rough running TR4A.

[RobH]

It is counter-intuitive but there is really no danger from electrics being inside the petrol tank as long as here is liquid petrol in there too.    

I have posted this before:

Liquid petrol itself does not burn so although it sounds completely wrong,  immersing electrics in petrol is really quite safe.  it's the vapour that is flammable but that is only over a very restricted range of fuel/air mixes - 1.4 to 7.6 % petrol to air by volume or thereabouts.  Usually the vapour concentration in the tank is very much greater than that so there is no risk of fire from the sender.  The partial pressure of petrol is about 4.5psi under normal ambient conditions so as long as there is liquid petrol in the tank, as an approximation there will be around 30% vapour by volume which is too rich to burn.

Petrol vapour is heavier than air, so air will not readily enter the tank to dilute the mix even when the cap is off.  (That does mean the risk increases greatly if the tank is completely empty of course as the vapour then becomes more dilute, which is why one should be very wary of repairing tanks using hot methods,  or inserting any potential ignition source into an 'empty' tank . The risk is higher also in vapour displaced from the tank when filling it,  as that may well come within the flammability range when it meets the open air ) 

 

 

Edited March 15 by RobH
typo

[stuart]

12 hours ago, RobH said:

It is counter-intuitive but there is really no danger from electrics being inside the petrol tank as long as here is liquid petrol in there too.    

I have posted this before:

Liquid petrol itself does not burn so although it sounds completely wrong,  immersing electrics in petrol is really quite safe.  it's the vapour that is flammable but that is only over a very restricted range of fuel/air mixes - 1.4 to 7.6 % petrol to air by volume or thereabouts.  Usually the vapour concentration in the tank is very much greater than that so there is no risk of fire from the sender.  The partial pressure of petrol is about 4.5psi under normal ambient conditions so as long as there is liquid petrol in the tank, as an approximation there will be around 30% vapour by volume which is too rich to burn.

Petrol vapour is heavier than air, so air will not readily enter the tank to dilute the mix even when the cap is off.  (That does mean the risk increases greatly if the tank is completely empty of course as the vapour then becomes more dilute, which is why one should be very wary of repairing tanks using hot methods,  or inserting any potential ignition source into an 'empty' tank . The risk is higher also in vapour displaced from the tank when filling it,  as that may well come within the flammability range when it meets the open air ) 

 

 

Which is also how in tank fuel pumps are safe too.

Stuart.

[phil Dean]

I will have a go when the scope turns up.

 

Phil.

[phil Dean]

I've captured the slug although it was still abit of a struggle, see pictures below it looks and feels like some form of seal there is a ridge in it and as a rubbery feel to it. I have had a look as best I can with this scope around the rest of the tank and on the base there are small blisters of rust on the base of the tank but not big amounts.

Anyway see the pics and see if anybody can identify it.

Phil.

[stuart]

16 minutes ago, phil Dean said:

I've captured the slug although it was still abit of a struggle, see pictures below it looks and feels like some form of seal there is a ridge in it and as a rubbery feel to it. I have had a look as best I can with this scope around the rest of the tank and on the base there are small blisters of rust on the base of the tank but not big amounts.

Anyway see the pics and see if anybody can identify it.

Phil.

Possibly remnants of the seal that goes round the filler in the deck?

Stuart.

[brenda]

Could it be an old rubber grommet that goes on the body work for the fuel pipe. (Stuart got in first)

Mike Redrose Group 

[keith1948]

Hi Phil

There is a rubber anti-rattle ring on the fuel level float but that is O-ring shape without a groove. Is it the remains of a seal to the fuel cap? The gasket seal to the sender is flat so wrong shape. I think Stuart and Mike might be right. The seal between the filler neck and the deck although profile not quite as I remember.

Keith

[phil Dean]

Do you mean as arrowed here in yellow not red see both pics.

[brenda]

Possibly started like this and just dropped in at some time.

Mike Redrose Group 

[brenda]

[stuart]

Item 13 here https://www.moss-europe.co.uk/shop-by-model/triumph/tr2-4a/fuel-system-induction-controls/tanks-pumps-pipes/fuel-tank-pipes-pump-tr4-4a-1961-67.html

Deck grommet.

Stuart.

[phil Dean]

If it the same as Mike is showing in the picture above mine is still in place and how can that get into the tank its caught between the rear deck panel and the filler tube that goes into the tank. What ever it is digging thye slug out  it out hasn't solved the intermittent slight hesitancy.  I've just fought my way across town to go and see if I could get a paint match wouldn't you know I just got there and they were closing. crawling traffic both ways for 30 mins each way,and just coming back the last 1/2 mile I could feel it 1500 to 2000 revs starting to feel hesitant in pulling cleanly. Tried Roger's Idea of opening the tank filler cap no hissing noise. The car wasn't getting particularly hot just normal temperature in fact the fan didnt kick in until I stopped on the drive although I suspect it had been coming in then stopping, its set at 65 degrees. I wonder if it could be fuel vaporization !!!!

Phil.

[stuart]

57 minutes ago, phil Dean said:

If it the same as Mike is showing in the picture above mine is still in place and how can that get into the tank its caught between the rear deck panel and the filler tube that goes into the tank. What ever it is digging thye slug out  it out hasn't solved the intermittent slight hesitancy.  I've just fought my way across town to go and see if I could get a paint match wouldn't you know I just got there and they were closing. crawling traffic both ways for 30 mins each way,and just coming back the last 1/2 mile I could feel it 1500 to 2000 revs starting to feel hesitant in pulling cleanly. Tried Roger's Idea of opening the tank filler cap no hissing noise. The car wasn't getting particularly hot just normal temperature in fact the fan didnt kick in until I stopped on the drive although I suspect it had been coming in then stopping, its set at 65 degrees. I wonder if it could be fuel vaporization !!!!

Phil.

It doesnt mean that some DPO hadnt managed to drop one of them in the tank though.

Stuart.

[Charles Green]

Check for sticking valves in your float chambers - had a similar long-standing problem that I think I have just solved by installing new viton tipped needles and seats in the floats. 

[phil Dean]

Thanks Charles. I was at a car club film night last night and somebody else mentioned the same thing in fact I think there was something similar in one of the posts on this forum.

Phil

[keith1948]

21 hours ago, phil Dean said:

Do you mean as arrowed here in yellow not red see both pics.

Hi Phil

Referring to your top photo, the central disc arrowed in yellow should have a 1.5mm hole in it approx 10mm from centre and 20mm from the edge. It looks like a new centre on yours held in place by the R clip. Mine is original held in place by a star lock washer. The hole is there as a breather hole. A 1.5mm hole drilled anywhere on the inner raised part would suffice.

Keith

[John L]

Here's my fuel cap,   |Pictures are always useful.

John

[phil Dean]

Ah Ha now that's interesting Thanks for the Pic John

Phil.

[Andy Moltu]

Originally the fillers had a spire clip, but they can rust and need replacement. I too drilled an fitted a split pin as I wasn’t confident that the available spire clips were up to it and even the same size rather than a “near” metric size.