Need help with cold start issue.

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locky
Posts: 10
Joined: Tue Oct 30, 2007 11:31 am

Need help with cold start issue.

Post by locky » Tue Feb 16, 2010 9:30 pm

Hi all. I need some advice if possible. I have a 4.4 Range rover V8 with the Bmw M62 engine. My lpg system is an OMVL dream 21N.
The problem I've been struggling with for the last few months are starting the car from cold after it's been run on gas.
If I set the change over temp to 48 degrees (fuel trims seem to come off choke cycle at this point) I have no problems with cold starting.
I want to try to get the change over temp down as it's costing me a ton in petrol as half my journey to work is done by 48 degrees.
If I set it to 25 degrees change over is quick and it runs fine but the car won't start well from cold. It takes a lot of cranking.
Fuel trims look the same. Is there some thing thats adapting the warmup cycle that I'm not seeing? I'm using scantool to read long and short term trims.
Should it be possible to get a lower change over temp? I've chatted to others with change over temps of 20degrees with this engine.

Thanks all.

mak-uk
Posts: 288
Joined: Mon Sep 03, 2007 8:48 pm
LPG System: Prins VSI
Car: BMW 540iA Sport
Location: All over the UK

Re: Need help with cold start issue.

Post by mak-uk » Thu Feb 18, 2010 9:59 pm

Hi

I have the same engine and can change over to LPG at any temp I suppose but I don't set it under 30 degrees so as to keep the petrol injectors in good condition. Before closed-loop mode kicks in, the vehicle is in enrichment mode so it's going to be dumping lots of fuel in - this will be replicated on LPG.

I don't know why it's running that lumpy when cold but have u tried running on petrol a couple of days then checking? It could be that you have an air leak which is notorious around the inlet manifold on these engines.

Mak
Mak
Site Owner
2001 BMW 540i Auto Sport Saloon
~300 BHP; ~320 ft/lbs, Prins VSI system

locky
Posts: 10
Joined: Tue Oct 30, 2007 11:31 am

Re: Need help with cold start issue.

Post by locky » Thu Feb 25, 2010 10:36 am

Thanks Mark,

I've tried a couple of times running on petrol for 3-4 days then checking fuel trims on lpg by switching over. I've got a perfect rich lean toggle at all rpms now. It just doesn't like running with the change over anything below 50 at the moment.
If I set the change over to 30 or 40 degrees the fuel trims just go straight to +25 and put the engine light on.
I can get it to run with a lower change over if I make it rich on the lpg side but then it puts the engine light on when fully warm. My car seems to stay in an enriched cycle upto about 80 degrees engine temp. The lpg doesnt seem to replicate it very well.
I might try tightening down the inlet manifold this weekend

mak-uk
Posts: 288
Joined: Mon Sep 03, 2007 8:48 pm
LPG System: Prins VSI
Car: BMW 540iA Sport
Location: All over the UK

Re: Need help with cold start issue.

Post by mak-uk » Thu Feb 25, 2010 7:02 pm

When switching over to LPG, it should follow your petrol signals and so the fuel trims shouldn't be THAT out. +25 sounds like an air leak to me.
Mak
Site Owner
2001 BMW 540i Auto Sport Saloon
~300 BHP; ~320 ft/lbs, Prins VSI system

locky
Posts: 10
Joined: Tue Oct 30, 2007 11:31 am

Re: Need help with cold start issue.

Post by locky » Thu Feb 25, 2010 11:55 pm

Thanks Mak.

I'll give the manifold a check over this weekend.

capcarap
Posts: 11
Joined: Fri Mar 05, 2010 12:36 pm
LPG System: stag 300
Car: Fiat marea

Re: Need help with cold start issue.

Post by capcarap » Fri Mar 05, 2010 12:57 pm

Hi
i had problem on -15 C with starting engine.My problem was water in fuel .Water condensate during long period of time cause we on lpg do not use (thankfully ) too much gasoline.I consumed old fuel and put fresh in tank and no problem any more.always put additive like flash lube in gasoline when putting fresh gasoline in tank.

locky
Posts: 10
Joined: Tue Oct 30, 2007 11:31 am

Re: Need help with cold start issue.

Post by locky » Sun Oct 17, 2010 10:53 pm

Well I seem to have this issue sorted. But in a strange way. My car always seems to run with LTFT at -2 on petrol. So I was matching this with the gas. I did ANOTHER autocalibrate (probably my 20th) and it gave me a very lean map. I added 5% which brought my LTFT to +2 but the car starts and runs perfect. Lot more power than before also. Is there any risk running the gas a bit lean?

mak-uk
Posts: 288
Joined: Mon Sep 03, 2007 8:48 pm
LPG System: Prins VSI
Car: BMW 540iA Sport
Location: All over the UK

Re: Need help with cold start issue.

Post by mak-uk » Mon Oct 18, 2010 4:33 pm

Anything between -10 and +10 fuel trim is seen as acceptable so between -5 and +5 is very good indeed.
Mak
Site Owner
2001 BMW 540i Auto Sport Saloon
~300 BHP; ~320 ft/lbs, Prins VSI system

locky
Posts: 10
Joined: Tue Oct 30, 2007 11:31 am

Re: Need help with cold start issue.

Post by locky » Mon Oct 18, 2010 6:36 pm

Thats great. Thanks Mak. I could actually get it to dead 0 but again it still caused starting issues.

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