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Starter Circuit woe. Help needed

JOHN OF LONDON

Active Member
Joined
Jun 13, 2016
Messages
82
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uk
The story so far.
Sunday morning. Try to start the 80. All that can be achieved is 2 or 3 clicks from relays. After some time managed to locate the starter solenoid hiding in the wing; it appears to be making a satisfactory click when it should. There are two connectors, one with thin wires assumed to be the switch circuit and one with thick wires which presumably operates the starter. Investigation with the meter finds that the thin wires are respectively a live wire connected to the starter position on the ignition switch and an earth, as you'd expect. However, both the thick wires are 0 Volts regardless of ignition switch position.
Obviously this is a fusible link problem! Visually inspect fusible links - they look perfect. Separate the connector. 13volts at both. Test for continuity from each of the spade terminals in the plug with the thick wires at the starter solenoid. No continuity. The two wires leaving the fusible link connector are red and black, the two wires arriving at the solenoid are white and black/red. Connecting 12v to the black/red spins the starter, but doesn't activate the 12/24 changeover relay. Engine starts happily if ignition is on but various warning lights stay on. Voltmeter indicates that battery is charging. Using the ignition switch to try to start activates the 12/24v changeover switch.
It seems to me that the obvious answer is the right one: there is a break in the continuity between the fusible link and the power side of the starter solenoid, and this is also affecting the warning lights. This, it seems to me, is more likely to be a failed connector rather than a broken wire. The wires at each end seem to disappear into the main harness and through the bulkhead and, as they are different colours, might be powering some other items on the way.
Today I have taken off the glovebox to see what can be found behind it in the wiring harness. Nothing obvious and no sign that the loom has been interfered with by a PO.
I need either some expert assistance or a copy of the full wiring and connectors from the EW book. Please.
 
I think for a modest fee to Crispin you can become a supporter, free yourself from irrelevant ads and open up the downloads section where the FWMs reside. These will contain detailed wiring diagrams.
 
I’m assuming you’ve checked all your fuses and swapped your starter relay for its neighbour?
 
Thanks SC,
I'd be happy to pay a fee to access the books if I had any idea how to go about it!
Yes I've looked at all the fuses under the bonnet and in the block by the steering column; any others I should be looking at? Should there be a fuse on the starter feed as well as the fusible link?
John
 
Send @Crispin a PM and ask to be a supporter. I think there’s a link somewhere that does this in one click but I’m darned if I can remember where. There are no other fuses I’m aware of. If you test volts across the fusible links or fuses all should say zero.
 
Thanks SC,
I see if I can find the link and PM if I fail. I got 3 or 4 ohms resistance across each of the fusible links and there's no sign of them having been hot.
John
 
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Thanks SC,
I see if I can find the link and PM if I fail. I got 3 or 4 ohms resistance across each of the fusible links and there's no sign of them having been hot.
John
Like I say, test voltage across them, ideally under load. Should be zero. You can get 3 or 4 Ohms from surface contaminants, contact resistance and non nulled leads. From what you say they should be fine.

Have you located and swapped the start relay? I believe it’s in the drivers footwell but once you’ve downloaded the FSM you should be able to locate it.
 
Have you checked both battery's are good ?
If the L/H one is U/S then this can give the fault you describe .
Often the simple things are the cause of a fault .
(it may of course be you have already carried out basic checks and drop tested both Batts )
 
is the netral safty switch on the trans (if its an auto) working ok?
 
Good morning all, back to the job in hand.
SC, I'm a bit surprised that you think there may be another relay. The one I found is marked Starter Relay and actuates when the key is turned to Start. The output from this relay goes to the starter motor and turns it when 12v power is directly connected to it. (In fact it turns it so well I could believe a PO has fitted a 12v starter motor! I'm going to have to take the starter off so I'll check it out) The problem I have not solved is that there is no power arriving at the high amp side of the starter relay. I think I have eliminated the fusible links as a cause of the problem and I have checked all the fuses I can find. Thinking about the problem overnight the only possibility is that there is a fuse on the power side of the starter relay so I will remove and test the big under-bonnet fuses. Visually they looked OK but...........
John
NB
Yes the starter relay low amp side is clicking as it should so, by definition, the auto interlock is not the culprit and no I've not done a drop test on the batteries but each will spin the starter and start the engine if connected direct to the starter.
 
The story continues!

First SC. I can't read my multimeter right! The resistance across the fusible links is .3 ohms. Voltage drop under load is 0v - so I think the links are OK. I followed your advice and paid up as a supporter - been meaning to do this for a while! However I've seached the downloadable files and not found anything helpful; perhaps I'm looking in the wrong place. Ideally I need a 1994 EWD Europe edition; I keep looking for a 2nd hand one but - no joy.
Since my last post I have found that the terminal post on the startner motor was loose. This may have been a source of intermittent failure and made it self known with a dead short (luckily with jump lead not the vehicle wiring) I found a new Denso starter on E Bay for £175 so bought it quick; sadly its a 1996 starter so I have had to make a new fly lead to install it. I will reassemble everything when the rain stops and see if the problems have gone away.
I am hoping though that someone out there can help me understand the wiring. It seems to me that the starter motor is a hybrid 12/24v device. The solenoid appears to be operated at 12v with 24v for the power side; is this right? I am also confused by what appears to be a fusible link on a light green wire attached to the passenger sided battery. This will supply 24v when the changover relay operates; perhaps it feeds the starter relay through another hidden relay. Oh, for a wiring diagram!
John
 
The wiring in the FSM should be the same as it’s an 80 series and there isn’t much difference between the 1990 and the 1994 so this one
5C080AFE-5A67-445C-8EED-668C0BC2A036.png

should be relevant.

Yes, the starter has a 12v solenoid and yes it should be 24v on the main contact. Just check the amount of teeth in the pinion. There’s 12 teeth type and there’s 11 teeth type. If it’s wrong you can swap the pinions.

However, you say there was a short on the Main contacts. The solenoid is maintainable and terminals can be easily and cheaply replaced. There’s plenty of info on here about that one which usually manifests itself with either a clonk from the solenoid followed by nothing or the starter running on at half voltage after the key is returned from starting. The first is totally burned contacts the second, welded contacts. I didn’t think from the symptoms you posted that you had this issue. There is a kit available with contacts and plunger that is uprated. Robson and Francis can supply along with the pinion if needed.

The green fusible link could be voltage sense for the alternator from the second battery where iirc the alternator connects
 
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The wiring in the FSM should be the same as it’s an 80 series and there isn’t much difference between the 1990 and the 1994 so this one View attachment 149998
should be relevant.

Yes, the starter has a 12v solenoid and yes it should be 24v on the main contact. Just check the amount of teeth in the pinion. There’s 12 teeth type and there’s 12 teeth type. If it’s wrong you can swap the pinions.

Just to be sure I read this right Rich??
 
Thanks SC. I have studied the wiring diagrams and I think a bit of light is shining through; only a bit though.
Firstly both the wiring diagrams at ST14 and ST15 seem to indicate that the starter relay is fed from the starter battery and thus will be at 24V when the changeover relay operates. The relay actuation is from the ignition switch at 12v. Logically I would expect the starter to be purely operated at 24V, it is after all used in the 1HD-T in commercial vehicle applications where everything is 24V. I think mine has the temperature sensitive timer on the glow plug system so the starter relay is fed through a fusible link marked FS 0.5G on the circuit diagram. This may be my light green wire??!
When the rain stops I will go and investigate furrther.
John
 
Yes I observed the typo - but both of mine have 12 teeth.
The connection post on the old starter has pulled out of the casing. A quick look inside shows that it was previously soldered direct to the solenoid coil wire with virually no insulation. I think it is a cheapo Chinky thing but I've passed it on to our local Guru to decide if its worth repairing. If its not I'll buy another of the genuine ones for £175 delivered.
 
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Nothing wrong with that internal connection John. That’s perfectly normal (apart from being broken that is) and I thought you meant the battery connection which can be loose if not tightened correctly (if that makes sense).
So are you saying that swapping the starter motor has now cured your starter woes?
 
I don't know yet! Rained off and lots of reassembly to be done. Odds should be in my favour on the "only one thing goes wrong at a time" principle. I'm an optimist!
 
Thanks SC. I have studied the wiring diagrams and I think a bit of light is shining through; only a bit though.
Firstly both the wiring diagrams at ST14 and ST15 seem to indicate that the starter relay is fed from the starter battery and thus will be at 24V when the changeover relay operates. The relay actuation is from the ignition switch at 12v. Logically I would expect the starter to be purely operated at 24V, it is after all used in the 1HD-T in commercial vehicle applications where everything is 24V. I think mine has the temperature sensitive timer on the glow plug system so the starter relay is fed through a fusible link marked FS 0.5G on the circuit diagram. This may be my light green wire??!
When the rain stops I will go and investigate furrther.
John
My diagram would be ST 14 and I suspect yours also. You are correct in saying the fusible link FS 0.5G is for the start solenoid which is at 24v when the changeover relay is held in by the timer during the start sequence. The start relay closes contacts to send 24v to the coil terminal on the solenoid.

If you’ve been getting short circuits previously on your coil terminal I would suspect and test anything in that line from the battery in case a, the fusible link has gone and b, the relay contacts have been damaged.
 
Well I've finished rewiring the electric fan, which is what I was doing when the starter decided not to work, I've reassembled all the bits and it started first time.
So what have I learned. First lesson is that following a logical fault finding proceed sometimes doesn't work. I started by listening to the various clicks when trying to start and decided to look for the problem by eliminating probable reasons one at a time. I started by connecting a wire from the DS battery direct to the starter. No problem, starter span and turned the engine almost as well as it does with 24V. From this I concluded that the starter was ok and the problem lay elsewhere. Secondly I checked the fusible links. They tested fine. Batteries are fairly new and thePS battery was spinning the 24v starter on its own so that was ok. DS battery has not given any previous problem so was an unlikely culprit. Having only the Haynes manual to look at I then made an assumption that, as shown by Haynes, the starter solenoid was directly powered from the DS fusible link via the starter relay. This led me off to spend many hours in confusion trying to find out/work out or understand why there was no power arriving at the high current side of the starter relay. Not until StarCruiser (you're a star!) found me a proper wiring diagram as a supporters' download on this forum did light dawn. It transpires that the power side of the starter relay operates at 24V and is fed by its own little fusible link direct from the PS battery which I had left unconnected when searching for the starter relay feed. 2nd lesson - Don't guess get the wiring diagram!
So having solved the mystery I was still no nearer knowing why the starter, which seemed to operate properly with a jump lead direct from battery to starter solenoid, didn't work so I went back to a direct jump lead from battery to starter. At this point I noticed that the connection post on the starter was wobbling a bit, so I wobbled it about. Bingo, I then got three results from different wobbled position. 1 - normal working. 2 - Nothing and 3 - a real hot wire!
So starter removed and inspected etc - see above.
 
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