Still overflowing from the carbs, at a loss now, run out of ideas

[Moraystag]

Following on from my previous post started on Sunday.

My replacement needle valve arrived from Paddocks today, took a while what with the Monday holiday, but glad to see it arrive.

Fitted new valve, checked the float heights, reasembled, and fitted to the manifold. Primed the pump, and left it for a while, no overflow, looking good I thought to myself. Fired the beast up, still looking dry. Ran it up to temperature, keeping the revs at about 2000 to 2500, still looking good, and at this point I was pretty optimistic. Dropped the revs and she's ticking over at 650-700 revs, temperature normal.
Damn and blast, they started to overflow again.
Went through the exact same again, strip down check needle valve, back together and fitted to the manifold.
Same process again as above, and still they start to overflow when idling at normal temp. Pretty much at a loss what else I can do now.
I fitted a new fuel pump at the weekend and that's the only thing that I have done apart from continually removing needle valve, refitting, set float heights with little or no improvement. Valve looks good.
Anyone any idea what else I can try, as I had a 110 mile run organised for Saturday, but looks like I'm goosed now for this one.
Any help would be greatfully accepted.

Mike

[AlanD]

it sounds like you have too much pressure at the pump Mike, have you checked it, if everything is fine in the carbs and set how it should be i cant think of anything else, someone else will come along i'm sure with a good cure, i'm proberbly way out

[Moraystag]

Alan, I'm wondering if it's the pump as well, but I have no idea if you can screw the pump pressure down a bit???

Mike

[AlanD]

i'm not sure myself Mike, i know some pumps that were offered in the past were not as they should have been, what i'm thinking is, constant pressure, ie the more you rev the more it would use so no overflow, but on tickover with the same pressure it would cause it to overflow.
i'm sure the pressure is set, no adjustment, i think the pressure should be no more than 6psi, Russ will know the ins and outs on the pressures

sorry i cant help more

[Firept]

Mike.
Fit a Malpassi (http://www.officinamalpassi.it/ ) filter king or similar and adjust the pressure to suit. (ebay-280730323345 )
I did this as the pressure was a bit on the high side so adjusted it down and all is fine.
If you need to borrow a pressure gauge send me a PM dont but one.

Paul.

[Moraystag]

The Malpassi looks good. Would you fit this under the bonnet or at the pump.
The funny thing is that my carbs only overflow on the right hand / drivers side, but I would have thought that both would leak if the pump is overpressurising??,

Mike

[Firept]

Mike.
Not got the manual to hand but I think it should be 2.5psi at the carbs. I fitted mine in the engine bay mounting off of the wiper motor platform.
The pressure from the pump before adjusting was about 5psi but this is from memory.
On the filter king there is a take off point that you connect the pressure gauge to, then run the engine and adjust the pressure to suit.

Paul.

[Staggard]

Hi Mike, I've had this when the fuel has NOT actually leaked past the needle itself but past the thread and the fiber/ally washer. So to check it I turned the carb upside down with the bowl off put a piece of pipe in place of the fuel pipe with just the weight of the floats blow down the pipe and apply some soapy water around the needle valve and look for bubbles to where its leaking past. Cheers Graham

[martin]

Hi Mike, I've fitted a FilterKing, get the V8 one, with a place to screw in the gauge, and get the gauge as well, about £15. My electronic pump was putting out about 4 psi, I've knocked it back to 2 1/2. It seems like a lot of expense, but you will never have to worry about pressure again, even if you have to replace the pump in the future. Replacement filters are about £5 but as they're so large they last well. It's also a big advantage to be able to see if any gunge is settling in the glass bowl. Martin.

[Marco Polo]

Hi Mike,
Have you checked the floats aren't perforated? If they sink the valve will never close fully.
regards,
Raoul

[elvimto]

Mike,
pump pressure should be 2.7 psi, I fitted a fuel pressure regulator that has a port for a gauge and set it. i hope you can find the problem.

cheers Stuart

[Moraystag]

Am going into the nearest town this morning to se if I can get a fuel pressure regulator quickly to get me on the road for the weekend, failing that, I'll have to get one over the net. The ones suggested by he other guys looks to be ok.
Is there anything I can do to reduce the pressure temporarily. However the pressure is the only thing that I have'nt tried, but not sure if the fault does'nt lye with the carbs. Only problem is I can't keep stripping them down the way I am, because it does'nt seem to be getting me anywhere.

Mike

[Moraystag]

Yes Raoul checked them yesterday and they seemed ok. I would have thought that they would be full of fuel if they ae bust???

Mike

Hi Mike,
Have you checked the floats aren't perforated? If they sink the valve will never close fully.
regards,
Raoul

[milothedog]

Mike,

Try letting the car pump some fuel (from the carb connection) in to a glass container. Then let it settle and see what you have ! even though you fuel filter might be new small particals can come through (see Stagdads previous thread) it only takes the smallest bit of debris to stop a needle valve sealing.

Ian.

[Moraystag]

Well guys managed to buy a fuel pressure regulator locally, fitted it and believe it or not the carbs continued to overflow again on the right hand carb. Removed and rechecked float height and needle valve for the 6th time. This time I set the float height at about 18mm, fitted back into the car and bingo, no overflow.
Yipee, unfortunately my happiness was short lived, as the left hand started to overflow at idle.
So off they came again, checked needle valve, and set float height at 18mm on the left side.
All fitted back again, and reduced the regulator pressure to 2 psi.
Fired the beast up and let it run for some 20 minutes at idle, and believe it or not, I may have cracked it, but I still have to go for a decent run.
Tomorrow will tell as I have a 100 mile round trip to Inverness, this will be the do or die test.
If these b****y carbs overflow again, they will have to go back to where they came from, as I can do no more with them.
Fingers crossed, but I will not hold my breath.

Mike