Can't start, won't start

[Robotsan]

Haven't started my 280z for a few months so thought it was well overdue. Tried to today but nada.

I keep the battery in the car but disconnected all the time, and the battery is showing 12.5v with a multimeter.

When I turn the key to ACC the dashboard volt meter shows 12, but when I turn it to ON, the volts drop to 9 or 10.

But when I turn to START, the volts drop to below 4 and nothing happens at all at this point in terms of starting.

So then I tried turning the headlights on, and that also sends the volt meter to under 4, and the headlights don't even come on at all.

Then when I turned the headlights off and tried to start it again, I got a weird buzzing sound from the passenger (right hand) footwell, like a relay or something maybe?

Is the battery likely to be knackered? But surely if it's showing 12.5v it's ok?

Took a video to show what's happening/not happening..

 

[jonbills]

It does sound like a knackered battery to me. Do you have a charger?
or maybe you've introduced a short in the 'on' position. Measure the amps out of the battery with a multimeter would confirm I think.

 

[grb184]

Sounds like it’s the battery, if it drops under load ! , you could try jump starting from another car that would confirm it

 

[MCBladeRun]

Is the battery old? Does sound like the cold cranking hours ain't doing their job, ain't got no grunt to it

 

[SacCyclone]

Yes, that battery was in the car when I got it so it is old.
Start with a new battery and replace the battery cables while your there as those that are in the car were knackered too.
Mike

 

[Robotsan]

It does sound like a knackered battery to me. Do you have a charger?
or maybe you've introduced a short in the 'on' position. Measure the amps out of the battery with a multimeter would confirm I think.

I've only ever checked the voltage before, but will check the amps .. from Googling, you check the amps "to ensure whether the battery can supply sufficient current to a load".. is that right? Any idea what it should read?

 

[Robotsan]

Yes, that battery was in the car when I got it so it is old.
Start with a new battery and replace the battery cables while your there as those that are in the car were knackered too.
Mike

Thanks Mike, I'll try putting the battery from the Mini in it tomorrow then. That should tell me.

Regarding the cables, I'm assuming they're a generic thing, not Datsun-specific? I would like to have some easier to use ones, with a different type of connection if such a thing exists?

 

[jonbills]

I've only ever checked the voltage before, but will check the amps .. from Googling, you check the amps "to ensure whether the battery can supply sufficient current to a load".. is that right? Any idea what it should read?

I'd think the load should be somewhere less than 10a.
put the multimeter in series between battery and + terminal and see what it reads when off and when ignition on.

 

[SacCyclone]

Thanks Mike, I'll try putting the battery from the Mini in it tomorrow then. That should tell me.

Regarding the cables, I'm assuming they're a generic thing, not Datsun-specific? I would like to have some easier to use ones, with a different type of connection if such a thing exists?

Cables are generic, just measure out the correct length you need with a piece of string with a little added. Good to go.

 

[Robotsan]

Cables are generic, just measure out the correct length you need with a piece of string with a little added. Good to go.

Ok, well the reason I ask is there's more wires than I'm used to seeing .. a second, smaller red one coming off the positive, and some smaller black ones coming off the negative. From looking in the BE page of the FSM the latter appears to be a fusible link to the EFI system. One must be an earth I guess?

The red one goes into a white sleeve then through these 2 white plugs, back to red again..

So can I just disconnect these small cables from the terminals, and reattach when I install the new main cables?

 

[toopy]

Try here for electrical bits https://www.autoelectricsupplies.co.uk/

or https://www.carbuilder.com/uk/electrical

 

[toopy]

I'd think the load should be somewhere less than 10a.
put the multimeter in series between battery and + terminal and see what it reads when off and when ignition on.

and be careful not to move the key to start position momentarily by accident, as your multimeter will likely be toast!

 

[Rob Gaskin]

Ok, well the reason I ask is there's more wires than I'm used to seeing .. a second, smaller red one coming off the positive, and some smaller black ones coming off the negative. From looking in the BE page of the FSM the latter appears to be a fusible link to the EFI system. One must be an earth I guess?

The red one goes into a white sleeve then through these 2 white plugs, back to red again..

So can I just disconnect these small cables from the terminals, and reattach when I install the new main cables?

View attachment 56173

You need to sort that lot out. It looks like someone has been lazy when fitting 'add ons'. Also that main black lead looks small to me.

A bit of WD40 would be good too.

 

[Healey 12]

Thanks Mike, I'll try putting the battery from the Mini in it tomorrow then. That should tell me.

Regarding the cables, I'm assuming they're a generic thing, not Datsun-specific? I would like to have some easier to use ones, with a different type of connection if such a thing exists?

I bought these for my rally car , work very well ( clamp very tight) and have the points for extra cables

 

[candy red]

I would give all the connections up first some of them look pretty ropy if the rest of your connections are possibly the same anywhere it’s not gong to make life easy find the fault

 

[Rob Gaskin]

That main red cable running across the battery clamp is a fire waiting to happen!

 

[Robotsan]

You need to sort that lot out. It looks like someone has been lazy when fitting 'add ons'. Also that main black lead looks small to me.

A bit of WD40 would be good too.

What gauge should the black lead be? And should they both be the same?

Re: the other wires - are you sure it's not just because it's a 280z? I've found pics of other 280z batteries online and they seem to have the same wiring. For example:

I’ll be back – [Battery] Terminator

Every now and again, i jump in the car to fire it up only to find it won’t start. No ‘click’, no turn over. Baaaahhhh now what is it?! After a few times of this happening over the…

dailydatsun.wordpress.com

 

[Robotsan]

That main red cable running across the battery clamp is a fire waiting to happen!

I was thinking it's stupid having a metal clamp! Ok, I'll stick a load of electricians tape over the clamp for now and will try to source some sort of plastic hold down clamp for long term.

The car isn't going anywhere soon and it lives with the battery disconnected so hopefully no immediate risk.

 

[Robotsan]

Well I got the car started using the battery from the Mini. Ran lumpy and smoky for 5 min then was clean and idled nicely for another 25 min.

Stuck the original battery back in after giving the terminals a good sand and clean (as well as the connectors on the cables) and it started first time on the old battery too. So I think it was just not making a good enough connection.

 

[Robotsan]

Could someone else with a functioning 280z please confirm for me if these other smaller cables are there on their car too? @yellowz / @Larby maybe?