HDJ81 24v Starting System Issues (1 Viewer)

[AirheadNut]

Thanks for your suggestions! I went ahead and tried to hotwire the starter by putting a jumper across the white plug that goes to the starter relay. (12V power, not the relay signal plug) Nothing happened. Then I unplugged the connection that is right at the starter, and jumpered from the +12V at the white plug. Still nothing. So I ran a wire from the battery directly to the plug at the starter and it cranked right up. Out came the voltmeter. While there was ~11.5V across the battery terminals, there was only 10-10.5V at the white plug on the starter relay.

So the starter works fine, the relay works fine, but there is not quite enough voltage in the system to get the starter solenoid to engage. Any tips on how to track down the voltage loss?

 

[mudandrock]

11.5 volts on the battery sounds like the main problem. What's it do when you put jumper cables to the batteries?

 

[Alic]

Really it is not all clear.
Starter has small one pin plastic black plug - "plus" from the starter relay that give power to pull-in relay in starter.
As i understand, you give + to that plug and starter begins to crank?
If so then starter relay is not working or no signal from ignition switch.

For my experience 24v starter may start engine with 16 volts on batts so if you have even 10V on each batt - it will start engine.
May be you should take temporary another batts from another car to test them. May be your ones are dead.
And I recomend you as I said before make additional ground from batt - to engine.

 

[mudandrock]

This time of year your glow plugs are kicking on stealing even more voltage from those batteries. Either way, you need good strong batteries on the HDj81. Weak batteries are the number one killer of alternators and the 12/24 converter switch

 

[AirheadNut]

Sorry, let me clarify. The starter relay does work properly, and it is getting signal from the ignition switch (ST and E). There is power to the white plug (B). When I put a jumper between B and MG, I got nothing, but when I ran +12v to the black plug on the starter (terminal 50) the engine cranked. I think there is not quite enough voltage at the B/MG plug to engage the starter.

I am going to have the batteries tested to see if they need to be replaced, but I think that my voltmeter reads a volt or two off; I tested it on several other batteries and got 11.5v on all of them. Also, if I turn the ignition to the 'ON' position and jump the starter, the engine will start on 12v.

 

[AirheadNut]

 

[Alic]

Thank you - now it is very clear what you do.
So the problem is in the wire from MG to Terminal 50 or from BATT to B.
I think you should simply get out that wire and inspect it. Also get out all pins from plugs and inspect them and clean. May be wire is strongly coroded or may be broken near the pin at terminal 50 plug.
There is no other problem I see if your starter works on direct + from batt to pull-in relay.

 

[AirheadNut]

Thank you - now it is very clear what you do.
So the problem is in the wire from MG to Terminal 50 or from BATT to B.
I think you should simply get out that wire and inspect it. Also get out all pins from plugs and inspect them and clean. May be wire is strongly coroded or may be broken near the pin at terminal 50 plug.
There is no other problem I see if your starter works on direct + from batt to pull-in relay.

Exactly. I will probably start with the MG-Terminal 50 wire as that is where I think the problem was the first time, most likely in the black plug at the starter. I will also see if I can get a different voltmeter to compare results with mine.

 

[AirheadNut]

So I've just done some more testing: I have finally made a good, reliable connection at the black plug near the starter, but that didn't fix the problem. I tried putting a jumper between the B and MG terminals at the starter relay again, but still no luck. I then put a jumper from the battery to MG, and it cranked just fine. Conclusion: there is just not enough voltage/current at the B plug to get the solenoid on the starter to engage. However, I am not sure where to look to find a bad connection before the plug at the starter relay.

 

[Alic]

How do you put the jumper? Do you have a pic?
I think you simply shoud go through the wire from B point to Batt.

 

[Alic]

You are almost there. Do break down!

 

[AirheadNut]

Here is the current jumper. I tried a jumper between the two sides of this plug, but nothing happened.

 

[mudandrock]

Did you try different batteries yet?

 

[mudandrock]

You've got some fusible links coming off the battery there too Dane, check them for continuity

 

[AirheadNut]

I am going to have the batteries tested tomorrow. I have tested two of the fusible links, but still need to do the other two. Both tested ok, but one could use replacement due to cracking insulation.

 

[AirheadNut]

Both batteries tested good. I guess it is down to tracing the wire through the engine bay, a project for next weekend.

 

[AirheadNut]

Well, to wrap up, rather than tearing apart some of the dash and a bunch of the engine electrical trying to trace the wire I just ran a new fused wire from +Battery to the B/MG plug. It starts with the key now!

 

[mudandrock]

Atta boy!

 

[Alic]

Well, to wrap up, rather than tearing apart some of the dash and a bunch of the engine electrical trying to trace the wire I just ran a new fused wire from +Battery to the B/MG plug. It starts with the key now!

Good experience!

 

[AirheadNut]

Had someone asking about this problem, so I figured I would post some updated wiring diagrams I made to illustrate what happens in the 24v start system when the key is turned:
Diagram 1: key in RUN position, red is hot and blue is ground

Diagram 2: key in START position, red is hot and green is the circuit I had to fix by running a new wire from the fusible link to terminal B on the starter relay