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Hamish

Frustration and joy at Aintree sprint.

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As many of you know I have been chasing an intermittent misfire on my 3a.

being intermittent it’s been a devil to replicate thus find. 

Didn't appear on the dyno before this event so I thought it would be ok. 

The weather forecast was great what could go wrong. 

Watch the video of my runs the  camera ran out of battery for my last and my fastest ever run but you can see the difference

a misfire run was 70-72 seconds

my best run59.98

and no it wasn’t fuel surging away from the tank pick up on the bend

 

 

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Neil it’s Seems to be fuel as it was fixed in the end with blowing the fuel line through back to the tank. 

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Hi Hamish,

What is the status of the tank? has it been coated internally with sealer. It sounds like there are flakes of something moving over the outlet mid corner with fuel as it slops around . I would be tempted to get hold of an endoscope and have a long look at the internal surface for flakes or sludge floating around.

Rgds

Rod

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3 minutes ago, Hamish said:

Neil it’s Seems to be fuel as it was fixed in the end with blowing the fuel line through back to the tank. 

Then you are under pressurized or  the tank is not venting air in. Strange though as all cylinders go of song at the same time 

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All went wrong at the same time and at the same point on the track.

fuel tank half full so not starvation on that bend  

I resorted to a lunch time road run aintree good for the m57 which is why the race numbers taped up  

it was ok on the slow roads but happened on the straight motorway  so not bend related

Pressure good 2. 2lb ( dyno the week before)

tank well vented with both the top pipe vent and an enlarged breather hole in the cap.

suspect a small rubber pipe that joins two rigid sections of the metal fuel line breaking down.

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13 minutes ago, Rodbr said:

Hi Hamish,

What is the status of the tank? has it been coated internally with sealer. It sounds like there are flakes of something moving over the outlet mid corner with fuel as it slops around . I would be tempted to get hold of an endoscope and have a long look at the internal surface for flakes or sludge floating around.

Rgds

Rod

Rod

i have had a good look in the tank. Nice and shiny not coated. 

I have also syphoned it out - like vacc ing it out a few times. 

I suspect a pipe see above

Edited by Hamish

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3 minutes ago, ntc said:

Hamish

I stuck the bose on and still think electrical,good luck in finding it.

Thank you

i need it. Been chasing it for ages. 

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must admit that i am with Neil.

Although as your work on the fuel line seemed to rectify it. So i would run a complete new line even if a temporary one,and certainly double check your venting of the tank.

Do you think you may have moved some electrical wiring when you did your foot pump trick ????

Roy

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Hi Roy

i don’t think I have disturbed any connectors.

i have separately gone through all the lucar connections and crimped them tight.

i have changed to in electronic ignition module (misfire happens with old points and condenser and new points /cond as well as the electronic)

new  ( genuine) plugs, new red rota arm, new coil ( non ballast)

new engine bay fuel pipe, filters changed type filter changed, 2 mechanical fuel pumps, electric fuel pump, carbs and jets cleaned and blown through.

Certainly on the day at aintree it was blowing through the fuel line back to the tank that then allowed the car to run well on more that one full on competitive run.  

Have now taken off the old rubber joining pipe ( looks like it should be a compression fitting !) No. 30 in the pic

and it looks and feels very soft almost jelly like on the inside where it would come into contact with the fuel. It was also very well sealed to the rigid pipe ( had to cut it off) so no air leaks.

replaced temporarily with a modern fuel safe pipe. Whilst I decide on new fuel line ! And type ?

 

60BFAE88-027E-4034-9C76-4D47F97BC895.jpeg

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Hamish,

The blowing back through the fuel line to the tank is exactly the remedy I have had to use on more than one occasion. Last time was 2 weeks ago after refueling - I initially panicked when it cut out as I thought I might have put diesel in.

I have concluded that there must be a random bit of crud sloshing around in the bottom of the tank that covers/blocks the outlet pipe from the tank. - I cannot see anything though.

My solution will be to replace the outlet pipe from the tank with a new one that has a 3/4" of plain pipe before the olive and nut, giving an upstand inside the tank - in fact just like an original fuel tank outlet pipe was made....instead of the rather splendid flexible one I have from a Land Rover that has the olive flush to the end of the pipe.

Will be doing the job once the fuel level has dropped to almost zero.

Cheers

Peter W

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It’s something I have thought about as well (together with a straight through replacement with braid as suggested by Steve small whom helped me at aintree)https://www.motamec.com/info/instructions_AN_JIC_hose_fittings/

but I also thought that there would be merit in multi cross drilling of that short up stand pipe so no one hole could be blocked by random crud ( the unseen crud I tried to remove by syphoning with a hose pipe multiple times. Sort of vacuuming it out.) 

but I hope the issue was the joining pipe.

as per my other post 

what is the thread size on the tank outlet fitting ?

 

Edited by Hamish
Web site

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On 7/8/2019 at 12:35 PM, Hamish said:

It’s something I have thought about as well ( together with a straight through replacement with braid as suggested by Steve small whom helped me at aintree)

but I also thought that there would be merit in multi cross drilling of that short up stand pipe so no one hole could be blocked by random crud ( the unseen crud I tried to remove by syphoning with a hose pipe multiple times. Sort of vacuuming it out.) 

but I hope the issue was the joining pipe.

as per my other post 

what is the thread size on the tank outlet fitting ?

 

I have not checked a fitting but I think it is 1/4 BSP threaded. 

Have now checked the item it is 1/2" unf x 20tpi

Are all your fuel pipes to the pump 5/16" diameter?

Here is the joiner (item 30) stating 1/4 BSP for 5/16" pipe.  https://www.vintagecarparts.co.uk/products/438-equal-ended-union-five-sixteenth

Moss is cheaper for the joiner (060172) https://www.moss-europe.co.uk/union-5-16-060172.html

Good idea on the cross drilling.  I will do that.  I had thought about using a spray gun pick up filter fitted to the pipe upstand inside the tank, but could not be sure it would stay in place. 

Cheers

Peter W

 

Edited by BlueTR3A-5EKT

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Peter

yes all looks older type original style rigid fuel pipe 5/16 

the new engine bay flexible “rubber” pipe is either 5/16 or 8mm bore. 

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In the meantime, any merit in sweeping the bottom of the tank with a magnet in case there is a small bit of crud and it is metallic? Or is that a massive spark risk?

Bizarrely I have a similar problem at present with my central heating system. Random radiators refuse to heat up. When bled, the water is clear but the system magnet has to be cleaned on an almost daily basis of metallic crud from the old radiators. I think I have a crudberger moving around the system which is only gradually being skimmed off!

Miles

Edited by MilesA

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part 30 may well be your answer but if not try a tempory pipe front to rear if you have a connector that fits the tank.

i have just had a new NKG plug fail after 10 mins so dont discount electric

 

ROY

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UPDATE

 

Have now checked the tank pipe union it is 1/2" unf x 20tpi

 

Peter W

 

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4 hours ago, roy53 said:

part 30 may well be your answer but if not try a tempory pipe front to rear if you have a connector that fits the tank.

i have just had a new NKG plug fail after 10 mins so dont discount electric

 

ROY

 

Where did you buy the plugs? Lots of fakes about. 

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9 hours ago, Hamish said:

Hi Roy

i don’t think I have disturbed any connectors.

i have separately gone through all the lucar connections and crimped them tight.

i have changed to in electronic ignition module (misfire happens with old points and condenser and new points /cond as well as the electronic)

new  ( genuine) plugs, new red rota arm, new coil ( non ballast)

new engine bay fuel pipe, filters changed type filter changed, 2 mechanical fuel pumps, electric fuel pump, carbs and jets cleaned and blown through.

Certainly on the day at aintree it was blowing through the fuel line back to the tank that then allowed the car to run well on more that one full on competitive run.  

Have now taken off the old rubber joining pipe ( looks like it should be a compression fitting !) No. 30 in the pic

and it looks and feels very soft almost jelly like on the inside where it would come into contact with the fuel. It was also very well sealed to the rigid pipe ( had to cut it off) so no air leaks.

replaced temporarily with a modern fuel safe pipe. Whilst I decide on new fuel line ! And type ?

 

60BFAE88-027E-4034-9C76-4D47F97BC895.jpeg

 A case of ethanol destroying an old rubber pipe? 

Also part 30 should be readily available at your local plumbers merchant.

Iain

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2 hours ago, iain said:

 

Where did you buy the plugs? Lots of fakes about. 

TR Shop stand at the spares day Stoneliegh  so think they  are real ?

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Great 2nd & 3rd runs, misfire sounds like fuel starvation. What do you rev up to ?

Keith

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2 minutes ago, Long Door said:

Great 2nd & 3rd runs, misfire sounds like fuel starvation. What do you rev up to ?

Keith

Hi Keith. 

In competition I probably touch 5.5k at the short tight tracks like Curborough fig of 8 but not held there.

H

 

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