LPG ECU piggy-backing causing main ECU failure? V6

[Ron Miel]

Relevant maintenance/repair/trouble-shooting history, this year:

Very poor starting in freeze up (and particularly, the damp-everywhere thaw), February-ish. I changed dizzy cap, rotor arm and plugs - problem solved.

LPG consumption up a bit all year but no action taken until last weekend - I then changed the O2 sensor with a "universal", everything else having been changed by then! The old (original Denso) one was indeed gunged up, and I am now checking ongoing consumption. Something is happening anyway, as mid power range LPG running (not accelerating) is now noticeably (even) quieter. Believe gunge up was due to a period last winter when Flashlube over-dosing accidentally took place for a while.

Very rough running and power down, on petrol. Surging and stalling at idle on LPG. I changed the air filter - LPG problem solved. Petrol problem partly solved but power still a bit down, with a misfire on tickover.

Water pump bearing noisy. Water pump changed by Bongo friendly, V6-experienced, garage. While changing the water pump, the garage discovered cambelt hydraulic tensioner seized, so tensioner replaced, and cambelt for good measure at the same time. Oil seals fine. Full annual service carried out. Garage declared misfire due to a need to replace the HT leads, so all leads were replaced. Problem not solved, so garage then delared "it can only be a failed injector" (it is being ECU-pulsed), and the misfire is on number 4.

After a quote from Mazda of £360 ex Japan for a replacement injector and O-rings, I fortunately, with help from cheffy24, found a good one at a breaker in Devon and collected it while down there anyway.

Same Bongo-friendly garage fitted the replacement injector. Misfire not cured. Technician had gone home when I collected the van but the salesman-owner said "it must be something inside then, probably a burnt out valve - it happens with all LPG conversions". I pointed out that Flashlube has been used thoughout and that, if anything, this forum has rung to the cries of peeps who don't use Flashlube, and do not burn out valves - as Bongo valve seats are not soft anyway. Then showed him that switchd over to LPG, there is no misfire, therefore no burnt out valve. We then agreed, it might be an ECU-related fault and he offered to do an ECU substitution test when he's got another V6 in.

Next day, I reset the ECU, with no improvement - still misfiring on one cylinder during petrol idling. Spoke to the technician who had changed the injector, who confirmed that the compression on the misfiring cylinder is good, and is the same as others he checked, and that the injector is still being ECU-pulsed. However, his opinion: "LPG conversions wreck engines!!!!!!!!!!!!!!!!!!!!!". Said they've had lots of problems with 2.0 litre Bongo LPG conversions, in particular, where piggy-backed LPG ECUs had apparently interfered with main engine ECU functions, possibly due to signal loom interconnection issues. They don't do LPG, and in the end had junked several engines they could not fix!!!???????.

First I've heard of it but the interaction sounds feasible. Anybody else met any problem of that nature? Might need to go and see Paul at lpgimports. Are you there, Paul?

Cheers,

David

[g8dhe]

It does indeed sound a perfectly acceptable explanation !
Accept for one thing the garage have obviously never actually found the real problem on all the junked engines - so really they have no idea what so ever as to the cause - its very easy to come up with what sounds like a perfectly feasible explanation - provided you don't investigate to the very end
My take on an explanation like that is if its an actual design fault then every installation would suffer the same problem - obviously not. If its a case of a design close to tolerance limits then its possible, but changing the boards one at a time would remove the item close to tolerance and the problem would be solved why haven't they done this on previous junked engines ? I think their scratching for ideas and are happy to jump on any passing band wagon of an explanation It doesn't help solve the problem, I do appreciate, but unless they can very methodically remove each possible cause and finally identify the component that is faulty they won't learn what the problem is, in the mean time your wasting time/money for them to self train.

[haydn callow]

Have you tried turning off the flash lube ??

Is the misfiring plug 'sooty' ?? (if so "sweep" it)

[haydn callow]

This forum is running painfully slow

[mikeWalsall]

Maybe we should start a Bongo Forum Poll to who as what make of LPG system fitted ... and what issues (if any) have they had ..!!

I was going to get my V6 converted by the guy who fitted the Zavoli Alisei N LPG system to my Toyota about four years back .. as she has always been 110% trouble free ..

But .... with some of the 'issues' reported in the LPG converted V6 I have entrusted mine to some one with Bongo specific expertise ... lpgimports Coventry ... who are fitting a Romano RISN LPG system ... Paul collected it from my house on Wednesday ...

As a matter of routine I am having Flash lube fitted .. On my 'lean burn' four cylinder 16v DOHC 2.4 Toyota I have it set at one drip every ten seconds (at tick over vacuum) .. I have no idea to what the 24v DOHC six cylinder 2.5 Mazda should be set to ..



The guy who fitted the LPG to my Toyota ... and coincidently Paul ... both mentioned that the ignition system needs to be 100% OK as any problems will be exaggerated with the use of LPG ...

[Ron Miel]

It does indeed sound a perfectly acceptable explanation !
Accept for one thing the garage have obviously never actually found the real problem on all the junked engines - so really they have no idea what so ever as to the cause - its very easy to come up with what sounds like a perfectly feasible explanation - provided you don't investigate to the very end
My take on an explanation like that is if its an actual design fault then every installation would suffer the same problem - obviously not. If its a case of a design close to tolerance limits then its possible, but changing the boards one at a time would remove the item close to tolerance and the problem would be solved why haven't they done this on previous junked engines ? I think their scratching for ideas and are happy to jump on any passing band wagon of an explanation It doesn't help solve the problem, I do appreciate, but unless they can very methodically remove each possible cause and finally identify the component that is faulty they won't learn what the problem is, in the mean time your wasting time/money for them to self train.

I'm not going to slag off the Bongo-friendly as they've already been doing the equivalent of "changing one board at a time" - not that interaction in the wiring looms is board-based, and not that I would let them start pulling boards out of ECUs either. It's not their area of expertise. I used the term "trouble-shooting" in my opening para because that, in my view, is what their technician has been doing - substitution trouble-shooting. We all have to do that at times, garages included, especially in V6 Bongos with uncertain OBD outputs - certainly not western OBD 1 or 2. They didn't, and don't, claim to be LPG experienced - but they clearly don't like having to work on LPG converted engines. They would, if they had to pay the fuel bills

The only reason they suggested possible LPG wiring loom issues really is that on occasion they've "moved things around" or remade connections, and seemed to resolve problems - but they haven't done it enough, on enough vehicles, with enough different LPG kits, to convince me, hence I might call in on LPG Imports when I'm going that way. I can live with the idling misfire and power reduction on petrol meanwhile - it just makes me more dependent on LPG than I want to be, as I don't like unnecessarily driving an unbalanced engine. For the moment though, any decent journey involves pre-planning my LPG fill up points - nuisance!

[Ron Miel]

Have you tried turning off the flash lube ??

No. How would that affect a persistent misfire on just one cylinder, with good compression, injector, plug, HT lead, dizzy cap and rotor arm - and on petrol only?

Is the misfiring plug 'sooty' ?? (if so "sweep" it)

No, it isn't.

[Ron Miel]

Maybe we should start a Bongo Forum Poll to who as what make of LPG system fitted ... and what issues (if any) have they had ..!!

BiGas - installed in October 2008, by SVS, Wimborne, for Imperial Motors, as part of our camper-conversion deal. I have noticed (on the Tinley Tech website) this week, that the current (pun not intended) BiGas injector loom is plug-compatible to piggy-back on either Bosch or "Japanese" (Denso?) injectors, whereas early ones were apparently solder-connected. Can't see what mine is (or rather, the weather's been too foul since I saw that to re-check) but, if I've got the soldered version, that may be where the problem is - but it's the petrol side that's misfiring, so that would probably imply a cut-and-solder job. Annual LPG safety/filters-change service is booked for next Wednesday, so if I've not worked it out by then, I'll ask them to have a look. They are just a fairly local BiGas installer but with no Bongo experience, so I'm not sure I would want them delving more deeply than that, though - I think the engine casing (handbrake-mounting, and a lot of wiring which runs under it in our conversion) has to come right off to get at it, both sides. Best move on your part, to go to Paul, I think. If he doesn't pick up meanwhile, do me a favour please, and ask him to read this when he has the time.

As a matter of routine I am having Flash lube fitted .. On my 'lean burn' four cylinder 16v DOHC 2.4 Toyota I have it set at one drip every ten seconds (at tick over vacuum) .. I have no idea to what the 24v DOHC six cylinder 2.5 Mazda should be set to ..

The guy who fitted the LPG to my Toyota ... and coincidently Paul ... both mentioned that the ignition system needs to be 100% OK as any problems will be exaggerated with the use of LPG ...

I think that Flashlube rate is also about right for the Bongo V6, although I've fine tuned mine over time by litres LPG consumed against litres Flashlube used, without re-checking the drip rate. It's now deliberately running at about 60-70% of the prescribed dose rate, to ensure it can't creep back to an overdosing rate unnoticed, as it did last winter when the engine covers weren't lifted often enough to keep an eye on it. The stop/start running in winter, with less long runs, was probably the cause of that, with max Flashlube consumption just when you don't need it, idling cold/full vac. I think the electronic Flashlube kit, also ECU-connected(!), is meant to correct for that, so I might get round to fitting mine this spring - but one thing at a time!

I believe, and so does my "Bongo-friendly", that my ignition is well up to scratch.

Cheers all for replies

David

[mikeWalsall]

I do not know much about any particular LPG system .. I took my Toyota in for a gas service a couple of months back and the fitter mentioned that I 'may' need a new set of (gas) injectors at the next service as I had missed last years service (through no fault of mine at the time) ... and they may be getting 'fouled' ..

I chose the Romano because they have individual injectors to each cylinder (ie: they are not grouped on a rail) so each one can be removed individually / dismantled and be physically cleaned ...

While Paul from lpgimports was here the other day he looked through the fitting manual for the Zavoli system (fitted to my Toyota) and remarked that although the main hardware was different from the Romano system he generally fitted ... the Electronic Control Unit (ECU) / operating systems where identical, as are on a lot of LPG 'kit' systems .. as most are sourced from the same electronics manufacturer ..

It is the LPG (laptop) software and the individual setting / parameters for various engines that dictates for correct / efficient engine operation .. so I can only assume that a 'none Bongo .. LPG savvy' garage would struggle more in troubling shooting any system without the right expertise with LPG and software 'back up' ..??

[Rhinoman]

I don't understand (I've had a glass or two!). My first thought as that the ECU is retuning to suit the LPG and when you switch back to petrol it needs to recalibrate but that would affect all cylinders.
Its a pity you don't have a scan tool to see what the ECU thinks is going on. The compression is good so the engine should be good, it only misfires on one cylinder but its not the injector or the ignition system, the ECU pulses the injector so the ECU should be good. So there isn't anything wrong with it but it misfires, they must have missed something they go back over it again.

[Ron Miel]

I don't understand (I've had a glass or two!). My first thought as that the ECU is retuning to suit the LPG and when you switch back to petrol it needs to recalibrate but that would affect all cylinders.
Its a pity you don't have a scan tool to see what the ECU thinks is going on. The compression is good so the engine should be good, it only misfires on one cylinder but its not the injector or the ignition system, the ECU pulses the injector so the ECU should be good. So there isn't anything wrong with it but it misfires, they must have missed something they go back over it again.

No! A eureka moment perhaps - I just found this http://autogashelp.co.uk/InjectionSystems2.aspx, which suggests to me that, if he's got it right*, the fault is probably either in the LPG ECU, or the wiring from it to that particular petrol injector.

Maybe this is something our local Bigas installer/servicing outfit will be able to check out after all, directly at the LPG ECU wiring interface - or I will? I had, until now, blithely assumed that the piggy-backing just meant parallel pick up of switched negatives at the petrol injectors but should have realised that would not switch off the petrol injectors while in LPG mode. Of course, the LPG also has to generate altered pulse lengths to suit LPG-specific injection and mix requirements at different engine loads/speeds.

*(The only bit I perhaps question is this: "A greatly reduced signal is sent to the petrol injector which is not strong enough to open the injector, but is enough for the petrol ECU to not see a fault." Doesn't he really mean not long enough, in duration, to open the petrol injector, rather than not strong enough? After all, the main ECU just provides a negative to an already live solenoid, so unless resistance is added, the applied voltage isn't altered - or is that what it does do?)

[New Forest Terrier]

This sounds most complicated David and comes on the heading of absolutely rotten luck. It sounds awfully like the problems I had with a LPG converted Range Rover that suffered a ecu failure after four years running on LPG.

That was back in 2004, converted in 2000 when LPG kit was a lot more primitive with single point rather than multi point injection. I had a series of problems with the poor quality of the kit plus the original converter went out of business, making servicing almost impossible. In the end the Range Rover was worth less than the cost of the repairs needed, replacment ecu and new LPG kit, so we parted company. Much mourned and much regretted. The actual cause of the final problems was never found do the lack of any expert knowledge in this area at the time.

We now have a good local converter and I got the courage last year to have my Jeep converted with a Prinz system. So far all good, even the previously reported as failing lambda sensor tested as perfect on the last MOT. Low compression engine no flashlube needed, could be the LPG degrunged it? I was just considering taking the plunge with the Bongo when I read this. I will certainly hold off untill your problem is resolved as I do not want anything similar to happen to the Bongo.

I have been recommended not to have flashlube by one Bongo specialist and to have it by another. Decisions, decisions. Now back to dithering convert or not. If it wasn't for the Rangie disaster, it would have been done last year but the Jeep was thirstier and less loved so came first.

Just hpoe you solve this one David, so I can finally get mine converted on 73p a litre.

[Ron Miel]

This sounds most complicated David and comes on the heading of absolutely rotten luck. It sounds awfully like the problems I had with a LPG converted Range Rover that suffered a ecu failure after four years running on LPG.

That was back in 2004, converted in 2000 when LPG kit was a lot more primitive with single point rather than multi point injection. I had a series of problems with the poor quality of the kit plus the original converter went out of business, making servicing almost impossible. In the end the Range Rover was worth less than the cost of the repairs needed, replacment ecu and new LPG kit, so we parted company. Much mourned and much regretted. The actual cause of the final problems was never found do the lack of any expert knowledge in this area at the time.

We now have a good local converter and I got the courage last year to have my Jeep converted with a Prinz system. So far all good, even the previously reported as failing lambda sensor tested as perfect on the last MOT. Low compression engine no flashlube needed, could be the LPG degrunged it? I was just considering taking the plunge with the Bongo when I read this. I will certainly hold off untill your problem is resolved as I do not want anything similar to happen to the Bongo.

I have been recommended not to have flashlube by one Bongo specialist and to have it by another. Decisions, decisions. Now back to dithering convert or not. If it wasn't for the Rangie disaster, it would have been done last year but the Jeep was thirstier and less loved so came first.

Just hpoe you solve this one David, so I can finally get mine converted on 73p a litre.

It WILL be sorted, and I will keep posting until it is - so fear not, and get the Bongo converted as well asap

It's only 67.7p/litre locally today BTW, and, according to Go-Autogas, it's as low as 59.7p at Flogas, St Austell - best in the UK right now.

I don't even mind all the bits I've changed as part of the trouble-shooting. She'll be 11 years old ex works in 6 days time (albeit first reg, in Japan, 1 April 2001), and I mean to keep her rolling, so even those items which were not actually needed immediately are timely investments in that cause. The spare injector I now have only cost me £40 to replace with the one from a breaker, so if anybody needs one, that's the price. Learnt a lot of useful stuff too - in particular, always make sure you've done enough reading up to be able to double-check what the spanner man says

[The Great Pretender]

Ron, sorry if I have missed something as I just speed read most of the posts.
Going back to first principals, why are they certain of the cylinder that is the problem? As replacing the injector didn't cure the problem could the connector be causing the misfire or could it be another cylinder with a dicky injector?
Sometimes you get blinkered and look to deep for problems.

[Ron Miel]

Ron, sorry if I have missed something as I just speed read most of the posts.
Going back to first principals, why are they certain of the cylinder that is the problem? As replacing the injector didn't cure the problem could the connector be causing the misfire or could it be another cylinder with a dicky injector?
Sometimes you get blinkered and look to deep for problems.

Yep, you've missed something. It's all set out above