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PostPosted: Tue Nov 01, 2016 9:46 am 
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Joined: Mon Sep 16, 2013 11:53 am
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Over the past week noticed slight intermittent misfire especially under load and twice switching back to petrol.
Quick check over and nothing untoward found on any of the usual culprits.
Plugged in diagnostics, found petrol injectors firing at the same time as running LPG, also managed to capture a change over to petrol at 120s, this while steadily increasing revs, at about 1400rpm
Scope capture below, traces from top to bottom:
RPM
Petrol Injector 1
Petrol Injector 2
Petrol Injector 3
Petrol Injector 4
Coolant volts
O2S11 volts
O2S12 volts
DPFE volts
Time ms
Image

ANY suggestions, no matter how obscure, welcomed.


Last edited by adam.grafton on Tue Nov 01, 2016 3:21 pm, edited 4 times in total.

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PostPosted: Tue Nov 01, 2016 10:56 am 
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Joined: Wed Sep 29, 2010 5:01 pm
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Location: Yorkshire
Forget the changing back to petrol and O2sensors reading full rich for the moment - both likely due to the engine running very rich due to receiving both petrol and LPG fuelling at the same time.

Running on both fuels at the same time is the problem - Does this Transit have the relays under the dash that disable petrol injectors, and if so are they switching?

There is a sticky thread about how to post images on this forum, we can't see whatever you tried to attach.

Simon

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PostPosted: Tue Nov 01, 2016 11:30 am 
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I can, the picture appears in the post perfectly.

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PostPosted: Tue Nov 01, 2016 1:55 pm 
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not running "very" rich, just a little more so than usual,
plugs are dark tan centre, edges dark grey
rather than the usual dark creamy beige colour electrode

relays are under dash,
tested and all working ok when individually tested earlier this year
have moved all 2 slots along in sequence on Sunday, no effect
have probed outputs with Fluke 177, no response, DMM might not be quick enough to monitor change
may have to monitor with scope later


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PostPosted: Tue Nov 01, 2016 5:41 pm 
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Joined: Wed Sep 29, 2010 5:01 pm
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Location: Yorkshire
Gilbertd wrote:
I can, the picture appears in the post perfectly.

Ahh, then I suspect it was dodgy internet at my end while I was sat in a car in the yard! :roll:

Don't read much into plug colour while running on LPG.

If the engine was supposed to be running on LPG but also receives petrol, the standalone LPG system will attempt to lean LPG mixture right off, so only a bit flows to the engine - so it might be just a bit rich.

In what respect are relays working OK? Have you tried pulling those relays to see if the engine will run on petrol / on LPG? I was thinking more along the lines of the switching signal to relays not working.

Simon

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http://www.Lpgc.co.uk
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