 68 Mk2 Vitesse too, & as I've owned her since 1970 I assume it's original!

See attached re Choke Cable Set Up I never knew about the 5/16in drill spacing, and my choke was a bugg*r to set up either on or off so I set it up using the 5/16in drill as spacer and the choke is now great with progressive operation, if I remember it was PeteL who posted this snippet of knowledge.

[chrishawley]

Really just to confirm the above responses.

The cold start device is on the front carb as per image attached.

 

The little transfer pipe allows a splodge of extra fuel to get to the rear carb when the cold start unit is 'open'. Engine may start if only the front carb is getting enrichment but might be lumpy/bothered 'till warm.

I've not myself experienced a cold start valve becoming blocked but I have had them leak like crazy because of detritus getting between the disc surfaces and causing scoring. So I can picture that such detritus could lead to blockage.

Still thinking in 'first aid' mode a can of Carb Cleaner (any motor factor) might be useful. A forcible squirt back up the cold start device through it's outlet tube might just dislodge any sediment. That's hardly scientific (apols) but it can't do any harm.

You mentioned that fuel delivery seems good but it's still worth checking the y-pipe that conducts fuel from the inlet on the front carb to the inlet on the rear. If never been cleaned it can be pretty chocker with gunge. 

 

[dougbgt6]

Depends what you mean by front!
neaest the bulkhead or nearest the radiator? 😆

Have a look, you will find it and decide, is it on the front or the back!

db

 

[Stratton Jimmer]

My choke is on the front carb CDSE with front being nearest the radiator.

[dougbgt6]

OK I admit to being Left handed and dyslexic. My carbs are as in the picture above.  But in a left to right sense the choke is on the one on the right which is behind the one on the left or to put it another way at the back of the one on the left. 

Doug

[Pete Lewis]

glad thats sorted  Ha !

Pete

[euan douglas]

Still fiddling about trying to get it to start but no luck yet.  Will keep at it and let you know how I get on.

Purely as a matter of interest - what is the identification number for the late MK3 car?  Looking at the Burlen/Zenith site and others only serves to confuse.  From what I can see they could be 3432F and R or 3369F and R or 3507F and R.  So assuming they are original which should they be and are there any real differences between them?

Thanks again for answering somewhat fundamental questions!

Euan

 

[dougbgt6]

Euan,

I've still got the original carb tag, I'll have a look tomorrow, when it's not so cold in the garage. Difference I guess is what we've talked about already, the one and only choke mechanism!

Doug

[euan douglas]

Thanks Doug.  Yes, I don't know where all the mild weather is that they keep talking about - it's baltic up here!

Euan

[euan douglas]

Car now starting and running fine.  What was the problem - just a big split in one of the carb breather pipes, so new pipe fitted and now starting fine.  It just goes to show you should look for the simple things first but as we're human the most unlikely is the first port of call!  At least I now know a lot more about Strombergs!

Thanks to all for their advice.

Euan