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MG MGA - Fuel sender unit

Hi
I wonder if anyone can help with a couple of questions please. The first for assistance please, the second is really just out of interest
1. I have just ordered a new fuel sender unit from Brown & Gammons that apparently comes with new improved "Peter Edney style" rubber gasket. But I am unsure how this will earth properly if I am using a rubber (or cork for that matter) gasket and sealant on all the screw threads? I guess I should ensure the sealant is only on the screw threads and not around the heads? Or am I missing a trick?

2 On looking at both Barneys site and the archives, it appears I currently have a different type of sender. You will see from the attached photo that it does not have the face plate that all the others all seem to have - Do you think this is a non MGA design?

Many thanks, Graham

Graham V

Your old sender unit is not original for MGA.

Even with rubber gasket and thread sealant, the device will still ground through the screws. If you put nylon washers under the screw heads, then maybe not grounded.

If the steel fuel pipe has been cut an connected with hoses, the tank may not be grounded to the chassis.
Barney Gaylord

Thanks Barney.
Graham V

Graham

You may have problems with the screws Peter Edney provides. They seem marginally thicker, and are longer, than other ones. I have just fitted the new superb US Moss tank which will definetly not take them although you could just get them to go in my old worn tank. I have gone back to the Moss screws but they are too short to cope with the thicker Edney tank so I have gone back to the Moss cork gasket and all seems fine.

Paul
Paul Dean

Thanks Paul. I have ordered it from Brown and Gammons with the screws they recommend. So I will see.
Thanks for telling me, it's good to know to look out for that.
Graham V

I fitted my new Moss tank with the Peter Edney seal and screws. Worked absolutely fine. No problems.

Steve
Steve Gyles

Thanks Steve - Good to know. I will test it all out before I get it messy with sealant. I'm planning on using Hylomar Blue. Have used it before with success.
I was also planning on putting a ring terminal on one of the screws as per my existing setup, to be sure I get a decent earth as dont have steel fuel pipes. Make sense?
Thanks, Graham
Graham V

Graeme

What are your pipes made of then?

Steve
Steve Gyles

Steve
I've got flexible fuel lines - you can just see it in the photo I posted above
Graham V

Graham

In that case I guess it does make sense as Barney has already indicated. I was surprised with Paul's problems with the screws. I checked them out on the original and new tank. I found they screwed up ok with both.

As Paul mentions, the new Moss tank is an excellent bit of kit.

Steve
Steve Gyles

A couple more points. Comparing the Moss and Peter Edney screws they are definitely different threads. I used the normal tests of putting them side by side and seeing if the threads mesh, they don't. Visually the PE ones are also a larger diameter, difficult to measure without a micrometer but visually it looks like about 0.5 mm. Clearly with some tanks including the one I have just scrapped, a Moss one from 20 years ago, both screws will work as the thread on the tank is quite short hence giving you the flexibility. Steve it is interesting that your PE ones work with the new Moss tank as my PE screws actually don't even get the through the hole in the tank leading to the thread. I have also dug out an old rusty tank in my garage loft that is almost certainly an MG original and with that I can certainly engage the start of the thread with both screws but while the Moss one goes in, albeit tight, the PE won't go in. Of course I must speak to PE but it might be late next week as I am about to go on hols. Steve of course it is possible that PE have changed the screws they are shipping, are your Moss and PE screws visibly different as above?

Different point. Graham I haven't used any sealant and so far fine. If you are going to use sealant use the minimum you can get away with. Personally I wouldn't put sealant on either type of seal but if any threads leak, when fitted with nylon washers, I would apply a touch and only to the ones that leak. By the way the reason I am wary about sealant is the tank I have just scrapped didn't have a perfectly flat surface for the sender unit hence I had to use sealant to have any chance of sealing it and one time the excess got in the tank and kept blocking the fuel pick pipe! Clearly this tank should have gone straight back to Moss all those years ago.But their current offering really is excellent and in the documentation with it accepts that there were problems with some of their older designs..

Paul

Paul Dean

Paul

Very odd. It was July last year he supplied them. I initially used them on my old tank, then transferred to my new Moss tank; all without any issues. I didn't really think about it at the time as it all screwed in and sealed quite satisfactory. I believe the old tank was original (looked pretty decrepit and well dented). I discarded it and the fittings so I cannot now make any comparisons.

Steve

Steve Gyles

Some years ago now someone, and I can't remember who, started a thread asking what was the thread of the sender-tank screws.

At the time I had two tanks out of my car, the original and a replacement, so I checked the old slotted hexagon head screws and they fit perfectly well into the new tank . I replied saying they were definitely UNF and I think I said they were no. 8. I can't be sure because I can't find the thread in the archives.

Someone else replied later saying they were equally sure they were 3BA.

In my 1600 SPL the screw number is ARG923 and it states that it replaces an earlier screw with number ACB5468. There is no mention of a changeover date.

Could it be that the earlier screws were 3BA and they were replaced later with 8-36 UNF?

The two screws BA and UNF have respective diameters of 4.10mm and 4.17mm with 34.8 and 36 tpi. With this difference of tpi the wrong screw would bind after a turn or two.

My car is July 1960. Perhaps the changeover was with the 1600 introduction.

But against this whole supposition is the fact that Todd Clarke only supplies one type of sender-tank screw irrespective of year of car........................Mike
m.j. moore

Mike

I think the thread you referred to was from 2012 and titled "fuel tank sending unit screw thread?"

Steve
Steve Gyles

Paul
Not sure if you are recommending I use nylon washers? There are no washers on my current set up (altho its not a standard sender unit), and I cant see any in the parts diagram.
After all my care, the sender unit arrived today from B & G but it had the cork gasket. I called and they have happily agreed to send me the rubber one. It seems they stock both under the same parts number.
Graham V

Yes I would use nylon washers.

It is interesting what Mike says about screw diameter. I have measured my Moss ones and my PE ones albeit crudely probably only to nearest quarter MM but the difference is very clear. The Moss ones are 4mm and the PE ones are 5 MM so no wonder I have a problem.

Paul
Paul Dean

Yes that's the one Steve; such an obvious thread title!

The working of this forum is definitely the best of any forum I've been on but even so I think it would benefit from the use of key words because I often can't find old threads in the archives................Mike
m.j. moore

I have now emailed Peter Edney about their 'large' seal screws so I will update the list in due course.

I agree with Mike about key words. Also long running threads often wander well away from the thread title hence you can remember a discussion but you can't find it as it is in a thread that is about something completely different! We could sort this one by starting new threads when the subject 'wanders.

Paul
Paul Dean

I guess we are all guilty of wandering off topic. Even on this thread we have started on search engines! For Mike's interest I searched Fuel sender threads 3 BA. Include all words.

Steve
Steve Gyles

Just in case it is of assistance to anyone, and also for the archives, I finally got around to fit the sender unit today.
To recap, it came from B & G and included a rubber gasket, although the coil section's gasket was cork.
The rubber gasket looked well made; nice and thick with ribs around the edge on both sides, and ribs around each screw hole. The screw holes were snug, such that the screws would not fit the gasket holes without screwing with a screwdriver.
Based on Paul's advise, I put no sealant on the rubber gasket, but I did use a tiny amount of Hylomar Blue on the cork one.
The screws fitted without problem, and as the rubber gasket was nice and chunky, it squashed up nicely as the screws were tightened, so although my tank is in quite good condition, if it were not, I think it would have sealed well on any imperfections on the surface.
And so far no leaks.
What a pleasure to see the guage working again!:)
Thanks for all the helpful input, as always such a great forum.
Graham V

This thread was discussed between 16/04/2016 and 03/05/2016

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