LPG on P38 backfiring...

[deano2469]

Hi Guys, on to more quirks with my P38, I have the EAS sorted now and its time to fix up a few other issues. It had LPG on it when i bought it and it used to backfire a lot. This forum put me on to the plugs and a friend told me to close up the gaps on them. Which I did and went a year without a backfire. changing oil, filter and plugs every 10,000. After car was off the road for EAS rebuild, the battery is now on its way out, I get random faults on cranking , which happened last time battery died so thats ok...new one on the way. The issues i'm also getting are faults when i turn lights on at night and when going to high beam i get a gearbox fault or whole dash and everything goes off for a split second and back on. i also get a backfire again...its only under acceleration and its rare. Ichanged the MAF to a spare i had and that made it worse...onw i'm back on no MAF at all.Seams to be better. I have power to the MAF when on gas at idle so I assume its controlling something. I used to think all that was shut off on LPG but no.Can anyone shed some light on some of these issues..i'm kinda hoping the battery is the cause of most of it but not sure..on a tight buget so might take a few weeks to replace...the headlight and backfires are getting annoying...more than usual.

cheers in advance

P.S...I mentioned in LPG section and got good advice on plugs but not the voltage draining stuff.:confused:

[daf11e]

Deano in my experience over the past 8 years of ownership I can assure you these cars do not like iffy batteries.....I have changed mine a few times and on each occasion the electrics were haywire, from gearbox fault to lights. See how you go with the new battery....."oh and get a good one".....The one I currently have is Optima , some prefer others but this one has been excellent.

[deano2469]

thanks daf11e, i am hoping this is the case, i will keep an eye out for that brand. My brother has a friend who sells Turbo batteries and from his experience they are really good too.

[ian4002000]

Yep, Put a new battery in first, then look for other electrical problems.
P38's are most likely voltage sensitive so if the battery is low you are likely to get many problems

[bruce p38]

Ill back that up!
My vehicle had exactly those symptoms with an old battery after purchase. Asked the fine men of this forum who all said fit a decent battery that holds all its power. I did and no more ghost faults.
Good Luck

Bp38

[TheTree]

Also check the earth points, especially the one to the chassis on the shock turret and the one from there to the block.

There was a LR service bulletin about these earth points and the ECU one under the back of the drivers seat

Steve

[deano2469]

thanks, Bruce P38, thetree and ian4002000, I replaced battery yesterday and also took earth off strut tower and cleaned up joint. It looked fine but now better. I have not yet looked at earth under seat as was too dark but that is next. I started and got no faults but as soon as i flashed high beams i got a gearbox fault again. also when i put my foot on brakes the lights all dim. I checked alternator and is all good at 13.88 volts when running..kind of hoping the earth under seat is it. Anything else i should look for guys?

thanks again.

[daf11e]

Deano there is a great. Electrical checklist on RRNet ...p38 electrical sticky...it covers,common symptoms,battery test,check charge circuit with no load,check charge circuit with full load,check cables for voltage drop,check alternator.etc etc...I believe it is a great way to methodically check everything....that's what I would do next IMHO.

[deano2469]

Hey daf11e, thanks man, I just found the page today at work. I will go through it all, step by step. I'm on my second alternator so far so hope that's not the issue, anyway, we will soon see.

Cheers.

[deano2469]

Also check the earth points, especially the one to the chassis on the shock turret and the one from there to the block.

There was a LR service bulletin about these earth points and the ECU one under the back of the drivers seat

Steve
Hey mate, the earth behind drivers seat...I am having drama finding it, will i need to take up carpet and sound deadening to find it? a rough idea will do, i got the front and sides of BECM sorted , all is tight and corrosion free.

Thank you.

[TheTree]

Hi Mate

You need to remove the A/c ducting and lift the carpet, it's behind the BECM almost on the rear passenger floor.

A bit of a bugger to get at !

Good luck
Steve

[deano2469]

Thanks mate, will check it out tomorrow.

[TheTree]

The other spot is behind the kick panel where the bonnet release is, the panel is held on by a screw and a clip.

There is an earth point there, and a white connector which tends to get corroded as well

Steve

[deano2469]

hi again, well i looked at all those places, undid the bolts and moved around and re tightened.There was no sign of corrosion at all in any spot. I did the two in engine compartment too as when i go to high beam the radio turns off and on and they were listed.If engine is running its not so bad and if i switch on and off a few times only the first one or two will turn radio off and on...still no dash faults though so i think new battery helped. I read in a forum that at 2000rpm i should be getting 14.4v or so from alt but i get 13.54, so i swap out alternator to a spare i had, this one does 13.78v , i always thought that was normal. My radio is aftermarket and the wiring is a birds nest...i unplugged it and found no change so must be ok. I will get new relays to replace the ones under kick panel, failing that i might have to bite bullet and take to an auto electrician.

thanks again for assistance.

[davidsonsm]

Could your issues be related to the engine bay fuse box? Is there any evidence of hot spots or over heating when you inspect under the relays?

[deano2469]

I thought of that too Davidsonsm, I am on my second fuse box now, the old one had cracks all over it. i think its ok. The relays, the yellow ones all have a little browning on them but have been swapped with other spares and found to be ok. i am planning on taking it out again and going over it. I could not see where one of the relays was related to the lights. Thanks for the idea though.I will check again.

[TheTree]

In order to get 14.2V you need as much load as you can put on so headlights on high beam and HEVAC fans flat out. Then hold the engine steady at 2000 RPM and measure the voltage

Steve

[Hoges]

Along shot, but check out Relay #11. The relays are numbered vertically from the top LHS of the fuse box ...check the diagram under the lid. Relay #11 is involved with high beam. I am thinking that also you may have an issue with the BECM (hopefully not!) As best I can determine when you use the high beam, the act of blipping the indicator stalk sends a message to the BECM which activates relay #11.

It may be worth removing relay 11 and seeing if it has an impact on the radio etc. I haven't done this to test my theory :wasntme: just trying to eliminate possibilities.

[deano2469]

Hi hoges , I played with relay #11 it looks ok, not burnt. I removed and flicked high beam, no difference. If I was to replace BECM...god forbid , but if I do, do you know if any other computer needs to pair with it on the change or just the unit alone.

Sent from my HTC One XL using AULRO mobile app

[TheTree]

Hi hoges , I played with relay #11 it looks ok, not burnt. I removed and flicked high beam, no difference. If I was to replace BECM...god forbid , but if I do, do you know if any other computer needs to pair with it on the change or just the unit alone.

Sent from my HTC One XL using AULRO mobile app

If you replace the BECM your key remotes will no longer work and your ECU will need to be paired, unless you have a Bosch system in which case you need to fit them as a pair.

Much easier just to get the BECM repaired, which is the path I am taking.

Steve

[deano2469]

Thanks Steve, could you tell me where you are looking to get it repaired. I have seen places in the USA and UK but not in Australia. I have a rear window that wont move either, replaced motor and plug has a burnt pin so assume BECM as well for that. might be an option if not too pricey

Cheers

[TheTree]

Hi

Rupert Prior on this forum does BECM repairs as per this thread

http://www.aulro.com/afvb/p38a-range-rover/206998-lost-power-internals-hevac-windows-etc.html

He also suggests LabElectroniucs for major repairs

Labtronx Home (http://www.labtronx.com.au/)

Steve