Just doesn't start

[Wojzilla]

Ok a tricky one....
I've got a VS (dual fuel), when its cold the car starts fine, if I drive it (even for 5 minutes) and leave it for 15-60 minutes then come back to it chances are it won't start.

What happens is it will turn over but there's no spark (pulled a lead off and checked). If I try every 5 minutes it will eventually start, usually after 3-4 attempts.

I'm pretty sure its not the fuses but i've checked all of them, also changed the EFI relay with the Horn (thinking a relay problem). I've disconnected the battery for 10 minutes thinking the computer needs a "reset" but that achieves nothing apart from clearing all the settings from my head unit :bang:

I can hear the fuel pump start up when i turn the key to 'on' so pretty confident its not that, plus it doesnt start on LPG either.

I've done the paperclip computer test, nothing wrong either.

What baffles me is how there's just no spark

The biggest problem is that it never decides not to start somewhere convenient (like at home) rather in a shopping mall carpark where I can't really do much.

I'm hesitant to take it to a mechanic seeing how intermittent it is, I would rather find the problem (and pay to get it fixed) rather than have someone tell me its fixed when really it will come back in a few days.

Any ideas?

 

[sircruisealotVS]

hmm, that is a bit of a weird one...next time it does it, turn the key to accessories for a second or two first, then try to crank it over.
id really just be guessing to try and tell you what it is thats causing this, but just check over all the applicable parts....battery, alternator, starter motor, coil packs, leads.

 

[hako]

Sounds a bit like a crank angle sensor (CAS) on its way out. They tend to fail when hot (with no spark) and when they cool slightly they will work again. This gets worse to the point that they just don't work.

 

[sircruisealotVS]

i was thinking CAS at first..but he said it still did it after like 60 mins from the engine being on..which is plenty of time usually for it too cool enough.
im not saying its not the CAS, just very strange.

 

[Wojzilla]

Hmm, would a faulty CAS register an error code? I really need to get it to fail at home and not when im out and about. I was also told that pouring cold water on the harmonic balance could resolve it.

Whats wierd though is if I get out (say at a servo) fill up and get back in it will start. Leave it for more than 20 minutes and chances are it wont. The missus says she had problems when she went out for lunch at work then came back to the car 2.5-3 hrs later.

Thanks for the suggestions though, will definitely check it out.

 

[maginoodle]

the cas doesnt always register a code. if you dont know how long its been on there for put a new one on and try it. If it does it again feel the coil packs to see if they are hot, they can cause the same thing but it is most likely the cas.

 

[slowr8]

Does it ever stop while driving, or only when you stop?

 

[Wojzilla]

Does it ever stop while driving, or only when you stop?

It _used to_ die occasionally when on LPG and breaking hard into a corner but it would start up immediatley after. Also had problems with the fuel pump before.

I've replaced the
Spark Plugs
Leads
Pump
Filter
Had injectors cleaned

this was about 6 weeks ago, since then it has died while driving once and it started up instantly after.

 

[maginoodle]

definately sounds like cas needs replacing

 

[Wojzilla]

Cool, how easy is it to do? Do i need to take the radiator out to pull the harmonic balance out?