GT6 Starting issues, or ist it just me?

[Ian Cooper]

Hi again.

My GT6 Mk2 restoration is progressing quite well but I have starting issues which are a little infuriating.

Rebuilt engine, rebuilt carbs, electronic ignition.

Sometimes I jump in, turn the key and she fires straight away (no choke, a microscopic amount of throttle).

Sometimes that doesn't work so I give her a small amount of choke and off she roars.

Sometimes neither of those work, full choke doesn't work, but it sounds as if it's interested.

Sometimes a small amount of choke sees her 'catch', rev up and then die, after which she turns into a pig (best then to come back the following day coz she ain't going to go.

My feeling is that it's a temperature thing because she lives in an 'integrated garage which never really gets cold.

I just can never tell which of the above outcomes I'm going to get, so when it fires first pull I think ah sorted then the next time I can end up cranking away with little or no interest.

When she is running she's great, picks up well idles a little rough until fully warm then fine.

If I try to start with lots of throttle, or blipping the pedal, I just get gallons of fuel all over the floor from the air cleaner box.

Any hints clues or even bollockings very welcome, anything that gets me to consistency.

Cheers

Ian

[NonMember]

29 minutes ago, Ian Cooper said:

If I try to start with lots of throttle, or blipping the pedal, I just get gallons of fuel all over the floor from the air cleaner box.

You shouldn't ever get that. Ever.

So first off, please confirm that you're running standard carbs and manifolding, not some wacky triple Webber monstrosity that's miles into the "you're on your own with that, mate" territory.

If you're getting fuel into the air cleaner box then the float chambers are overflowing. This could be that the needle valves are stuck open (gummed? rubber slivers?) or the fuel pump is putting out too much pressure (especially if you've fitted a new one). You need to sort this out and get the float levels right before going any further. Once you've done that, you'll probably have to re-set the mixture to the right place, instead of miles out but compensating for the wrong float level.

[dougbgt6]

Ian,

Yeh, suspect Rob's right, sounds like the dread rubber slivers, It's deja vu all over again, we talked about RS earlier on another thread. It's a very common problem 

I like  "you're on your own with that, mate" territory. Might use that myself 

Doug

[poppyman]

After you have started it Ian, are you taking it out for a run? If not it could be that what is causing the problem.

Tony.

[Ian Cooper]

Hi all thanks for responding.

I can confirm it's a standard carb/inlet setup but a S/S tubular exhaust (not a performance upgrade just std setup).

I haven't taken it for a run as it's not finished, no bonnet, doors, tailgate, interior as yet, but I do run it fully up to temp before shutting down.

Ian

[Pete Lewis]

agree about the fuel but you need to remove the air filters and identify that the fuel is coming from the breather hole in the front face or out  the main carb throat 

rubber  slivers  yes pesky little blighters jam the back of the needle float valves

continual cold starts will never clean  sooty  off the plugs needs a good few hot cruising to burn that back 

if its coming out the throat not the  breather hole let me know

pumping the throttle is a total waste of time .as it has no constructive purpose

at this time of year in a nice garage i would still expect to use choke to fire up . 

remind me does the MK2 have CD with  thames barrier choke or CDS start valve on the front carb ???

Pete

[Ian Cooper]

Hi Pete.

The fuel is coming out of the main carb throat. I hear the rubber slivers debate but thought I'd done as much a I could to avoid fuel contamination, tank has been cleaned and coated inside, all fuel pipes and hoses are brand new and I've fitted an additional fuel filter before the new fuel pump, the carburettors have been cleaned and rebuilt professionally but I suppose it is still possible I have that problem.

I accept I can't fully clean the plugs without a 'good run' but as I say she often starts first or second pull I just can't understand the variation between Good and Abysmal, today she started really well First off but after a couple of hours total no go???? I have the CDS valve on the front carb.

The throttle blipping only kicks in just after I've finished pulling my hair out and I suspect that's the cause of the flooding.

Thanks again Pete.

Ian

[Pete Lewis]

no any flooding from  the throat is either a high fuel level or the O rings and sealing washers of the adjustable jet are at fault 

What air box do you use ( sorry  I should know by now ) 

do make sure the holes on the front face are not covered by any filter element or air box .

if you look down the air piston the two holes in the bottom Must be engine side if the diaphragms are installed correctly 

and take the starter valve off and clean its progression holes and with a flat surface clean the disks with fine oily wet and dry 

add a bulb to make sure when you are cranking the coil is always being fed 12v 

Pete

 

 

[Steve P]

I have been through at least 3 modern pumps,all rubbish,the levers have sharp edges and pressure is too high,that`s why i went electric.

Steve

[Ian Cooper]

Standard airbox and filters, I'm trying to stay as close to original as possible.

[Pete Lewis]

have you rebuilt the carbs , ???

good place for do and donts  with nice photo's is https://www.buckeyetriumphs.org/carburetors

ignor the TR or 175  the basics are all the same for 150

so i guess its double check for rubber slivers in the supply up to the needles , recheck the 18mmm float height,m  do check if the float has two valve arms that it is not upsidedown,  can you get a gauge and test the pump pressure ???

has the jet got decent fitting ) rings and the often lost ally sealing washer 

just some ramblings 

edit   just check the filter elements do have the breather  holes aligned with the filter box and carb face 

ie  its easy to get the box lined up but the filter is upside down ,

any blocking of the breather holes would force excess fuel up the jet orrifice 

Pete

[Ian Cooper]

I haven't rebuilt the carbs they were done by Bill Moore (Solutions Ltd), who was recommended by Bromsgrove Engine Services who rebuilt the engine and they, in turn, feature in a number of Fuzz Townsend's Car SOS.

So I was hoping these were good people to use for the rebuilds, and as I say there are times when the engine is absolute sweetness and light and times when it takes to the Darkside, which is what is so irksome.

I'm loath to carry out a lot of teardown unless I know a definite cause as I know, from when it performs well, it performs really well.

Thanks

Ian