Hot start issue. What's my next move?

[Rubber B]

My RX8 is becoming slower to start when the engine is hot. Last week I dropped my daughter at school and when I got back to the car (after about 10 mins) it wouldn't start at all. Had to sit and wait another 20 mins and then try again. Then yesterday I stopped to put petrol in it and had to crank it loads before it started. Very worried!

I live in North London (N20). Is there somewhere near here that you could recommend for a compression test and an honest appraisal of whether it needs a rebuild or just some tlc on the ignition system (eg coils, leads, starter motor)? I have it serviced it at a Mazda main dealer, but I get the impression from the forum that you guys wouldn't recommend going to a main dealer for this kind of thing.

All help gratefully received!

PS In case it's relevant, my car is a 54 plate 192 with only 48k on the clock.



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[kopite72]

Compression test, the results will determine what you do next

[Nickp47]

Yep defo compression test, it would be a bit unlucky for it to be low at 48k but it happens . Being a 54 it may have the crap starter etc so that could be a cause.

I’m in SL6 and can do the test for you or if it’s any good I’m going to Bedford Monday afternoon so could meet you somewhere en route that’s closer for you.

Alternatively, TPS are round the M25 in Orpington

[Rubber B]

Thanks very much. I think it does have the crap 1st gen starter motor. And I've never changed the leads but I will have to get a compression test. SL6 and Bedford are both quite far from me but I will check out TPS. I haven't heard of them before.

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[rx8hunter]

In all honesty I would check the cranking speed via OBD before anything else, if you get something like <200 rpm then it would probably be worth getting an upgraded starter on it.

[Rubber B]

In all honesty I would check the cranking speed via OBD before anything else, if you get something like <200 rpm then it would probably be worth getting an upgraded starter on it.

That's a really interesting idea. I just found a Bluetooth OBD module I had laying around. I downloaded the Car Scanner app fro the Google Play store and connected to the OBD. I can see the engine RPM in the app but I can't see how you measure the cranking speed. Do you have any idea how I can do it with an Android app? Sorry for my ignorance.

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[Jester*]

I'd take it to TPS and get the guys to give her a good looking over.

I don't think many of us value Mazda as a go to place for a rotary anymore!

[warpc0il]

In all honesty I would check the cranking speed via OBD before anything else, if you get something like <200 rpm then it would probably be worth getting an upgraded starter on it.

That's a really interesting idea. I just found a Bluetooth OBD module I had laying around. I downloaded the Car Scanner app fro the Google Play store and connected to the OBD. I can see the engine RPM in the app but I can't see how you measure the cranking speed. Do you have any idea how I can do it with an Android app? Sorry for my ignorance.

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Just read the engine rpm while cranking on the starter.
Floor the accelerator to force deflood mode, so she doesn't actually start

[Rubber B]

Thanks @warpc0il! I just did that and the RPM while cranking was about 178, so maybe a new starter would help.

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[warpc0il]

Also check the condition and tightness of the battery terminals and where the negative cable from the battery bolts onto the frame below.

Any significant resistance means that the starter doesn't get all the power it needs.

178 rpm is not a good place for hot starts, even with reasonable compression.

[Rubber B]

Hmmm, thanks for the tip. I just tightened the battery terminals and there is an issue with the positive clamp. As much as I tighten it, it remains loose.

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[PaulAV]

That's a common fault with the battery terminals, they stretch, replacement is the best option, a temporary fix is to split a piece of copper pipe lengthways and fit over the terminal post on the battery, or a bodge is a screw down the side of the post, but this can damage the battery post

[JeradRx8]

178 rpm is low, that's definitely not going to help you. But once that's sorted I think a compression test is still always a good thing to do, at least then you know where you stand with the engine.

[warpc0il]

If the battery clamp still has the grey plastic spacer in the middle of the bolt, remove the bolt, throw the spacer away, replace the bolt and you should be fine.

The spacer is there because the Japanese standard for battery terminals is very slightly fatter than the European standard.

Your battery is unlikely to be the original so will have slimmer posts.

As they're tapered, you also need to be pushing down as you tighten.

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[Rubber B]

I checked mine and it doesn't unfortunately have a plastic spacer on the positive clamp so that's not the problem on my car. Sounds like a good tip generally though.

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[Rubber B]

178 rpm is low, that's definitely not going to help you. But once that's sorted I think a compression test is still always a good thing to do, at least then you know where you stand with the engine.

Agreed. I may try and get hold of an uprated starter and have it fitted by a local mechanic (so not someone who would be able to compression test it unfortunately). But I agree that I should get one!

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[Rubber B]

Thought I would update this thread. I decided that I would pay a visit to TPS as suggested by several people here.

Got a compression test and (thankfully) it was good! Front: 6.7- 6.8 - 6.9, Rear: 6.9- 7.1 - 6.9.

So I got the uprated 14T start motor fitted, plus a new set of plugs and leads. And it's amazing! It now starts super quickly. Cranking RPM is now about 285.

Spent ages chatting to them, with a fellow owner who was in for a service. They really know their stuff and I learnt loads. Plus they did a thorough underbody inspection and polished my headlights for free.

Really very impressed. Will go back there.

Thanks again for all your help and advice, which turned out to be spot on.



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[JeradRx8]

Excellent news, fault fixed and healthy figures! Couldn't have had a better outcome haha

[chriskirkham]

Was good to meet you, your compression test figures are excellent. Service on mine, carried out with usual attention to detail and also a useful underside inspection, I'll be back there shortly for some bushes to be replaced on rear suspension.

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