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Metering Unit Fuel Return Pipe Union


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I've noticed when on choke there's a fine squirt of fuel from around the return pipe union on the m/u. It doesn't seem to be there when the choke's fully closed. I bought a replacement pipe and on taking the old one off I noticed the union was a bit "waggly" and on closer inspection isn't sealing properly - I suspect this has been cross-threaded and that's what's now causing me the problem. I'm still going to replace the old pipe anyway but would I be okay using PTFE tape to improve the seal, or should I take the m/u off and get the hole re-threaded?

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11 hours ago, boogie said:

I've noticed when on choke there's a fine squirt of fuel from around the return pipe union on the m/u. It doesn't seem to be there when the choke's fully closed. I bought a replacement pipe and on taking the old one off I noticed the union was a bit "waggly" and on closer inspection isn't sealing properly - I suspect this has been cross-threaded and that's what's now causing me the problem. I'm still going to replace the old pipe anyway but would I be okay using PTFE tape to improve the seal, or should I take the m/u off and get the hole re-threaded?

Hi Boogie

This can be a bit of a tricky one? I assume that you are talking about the straight adaptor that screws into the flange on the M/U as the thread that screws into the flange is UNF and on the other end it is a male gas pipe thread. The replacement ones that Rimmer & Moss are selling are not well threaded and look second hand to me? As I did buy one! But PTFE tape may cure your problem. My original M/U had a hard red fibre washer to seal the flange which I found unobtainable from the usual suspects and also from a local pipe fitting stockist.

Bruce

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9 hours ago, astontr6 said:

I assume that you are talking about the straight adaptor that screws into the flange on the M/U

Thanks Bruce, and spot-on with the adaptor/union on the m/u flange. I've tried PTFE tape but it just tears up and doesn't stay in place. I've added a bit of thread-lock and will see how this goes

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I could do with a replacement union too, the flats are badly rounded off and re the fibre washer, that's passed it's best too, a copper washer replacement might be the way to go.

Thanks Bruce for the heads-up on the replacement unions being below par. If anyone knows who supplies decent unions, please let us know.

Richard.

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15 hours ago, Richard71 said:

I could do with a replacement union too, the flats are badly rounded off and re the fibre washer, that's passed it's best too, a copper washer replacement might be the way to go.

Thanks Bruce for the heads-up on the replacement unions being below par. If anyone knows who supplies decent unions, please let us know.

Richard.

Hi Richard,

The killer is that gas pipe thread on one end that is what I was told it was by a local hose/fittings stockist! The other end is 1/4" UNF. For me it would have been a simple job to turn up a proper replacement adaptor.

Bruce.

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I'm sure I was told you can convert the screw in type return to a push on type by using a brake bleed nipple of the relevant size....... I just can't find the post the told me what size ! 

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