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stopping backfires on startup 

 

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 Post subject: stopping backfires on startup
Posted: Sat Jul 23, 2011 10:29 pm 
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ok ive got an EF with impco 200 mixer..

it occasionally backfires during startup (maybe every 1 in 5 to 1 in 10 starts)...has never backfired any other time in the 5 years ive had the car

ive tried different leads and plugs (havent tried iridiums or platnums), ive run conduit over the leads and tried to separate the leads from each other...mixtures are good (checked with wideband o2)...

would like to hear from people with EF and AU's (coilpack cars) if youve had this prob and if u solved it, how...

 

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 Post subject: Re: stopping backfires on startup
Posted: Sat Jul 23, 2011 10:39 pm 
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Simple solution, really.

Start it on petrol and flick it over to gas when the engine is warm.

 

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 Post subject: Re: stopping backfires on startup
Posted: Sat Jul 23, 2011 10:59 pm 
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cheers...im not the only one on here at this time on a sat night :o ...

because there is residual LPG in the intake this doesnt help...trust me ive tried that...

 

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 Post subject: Re: stopping backfires on startup
Posted: Sun Jul 24, 2011 1:29 am 
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Should already have a petrol start unit, so starting on petrol already should be happening when cold.
I take it it happens hot also.
I know I've been told SVI systems can have a backfire issue on EF's, mainly if there is an aftermarket cam installed due to the wasted spark setup (coilpack).
Not sure how you can fix the issue, other than a antibackfire flap, and your plugs are gapped to LPG specs, and your leads are okay.
I think Mick at Mick's ProGas might have some advice - PM if you want his no.

 

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 Post subject: Re: stopping backfires on startup
Posted: Sun Jul 24, 2011 6:34 pm 
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i removed the petrol start module because it was making it slow to start when the motor is hot...

generally it doesnt backfire when the motor is hot, moreso when its warm.

how i avoid backfires is to run the lpg out of the intake when im turning the motor off...prob is my missus forgets to do this alot...id like a system that operates seemlessly...

 

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 Post subject: Re: stopping backfires on startup
Posted: Sun Jul 24, 2011 7:10 pm 
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PoweredByCNG wrote:
Simple solution, really.

Start it on petrol and flick it over to gas when the engine is warm.

not really a option when the car is straight gas or the pump is disconnected

i have the odd issue with mine at times but its come good since i replaced the leads and coil
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 Post subject: Re: stopping backfires on startup
Posted: Tue Aug 02, 2011 12:36 am 
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This is why they mostly don't run impco's on anything later than an ED. Should be using an OMVL or similar. Impco's are better suited to earlier models.

Where is your 200 mixer placed?

 

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 Post subject: Re: stopping backfires on startup
Posted: Mon Aug 08, 2011 11:16 pm 
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my mixer is on a pipe about 1 to 2 foot from the TB...

its been an extremely reliable system for the 5 years ive had it, no other complaints other than this

 

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 Post subject: Re: stopping backfires on startup
Posted: Mon Aug 08, 2011 11:22 pm 
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what gap are you using on the plugs?

 

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 Post subject: Re: stopping backfires on startup
Posted: Tue Aug 09, 2011 12:47 am 
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The Judge wrote:
This is why they mostly don't run impco's on anything later than an ED. Should be using an OMVL or similar. Impco's are better suited to earlier models.
Why's that ??
My EL run happily with a 200M mixer - did have backfires, due to old spark plugs, New plugs cured that.
gogetta wrote:
i removed the petrol start module because it was making it slow to start when the motor is hot...
You probably should've left it in, and experimented with the adjustment pot and the jumper connector.
gogetta wrote:
my mixer is on a pipe about 1 to 2 foot from the TB...
That's the one that runs over the rocker cover ??

 

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 Post subject: Re: stopping backfires on startup
Posted: Tue Aug 09, 2011 7:29 am 
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snap0964 wrote:
The Judge wrote:
This is why they mostly don't run impco's on anything later than an ED. Should be using an OMVL or similar. Impco's are better suited to earlier models.
Why's that ??
My EL run happily with a 200M mixer - did have backfires, due to old spark plugs, New plugs cured that.


Yeah Impco air valve systems run fine on the late stuff, the only reason it's not used on BF and later is it can't be made to meet the emissions requirements of the those cars.
The only thing I don't agree with is the fitting of the 200 mixer, A 225 would be better, especially on the barra motor.

 

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 Post subject: Re: stopping backfires on startup
Posted: Tue Aug 09, 2011 5:15 pm 
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Is there off the shelf intake plumbing to mount the 225 to the BBM manifolds ?? - I've only ever seen stuff for the 200 mixers.
I had to make up a custom setup to suit - and as you say, well worth the effort for the better CFM flow.

 

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 Post subject: Re: stopping backfires on startup
Posted: Tue Aug 09, 2011 9:18 pm 
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snap0964 wrote:
Is there off the shelf intake plumbing to mount the 225 to the BBM manifolds ?? - I've only ever seen stuff for the 200 mixers.
I had to make up a custom setup to suit - and as you say, well worth the effort for the better CFM flow.


From the TB to the mixer should be the same as for the 200.
From the mixer to the air box would need to be custom. But it would only need to be a modified version of the typical 3inch stainless pipe most people have.

I had thoughts of trailing a 425 as i've got one here from a 165kw Holden v8 that has 3inch outlet adapter on it. But it would mean reco'ing one of my spare converters and fitting all the impco under bonnet gear. My car has simple mixer with a landi LSE98 conveter. Probably more work then I really want to do.

It may take a bit experimenting with different gas vavles, but I think it could be made to work quite well, given the similar power curve of the old holden 5L and the ford I6.

 

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 Post subject: Re: stopping backfires on startup
Posted: Tue Aug 09, 2011 11:57 pm 
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Yeah I'm assuming you're meaning the EF alloy pipe across the rocker cover - there's no way at all to use the EL 200M mixer setup piping.

BenJ's setup here post1006466.html is a takeoff of how I did mine - I made the mixer bracket for him. On that page mentions the 50CFM better flow, shorter vapour line to the converter, etc. The other thing of course is he needs a heatshield below the mixer.

A 425 would be nice I suppose, but I was surprised how good the 225 was in lieu of the 200 mixer.
Better still, just have to fit my other JX Autogas SVI kit (the one you don't like).

 

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 Post subject: Re: stopping backfires on startup
Posted: Wed Aug 10, 2011 7:22 am 
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snap0964 wrote:
Yeah I'm assuming you're meaning the EF alloy pipe across the rocker cover - there's no way at all to use the EL 200M mixer setup piping.

BenJ's setup here post1006466.html is a takeoff of how I did mine - I made the mixer bracket for him. On that page mentions the 50CFM better flow, shorter vapour line to the converter, etc. The other thing of course is he needs a heatshield below the mixer.

A 425 would be nice I suppose, but I was surprised how good the 225 was in lieu of the 200 mixer.
Better still, just have to fit my other JX Autogas SVI kit (the one you don't like).


200 is rated at 276cfm
225 is rated at 329cfm
425 is rated at 460cfm


I'll dig out the impco cross over pipes at work and double check the info I gave you.

 

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