Petrol starvation, or not petrol starvation that is the question

[Pete Lewis]

The other clue could be when stopped the heat soak raises the fuel ratio and its too rich to restart 

Have you tried leaning it off as a test

Pete

[Chris A]

56 minutes ago, Pete Lewis said:

The other clue could be when stopped the heat soak raises the fuel ratio and its too rich to restart 

Have you tried leaning it off as a test

Pete

After a day just thinking about it plus all the suggestions and help from here I am beginning to think that for some reason after stoping he car petrol and or valour is causing a very rich mixture hat evaporates after a while and then he car will restart and run ok.

I will be going along this route tomorow I hope, I have some free time in between meetings about our club event coming up on the 23rd.

 

[Pete Lewis]

Over many years I have always found the idea of vapoirising to be an excuse that is caused by other problems 

Pete

[NonMember]

Well, after a good heat soak both the pump and the carb get well hot. The heat in the pump tries to push fuel into the float chamber. Meanwhile, the heat in the carb evaporates what's there already, some of which gets into the inlet manifold. You then have a way-too-rich vapour waiting to be sucked into the engine, where it won't fire.

However, this normally only means you get a long cranking time waiting for the fresh air to arrive.

[Chris A]

Hi Nonmember

I like your reasoning. I'm not a tech nerd so can't either support nor contradict you, but my version of logic would say it sounds very plausible. However, Wouldn't repeated cranking just make it worse?

When I have tried to restart the motor I haven't cranked it too much due to thinking all I would do is add more petrol to an already oversupplied engine. Your view would also confirm what I have started to think is that the rich mixture if left a while dissipates, evaporates, gets sucked back out, or whatever and the engine is 'clear' to start as usual.

My first plan of attack is going to be along the lines of this rather than any electrical problem.

Thanks for the contribution

 

[dougbgt6]

I've had something like it. Started the car with the engine running on full choke. Ran for a couple of minutes then stalled and no amount of churning, choke in or out, could restart it. Left it 10 minutes and all OK. Basically flooding. But how you've got your engine to that point is the question, my engine was cold yours is hot. Whatever, time to adjust the mixture, do you have a Colour Tune?

Doug

[Chris A]

I have just received a Colour tune, ordered it before this problem came up.

I have tried weakening the mixture, before the colour tune arrived, but then had a real problem resetting tick over - had to turn the ajusting screw virtually fully in.

Tomorrow I will again go through the motions and try the colour tune as well. Fingers crossed.

I am also beginning to wonder if something in the carb has given up the ghost, not knowing carbs I need to dig into the manuals . . .

[Chris A]

Progress report: I used my new colour tune and it confirmed the mixture is rich, however turning the mixture screw several complete turns didn't alter the flame colour at all, or at least not noticeably. The booket puts this down to wear on needle/jet.

So, time for me to read up on the carb, I've never done anything to it other than top up the damper oil. If any of you have guidance I would be very grateful for it.

Will a well placed whack with a hammer help? Or do I have to stick my fingers down its throat? Maybe, heaven help me, take it apart and do sometghing and/or replace needle/jet. 

I suppose the problem has been there for a while and gradually getting worse until it reached 'critical mass' proportions.

Right, now where are my workshop manuals and my glasses....

[Pete Lewis]

there are a number of manuals you can read up on the basics 

Burlen fuel sysytems  have a section to down load  and places like buckeye triumphs have excellent pictorials 

http://zenithcarb.co.uk/zencdcdsseries/?SID=vhs8cq91rak06p3fbobshcenf5&___store=zenith

http://www.buckeyetriumphs.org/?page_id=347    mostly TR based but the basics are all very relevant 

on a 13/60 i guess you are dealing with a stromberg   CD150  

it most likely has what i call the thames barrier type of choke  , take off the air filter and a part of the throat rolls up to lift the piston and close the airway  

make sure this rolls back to completely flat when the choke is pushed home  .....does it return ok  ???

see if there is any amounts of resisual fuel in the carb throat ?

remove the dashpot damper  and lift the air piston. let it drop it should drop and give a light clunk as it bottoms .  ...does it ??

make sure the air filter has not been rotated and the element is covering the holes in the mounting face 

the filter has holes to match they must align fully , easy to have one upside down  ???

let us know and come back for more simple clues 

Pete

 

 

 

 

 

[Chris A]

Hi Pete, yes it is the Stromberg standard item and filter.

I'm a bit confused about your comments regarding the air filter. I did change it AFTER the problem started in case it was blocked. It is the GF1015 type.

Thanks for the tips I'll not be able to try them out until maybe Friday. Have to go for lunch today at my local bistro then take SWMBO to collect some 'stuff'. Tomorrow is shopping for us in the morning then shopping & ordering for the club event in the afternoon. Hard life being retired!

 

Edited September 12, 2018 by Chris A

[Chris A]

Hi Pete, yes it is the Stromberg standard item and filter.

I'm a bit confused about your comments regarding the air filter. I did change it AFTER the problem started in case it wa

  

Thanks for the tips I'll not be able to try them out until maybe Friday. Have to go for lunch today at my local bistro then take SWMBO to collect some 'stuff'. Tomorrow is shopping for us in the morning then shopping & ordering for the club event in the afternoon. Hard life being retired!

Edited September 12, 2018 by Chris A
Human typing error

[poppyman]

I know what you mean..... Yawnnnnnn. What to do next... mow lawn or go out for a drive?  I think i know...

Tony.

[Chris A]

35 minutes ago, poppyman said:

I know what you mean..... Yawnnnnnn. What to do next... mow lawn or go out for a drive?  I think i know...

Tony.

Did lawn this morning, so merit lunch as a reward

[Nick Jones]

Re Colourtune:

If you manage to get a truly blue flame at idle, you won't like the way it drives as it'll be too lean everywhere else in the rev/load range.

If you can't get a blue flame at idle even after much winding of the mixture screw then there is a problem (you'd guessed that?), but maybe not the one you were thinking of.  Strombergs have a fixed jet and needle (unlike majority of post 1970 SUs) and wear is therefore extremely slow.  If you pop the top off the carb and have a close look at the needle and jet, wear will show up as rub marks on the jet (esp near the piston end of it) and the jet orifice being visibly oval.  Both of the above point to the jet being improperly centered at some point in the past.  If no signs of contact or ovality then there is a good chance they are fine.

Rich running at idle is often due to the fuel level in the float chamber being too high. This might be just because it's set wrong, because the needle valve doesn't close off properly (if bad the engine will falter and stall due to going really rich after idling for a while), or because you have a repro fuel pump delivering at too high pressure.  Fuel boiling gently in the float chamber might have a similar effect.  All of the above could be related to your hot start problem.

Nick

[Chris A]

Thanks Nick. More pointers to the carb needing a look at.

[Pete Lewis]

Is this a stdn air box and paper element or a pancake ??

What ever the  front face on the carb has round drilled holesn as float breathers and the rectangular for the suction chamber vent

If the  filter is upside down these get covered  and cause lots of nasty problems 

Pete

 

[Chris A]

Pete: standard air box and paper filter. Now I know what those 'spare' holes are for. I'll double check nothing is blocking them.

I've started to read the Buckley Triumph article on the carb and suddenly thought 'clockwise', ok - clockwise when you look down on the carb in place or if the carb was being held upside down with the adjusting nut upmost. I assumed clockwise is based on the carb still mounted to the inlet manifold. 

[daverclasper]

Clockwise looking from the top will richen as your screwing the jet away from the needle

[Pete Lewis]

the jet adjuster is a normal thread , so which ever way you look at it screw it into the case to  raise the jet and lean of   unscrew it to 

lower the jet and make richer 

the slot in the adjuster  nut is made to take an old penny

to centralise if the piston is reluctant to drop witha clunk undo the big nut above the adjuster  1/2 a turn  drop the air piston fully and tap the jet holder , then nip the nut up

its best to do centralising with the adjuster screwed up till it just contacts the 'held down ' piston then jet and needle are at their  best 

 ' fit'   this obviuosly upsets the mixture setting , so always count the turns so you can revert back from whence it came  if you are unsure 

3 turns down from fully up is a good  starting setting.

have a go you cant blow it up.... !!!!  

[Chris A]

Pete: You saved my brain from blowing up:  'the jet adjuster is a normal thread , so which ever way you look at it screw it into the case to  raise the jet and lean of   unscrew it to lower the jet and make richer ' Clear and simple, just what I needed

The hayes manual I have says'Turning the nut clockwise raises the jet and weakens the mixture' I had simply latched onto 'clockwise = weaker' and with the carb in place and working from above turned it clockwise which of course undoes the unit & hence makes the mixture richer. Obvious really but on a simple first read for an old git . . 

Had I read my Autobook version I would have seen 'Screw the adjusting screw up to weaken the mixture and down to enrich it'. Much clearer for the same old git to understand.

The Buckley site says 'Turning the orifice adjusting screw, when looking on this clockwise decreases the mixture strength; anti-clockwise will enrich.' WHEN LOOKING ON THIS. Ah! that also helps.

I was so brain dead last night I had to go and get a nut and bolt to see which way you turned it to do it up - Don't tell anyone, please, our secret?

So in effect I may well have by error when trying to reset the mixture grossly over enrichened the mixture instead of slightly weakening it.

I'll start from scratch with a basic resetting of the mixture, confirm the airfilter gasket is on correctly and not blocking the vent holes and see what that does.

Hopefully I will be able to give it a go tomorrow.

Thanks to everyone so far, in particular Pete for saving my brain.

I'll report back after I've had another go - as long as I don't blow it up. 

[Chris A]

Well 
Pete you were right it didn't blow up.

Thanks to all on here I have sorted it. It was simply running far too rich.

My first attempt at weakening the mixture actually made it worse as I misinterpreted the instructions in the manual, well they weren't very precise ( my excuse and I'm sticking to it).

Pete: I followed your tip and left the mixture just on the edge of rich. Basically a blue flame with hints of yellow.

It also helped, again thanks Pete, in having the correct tool for adjusting the mixture screw. I had been using a 10 centimes of a Euro coin. In my old collection of bits I do have a genuine old penny coin, this worked much better.  Car has been taken out for a run to test it all OK.

Beer well earned!

[Pete Lewis]

Very pleased its all come together  and no costs 

Always a bonus ,  so a penny well spent   Ha !!

pete

 

[Chris A]

6 minutes ago, Pete Lewis said:

 

Always a bonus ,  so a penny well spent   Ha !!

pete

 

Not going down this route. 

[Richard C]

I've been struggling with a very similar engine issue for most of this summer - symptoms indicating fuel starvation/vaporisation that disappear when the engine cools - no apparent problem when the engine is allowed to warm with the bonnet up. To cut a long story short, the fuel supply and carb were thoroughly overhauled but the problem persisted, so thoughts turned to ignition. Points and condenser replaced - no difference. Coil replaced - solved! I'd not heard of coils failing in this intermittent temperature related way before, there was no external evidence of it overheating, but it was definitely the culprit.

[Pete Lewis]

Coils will fail like this if polarity is reversed 

Often coil windings are too tightly wound, and heat expands the bobin and makes a wire fracture, it cools and the break can be remade

 might sound odd but its happens