Sensitive SU’s Healey 3000

[goodwoodweirdo]

Hi guys need a little advise on a friends big Healey... when cold she’s tough to start, the engine catches first time and will only run on idle the moment you touch the gas or choke she stalls. If I can keep her running for 30 / 45 seconds then she’s warm enough to give gas .... when warm she’ll restart and run fantastically...

I believe she’s fitted with HS4’s and the car had a full service and carb sync a year ago...

I’ve added oil in the dash pots but don’t want to over fill..

Any ideas .....

Thanks Matt

[jellison]

Are Hs4's std on that and how many? 2 or 3?

Seems on the small side I'd have tought 3x HS6's would be more in keeping with the size of the lump.

[goodwoodweirdo]

just the two...

once running she runs fine...

[chrisr29]

Is there any choke mechanism on those carbs? Sounds like it's lacking in cold start enrichment, the fuel will stick to the inside of the manifold untill it's warmed up, where upon it all gets digested by the engine in the correct manor.

[jellison]

Not sure then.

Hard one as one warm the issue in not there.

Either way pop triple 45 webbers on it

[theadman]

Depending on model of 3000, carbs ex factory were as follows:

Mk1 (BT7, BN7) 2xHD6 Engine type 29D
Mk2 (BT7, BN7) 3xHS4 Engine type 29E
Mk2 (BJ7) 2xHS6 Engine type 29F
Mk3 (BJ8) 2xHD8 Engine type 29K

It might be worth checking the engine type against the carbs as there have been many engine swaps over the years. I'm not sure how sensitive the engines are to having the correct carbs and how easy it might be to solve the problem by re-jetting what you have on the car currently.

Hope this provides some help, if not the solution.

[dmulally]

I dont think it will matter which SU's are on it as they are very versatile IME. I would start with the basics first which would be choke, fuel filter, fuel lines then fuel pump. All are pretty easy to check.

After that I would take off the carbies for a field strip. My old Imp had twin SU's and a similar problem. When I pulled them apart the sludge I found was alarming seeing as I had just put in a brand new fuel tank and lines.

If doing all that doesnt sort things out perhaps look at ignition timing. (I have no idea about Healeys, sorry!)

Good luck.

[dmulally]

The more I think about it the more I think it is fuel starvation.

[guru_1071]

i would take the dash pots of and check to see that the jets are both level in the carb bodies, if not adjust them up to the top and back them off four or so flats (so you know the mixture is a little rich and equal)

then pull the choke on and off and look to see if the choke tubes are returning to a level place (you will see them down the middle of the jet tubes) - sometimes the chokes will stick, or even be different lengths.

once you are happy that all thats right, refit the pistons and warm the car up, you will then be able to balance the carbs and adjust the mixture, make sure that you turn the jets one flat and equal across the pair of carbs.

i think your problem is in the sticky choke, mixture area - my mini has just done a similar thing!

[healeyfan]

It might just be that you are not pulling the choke control out far enough. The extra few millimetres makes all the difference if the car hasn't been used for awhile or the weather is cold. You can usually tell as they will start on 3/4 cylinders and gradually the rest will join in. When it's warm weather they're usually fine. Wait a few months before taking more drastic action. However it's not a bad idea to warm the engine up first before driving off. The pleasure of not having fuel injection and an electronic brain but all part of the classic car experience.

[goodwoodweirdo]

I get the car back at the weekend, needs a better look.... two pumps on the gas and she'll run its just a balancing act to keep her ticking over... pull out the choke she'll cut out and wont start ... so its as if the choke is making the mixture to rich...

cheers M

[Hooli]

No idea if your SUs can suffer it, but my old Midget managed to rattle the jets out the bottom of the carbs so only the linkage to the throttle held them up. Took a while for me to notice as you can't see underneath with them fitted.

[aw51 121565]

goodwoodweirdo said:

I get the car back at the weekend, needs a better look.... two pumps on the gas and she'll run its just a balancing act to keep her ticking over... pull out the choke she'll cut out and wont start ... so its as if the choke is making the mixture to rich...

cheers M

When you pull the choke out, does the engine speed increase?

When set up properly, pulling the choke 'out' just a little (1/4 travel, maybe?) should cause the engine to reach its "fast idle speed" then pulling the choke 'out' further (as one would from stone cold) should then cause mixture enrichment but allow the engine to idle at or near its "fast idle speed" and not stall.