dead system

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Nevstah
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dead system

#1 Post by Nevstah » Tue Dec 11, 2018 3:34 pm

Hi

Driving the other day and the LPG system (Bigas SGIS) went dead. The 30A fuse that connects direct to the battery had blown.

The wiring loom looked ok with a quick glance, so I opened up the SGIS ECU and it looked and smelled in a pretty bad state. I've not done any testing because I wouldn't know where to start but I'm assuming the ECU is toast.

My question is - is this a symptom or cause? ie. did some part in the ECU expire and cause a short to ground, blowing the fuse? Or is it more likely some other part or wire in the system has caused a short which drew too much current thru the ECU before the fuse blew and caused the mess I'm looking at?

If it makes any difference, the vehicle is a 4.0 V8 Range Rover p38 (bosch/thor)

thanks

Gilbertd
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Re: dead system

#2 Post by Gilbertd » Tue Dec 11, 2018 5:57 pm

Blimey Nev, you're popping up on every forum these days, here, rangerovers.pub and rangerovers.net (where I use Richard_G). It would depend on which bit of the ECU circuit board has burnt out. If it is the output side that drives the solenoids then it should have taken the fuse out first (unless someone has been daft and fitted a 30A fuse or something equally over rated. Equally it could be something that failed on the control side and caused it to burn out that. A photo of the board might help but it sounds like you need a new ECU in any case.
'96 Saab 900XS, AEB Leo, sold
'93 Range Rover 4.2 LSE, Lovato LovEco, sold
'98 Ex-Police Range Rover 4.0, Singlepoint AEB Leo, my daily motor
'97 Range Rover 4.0SE, eGas multipoint, a project.....

Proud to be a member of the YCHJCYA2PDTHFH club.

Nevstah
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Re: dead system

#3 Post by Nevstah » Tue Dec 11, 2018 9:25 pm

Yep maybe my avatar should be Tigger!!
I figured this forum would be the best place for LPG help and advice!!
I tried to take a photo because it doesn't really mean much to me but the light wasn't good enough, I'll try again tomorrow.
I'm just frightened of buying a new ECU, plugging it in and getting that one too

Brian_H
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Re: dead system

#4 Post by Brian_H » Tue Dec 11, 2018 9:34 pm

You say it smells? What of? Burning smells, or does it look like its possibly got wet inside?

Nevstah
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Re: dead system

#5 Post by Nevstah » Tue Dec 11, 2018 9:47 pm

I can only describe the smell as *that sharp burning electric smell*
It looks dry enough inside, just old enough to be fit for a museum!
Pics attached, hopefully they are OK - shout if not or if you need more detail etc. If I havent attched the pics correctly, ie if there is a better way, please let me know :)
Attachments
sgis1.jpg
sgis1.jpg (416.13 KiB) Viewed 962 times
sgis2.jpg
sgis2.jpg (313.54 KiB) Viewed 962 times

Brian_H
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Re: dead system

#6 Post by Brian_H » Tue Dec 11, 2018 9:57 pm

I'd be inclined to check the wiring running to your tank and vapouriser solenoids, Did it still run on petrol like that? If so then seems reasonable to assume the injector cuts circuit is ok, but checking resistance of the gas injector coils wouldn't be a bad idea either before plugging a new ecu in.

Gilbertd
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Re: dead system

#7 Post by Gilbertd » Tue Dec 11, 2018 10:05 pm

That looks to be the switching relay and it has certainly got very hot so checking for a short on the wiring to the solenoids would be a very wise move before plugging a new ECU in. That's also an early ECU with the MAP sensor built in, later ones have it mounted externally.
'96 Saab 900XS, AEB Leo, sold
'93 Range Rover 4.2 LSE, Lovato LovEco, sold
'98 Ex-Police Range Rover 4.0, Singlepoint AEB Leo, my daily motor
'97 Range Rover 4.0SE, eGas multipoint, a project.....

Proud to be a member of the YCHJCYA2PDTHFH club.

Nevstah
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Re: dead system

#8 Post by Nevstah » Tue Dec 11, 2018 10:08 pm

Yes, it defaulted back to petrol and the lights on the dash switch are all out. It's still running fine on petrol with the ECU unplugged so no immediate issue there.
I'll go digging and find the wiring that goes to the tank, there seems to be only one solenoid in the engine bay and 2 reducers/vapourisers
I'll check the resistance of the injectors, but any idea what they should be? No idea what brand they are, just that they are bright red. I'm guessing all injectors should be basically the same?

Nevstah
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Re: dead system

#9 Post by Nevstah » Tue Dec 11, 2018 10:14 pm

Hmm, in that case, of its not a huge deal then I'm tempted to pull out the lpg loom as much as I can and check it through. It looks well cut and sliced here and there, I'm not sure where the car loom ends and the lpg loom starts

Brian_H
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Re: dead system

#10 Post by Brian_H » Tue Dec 11, 2018 10:23 pm

Nevstah wrote:
Tue Dec 11, 2018 10:08 pm
Yes, it defaulted back to petrol and the lights on the dash switch are all out. It's still running fine on petrol with the ECU unplugged so no immediate issue there.
I'll go digging and find the wiring that goes to the tank, there seems to be only one solenoid in the engine bay and 2 reducers/vapourisers
I'll check the resistance of the injectors, but any idea what they should be? No idea what brand they are, just that they are bright red. I'm guessing all injectors should be basically the same?
They vary by type, but you have several examples there of the same type, so you should see the same reading from them. I think the tank or vapouriser solenoid wiring much more likely as its more exposed to the worst of the weather etc anyway. Post a photo if necessary and someone may be able to identify them, I know some valkek ones are red.

If theres only one shared feed to both vapourisers it would make sense that you'd only have one solenoid at the front, I've nicked this bit from Simon from another topic to save typing it out again
LPGC wrote:
Tue Dec 11, 2018 12:56 pm
Yes the relay in the ECU could be burned out.
Might be best to try the solenoid output from the ECU for 12v directly (near the ECU, in case there is a break or short on solenoid wiring) and test during the short window of time between when the ECU switches on solenoids and switches them off (due to detecting low gas pressure). Unless you know solenoid wiring between ECU and solenoids is all good and have checked resistance etc. Each solenoid coil should be around 16Ohms so with two in parallel and both plugged in should be 8Ohms, plus maybe another 1Ohm for the resistance of the wiring, trying one at a time could show up a problem with a coil or wiring that trying both at the same time couldn't (e.g. high wire resistance with low coil resistance).

Nevstah
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Re: dead system

#11 Post by Nevstah » Tue Dec 11, 2018 10:38 pm

Just while I think on, the fused live to the system is direct to the battery, should it not be switched via the ignition? Won't it bea potential battery drain if it's always on?

Gilbertd
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Re: dead system

#12 Post by Gilbertd » Tue Dec 11, 2018 11:40 pm

There will be two feeds, a permanent live and an ignition switched. The ignition switched is usually picked up from one of the petrol injectors but should have another fuse in it. On a AEB based system it is usually a white/red wire. the permanent feed doesn't draw any current until the system is woken up by the ignition switched feed so won't drain the battery.
'96 Saab 900XS, AEB Leo, sold
'93 Range Rover 4.2 LSE, Lovato LovEco, sold
'98 Ex-Police Range Rover 4.0, Singlepoint AEB Leo, my daily motor
'97 Range Rover 4.0SE, eGas multipoint, a project.....

Proud to be a member of the YCHJCYA2PDTHFH club.

LPGC
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Re: dead system

#13 Post by LPGC » Wed Dec 12, 2018 12:21 pm

If it'd had the recommended 15A fuse it would most likely still be OK, with the 30A fuse if a solenoid coil is partially shorted making it draw too much current the relay will have to flow more than it was designed to. Wouldn't be surprised it you find a partially burned tank solenoid or front solenoid coil too.
These old ECU boards and components often look scorched etc but still work OK, though I doubt this one will be OK. Could mess about trying to replace the relay and resistors etc but if you also had to replace silicon bits you'd probably struggle to find replacement components so attempting repair probably isn't worth it. Would be difficult to find a same spec old ECU that would be a slot in replacement for this one so repair may also involve fitting a new ECU plus loom and will involve re-calibration.
Full time LPG installer
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Nevstah
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Re: dead system

#14 Post by Nevstah » Wed Dec 12, 2018 5:09 pm

Oh dear! That sounds quite expensive!! :'(

Gilbertd
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Re: dead system

#15 Post by Gilbertd » Wed Dec 12, 2018 6:35 pm

Looks like this is going to be your best bet https://tinleytech.co.uk/shop/lpg-parts ... ical-pack/ plus maybe £20 or so to replace any shorted solenoid coils that caused the problem in the first place.
'96 Saab 900XS, AEB Leo, sold
'93 Range Rover 4.2 LSE, Lovato LovEco, sold
'98 Ex-Police Range Rover 4.0, Singlepoint AEB Leo, my daily motor
'97 Range Rover 4.0SE, eGas multipoint, a project.....

Proud to be a member of the YCHJCYA2PDTHFH club.

LPGC
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Re: dead system

#16 Post by LPGC » Thu Dec 13, 2018 10:16 am

The ECU and loom Gilbert linked to is probably a good bet, particularly if the new ECU loom is the type that comes with Supaseal connectors to connect to petrol injector break wiring and your existing setup has the Supaseal plugs in petrol injector break wiring, because this could save quite a bit of re-wiring during fitting making some of the wiring just a plug in job. But not all recent looms for these types of ECUs have the Supaseal connectors.

Don't be tempted to try using the new ECU with (the rest of) your old loom though, it can't work anyway because the old loom at least doesn't have the wiring for the remote AEB025 map sensor... so there's no point in trying to use it with the old loom. Trying to use it with the old loom may damage the new ECU because other pinouts are likely to be different.
Full time LPG installer
Servicing / Diagnostics / Repairs to all systems / DIY conversion kits supplied with thorough tech support
Mid Yorkshire
2 miles A1, 8 miles M62,
http://www.Lpgc.co.uk
Twitter https://twitter.com/AutogasSimon
07816237240

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