15 captured repliesPartial discussion capture · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHNot starting when hot.
Leading reported evidence
Install battery about 3 months ago
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
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0
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1
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Read evidence and context
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Performed · outcome unconfirmed · Original poster
I fitted a new battery about 3 months ago, so it turns over really well and generally starts straight away.
Leading evidence: 'Install battery about 3 months ago' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Install battery about 3 months ago' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Suggestion
The resistant was changing when HOT was what I was told
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
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Suggestion · Original poster
They even ran some jumper leads from some points to see if it improved.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
15 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
911uk: 1 discussions
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Generation: 20261026T165820Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
1999 C4 3.4
A couple of times recently I've driven for about 30 minutes, stopped for about 30 minutes and when I've gone back it won't start. I fitted a new battery about 3 months ago, so it turns over really well and generally starts straight away. I've tried opening the doors and locking/unlocking to see if it's an immobiliser issue, but that doesn't seem to make any difference. Last time I was at home so left it about an hour and it started straight away. Today, after some messing about it suddenly started after about 10 seconds turning over.
Any ideas guys please.
A lot of the time this is down to the battery, starter or earth cables. They are fine when cold but once warm expand and cause continuity issues.
Cleaning up of all the cables, battery, engine to chassis and around the starter motor where they connect is a no cost fix... if this is the issue?
Yes it's turning the engine, just doesn't make any attempt to fire up. Leave it half an hour more and it fires up first time.
I had an Impreza that wouldn't start when hot and on them it's a common a common fault with the crank position sensor. Is that possible on these.
I have had this problem. It is the crank position sensor breaking down. When it is failing it works fine when cold, but when hot,it creates a lot of 'noise' meaning the crank position can't be heard. Position sensor failure has been discussed a lot on here.
In my case, no code was thrown up! I checked out all the other obvious culprits like Steve997's suggestion of corroded cables to no avail. The CPS Bosch part wasn't expensive, so was worth a punt!
For some strange reason you dont tend to get a fault code for this .
My best guess is there is a signal but its too weak for the car to understand it or that the spin over is too brief for a code to be generated .
Symptoms like this are classic CPS failure though .
Starter cable faults tend to give low battery charge or slow spin over of the engine when hot .
I've had the car about 3 years. For the first 2.5 years it was really slow when turning over. I got the garage to check out all the cables as suggested on here and they couldn't find anything. They even ran some jumper leads from some points to see if it improved. The battery was supposed to have checked out good as well. About 6 weeks ago it wouldn't start and flattened the battery quite quickly so I just went and bought a new battery and since then it's turned over really fast. So I don't think there are any earth or connection issues.
Does this look like the part.
https://www.eurocarparts.com/ecp/c/...4394fc74c14d76499abf50c897efc123e64e0b&000440
