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Post by 71coupe on Sept 27, 2014 16:51:10 GMT
Hi folks,
Whilst having making a 'to do' list of stuff that needs work under the bonnet, I found the end of what seems to be a fuel (?) pipe that had been tucked neatly out the way by a previous owner.
Its a rubber coated pipe with a thread at the end. The end was tucked under the brake fluid reservoir. I traced the pipe back over the arch of the bulkhead and back via the n/s of the underside. Presumably it heads into the petrol tank from here?
I was wondering if this is a left over form the now removed AED fitment? The car runs ok without it but, I would feel happier knowing what it was and why its been disconnected.
Another possibility is that it maybe linked to the fuel reserve but, I seem to recall that is in the centre of the car.
Being a masochist I am considering replacing the AED at some point in the future!! In the meantime will I need to blank
the end of the this pipe for safety reasons or is gravity doing the job for me? It hasn't shown any sign of leaking that I can see.
Thanks in advance for your help.
Andy
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Post by Simon H on Sept 27, 2014 16:57:56 GMT
The only pipe I can think of that gets close to that description is the fuel return pipe. Maybe a previous owner fitted a new return pipe for some reason and tucked the old one out of the way rather than remove it.
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Post by 71coupe on Sept 27, 2014 17:17:34 GMT
The only pipe I can think of that gets close to that description is the fuel return pipe. Maybe a previous owner fitted a new return pipe for some reason and tucked the old one out of the way rather than remove it. Wow, that was quick, thanks Simon! That makes sense the car now has HIF6 carbs instead of the standard HS6 . I'm not sure that a replacement spill return has been rigged up though. I might investigate further tomorrow. Andy |
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Post by Deleted on Sept 27, 2014 17:27:43 GMT
Mine too has HiF6 carbs and a mystery pipe underneath the bonnet that used to be the fuel return pipe.I believe the original function was to combat fuel vaporisation (I had an old V4 Corsair with the same set up).
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Post by 71coupe on Sept 27, 2014 17:33:43 GMT
Mine too has HiF6 carbs and a mystery pipe underneath the bonnet that used to be the fuel return pipe.I believe the original function was to combat fuel vaporisation (I had an old V4 Corsair with the same set up). I believe HIF6's were standard on P6Bs as were the single choke setup. I much prefer the separate float chamber on the HS6. much easier to prime the carb if you needed to. Andy |
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Post by Simon H on Sept 27, 2014 21:26:53 GMT
Mine too has HiF6 carbs and a mystery pipe underneath the bonnet that used to be the fuel return pipe.I believe the original function was to combat fuel vaporisation (I had an old V4 Corsair with the same set up). The HiF6 carbs must have better float chamber needle valves than the HS6s. If the return pipe is blocked the HS6s dump fuel out of the overflows at an alarming rate. |
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Post by richardlamsdale on Dec 5, 2014 21:20:14 GMT
My car still has HS6 carburetters and the fuel return. There's a brass screw-valve in the return pipe, just after the rhs carb fuel bowl, presumably to 'turn-off' the return pipe. I just wondered if the valve is standard and why you'd want to turn-off the fuel return?
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Post by Phil Nottingham on Dec 5, 2014 22:33:00 GMT
Not standard and spill return should be present and working with or without AED. The inlet to the return should be much restricted though
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Post by barryr on Dec 6, 2014 0:08:41 GMT
Plus it's dead handy having the return when you inevitably end up fitting an electric fuel pump!
I resisted doing that for so long and I've no idea why. Now I turn on the ignition, hear the pump prime up the carbs and bang it starts with no cranking. I can hear the return trickle back in the tank.
Haven't even had to fit my electronic ignition yet either!
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Post by johnwp5bcoupe on Dec 6, 2014 8:31:52 GMT
I wouldn't run the HS6's without the spill return especially if you have an electric pump fitted unless you like the risk of flooded carbs  |
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Post by johnwp5bcoupe on Dec 7, 2014 9:15:30 GMT
Plus it's dead handy having the return when you inevitably end up fitting an electric fuel pump! I resisted doing that for so long and I've no idea why. Now I turn on the ignition, hear the pump prime up the carbs and bang it starts with no cranking. I can hear the return trickle back in the tank. Haven't even had to fit my electronic ignition yet either! Just to confirm, I meant my car didn't have a valve but certainly has the spill return pipe in situ. In some defence of the mechanical pump, the increased cranking time allows some oil to circulate before the engine fires. If I haven't used the car for a while it takes some to to prime up and start but the oil light has gone out by the time it does! My normal way of starting after a lay up is to remove the 12v feed from the electric pump and crank until I have oil pressure. |
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Post by Deleted on Dec 9, 2014 10:56:54 GMT
My Rover also has the pipe for the return blanked off,possibly when its been converted toi the later carbs. I think I might rig up a T junction in the line to the carbs and re-instate it.
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Post by richardlamsdale on Dec 23, 2014 20:05:30 GMT
Here's the mystery fuel tap in the return from the rhs carburetter on my car, as mentioned above. Someone has gone to great lengths to fit this, as it looks standard, but I can't think why someone would have bothered. When I bought the car it was closed, even though the car has an electric fuel pump, but it's been open for a few months now and there doesn't seem to be any problems - I did think maybe it was closed due to problems with the fuel return, but that doesn't seem to be the case.  FullSizeRender by Rover_P5B_Coupe, on Flickr |
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kaiser
Rover Fanatic
worth his V8 in gold!
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Post by kaiser on Dec 23, 2014 20:38:25 GMT
Here's the mystery fuel tap in the return from the rhs carburetter on my car, as mentioned above. Someone has gone to great lengths to fit this, as it looks standard, but I can't think why someone would have bothered. When I bought the car it was closed, even though the car has an electric fuel pump, but it's been open for a few months now and there doesn't seem to be any problems - I did think maybe it was closed due to problems with the fuel return, but that doesn't seem to be the case. FullSizeRender by Rover_P5B_Coupe, on Flickr This to me looks like the overflow. If the float or the needle does not work correctly, the fuel will overflow and it is usually directed into a small pipe and dumped. It looks as if the previous owner has tried to stop this by installing this valve. It makes no sense to me, as the same effect could have been obtained by simply blocking the overflow. It does not work, however, because if the petrol is not at the desired level, it will run into the inlet manifold, and if you have an electric pump, it can fill a cylinder completely preventing the engine from turning over on the starter, and or diluting the engine oil. I can see no good reason for this addition. But I might be wrong.  |
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Post by enigmas on Dec 23, 2014 22:10:51 GMT
Here's another take on the device. Hopefully it's not the fuel bowl overflow as it makes no sense and is illogical from a mechanical/operational viewpoint. If the line returns to the tank then it could function as an anti-percolation device. During hot weather and or high under bonnet temperatures the fuel can percolate and gas in the float bowl causing erratic fuel bowl levels and engine operation. By allowing a return bypass (small return bleed) to the tank the fuel is kept cooler in the bowl and any vaporised fuel is also exited to the tank. Why anyone would including a valve is a moot point as it could be left open all year round. A better solution is to solder the end of a return line shut and then drill a small hole (1/16") through the solder plug...this is now becomes a metered bleed return.
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Post by Steve P5b on Dec 23, 2014 22:51:47 GMT
Here's the mystery fuel tap in the return from the rhs carburetter on my car, as mentioned above. Someone has gone to great lengths to fit this, as it looks standard, but I can't think why someone would have bothered. When I bought the car it was closed, even though the car has an electric fuel pump, but it's been open for a few months now and there doesn't seem to be any problems - I did think maybe it was closed due to problems with the fuel return, but that doesn't seem to be the case. FullSizeRender by Rover_P5B_Coupe, on Flickr This to me looks like the overflow. If the float or the needle does not work correctly, the fuel will overflow and it is usually directed into a small pipe and dumped. It looks as if the previous owner has tried to stop this by installing this valve. It makes no sense to me, as the same effect could have been obtained by simply blocking the overflow. It does not work, however, because if the petrol is not at the desired level, it will run into the inlet manifold, and if you have an electric pump, it can fill a cylinder completely preventing the engine from turning over on the starter, and or diluting the engine oil. I can see no good reason for this addition. But I might be wrong. Without knowing which electrical pump is fitted, I'd say it's a cheap pressure regulating bodge Richard, leave the valve open until you can fit an adjustable pressure regulating valve or the correct mechanical pump. |
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Post by johnwp5bcoupe on Dec 24, 2014 7:20:50 GMT
Like Steve I think it looks like an attempt to regulate the fuel pressure? he may have had shut off valve probs? and this was his solution?
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Post by Deleted on Dec 24, 2014 11:18:15 GMT
If it on the overflow side surely the whole point of an overflow is to allow excess fuel to escape unhindered?. In the event of the needle valve sticking open or being held open by muck,with nowhere to escape (the screw down valve closed) it will flood the carb abd try and fill the manifold and cylinders.It might have made more sense if the valve was on the fuel in side where it could function as an anti theft device although it would probably be more of a nuisance value that a serious security device.
Incidentally,when I had to leave my P5b on a public car park for days at a time I used to swap the rotor arm with an old one where the inner notch had broken and the arm fitted in just about any position making the timing way off. Trying to start the engine resulted in all sorts of bangs and noises and would delay at least any potential joy rider.
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Post by richardlamsdale on Dec 24, 2014 19:57:28 GMT
The tap is in the return side, after the right-hand-side carburettor fuel bowl, so is in completely the wrong place to regulate fuel pressure to the carbs, as has been mentioned. The pipe then goes back around the rear of the engine and seems to return to the fuel tank, as far as I can tell. The car is fitted with a Facet electric fuel pump on the nearside of the engine bay.
It's fascinating how old cars accumulate these 'fixes' over time. I'm all for going back to originality, but I think it will be a slow process with this car!
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Post by johnwp5bcoupe on Dec 24, 2014 20:49:00 GMT
The tap is in the return side, after the right-hand-side carburettor fuel bowl, so is in completely the wrong place to regulate fuel pressure to the carbs, as has been mentioned. The pipe then goes back around the rear of the engine and seems to return to the fuel tank, as far as I can tell. The car is fitted with a Facet electric fuel pump on the nearside of the engine bay. It's fascinating how old cars accumulate these 'fixes' over time. I'm all for going back to originality, but I think it will be a slow process with this car! Yes we realise the tap is in the return we were trying to guess why the only thing was to limit the flow of fuel in the correct place nope  |
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