GT6 Engine Query - Electrical of Fuel Problem

[92/38576]

I am new to this although I have been a member of over 20 years. I have an unmodified GT6 MK3 (owned for over 23 years) which for over a year runs for about 20 minutes on the road and then just stops whatever the weather or time of year. When this happens there is no sign of interest as she turns over on the starter motor. Today in the really hot weather she started first time ( as always) and I left it on tick over and it ran for 35 minutes whilst I sat beside it and listened. Temp gauge fluctuates as the thermostat opens and closes and she is not overheating. It did not misfire but again just stopped. I had a Gunsons Colour tune plug ready and whipped it in to see a nice big fat spark on turning over so my original thoughts on an electrical problem seemed to be wrong. I removed pump to carbs pipe and turned over again and good healthy pumping of fuel. I removed both drain plugs from bottom of carbs and both were full of nice clean fuel so I am at a loss. I know she will start first time when cold later on - any ideas please?

[dougbgt6]

OK we've had a few of these lately! You might like to have a look through the threads. But first of, when it happens, open the fuel cap. Is there a woosh? Does it then start? This would indicate a blocked vent. Another thing I have had is an accumulation of "sludge" in the fuel lines which drift about and suddenly cause a blockage. You stop, the blockage relaxes, and off you go.

 

There is a rubber joint in the fuel line, in the passenger side rear wheel arch, disconnect here, does the fuel gush out, or dribble? I disconnected the fuel level sensor from the top of the tank. You can then see the fuel outlet orifice. I used plastic strimmer cord to dyno-rod the fuel line. Beyond this is the path to the fuel pump where there may be more blockages. Certainly worth putting in a fuel filter if you haven't got one.

[Pete Lewis]

is the coil wired correct polarity ,,  dizzy lead same as battery earth   this gives unexplained  stops and restarts as does any green stuff down the Ht socket.

 

is the fuel cap venting ,  when it stops flip the  cap ,  any air flow into the filler?

 

debris blocking the back of the float needle valves , bits of rubber etc.

 

these are Strombergs carbs  ???

 

check condenser is secure  and the little earth lead on the moving plate, there are poor condensers available , has it been changed recently

 

Pete

[92/38576]

Thanks for the quick replies gents! I did a reply and it has disappeared somehow so this may appear twice but not exactly the same. 

 

Yes they are Strombergs. I get it MOT'd at the local Vauxhall dealer as they have a former Triumph apprentice as one of their senior guys and he has MOT'd it for years. They only charge £30 and I discussed the problem with him and he said he would love to have a go so I thought why not and it behaved itself ( the ony time in over a year of course!) and after an hour he said he could find nothing wrong and commented on how well the carbs were set up etc - he still has the tools. No charge from them for this as they found no fault.

 

I wondered about the tank not venting so my 35 min run today was with the flap open. Also tried different sets of HT leads, condensers, dizzy caps, points but not the coil yet as the only one I have spare is a a 6V with ballast resistor. All wires checked following your posts and are tight and correct polarity.

 

Fuel flow from pump is excellent so I had discounted probs before carbs but will check as you suggest tomorrow - also the carbs. All were serviced by me and new fuel lines throughout as part of a full rebuild about 3 - 4 years ago.

 

Once again many thanks and will advise how I get on tomorrow.

 

Hugh

[92/38576]

Still no wiser having stripped everything down as suggested- fuel good and spark - MOT tomorrow so the test will be whether I get there and back. Thanks again

[Pete Lewis]

Hugh , the problems many get are from disturbing the fuel hoses ,  them little slivers of rubber from inside the hose cause wonderful

problems ... even a few years on.

 

can you borrow a coil ?  to try 

 

Pete

[92/38576]

Thanks Pete. Got to MOT and back which is first time in 3 MOTs. I am sure (as I can be) problem is not electrical as Colourtune always shows big fat spark even when she will not start. I think next step is to purge fuel line and replace rubber hoses in wheel arch and at carbs although all seems to be completely clean.

[Pete Lewis]

the hoses are not that old,  ,but  if they go hard they can seem to have a tight clip but end up sucking air ,  this can end up with you use move than the pump will supply and after some demand its runs out in the carbs and you grind to a halt

 

the only way to check whats going on in the supply to the back fof the float needle valve is to remove it 

 

do you get a fat spark when she's died ??

 

how long do you leave her before restarts are possible     

 

Pete

[92/38576]

Yes I get a good spark even when it has died, hence my thinking it is not electrical. I leave it until it is cold normally because i have had to abandon it somewhere - then it starts immediately. It is one of best starting cars I have had in that it fires first time. Only thing I do if not run for several weeks is tickle the pump but normally I do not need to do that if it is just say a week.

[Pete Lewis]

definitely  has the symptoms of rubber slivers  in the float needle or something in the supply lines , or a floater in the tank

 

Pete

[Nick Jones]

The sudden stop suggests ignition to me.  Fuel starvation usually gives a short period of rough running before it stops completely and will often fire again briefly afterwards.

 

You seem to be saying that you have both fuel delivery and spark present immediately after it stops - which is odd as it's suggests it shouldn't have stopped in the first place  I can't think of a mechanical issue that would cause it to stop - not at least one that would then allow it to fire up again once cooled..  Presumably it's not flooding out (again, generally a period of rough running before it gives up)?

 

You could try squirting some easy-start or carb cleaner into the carbs just after it's failed and see if that allows it to run briefly.  It would prove the ignition side.  Have to say that I'm tending towards ignition - rotor arm (I've had very similar issues with the car dying after about 15 minutes running and stranding me in the same layby several times), distributor cap, coil, condensor/electronic ignition module, possibly ballast resistor or resistor wire.

 

Nick

[Dick Twitchen]

Pete's comment about a floater in the tank was exactly my problem 2 months ago.  Chased through all the other things mentioned, syphoned the fuel from tank and removed sender unit.  Initially could see nothing amiss so went to syphon the last of the fuel and disturbed a piece of what can best be described as a piece of plastic coated price tag about 15mm in diameter that was the same colour as the tank interior.  This was neutrally  buoyant and was being sucked over the outlet pipe, wait a while and it would float away; repeat!

Dick    

[dougbgt6]

Same thing happened to me, mine was a non floating fibre washer.

[92/38576]

Thanks for all the advice - which did not get the problem sorted! I have been using the car without any problems for about 2 years and thought I should advise the problem in case others had similar issues. I swapped distributors after discovering a lot of vertical play in the shaft. This sorted it and then I got the original one rebuilt through the club shop and swapped them back again. I can only think that it was settling when cold and allowed the car to start and run perfecty and then by some quirk always moved when it was switched off, left for about 1/2 an hour and restarted. The shaft then dropped down and lost conact with the distributor cap. I wasn't clear exactly how this was happening and have left it for quite some time to make sure fault has not reappeared - it hasn't.