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PostPosted: Wed Sep 23, 2015 8:01 am 
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Hi there

I'm new to the forum but have been running an LPG system on my Merc V8 for a few years sadly with constant problems. I'm at the point of deciding if I should spend yet more money on the system or actually have it removed.

When I bought the car (a 2003 G Wagen) it had a system fitted but not working. I took the car to a local LPG specialist who diagnosed several problems including the gas injectors being fitted too high in the intake manifold. I basically paid for almost the entire system minus the tank to be replaced.

The car ran fine around town commuting etc for a few months however occasionally the car would hesitate when running on gas and then start shaking and run really badly. Switching the engine off and back on the car would be fine again. Mercedes found misfire fault codes when they serviced the car which I presume related to these incidents.

A few times a year I do long journeys through Europe and was looking forward to taking advantage of the plentiful LPG supply ! Again however the car would be fine for a bit and then do the shaking / misfire thing. Sadly this was a bit scary to deal with on the motorway to the extent my wife would not drive on LPG.

I took the car back to the LPG guys who serviced the system and made some adjustments. But this was a few months later as I don't use the car in the summer.

Again on our trip to Europe the same problems. So we just used fuel which was a real shame over the mileage we covered.

Again before the next years trip I took the car back to the LPG guys who said some injectors had 'burned out' and needed replacing. I was surprised as I estimate we had covered less than 6k miles on LPG maximum. Anyway I agreed yo having them replaced. This time the car went fault again a few days later, took it back to the LPG guys and they made some adjustments.

Once again went on our annual trip to Europe and did about 400 miles before the LPG packed up and could not be switched back in. The car would only run on petrol.

I have now left it like this but want to either get it fixed or removed.

I will add details of the system later today. I guess my questions are, is LPG suitable for this car / engine ? Have I just been unlucky ?

Thanks and sorry for such a long post !


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PostPosted: Wed Sep 23, 2015 8:20 am 
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markob wrote:
occasionally the car would hesitate when running on gas and then start shaking and run really badly. Switching the engine off and back on the car would be fine again.
Mercs, and possibly a few others, do this. If they detect a misfire on one cylinder, they switch it off in case the misfire was caused by something that could cause damage. A restart will put all cylinders back on again. So what starts as a minor cough, for whatever reason, on one cylinder, becomes a permanent misfire. No idea why it runs that rough though as I've run a V8 with a duff coil pack for 100+ miles so it was only running on 6 and while it was down on power and not as smooth as it should be, it still drove OK.

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PostPosted: Wed Sep 23, 2015 9:55 am 
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These engines will run very successfully on LPG if a good kit is fitted and set up well.
As mentioned, they will switch off cylinders as a form of 'limp' mode if they detect even a minor problem.
We have found the most common cause for this is lean running, this causes poor combustion and the car detects a mis-fire.
Normally, if the kit is ok and fitted well, it is just a matter of correct adjustment to cure the problem although we have known the single ignition coils to break down around where they fit onto the plug and cause a mis-fire so worth checking/changing them.


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PostPosted: Wed Sep 23, 2015 7:54 pm 
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Agreed with above replies.

If Mercs detect a misfire on a cylinder they will shut off fueling to that cylinder, and then you have to switch the engine off before it will again pulse the injector (supply fuel) to the cylinder on which the misfire was noted. This methodology is designed to prevent the catalytic convertor being damaged by having unburned fuel (due to the misfire) getting to it.

But as TinleyTech said, most Merc V8's are not at all difficult to get running very nicely on LPG.

Will repeat the message that your system may just need calibrating properly - this is most likely the case. Lean running has also already been mentioned. Other LPG issues on Merc V8s include overly long injector pipe runs (on Merc V8's with engine cover that doubles as air ducting) / insufficient water flow through the reducer (on Merc V8's where there is a water shutoff solenoid at the rear of the engine combined with Merc's unusual heater water plumbing).

Very successfully converted all models of Merc V8 including the various supercharged models.

Simon

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PostPosted: Thu Sep 24, 2015 6:56 am 
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Thanks for the input everyone, I guess I need to find a good LPG engineer to sort this out. Any recommendations for the London / surrey area ? I don't mind travelling further afield though to get it properly sorted !


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PostPosted: Thu Sep 24, 2015 10:20 am 
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Managed to take a look at some of the parts in the engine bay this morning, the two main components I can see say LOVATO on them TYPE RGJ (there are two of these) the computer has a small label on its wiring and says 4080052 - some googling shows this to be a LOVATO EASY FAST SMART 6/8 CYL. wiring harness

Is this a decent system to be starting with ?


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PostPosted: Thu Sep 24, 2015 11:29 am 
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Not bad but not that common. It's Italian as you've probably gathered and they do make decent kit as they have been doing it longer than most. Most Italian manufacturers use an ECU made by AEB and put their own label and firmware in it but I think Lovato use their own (but am willing to be corrected).

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PostPosted: Thu Sep 24, 2015 8:33 pm 
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Agree with above thoughts on Lovato. Software and setup options are very similar in looks and config to the usual AEB systems, all the same options... just looks like a re-arrangement.

Should be no problem with the Lovato or indeed most other ECUs on the Merc.

Have seen many Lovato installs where the reducer wasn't capable of flowing enough gas for the power of the engine... One of the difference between Lovato and most AEB systems is Lovato has the option of pulsing petrol injectors to make up any shortfall in fueling after LPG injectors are open full duty cycle (where other AEB systems would flash the lights on the switch signifying the system has momentarily switched back to petrol). This option is in addition to the usual AEB system option of adding a petrol addition above set rpm and set pinj (which Lovato can also do). The shortfall option usually gets the petrol pulse duration wrong, meaning inaccurate fueling under such conditions, but even where it gets the additional petrol pulse duration correct this option often leads to drive-ability issues... Where additional fueling is needed, the more usual petrol addition option usually works much better. Anything mentioned here might only affect drive-ability above medium/high loads

ECU already covered and neutral on that point, whether or not this is a decent system will depend on what reducer and injectors are fitted. Much will still depend on calibration.

Have a guy bringing me a Lovato system to sort out tomorrow who frequents this forum.

Simon

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PostPosted: Fri Sep 25, 2015 8:23 am 
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Once again thanks for the input above.

An interesting point mentioned by LPGC is the not being able to flow enough gas, I have thought this was an issue since the system was first working, If I ever needed to use a lot of throttle the system would always switch over to petrol, sometimes smoothly sometimes not. Afterwards I could always switch it back to gas and it would be fine though. I presumed it was normal but maybe not, the installers said it was when I asked them.

The times when the system has packed up in Europe it will typically be on a motorway, running on cruise control at 130Km so not heavy throttle. Quite often it did seem to happen when the motorway was climbing slightly so the load would have been higher.

The fact that the last time the system was fixed it needed new LPG injectors, would this indicate they are running too close to maximum / not getting enough LPG ?


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PostPosted: Fri Sep 25, 2015 9:22 am 
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markob wrote:
If I ever needed to use a lot of throttle the system would always switch over to petrol, ... I presumed it was normal but maybe not, the installers said it was when I asked them.

They fibbed. It is a consequence of under-specifying somewhere in the hardware. It can be difficult/expensive to provide a full-spec system on big engines. Customers tend to go for the cheapest quote (as everyone says their system is the best), so it is a "common" symptom in this world, but not "desirable".

markob wrote:
The times when the system has packed up in Europe it will typically be on a motorway, running on cruise control at 130Km so not heavy throttle. Quite often it did seem to happen when the motorway was climbing slightly so the load would have been higher.

That sounds like reducer icing under sustained load (as opposed to traffic-light racing). Could be poorly laid out water plumbing, could be simply underspec hardware again.

markob wrote:
The fact that the last time the system was fixed it needed new LPG injectors, would this indicate they are running too close to maximum / not getting enough LPG ?

No. The hammering that injectors get has little to do with load or stress.
Some simply last longer than others. Very few have anything like the longevity of petrol or diesel injectors, refer back to "cheapest quote" etc. which applies everywhere in the manufacture/supply chain.

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PostPosted: Fri Sep 25, 2015 10:42 am 
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Gilbert, Rosko and myself are all saying similar things.

I missed the 'RGJ' reducer info you provided, this model has an on paper spec of flowing enough gas for 150bhp, you have two of them so that should mean they can flow enough for 300bhp, in theory at least not far off the engine rating so reducer spec not really an issue (but this doesn't mean there isn't still a reducer plumbing or pressure setting issue).

When two reducers are fitted... The reducer outlets should be Y'd together before Y'ing again to the injector rails (ensuring all LPG injectors see the same pressure, further ensuring both sides of the engine get correct fueling). If both reducers are not set to the same output pressure then one reducer does nearly all the work, software will only show the higher pressure reading under most driving conditions, a problem can occur when more engine power is used than only one reducer (the one set to the higher pressure) can supply gas for and then pressure will quickly fall to the lower pressure setting of the other reducer. A bottleneck can be introduced where the common feed pipe (from the tank) branches to the two reducers. Water flow through reducers can be reduced (pun?), as almost invariably installers run water flow through multiple reducers in series - Combined with previously mentioned unusual Merc heater water piping, maybe involving heater water flow control solenoid, would suspect reducer icing (as Rosko said) as prime suspect.

You say the problem usually occurs on foreign motorways.. Hot countries, heater turned right down? If so, this could point to plumbing reducers to the wrong side of a heater water flow control solenoid, to confirm could see if the problem occurs with the heater set to maximum heat!

Simon

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PostPosted: Fri Sep 25, 2015 9:39 pm 
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LPGC wrote:
I missed the 'RGJ' reducer info you provided, this model has an on paper spec of flowing enough gas for 150bhp, you have two of them so that should mean they can flow enough for 300bhp, in theory at least not far off the engine rating so reducer spec not really an issue
Not necessarily. Remember we are talking an Italian system so that could be Italian horsepower they are quoting, which as every knows, Italian horses are smaller than everyone else's..... My Range Rover LSE had a Lovato system, admittedly a single point so completely different, but the reducer fitted was quoted as being good for up to 200 bhp. Now the 4.2 litre engine in the LSE is quoted at around 190 bhp but as it had 180 odd thousand on the clock I doubt it was producing that. At anything over a third throttle the reducer ran out of puff and couldn't cope. Using the same logic, I would suggest that a pair of reducers rated at 150 bhp each would probably struggle at anything over about 200 bhp.

Anything that makes the car different when running on LPG to when running on petrol is not normal if the system is adequately specced, properly installed and correctly calibrated. I consider petrol addition to be a bodge too. If you pay to get a car converted to run on LPG it should run on it all the time, not some of the time and switch to petrol, or add petrol at times when you are using the most. That's when you want to be running on the cheap stuff. To know what fuel you are running on you should need to have to look at the switch, there should be no difference at all to the way the car drives.

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'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.


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PostPosted: Sat Sep 26, 2015 12:23 am 
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It maybe really is completely different to a single point system mate.. 2x150bhp (even Italian rated) sequential reducers should still deliver at least 75% of rated performance in real terms... seems like that's confirmed to me too since I've seen various 130bhp engines running on one of these OK. For a normally aspirated engine to deliver near it's rated bhp it will need to be revving a fair bit, i.e. well above cruising at 85mph rpm (in the case of OP's 5L v8 Merc).

Agreed that no petrol addition should be necessary or invoked in setup on an install, was just pointing out that Lovato default settings invoke such by default when Ginj reached full duration.

Plenty of systems allow temporary and invisibly (no switch notification) switching back to petrol under similar conditions. Expanding on this point, I reckon around 10% of installs I put right are set to invisibly run on petrol at idle (which is generally near one extreme of problems regarding setup) and/or at higher engine loads... especially from done in a day installers. Lovato methodology could be interpreted as attempting to automatically improve on a full fuel switch situation under heavy load conditions, above I was also pointing out that this methodology usually fails. Again, as with all my related posts on other threads, agreed by default that no petrol addition should ever be necessary. You don't get a very good reputation for saving sporty type driver/owners of very high powered vehicles (same cases) lots of money on fuel and getting the best results by setting petrol additions. I probably convert more of that kind of vehicle than anyone else and all my installs run on 100% LPG when the switch says they are.

Simon

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PostPosted: Sat Sep 26, 2015 8:05 am 
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Once again, thanks everyone for your input, really appreciate all the information !

So, I am rapidly coming to the conclusion the system is either under specified or not installed very well.

To recap the car came with a system when I bought it and as it didn't work I negotiated the purchase price down to include practically having a new system installed. When I then took the car to the LPG garage I asked them to make it work and said I wanted a good system and they could replace as much of the old system as needed. As far as I am aware the only part they kept was the tank but they may have tried to use other parts such as the reducers etc. This work was done back in Feb 2012 and I paid just under £1200, since then I have spent a further £350 on new injectors and service work plus the car has been back to the garage 5 or more times for work to fix the system again.

I now regret having not visited this forum before having the work done, I think I would have ended up with a better system !

My dilemma now is wether I spend yet more money to get this working ? Perhaps I can sell off the old parts to offset some of the costs ?


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PostPosted: Sat Sep 26, 2015 8:08 am 
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I have just found some old documents, the original system on the car was a AUTOGAZ STAG-300 not usre if this helps though as it was supposed to be replaced by the LOVATO system


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PostPosted: Sat Sep 26, 2015 8:35 am 
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Stag make the ECU but at the time it was originally installed they were trying their hardest to get into the market by being cheap. They did this by bundling their ECU with the cheapest other components that they could find so it almost certainly had a reducer(s) and injectors that weren't up to the job. What you have now should be capable of working fine assuming it has been installed properly. Nozzle placement and coolant plumbing being the two main things that have both been mentioned by Ross and Simon.

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'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.


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PostPosted: Tue Sep 29, 2015 11:29 am 
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£1200 to replace the engine conversion (keeping the tank) on your model Merc.... You was robbed! Neither Stag or Lovato are expensive ECUs and none of the reducers or injectors mentioned are expensive.

Though should be able to get good results with either if installed and setup correctly... A simple enough vehicle to convert properly, should have been no need for return visits to the installers etc.

Simon

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PostPosted: Fri Oct 02, 2015 7:03 am 
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Thanks for confirming my fears, I won't be returning to that LPG garage then ! I'll update this thread once I have had the system looked at. I think I may take it to the Prins guys in Southampton. Not far from me and they have a good reputation from looking around on here


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PostPosted: Mon Nov 23, 2015 4:53 pm 
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Just a little update on this problem..

the battery on the car started to play up a few weeks back and so I replaced it, afterwards out of curiosity I thought I would try the LPG again and it worked !

Maybe disconnecting the battery cleared fault codes and allowed the system to work, not sure but I managed to get through 4 tanks with no problems.

This week the system is playing up again, only difference being the temperature. If I leave the system to automatically switch over it cuts out and drops one or more cylinders. If however I let the car get much warmer and switch it over manually it seems to run quite happily

Does this point conclusively to the reducer or plumbing not being right ?


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PostPosted: Mon Nov 23, 2015 5:38 pm 
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Mercs have a habit of dropping a cylinder if they detect a misfire on that cylinder. So if it changes over a little early and one cylinder gives a little cough, the petrol ECU sees that and shuts that cylinder off until you restart. It might just be that the changeover temperature has been set slightly too low.

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'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.


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