Starter motor / polarity direction

[npaisnel]

Hi all.
Glad to see forum is still going, been a long time since I looked in.

Have just been given a 1958 Dexta because they ran it out of diesel, filled it up and it would not start agsin…hmm.. think bleeding it was beyond them.
57E 15495

I went to put battery on yesterday and on battery tray was box with new solenoid and clock and new red battery lead to feed solenoid.

Next I look at the earth strap… hmmm that is odd… it is a negative earth strap.. big N on the terminal.


I phoned up the old owner… yes he says, always starts fine, black to earth and red to solenoid. He is commercial buildings electrician so I’d expect him to have noticed.

In the process of writing this, my messenger has just gone ‘ping’ and a mate who I also asked about this, reckons the starters are ‘shunt wound DC’ so no matter which way they are wired… positive or negative earth.. they always spin correct direction.


Is that the case ? Will starter always spin in correct direction regardless of polarity ?
Can’t go and check today as load of other jobs lined up..but this is sitting on my mind.


Yes, it has standard dynamo, not converted to alternator.


The complete wiring loom that comes out the side panel and runs to glow plug, dynamo and starter all look like original…no random wires, no dodgy blue / yellow crimp terminals, all tucked ‘correctly ‘. I have worked on Dextas since before I could walk ! my other 59 Dexta I had my first crash in aged 6, and it was first new tractor grandfather bought, I am now 56, and have seen many of them come and go on the farm. But never before seen one where all the wiring looks totally unmolested…that is apart from this negative earth strap.


Not looked at Dynamo control box yet… I know you can flash them to generate either polarity, but not sure if regulator needs changing to suit negative earth ?


Any one tell me about starter spin direction and the dynamo control box polarity issue ?

[Billy26F5]

The starter isn't shunt wired, unlike the dynamo, which is actually why the regulator works there. It is true however that the field coils are shunt wired in pairs, but then they're in series with the armature. I've read of many swapping the polarity and only needing to polarize the dynamo, so just try it, you can always go back to original. No need to do anything to the regulator, but it might be worth checking if charging is doubtful after polarising the dynamo. Glad to see you back too, a few pics would be nice, Davie has nice wiring too (as do the others). That looks like it's a September 58 or so, so pretty early.
Sandy

[npaisnel]

Hi thanks for the reply

Where did you find the info about the Chassis number showing month of production ..so far I have only seen info relating to which year.


"Shunt wired " was merely the term I was told that starter motors that only one direction are called.

I have a box of about 6 of them from derelict tractors that were dumped on me in various stages of dismantling..so I tested a few..and yes...they do only turn in one direction no matter the polarity.


The old beast needs a lot more work that I first thought.

I was told she was running before they ran out of fuel ..the bleed bolt on the injector pump had not been touched in years..they had obviously not touched it. It also currently has an plastic motorcycle / chainsaw small motor inline plastic fuel filter on the suction side fo the lift pump, not evn held on with jubilee clips, so as you operated the lift pump you could see air coming in the filter!

Mouse had made a nest behind the clock and the one wire was chewed. Also a non standard key switch fitted with all the lighting wires pulled off and taped over.

The wiring down the side to the starter and dynamo was all original..but so brittle a single movement cracked them.

Switch on the starter was frozen and the original solenoid works perfectly ..he supplied a new after market one and a new non original clock. I'll be putting the old solenoid back.

I had hoped to get her running quickly, stick on a new set of Sparex wings and take her to France around Normandy to a friends farm this summer ..a tour of Normandy on a running but un-restored tractor, but the money she will need has killed that idea.

Even with a fresh battery, and a boost starter/charger connected, I can't get her to rotate fast enough to get her bleed let alone running...but I was just using a set of jump leads with one clamped to the earth strap and the other to the starter wire.

Will try proper connections and make a basic start circuit wiring "loom" bypassing all the original wiring and then move on to swapping out starter motors if she still does not spin fast enough just to get her fired up ..check the colour for the smoke and see if hydraulics work. They guy was using it to plant/ re bank and harvest potatoes last year..so not expecting any major dramas...but I was expecting working electrics too!


Another question ..or two ...

I see on line references to 1956 Dextas...in though they started in 1957 ? or was America different ?

Also trying to see if I can get the original wiring diagram for the 5 terminal A+ A F D E dynamo control box. I have the original book but it just shows the D E A F 4 terminal box.
yes there is info showing the difference with the A and A+ regulator adjustment points and its wiring...but just wondered if such a thing as the original Pre 4 terminal wiring diagram existed..not found any on line yet..


OK i have waffled on enough for now.

[npaisnel]

I found a 5 terminal wiring diagram here:
https://www.tractorforum.com/attachment ... pdf.88707/

[Old Hywel]

You don’t need to spin the engine to bleed it. Merely slacken the bleeder on the injection pump and use lift pump till bubbles stop.
I’ve never needed to loosen injector pipe on a Simms pump.

[npaisnel]

I always like to see the diesel squirting from the pipe .. which does require turning it over.
But need to get that sorted first

[npaisnel]

a few pics would be nice,
Sandy

Sandy, since you asked.

Had to borrow a set of wheels as the previous owner wanted the row crops he had on it back. Spaced wide because first job was going to be chop the body work off it..but now just getting it running is the first job. It might just end up I get it running and weld some more bits to hold the wings up. just cant afford all the new parts at the moment. Want to see that the motor and hydraulics work first before spending money on thet inwork,

[Old Hywel]

If air is entering the plastic filter, it suggests a restriction in the tank tap/filter/primer. The tap assembly won’t unscrew without lifting the tank, but any blockage there must be dealt with to ensure a reliable supply of fuel.

[npaisnel]

It seems to be a new tap / primer pump assembly that has been fitted, but the plastic filter did not have any clips holding it.

But yes, I see what you are saying, should be no restriction to fuel being sucked.

Easy to remove the rubber hose from tank to see how much flow.
Tank only has 3 litre of fuel in it, so might just suck it out, blow low pressure air up it to see if I can do a quick clean if needed, just for now.

I’ll sort the starter motor/ wiring issue first, see if I can get it to run first. There should be enough fuel to get it to fire up.

Before I put 3 litres in, I looked in tank with torch, it looked pretty clean.

[Billy26F5]

I think you need a wiring diagram, here is the early one: viewtopic.php?p=59110#p59110 It came from here, well worth seeing: viewtopic.php?p=57867#p57867 The RB106/2 you have is slightly different from the RB108 used later on, as the feed to the ignition switch (and separate light switch after 09A-315817N, by then only RB 108 regulators) was through the regulator, with A going to the battery and A1 to the switch, between the two a few turns in the regulator series coil. I wouldn't be worried about the brittleness (all our wires are too), just keep an eye on it and check there's no chance of a short. Do make sure all connections are clean and tight and that the battery is in a reasonable state. Shunt wired means in parallel. Looks like someone's been in that dash before.
You need to fix that filter before doing anything else. Those filters are not big enough or fine enough for diesel. I would remove it, and replace the normal filter element. Make sure the fuel tap isn't blocked either and that there's no leak between it and the lift pump. Use copper pipes, rubber is not good here, I suspect it might well be letting air in.

You don’t need to spin the engine to bleed it. Merely slacken the bleeder on the injection pump and use lift pump till bubbles stop.
I’ve never needed to loosen injector pipe on a Simms pump.

I agree, but if the injectors have been removed then you do need to bleed them. You might need to check them, maybe the pump as well.
Don't forget to use the heater and primer when you try to start, Dexta's are not the best starters even with that but far worse without. I think you'll need more than 3 liters, a couple of gallons would be better. I was wondering about the tap, on Major's you certainly can remove it without removing the tank, I'll check on Davie later.
There were 5 prototypes by 1955, but production started in December 57, with 144 made in that short spell. No real science to the dating, it's more of a guess, casting codes would help on getting a better idea, as will the engine number, which should be close to 1415495 (not sure if both are expected to coincide, need to look in to that). Haven't yet found a monthly list for Dexta's prior to 62.
Those are all lovely pics, the front wheels look like fergie ones, and a very odd home made handbrake with some original parts. I also see one of your other Dexta's behind. The rear axle casting code is June 1959, so you might actually have a mix of parts here. Don't chop any of that tinwotk, a good clean and some good repairs and you'll have far better parts, as the repro stuff is hellish.
Sandy

[npaisnel]

Yea, wiring diagram, I did find correct one. It is printed out and waiting to be used.


https://www.tractorforum.com/attachment ... pdf.88707/

Yes, that fuel filter.. totally daft, I have taken out and checked the original filter… did not have one in stock… but it flows fine for now.
No copper pipe in stock either, but the Sykes flaring tool is sat on the seat now ready to go.

He ran it for a few years with the toy filter, so will get it running with all as is, just to hear it run and see if hydraulics lift.

On the one you saw in background I did full weld up repair of the old wings, with the FoMoCo stamp on. It was bought new by my grandfather, £495. Was the first vehicle I had a crash on aged about 6-7 years old. Jumped on it on brake side, which released the brake and I rolled about 10 yards over a hedge and in to a tree. 40 years later I got around to fixing the damage I did then to the nose cone !

This one though, all supports are non-existent, just a lot of tack welded steel angle and fibreglass. Think beyond saving, but not even looking at that yet.

Looks like new primer has been fitted. pre heat switch does not conduct.. already have it off… Will see if I can strip and clean.

Not checked to see if heater is working yet either. Will be getting Wilkes ammeter, jump leads and battery out later to see what it draws and if it gets hot.

Most of the ones I have seen have had a tap fitted, just prior to the pre heat injector, to block fuel leaking into the inlet manifold. This has no tap

Handbrake, yes, it looks like an International 434 type one.
None of original parts on RHS are there. It appears, in first clutch ‘feel’ to have had a dual clutch fitted… so might be a complete back end / gearbox transplant has happened in the past.
Had to go see friend in hospital at 2pm, so did not want to get dirty this morning… so no work on it today… will be interesting to see what the back end casting codes reveal.


Wiring, in the box, yes, someone been in before the mouse built its nest and chewed wires ! Yet all the wires foward of that looked untouched.

Front wheels,?yes fergie, but I do have some original narrow ones to go on my grandfathers…1959, also with outside lights and single clutch.

Just resigned my job flying air ambo out of Jersey, so with zero income, this is/was going to be an as little cost as possible job… just get her running. So yet to see.
Tomorrow I will wire a few new bits of wire around old wiring loom, and see if I can get it firing as it is.
Once I hear it running I’ll go from there

[Billy26F5]

I didn't see any fibreglass there (there certainly shouldn't be) but original is always best. I haven't had one of those switches apart but I've dismantled and fixed quite a few on other vehicles that manuals insist on replacing, just with a clean. You can maybe test the heater with the air hose off, then you can see the element glowing if it works without removing the heater. Your atomiser is the early one, it just has a spring loaded ball, it was changed on 09B-700977 but by regulation and it was intended for all tractors in Britain to have been changed. Here's the service letter: viewtopic.php?p=60535#p60535 Live clutches were available from the beginning but I agree it could be possible, a bit strange though as it's easier to leave the bell housing on the gearbox. A look at the casting codes will confirm many things. Why do you want a single clutch there? The Dexta live clutch was basically fine, unlike the Major one with its aluminium cover.
Pitty, sounds like an interesting job, I've always liked the idea of flying things but never got any further.
Sandy

[npaisnel]

Oh, no don’t want a singke clutch. Was just surprised to find it appeared to have one.

Resistance and ammeter will show well enough it is working or not. The less I disturb at the moment tye better.

Interesting about the tap. I had been told it was changed to prevent fuel leakage in to the inlet to prevent hydraulic lock if primer/ atomiser leaked fuel in to the manifold.

Since I am in Jersey it is possibly not law so might not have been done.

[Billy26F5]

The spring loaded ball was not on the very first Dexta's (up to 1409432), some of those also had a banjo there (up to 1404118). The ball was intended to avoid such issues, not sure how effective it is as Davie's primer is ok and he does still have the spring loaded ball as most countries didn't make the tap necessary.
Sandy

[npaisnel]

Have to look closer next time… or maybe a pic of it… think I took one.
Seem to remember I first thought it had a tap that had snapped off, but after taking pic I got distracted and never looked agsin

[npaisnel]

Well I got her running this afternoon, and she does not sound well. A random odd firing sound… then it is fine…then odd sound agsin… thinking valve train issues…
Will put a video up on YouTube shortly.

Regarding the atomiser tap.. yes, it does have one, but it has been fitted hidden..ideally need it 180deg around to see it under the bonnet.

Smiths tachometer, by the look of its bezel it had been apart before. I freed it up, so it should now read revs, but I believe like yours Sandy, the hour meter will not work. It turns over by finger, but the drive gear for it that sits on a worm gear is broken, shaft seized… see following pictures.

And also a few random shots of what might be casting codes… but not researched where they are.

Had brief look for engine number, but only saw what I guess is a casting code on LHS on main body of engine.

Took heater switch apart and cleaned that up, and put 12volt directly up the glow element, 21amps and if got nice and warm.

[npaisnel]

Ok
Here is video


https://youtube.com/shorts/-fvkRoGOjlI? ... FwvgmPx4u3

[Billy26F5]

First of all glad you're running. Sounds a bit like one cylinder is missing at times, might be worth checking injectors or maybe seeing the plungers all move nicely. A check of the tappet clearances is no bad thing either, but sounds more fuel related to me. See what you mean about the tap, you'll need a different thickness washer for that. Interesting find in the tachometer, I'll look out for it when we open Davie's one up. Glad the heater is working, looks like a lot of dirt in the switch. The gearbox looks like July 58, as is the LH axle housing. The RH axle housing is August 60 and the sump is also July 58. Might be an axle issue there that caused the replacement.
Sandy

[npaisnel]

Interesting about the castings, thanks

Put a proper piece of fuel pipe to lift pump yesterday…,had to reuse the old olives by drilling them out !
Seems to NOT be leaking.

Looked inside fuel tank, and blew air up through the tap. as a quick way to see if it chucked loads of sediment out up back in to the tank.
Looked very clean. Nothing obvious emerged inside the tank, and bottom of tank looked very clean… cleaner than I have seen any tank!

Only weird think is the blob of what I guess is solder from when threaded insert for tap was fitted, or repaired.
I tried to knock off that little solder/weld blob with long screwdriver, but it is solid

[Billy26F5]

Good stuff. Not ideal to reuse olives but that doesn't mean it's not going to work. Tank looks good, worth putting a filter on the tap some time. I think those are rivets but not sure, one of them looks odd but as long as it can't cause trouble there's no need to do anything.
Sandy

[npaisnel]

Yes in reality olives are only one time use..but when you do not have any, wont be the first time it has been done!

The tap end does still leak..so will need to get new one(s).

But that is next month ..off to France tomorrow.

Put a filter on the tap ? though there was a gauze one inside it any way ?

Trouble with Dexta ..have to take the steering wheel and tank off I think to get the tap undone? the primer pump is too long to rotate I believe?

[Billy26F5]

Are you sure it's the olive? I've had a few that leaked that just stopped when tightened, but that might just be luck. The olives are meant to grip better as they're used. Here's a poor pic of the filter on the tap wich is missing on yours

I'll get a better one tomorrow. I'm afraid it is a bit awkward, you can try doing it through the fuel tank if you dare but I don't recommend it, access is very poor.
Sandy

[Billy26F5]

Here is the better pic, the tank is low as we're a bit short and the others need it.

Sandy

[npaisnel]

That’s excellent.
Going to take a specially shaped stick to put one of those back !

[Billy26F5]

If you succeed it'll be much easier. Do make sure it's clean. Filters are available new, they're not quite as original but should do the job fine (original ones have a brass mesh, new ones use all plastic).
Sandy