Hi Ade,

And thanks for keeping it going, as well as finding time for an upgrade, from me too.

There's no particular board I would ditch, even tho' I'm electrically / electronically inept I like to look at the more techie stuff, I actually thought arduino was next to Tuscany at one time, amazing what one can pick up on here.....

I'd say a bigger font, me minces ain't all they used to be, but I've also learned how to sort that out with two fingers on the touch screen of me Chromebook!

keep it up, please.

Cheers
Stef

My only real bug bear is the colour scheme.
It's the same all over the damned internet. Fer chrissakes, it's a screen, not a piece of paper, it shouldn't have a light background.
I currently run a browser extension to deal to this, but always prefer that sites do it. So yeah... if you can enable "theming" in the forum software... and pick a dark one or three.

I access the forums by "show unread" so the boards/sub forums don't really matter to me. All seems good.

I am not sure but I think that that area is sealed by the close interferrance fit of a precision ground shaft in a bore. I think from memory that you have a manual on these pumps. That should tell you if there is a seal in that area, if not the shaft at least is badly worn or the bore it runs in or both.
I thought after you rebuilt the pumps you tested them to see if they worked by connecting the fuel line at least to them and see the fuel dribble out the top of the fuel line. I went one step further and connected the injector to the lines and watched the fuel atomise. If all you did was run fuel to the pumps and fuel came out it was just gravity flowing the fuel.
Might be worth replacing that pump or talking to a diesel repair shop to see what if anything can be done with that one. Is the other pump working properly after testing with a fuel line and injector hooked up so you can see it work?

Hi MikeNash.  I'll try to answer your questions first.
"The SSR you sent the link to is, I presume, normally closed and the thermostat (eBay UK item number:394041622609) closes at the set temperature thus disconnecting the supply."

No, all the higher voltage DC SSR's I've seen are normally open. You need a thermostat which opens on high temperature, closes on cold.  Just as a standard water heater thermostat does.  Of course with some simple electronics we can change a thermostat output to NO or NC (normally open or closed if you must, but keeping things simple is nice.

"My three heating element ports are 2 at the top, one at the bottom, is there such a thing as a SSR that, instead of switching the power off, diverts it? That would allow the upper element to raise the temperature of the top third and then use the lower one as a 'dump' for the rest of the day?"

This is easy if you have a standard electric water heater thermostat which already has just such an dual temperature element diversion from upper to lower elements (at least here in the US). You'll have to add a second SSR, one for each element, and use the water heater thermostat to just switch the  12V to the SSR control.  Replacement thermostats of any rating will be fine, since you will only be swiching about 6 ma of 12V via the contacts. 

Again, many ways to do this electronically, like a couple thermisters, a zener reference and a single quad op amp plus "glue" (resistors and capacitors) but I'm trying to avoid custom electronics.  If you can't find what you need, I can help with plan B.

Veggie,
It is wise to oversize the ampacity of a DC SSR and there is no penalty for doing so.  The higher rated once will have lower on resistance, and thus for small currents will not need much heat sinking, if any.  I agree that some skepticism in the rated ampacity should be applied, as they are made of Chinesium and specification were written by the marketing department.  I have used them well under the rating and they do seem to work and hold up fine.

Bruce,

I have several of those DC-DC relays ranging from 25 to 100 amps.
I have been reluctant to use them in any critical service because they only cost $12 
What do you think about grossly over sizing them?
For example, if there is a solar panel supply which max's out at 25 amps, then use the 100 amp SSR for switching the element load off when target temperature is achieved.
Do you think this would give the inexpensive SSR a fighting chance at staying alive more than a few months.
(I would also recommend to everyone to use the appropriate heat sink)