Read this: Trading and advertising on the forum - Conditions and how to enquire
These ads only show for users who are not registered or logged in
Mk2 Nb Slow Cranking, Battery And Alternator Issues
Posted 01 September 2020 - 07:28 PM
The alternator pulley is always stuck after winter so I free it off first and it seems fine afterwards. It's still the original and the car is on 98k miles so I think it could do with being replaced. But I've read it's a pain to do and also not all pattern parts are compatible. Is this true and what's the best one to get? Genuine is far too expensive for me! Or should I wait until it does need replacing? The belts do need replacing too though.
The battery seems to only hold a charge at 12.33v with the engine off. After a long 70 mile drive that's the reading I got. Even after charging it with my Ctek charger I watched the meter drop from 12.45v down to 12.33v. The battery is at least 7 years old so probably needs replacing. I've yet to test it with the engine running to see if the alternator is charging it properly.
There's also the starter motor to consider but how can I test this? Is there anything else that can cause slow cranking problems?
I do have a video I can put on if it helps.
Posted 01 September 2020 - 07:56 PM
Hmm. How long did you leave the Ctec charging? (depending on the model) it's a conditioner as well as a charger and can revive sulphated batteries quite well just by charging them really slowly. Might take a couple of days to charge a low battery.
One other thing which can cause slow cranking is a bad ground and there's a point which is notorious for cable fractures: Look under the car in front of the right rear wheel and you'll see a thick cable which ought to be bolted to the powerplant frame next to the differential. That's the far end of the battery ground cable and it often fractures at that point. It's the main ground connection between the bodywork and the powertrain. There's a smaller one, a braided strap, in the engine bay next to the dipstick, but it's not really up to the 100+ amps the starter motor wants.
Posted 01 September 2020 - 08:54 PM
Thanks for the info about the ground cable, I will have a look. Something I forgot to say is that I have a cut off switch fitted to the negative terminal, similar to the one MX5 parts sell. But I always make sure it's tight and it didn't crank for this long after fitting it.
Here's the video, hopefully it works.
Posted 02 September 2020 - 09:57 AM
Posted 20 September 2020 - 03:43 PM
I bought a new battery for another of my cars and tried it in the MX5 to see how it started. It cranked about 1 second quicker and definitely felt stronger.
Today I had time to look for this ground strap - it's no longer attached to the bolt!! I tried to undo the bolt and the head snapped off so I'm not happy!
How can I fix this? Does the PPF undo easily, it looks like there are 5 bolts? I don't think I'll be able to drill the old bolt out or a new hole in situ. Can a bolt and nut be used instead?
If I cut the end of the cable off what size terminal would I need to replace it and do you need a special tool to crimp them as they're pretty thick?
Posted 21 September 2020 - 12:19 AM
That's the other end of the battery ground lead.
It starts at the battery negative terminal and fixes to the side of the boot and then forward and down through the offside rear wheel well to the PPF. I managed to unscrew the original bolt on mine, but in your position I would either drill a new hole and tap it to M6 or drill a clear 6mm hole and use a nut and bolt but be sure to sand down the aluminium surfaces to make a solid contact as it needs to carry 100+ amps while cranking. You'll need about 1.5m of 16 sq mm cable to reach from the PPF to the spot in the boot where the original cable fixes to the chassis.
Posted 21 September 2020 - 12:40 PM
You can see how rusty that is in the photo so I'm a little reluctant to try undoing those bolts though! I could only get a small socket or spanner on the ground bolt with a pole on the end and even after spraying it I could feel it would snap on the first turn!
Would you advise replacing the cable completely and not just the end terminal? The other end in the boot looks in good condition. Can I leave the old cable there or should that be removed? I couldn't jack the car that high where it's currently parked so it was difficult to trace the cable's route. I'm guessing it needs to be quite high. Does the wheel and arch liner need to come off?
I'm amazed I've not had any other issues other than the car cranking slowly. It does suffer with idle droop when cold though.
Posted 21 September 2020 - 02:21 PM
Posted 21 September 2020 - 05:21 PM
I doubt if there's enough material in the remaining part of the crimp terminal to drill it and use that.
Posted 22 September 2020 - 06:57 AM
Posted 22 September 2020 - 09:55 PM
Do you know what size the Mazda bolt is as it doesn't seem to be M6 but closer to M8? The ring terminal hole is nearly 9mm.
I had a look behind the trim in the boot earlier. The cable seems to go down under the parcel shelf and is all taped up to the wiring loom. So if it needs replacing it looks easier just to leave it and put a new one in somewhere else but following the same route.
Posted 28 September 2020 - 08:16 PM
Also, will these crimps fit or can you recommend anywhere to buy some that are the correct size. I'm not sure about these looking at the thickness of my cable and going by the Q&As on Screwfix.
Posted 29 September 2020 - 09:04 AM
Those look like the right size crimps for the cable. 16mm² cross sectional area wire is about 5mm diameter.
Posted 17 October 2020 - 09:40 AM
Could it be worth adding a new one if I get some cable. Removing the old one looks like a pain so I'll just leave it there.
I didn't clean the one by the dipstick but if this didn't make any difference I can't see that doing anything. When operating the windows the clock light dims but I've not noticed any other issues.
Where is the starter motor located as I'll try cleaning the terminals up and check they're tight?
As the car started better with another more powerful battery, could it be the Panasonic one is knackered? Apart from that and the Westco what other GEL batteries fit these cars? I'm not keen on using a normal one as it'll probably leak.
Posted 17 October 2020 - 09:53 AM
I think you're probably right that if restoring the main ground didn't improve it, the remaining problem is probably that the battery just can't supply enough cranking amps, especially if a stronger battery worked better. Starter is at the offside rear of the engine quite low down.
It's a few years since I bought a battery and then I just went with a Westco so I'm not sure what the best deals are now.
Posted 19 October 2020 - 11:57 AM
One thing I hadn't mentioned is this slow cranking also seems to happen when the car is warm. Could that also point to the starter beginning to die?
I've decided I'll get a new battery after winter and go with the Bosch S5. As it's a sealed wet battery it should be fine and I'll get some clear tubing for the vent. I did look at the Westco but the price and short life from what I've read put me off.
0 user(s) are reading this topic
0 members, 0 guests, 0 anonymous users