Project Rusty Triumphs in Scotland - To gas or not to gas(less MIG) - 09/11/24

[N Dentressangle]

Do you have a waxstat in the Dolomite carb? Google will tell you what that is better than I can.

 

It's an utter cunt when they age, and produces symptoms similar to what you have. Costs exactly 2p to sort out...

[SiC]

I don't think SUs had anything as advanced as that? At most the HIFs had a bimetallic strip. But I don't think this is a HIF carb - I'd have to go back on the thread to find pics of the carbs. HS carbs have an external fuel float chamber. The HIF is on the bottom.

 

Are you sure there are no vacuum leaks? When you said the intake brake servo vacuum feed wobbled about in the intake, I guess it's not in a way unmetered air could get in?

[Noel Tidybeard]

the pipe to the servo looks absolute shit- if it aint vacuum tight car will run like a bag-o-shite and jubilee clips are well known for their ability to not be round when tightened- best way to give youself an airleak on a diseasel fuel line!

[lanciamatt]

I'm sure on one of your videos that it only fires when you release the key. I'm sure these had a 9v coil and a balast resistor for starting, with the wire from starter to coil for extra voltage for starting. Why don't you let it tick over on a quiet street until it gets hot and plays up. Then remove one of HT leads and put a spare spark plug in it and turn engine over. At least you will know whether you have a spark problem or fuel

[N Dentressangle]

I don't think SUs had anything as advanced as that? At most the HIFs had a bimetallic strip. But I don't think this is a HIF carb - I'd have to go back on the thread to find pics of the carbs. HS carbs have an external fuel float chamber. The HIF is on the bottom.

 

Are you sure there are no vacuum leaks? When you said the intake brake servo vacuum feed wobbled about in the intake, I guess it's not in a way unmetered air could get in?

 

They do - Triumph fitted them to the twin SU's on the the Dolomite 1500 (DAMHIK) and they're a total PITA when they inevitably play up.

 

Vacuum leaks would be the easy place to start though, I agree.

[SiC]

They do - Triumph fitted them to the twin SU's on the the Dolomite 1500 (DAMHIK) and they're a total PITA when they inevitably play up.

 

Vacuum leaks would be the easy place to start though, I agree.

TIL that. Not helped by that I was confusing myself on/misunderstanding what a waxstat on a carb is.

[SiC]

One other thing, I guess the earth between the engine block and body is good? Could be frayed/damaged/broken and its primarily earthing through the throttle & choke cables.

[Guest Hooli]

They do - Triumph fitted them to the twin SU's on the the Dolomite 1500 (DAMHIK) and they're a total PITA when they inevitably play up.

 

Vacuum leaks would be the easy place to start though, I agree.

 

I seem to recall them on my 1500 Midget too.

[captain_70s]

Right, research and tinkering.

 

Firstly I leaned off the mixture again as it was pissing un-burnt petrol out of the exhaust even with the choke off, I hoping it is now somewhere in the right ballpark as it isn't doing that but still pulls well. When starting it I flooded the bloody thing and nearly melted the starter solenoid...

 

Secondly the carb is a SU HS4 "FZX 1269" - This is a waxstat carb. This is now the main suspect as it is supposed to lean off the mixture when the engine gets hot. Given I set the mixture t'other day when the car was at operating temp and then when I went to run it today it was running way too rich when cool(ish) I think it could very well be acting up. I shall replace it with some pennies, removing it certainly shouldn't make things any worse... (famous last words)

 

I fear I may also having been chasing an un-achievable idle speed. I connected up a digital tacho I found in my big box of car related shit and it suggests the car, as set by ear, is idling at around 600-650rpm. Looking at the official workshop manual suggests that 750-800rpm is more correct. I fear I am spoiled by moderns/1950s cars with their silky smooth and quiet idle speeds...

 

I replaced all the oversized jubilee clips for ones of the correct diameter. I also cut the hose for the brake servo shorter and positioned the clip closer to the flange (heh) for a better seal.

 

The pipe for the brake servo wiggles about a lot but moving it doesn't seem to affect running unless you pull it right out of the inlet manifold (something I don't recommend you do). It seems the hole in the inlet manifold has gone oval (just like every other fitting on this car which should be round). I tried to seal it up by wrapping the end of the pipe in tape to widen it a fraction but there is no extra room in the hole to accommodate it along two sides of the pipe. 

 

I also checked the spark with the spark plug tester when the engine was hot and found it to be fine.

[Squire_Dawson]

The Waxstat carbs are good when they work. But everything has to be properly set up which can take days. My Allegro has one, gives nearly 48 mpg on the motorway.

[Guest Hooli]

Don't fiddle to long with a wax stat carb as it'll get too warm sat idling. Then it adjusts itself and you'll be going around in circles.

[captain_70s]

Aye, it mentions that in the book.

 

Issue being the car only gets properly hot while sat in traffic, even sat at 70mph on the motorway or climbing stupid inclines in the Cairngorms it sits at around the 1/3rd mark on the gauge. When I tinkering with it the bonnet is up and once again it won't get hot!

[Guest Hooli]

What stat is in it? My Midget (triumph engine) was like that with the original 74^oC stat. I put a winter stat (82^oC) in & it stat just under half all the time. Made the heater a lot better too.

[N Dentressangle]

OK, I think I'd remove the waxstat to take it out of the equation. Instructions here:

 

http://www.dunlopclassics.co.uk/waxstats.htm

 

As Squire Dawson says, a nice idea, but after 30 years probably long past its best, and can really bugger up any other adjustments you make.

[captain_70s]

I pulled the carb off the Doloshite today. The undersides were properly dirty, coated in oil and dirt. The entire engine bay is like this and really needs a good clean to make working on the car less unpleasant.

 

I attacked all the external surfaces with engine degreaser, a product that is definitely entirely suitable for use in one's living room*. 

 

 

I then found some coins to replace the waxstat, period correct of course.

 

 

It is now all ready to go back on the car, I'll apply a little bit of 3-in-1 oil to the moving parts and re-fill the dash pot before reassembly. This will at least rule out the waxstat as the cause of the hot running issues.

 

 

Hopefully that'll be done tomorrow morning, I'll also pull the 'stat and see which one is fitted. 

 

It was nice to have a car related task which could be done inside and off the street. A bit of a shame I've not got the money for a full carb rebuild kit while it's here but hey-ho.

[SiC]

How much play do you have on that butterfly valve? I believe they can be a known weak point of letting too much air through.

[captain_70s]

Very little to none, all the movements on of the carb which are visible without dismantling it are actually very nice.

[N Dentressangle]

Looking good, and a neat job of the Waxstat replacement. SU's are such basic, simple things, a good clean is often all they need.

 

A decent rebuild kit is quite pricey, if I remember, so a better secondhand one is a more economical replacement.

 

You'll definitely need to adjust the mixture now the waxstat's done - the jet will be sitting in a different place - but very easily done by ear. Plenty of info on the net, but if you just unscrew the big brass nut on the bottom until the engine runs sweetly, then screw it in again until the engine stutters, then back off a little until you have a smooth idle, you'll be about right.

[alf892]

Have you checked the piston moves freely?

[Richard]

3-in-1 oil is, or used to be, vegetable based and prone to leaving a ring of jelly on dashpots.

[captain_70s]

Carb is now fitted to the car, piston moves fine.

 

Naturally the stupid little thing that holds the choke cable to the carb has gone AWOL (again) so I'm back to wedging the choke on with a screwdriver but the car is back to a functional state. I re-adjusted the mixture and idle speed and it now seems to sit happily at 700rpm when warm, although by the time I was finished putting it back together it was dark and cold this this could well change. Really it's a job best done in daylight...

 

 

Due to this I also never managed to check which stat is fitted, given how cold the thing runs I can only assume it's got a 74 degree example.

I filled the dashpot with 3-in-1 but the throttle response is shit so I'm going to drain it and fill it back up with 20w50...

I'm also going to JB Weld the vac pipe for the brake servo to the intake manifold as I see no real reason why I'd ever need to remove it...

 

I may take it to work tomorrow if I can be arsed/it starts without too much of a fight.

[captain_70s]

I'll go down to the collection office to get some parcels before work, said I.

 

 

Result, one utterly dead Dolomite abandoned 2 miles from home, me just back in the door 10 mins after I was supposed to arrive at work.

 

Fucking shitbox, no amount of tinkering would get it going after it conked out. Full report when I finish work...

[Captain Furious]

Do not like - candidate for the ungrateful cars which repay your kindness by immediately stabbing you thread.

 

Looking forward to the write-up though.

[SiC]

Unlike.

 

Could you not do a quick Uber back home? That's my get of jail card for around Bristol with the missus.

 

Did you have the test light and spark tester with you?

Reckons the problem is getting worse?

[captain_70s]

Did get the spark tester on it, got a video I'll post later.

 

It didn't look great though, inconsistent flashing and it seemed to be flashing more than once per revolution. I was rushing though as late for work, it'll need a more detailed look.

 

By the time I abandoned the car I'd already told work I'd be late, so an Uber wouldn't really help.

[lanciamatt]

Is this car still on points and condenser?

[N Dentressangle]

That's irritating.

 

It does sound ignition related. I'd be checking all the wires were properly attached, and that side of things was working first.

[SiC]

Is this car still on points and condenser?

It's on electronic ignition iirc.

[lanciamatt]

If I lived up that neck of the woods I'd go round and help, it can't be owt major, they are so simple. I'd carry a can of brake cleaner too and if it does brake down, spray it in air filter and see if it trys to go then you know if fuel related

[captain_70s]

Is this car still on points and condenser?

At this point I wish it was!

 

Electronic ignition, pulled all the wires, cleaned contacts, reconnected, nothing.

 

Pulled HT leads, reconnected. Nothing.

 

Pulled plugs, wire brushed, replaced. Nothing.

 

Swapped the coil. Nothing.

 

Richened the mixture. Nothing.

 

 

The ever charitable Mr Fowler of this parish has offered assistance in recovering the car tomorrow.