I have just bought myself an electric fuel pressure gauge with a sender that has a 1/8-27 NPT thread. However it only screws two and a half turns into the connectors which I have. I thought my connectors were 1/8 NPT but on measuring they have 28 TPI.
Does this mean the various tails and two way/three way connectors I have are some other standard. Any ideas please.

If it's 28tpi and tapered, it's probably 1/8" BSPT.

I currently have the same problem with fitting a 1/8" BSPT pressure gauge to a 1/8"-27 NPT hole in a Filter King fuel regulator.

You could try talking to someone at Think Auto - they do adaptors for all sorts of stuff...

I'll second that, probably BSP, they are similar but the angle of the thread profile is slightly different and as you mentioned the pitch is is different on 1/8". 1/2" & 3/4" have the same thread pitch but should not be used together because of the thread profile.

See the link: Link

Rats. BSP they must be. I guess I will be fitting it after Stoneleigh. Should get to rummage through the adaptors there and find something suitable. What I would like is a T piece with two BSP female threads and one NPT.

Try a pneumatics or hydraulics suppliers, they usually have lots of different pipe fittings

thinkauto will have it or make it providing you know what the tweo threads are.

also take a look at VWP - they sell adapters too.

Here's what I bought from my local branch of Pirtek (suppliers of hydraulic hose & fittings) today - the hexagonal thing is internally threaded 1/8" BSP, the adaptor is 1/8" BSP one side and 1/8" NPT the other, and there's a sealing washer to marry the two together.

Should do the job nicely...
Rescued attachment adaptors.JPG