17 replies to this topic

[mattj99]

Hi All 

 

I'm hoping someone here can give me some help with an electrical problem I have.

 

The car is a 1987 998

 

On Sunday when starting the car I had a few strange clicks but it turned over ok and started.

 

The next morning I went to start the car, when I turned the ignition on it everything lit up and the radio came on etc. When I tried to start it I had one loud click and then the car lost all electrical power. I thought maybe the battery was flat and trying to start it had killed it completely so I took the battery in the garage and put it on charge for a few hours.

 

While I was waiting I checked the engine was free and could be turned by hand. I also had a check of the battery cable for any damage and did a continuity test between the cable and the body to make sure it wasn't touching somewhere.

 

When I put the battery back in the same thing happened, everything worked again radio, lights etc. but when I turned it over there was one loud click and it was dead again.

 

Thinking the battery must be dead I nipped to the motor spares and picked up a brand new battery. Unfortunately the exact same thing happened, one click and it was as if the battery was dead. I left the car for a few hours and when I came back to it I turned the ignition on and everything came on for a 30 seconds or so and then sort of faded out like the battery was flat.

 

Out of desperation I changed the starter as my mate had a brand new spare one still in the box so I popped that on to the car while I was charging the new battery. Unfortunately this made no difference.

 

Does anyone have an idea what could be causing this or what I can do to diagnose this issue?

 

Thanks

 

[mini-mad-mark]

Battery earth cable seems like a possibility - or more likely where it connects to the body to make earth 

 

Check by connecting a jump lead from the negative terminal to a good earth (subframe bolt maybe or fuel tank strap bolt) to see if it fixes your problem 

 

Remove earth cable and clean up the boot floor where it bolts to if the temp earth worked

[smurfomatic]

Could be a faulty solenoid, worth checking the connections and replacing if you have a spare to test with

[68+86auto]

There will be a loose connection somewhere, likely the earth cable between the body and engine.

[mattj99]

Battery earth cable seems like a possibility - or more likely where it connects to the body to make earth

Check by connecting a jump lead from the negative terminal to a good earth (subframe bolt maybe or fuel tank strap bolt) to see if it fixes your problem

Remove earth cable and clean up the boot floor where it bolts to if the temp earth worked

The boot earth strap is new and clean and the engine one looks good but I'll them both of and double check they are clean.

[mattj99]

Could be a faulty solenoid, worth checking the connections and replacing if you have a spare to test with

I thought that but I tested with a new boxed starter - with the integrated solenoid - and had the same issue

[mini-mad-mark]

 

Battery earth cable seems like a possibility - or more likely where it connects to the body to make earth

Check by connecting a jump lead from the negative terminal to a good earth (subframe bolt maybe or fuel tank strap bolt) to see if it fixes your problem

Remove earth cable and clean up the boot floor where it bolts to if the temp earth worked

The boot earth strap is new and clean and the engine one looks good but I'll them both of and double check they are clean.

 

Make sure to scrape a bit of paint off the boot floor where the cable contacts (add some grease over it to stop corrosion or blob some paint on once its fitted) - relying on the bolt to touch the cable then go through the nut and the nut to touch the boot floor is not totally reliable in my limited experience even using a new cable - regs

Edited by mini-mad-mark, 23 August 2023 - 08:48 PM.

[Aly-g]

I would agree with 68+86auto definitely sounds like a earth connection to engine.


Allan

[68+86auto]

It can be the positive lead too. Get a multimeter out and see where does and doesn't have power when you try to crank it.

[mattj99]

Hi All,

 

Thanks for the responses. An update. During last nights scrolling through the posts on here I found someone with a similar problem and it was suggested to try cranking the engine with the alternator disconnected.

 

This morning I disconnected the 3 pin connector from the alternator (and the coil HT lead so it wouldn't start)

 

With the alternator disconnected it will crank perfectly. Does this suggest the alternator has a fault?

Edited by mattj99, 24 August 2023 - 07:22 AM.

[bpirie1000]

I would actually go,with a faulty ignition relay.

Have a look on the inner wing near bulkhead on the left hand side as you stare at the engine. A square box about 1.5cm by 1.5cm.

Make sure this is not wet. Have seen numerous of these fail. Also same as a spot light relay if you have a spare one of those for reference/or swapping just to test.

[mattj99]

I would actually go,with a faulty ignition relay.

Have a look on the inner wing near bulkhead on the left hand side as you stare at the engine. A square box about 1.5cm by 1.5cm.

Make sure this is not wet. Have seen numerous of these fail. Also same as a spot light relay if you have a spare one of those for reference/or swapping just to test.

 

If that was faulty would that not stop it cranking all the time though? It will turn over with the alternator disconnected. I'm not doubting you just trying to understand how that would cause it.

[68+86auto]

That seems very weird. How many relays are fitted? there should only be one for the starter. If there are more then someone might have messed with it and the alternator can cause issues with relays.

[mattj99]

Actually scratch that. I had a spare hour lunchtime and I tried it again (still with the alternator disconnected) and had the one loud click and everything went off.

 

I'm off work tomorrow so I think it'll be a day of cleaning every connection, both the earth straps, properly inspect the battery cable, check the starter relay, and work methodically through it.

[mattj99]

Hands up if you had bad earth in the broken mini sweepstake?

I snuck off work early and spent the afternoon working through cleaning and checking all the connections and I'm pretty sure it was the boot earth. Ironically it's the one that I thought was nice and clean and had a good connection.

It's starting brilliantly now so thanks to everyone that replied.