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Delayed hot restart issue


=jon=
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Hi

Trying to nail down a delayed hot restart issue, just wondering if anyone has any bright ideas...

MS3 running EDIS & Thor injection. 

Starting sequence is pretty much sorted. At pretty much any engine temperature I can stop the running engine, and it will restart within a few cranks and run happily.

However from a delayed hot restart - stop hot engine, leave it for 5-10 minutes, try and restart and the following will happen:

1st turn of the key it will fire, then immediately die. By immediately, I mean run for 1/4 of a second or so.

2nd turn of the key it will crank, crank, crank some more but not attempt to fire - even for 10 or 15 seconds or so.

3rd turn of the key it will start and run immediately, along with a cloud of unburnt petrol out of the back. 

This is reasonably repeatable. I've tried altering the cranking fuel and ASE up/down for the ~60-70C range that leaving the engine for 10 mins or so but it doesn't seem to make a lot of difference. I've tried disabling air temp correction when cranking and that didn't help either. It almost seems like on the second turn of the key it's not sparking, or as if the ECU isn't resetting properly. 

Any suggestions? I'll post the msq later when I'm on the other laptop, but wondered if anyone else had run into this before...

Jon

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I was guessing on heat soak as well, as the underbonnet temps get very toasty on a v8 defender (40+C easily). What's really confusing me is the second lot of cranking where it won't even try and fire, then that it will fire immediately on the third go. Hence I'm wondering if it's something really odd like a bad relay or a megasquirt bug...

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Have you got mat/CLT correction setup? I have used this to pretty good effect to combat heatsoak problems. It basically gives you a curve that allows you to tell the ECU to lean towards either the air temp or the coolant temp under various conditions. 

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Nope - I don't have MAT / CLT correction setup yet - still trying to figure out if it's a heatsoak issue or something else. That it consistently starts/dies then cranks then starts/runs makes me wonder if it's something else. 

What sort of settings have you got setup if you don't mind me asking, has to be worth a try...

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23 hours ago, =jon= said:

Nope - I don't have MAT / CLT correction setup yet - still trying to figure out if it's a heatsoak issue or something else. That it consistently starts/dies then cranks then starts/runs makes me wonder if it's something else. 

What sort of settings have you got setup if you don't mind me asking, has to be worth a try...

Here's what I have, I set it up a few years ago on a hot summers day.

Note that this is a rover 3.5 running on MS2 with a hotwire top end in a Rover P6, and so the engine bay is a bit cramped compared to a defender!

The air temp sensor is just below the passenger side headlight, immediately below where the air filter bellmouth is. 

 

Screenshot_20210819-112103.jpg

Screenshot_20210819-112112.jpg

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  • 1 month later...
On 8/18/2021 at 6:10 PM, FridgeFreezer said:

Coil packs and crank sensors like to fail with heat so that's another avenue of investigation.

It appears that it was a failing coil pack - realised I had a misfire on LPG under load which was traced back to a failing coil pack. It's early days but it appears to have also cured the hot restart issues.

 

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