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PostPosted: Tue Oct 22, 2013 6:20 pm 
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Hi guys

I recently converted by mercedes CL 420 while I having many problems... one of the ones that keeps coming back is that the car keeps switching back to petrol. Now from what I can see it does this when I am driving at somewhere between 60 and 70 mph and then I take my foot off the acclerator ( I could be free wheeling down a hill or long decline) for about 30 seconds or so. I get a warning sound and then it swtiches back to petrol and I can not switchnit back until I restart the car.
I have brought it back to my installer and on the last vist he mentioned about the time out period for the lambda sensors. The way I understand this is.... when you have your foot off the acclerator you are running lean (little or no fuel) and after a set period of time the Prins VSI system will see this as a problem and switch the injectors off. His way around this is to extend this timeout period.

Has anyone come across this before.... Is it a feasible answer...is this xome sort of saftey timeout... Am I having the wool pulled over eyes.... Prins themselves in holland are not very helpful. My instzller is a Prins dealer, but ive had so many problems im not sure what is correct and not... so help in understanding would be great


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PostPosted: Tue Oct 22, 2013 7:19 pm 
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Looks like lpg system lost rpm signal...and turn to petrol...
when you take off your foot from accelerator and going down hill..petrol injection time is zero... when rpm drops close to 1k rpm ...petrol injectors wake up....
it must be easy to fix..
I work with kme systems there is option in lpg ecu do not signal when there is no petrol signal.you click that box problem sorted...

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PostPosted: Tue Oct 22, 2013 7:32 pm 
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jookul wrote:
Has anyone come across this before.... Is it a feasible answer

Yes, I've done exactly this for the same reason. Funnily enough the first time I got caught by it was on a Mercedes too.

Unlike KME etc. the Prins can timeout if the lambda sensors are inactive - it is a safety feature to allow the engine management to do its thing and manage a fault situation. The factory default timeout is quite short, 35s or so, and can be set off sometimes during normal driving as you have found.
I nowadays always extend that timeout to at least double.

Did you think you were being swindled or something, why the doubt?

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PostPosted: Wed Oct 23, 2013 6:00 am 
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Thanks forvthe replies...im not so much getting swindled, but I am havong a lot of probkem with the system and am constsnly back at the installers. I just need to understand whats correct and what isn't. Im not sure I have the rpm problem as I guess this would be more frequent, I do think its more the lamba timeout issue. I think I can possibly recreate which I am going to try to do over the next coming days. But I will also bring up the rpm quedtion to the installer again.


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PostPosted: Wed Oct 23, 2013 9:49 am 
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I don't understand why you don't just take it back and let him extend the timeout. Takes one minute.

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PostPosted: Thu Oct 24, 2013 8:18 pm 
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Hi guys

so I took it to the installer....a bit of ba k ground....so one of the problems is this.... when I driving eg 60 to 70 mph and I take my foot of the acclerator for more than approx 30 se onds, the car will switch back to petrol. I can recreate this all day everyday. I took it back to the installer and I know he is having a big problem setting up my car what he did tonigfht was to take some log files and also a file of seeting and he says he will send these off to Prins for them to have a look. I am a bit secptable about this.

I did ask him to change the lambda timeout to see is that makes a diffefence, but it seems he didn, t know which paramter to change....yeah I know....he is an approved installer. ?...

So can you guys tell me on a Prins VSI system for a V8 under what menu is the paratemer for setting the lambda timeout and what is the parameter called

Thanks


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PostPosted: Mon Nov 04, 2013 8:32 am 
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Hi Guys

Just wondering does anyone know the answer to the last question around setting the timeout.... Just to give you some more info. last week it looked like my evaparator/ reducer weas going over pressure all the time, so my guy changed it out in the hope that it would fix the switch over probrelm.

The error code we were getting was " too rich too long"... I think the logic was that the evaproator was supply too much pressure and hence gas, but also there was a overpressure alram as well. So that may have well been faulty.

But this morning I was able to recreate the switching back to petrol problem as mentioned above, so I'm not too sure how the reducer is affecting this problem... if at all. One thing to note on the recreation it seems that car has to be above a ceratin speed and rpm, if not the error does not recreate. ie it seems that i can have my foot off the acclerator for around 40 sec as long as the starting speed is around 40 mpg ish and rpm close to 1000 and I do not get the error, but if my starting speed is around 75 ish and and take my foot off then, then approx 30 sec later I get the faulty swiching problem. So speed and RMP has something to do with it???

Just another question did I read some where on this form, that if you have your foot off the acclerator too long and free wheeling that you can generate a over pressure problem for the evaparator.


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PostPosted: Mon Nov 04, 2013 1:14 pm 
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The parameter for the lambda signal timeout, that gives you a problem with foot off accelerator is "ETL" - it stands for Error Time Lambda.

This problem will not be affected by anything to do with evaporator.

Yes, you will have to be above a certain speed to see that problem - that's the way your car (not the Prins) works, the engine and vehicle speed needs to be high to begin with for the injectors to get cut off for a long time.

----

Overpressure alarms can be caused by poor water circulation to the evaporator (as well as other things).

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PostPosted: Thu Nov 07, 2013 10:27 pm 
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Thanks for the reply on the error time out. Im just wondering with the ETL paramater and with the fact that I was getting a lamba rich too long do you think that you could possibly be masking a real error.


Also this is a big ask.... im going back to my gas installer at the weekend and we are going to try and sort out my problems, he was taking about fladhing the vsi system and starting the setup again.... the big adk question is this


Does anybody have a standard set up for a 4.2 v8 thst you think in general works .... if I had a starting point I think thzt might help. I am meeting him this Saturday so any help before that woukd be great.... thanks agin guys for the support


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PostPosted: Fri Nov 08, 2013 11:48 pm 
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jookul wrote:
Im just wondering with the ETL paramater and with the fact that I was getting a lamba rich too long do you think that you could possibly be masking a real error.

No. You won't be interfering with the Mercedes engine management or its fault detection systems.

jookul wrote:
Does anybody have a standard set up for a 4.2 v8 thst you think in general works ....

I've never done a Merc 420 with VSI. ML500 and S500 are straightforward, yellow injectors, idle pressure around 2,1 bar, RC_inj factor around 110, should be very similar

Keep an eye on reducer temperature, in case the water plumbing is wrong.

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PostPosted: Sat Nov 09, 2013 7:57 am 
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Hi guys

thanks for all the great replys... ill bring that info to my guy here and see how he gets on. Just on the lambda sensor too rich too long. Do u think its posdible that unburnt gas could be entering my cat and doing damage, if so would that show up my normal merc eng mgmt system, bearing in mind my car is a 1998 and may not have all wizardry of a more modern car

I do have one or two other problems, but lets fix one at a time

thanks again and ill let u know how I get on


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PostPosted: Sat Nov 09, 2013 8:49 pm 
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Hi guys

a bit of an update.... so I think we are makjng a bit of progrress... wnet back to installer we still had an over pressure alarm. Based on this he replaced the regulator on the reducer. He also extended the ELT so it .

but on the test drive when we were texting if the ELT setting was working he noticed that the pressure in the reducer was increasing... so the senario is im driving at about 75mph and take my foot off the accelerator for more around 30 seconds and he says he noticed that the pressure in on the reducer read about 2.7 Bar as I then continiue to drive normzlly the pressure come down to approx 2.1 bar.

He says the is quite normal for pressure go build up in the reducer when you have your foot off the acclerator say cost to slow down the car rather than braking. The question here is.... is it normal for pressure to buikd up in such a scenario or should the reducer presscure stay constant not makker the drving style or if u have your foot off the acclerator and coasting


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PostPosted: Sun Nov 10, 2013 12:57 am 
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There is always some overshoot. The harder you push the pedal, the more gas is flowing through. If you lift off the pedal and coast, the car's engine management does its thing of shutting off the injectors altogether, but it takes time for gas flow to stop; only a split second but long enough for the pressure to creep up a bit. That high pressure is trapped until the injectors start working again. That's normal.

I think pressure has to get > 3.5 bar to set the overpressure alarm, should never happen unless there is some other problem. Did you keep an eye on T reducer temperature? Should be staying up at 80-95C during driving.

This seems to be the second time your man has changed the regulator/reducer/evaporator; that probably means there was nothing wrong with that.

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PostPosted: Sun Nov 10, 2013 5:33 pm 
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Hi
I didnnt get a chnace to look at the temp while drivning, but I did mention it while the car was on idle... he showed me the readings and reckoned they were ok.... water approx 80 degress gas was approx 50, so he reckoned there was no problem.

in reltion to the exaporator change, heas has changeed that once, and yesterday he then changed the inlet solinode valve the one that attaches to the side of the evaporator, he is now thing the vaulve was the problem of the over pressure alarm. Ill be back with him next week and we will cjeck again. I still need a bit of fine turning and we still don, know what mpg im getting it has been varying between 15 and 18 mpg and that is drving very mindly indeed.

so from what you are saying it looks like the pressure rixing in the evaporator as above is normal which is good

Also from the pervious coversation am I correct in saying that the " Lambda too rich too long" error that I was seeing is down to the ETL being too short and that it iz not a real error, its more the way the merc ecu works. I was worried there might be unburnt gas going into my cat convertor, but on our test drive yesterday ( presuming I try to recreate as mentioned previously) we noticed that my lamba comes back into operation when my rmp is 900 aprox and my speed approx 40 mph.

I am learning a lot about lpg from you guys, as I really appericate the support


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PostPosted: Sun Nov 10, 2013 5:45 pm 
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jookul wrote:
I still need a bit of fine turning and we still don, know what mpg im getting it has been varying between 15 and 18 mpg and that is drving very mindly indeed
How are you coming up with that figure? Not from the cars own trip computer by any chance? When running on gas that will read an almost random number of what it thinks it is doing on petrol when it is actually using no petrol at all. The only use for the mpg readout on the trip computer is to see how accurately you gas system has been calibrated. If it reads exactly the same when driving over the exact same road at exactly the same speed when on petrol as it does when on gas, the the gas system is calibrated correctly. If it tells you your mpg is getting better, a higher number, your gas system is rich, if it says your mpg is worse, a lower number, your gas system is lean. The opposite to what you are actually doing.

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PostPosted: Mon Nov 11, 2013 12:43 am 
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jookul wrote:
water approx 80 degress

You really really need to check if that is sustained while driving.

jookul wrote:
yesterday he then changed the inlet solinode valve the one that attaches to the side of the evaporator, he is now thing the vaulve was the problem of the over pressure alarm

It cannot be. Whether the valve is stuck open, stuck closed, or broken off altogether it cannot cause an over pressure - that is entirely down to the regulator (reducer) that comes afterwards. It can only cause under pressure.
System could go overpressure if the regulator freezes for example, or debris has got in there before fitted.

jookul wrote:
Also from the pervious coversation am I correct in saying that the " Lambda too rich too long" error that I was seeing is down to the ETL being too short

No, unless you kept at full throttle for longer than the ETL was set to before. That's not normally possible, but I suppose if testing included a drag race up a mountain it could happen?

It would be possible to confuse the Prins into thinking "rich" when coasting normally (and actually "lean"), by telling it the wrong sensor type was fitted.

Else it is/was down to some setting up issue. Since lots of fiddling has been going on, there is little point worrying unless it comes back again.

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PostPosted: Tue Nov 12, 2013 7:05 am 
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Hi

No im not reading the mpg form my trip computer.... im working it manually based on how much to fill up alsobased on what you are saying it seems I may be running a bit lean, but hard to say with my hilly route. I also had to add non standard air filters ( cone like cheap performance ones) to the car.... a long story but it was to do with getting the injector under the air box. But the job I got done was a bit cheap and we think this may also not be helping the car to run as well as it should. Im looking at changing that system again, but also it looks like my mpg since the last tune is v bad, but I cant say for certain yet till I fill as I am also having problems with my gauge and at the moment am basing this on my gauge reading.... still a bit of a way to go before we iron all the problem our


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PostPosted: Thu Nov 14, 2013 9:15 pm 
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Hi rossko

thanks for your reply around the rich toolong question. Im intrigued about how you were saying that the wrong sensor type could be set causing it to read rich when it is actually lean. That kind of sounds like something im getting. We only stopped getting the alarm cause we set the ETL to 58 secs. Im not too sure we actaully got rid of the alarm if the ETL was shorter.

The question is do you know what sensor type needs to be checked snd how to check it. Im going back tomorrow evening and I would like him to check it out, also id like to see how the over pressure error is. The reason im asking about the sensor is I think the car is running quite lean, and I presume if the sensor is set incorrectly then he could be setting up the car incorrectly. The RC is currently at 93 and I think it is lean. Also following the advice about the mpg indicator this would also indicate I am running leam. My mpg has also dcreased again since the last set up.

many thanks for all the comments and advice


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PostPosted: Fri Nov 15, 2013 12:13 am 
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Sensor sanity check: Allow car to warm up. Full throttle on the road - will give a rich reading. Allow to coast while at speed - will give a lean reading. If the laptop reports other way around, the sensor type is set incorrectly and signal is being misinterpreted.

I would expect a Merc to have a fairly standard 0-1V signal

The system doesn't actually use the sensor for setting up - it is connected for operator convenience. The operator may well be looking at it of course!

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PostPosted: Sat Nov 16, 2013 12:03 am 
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Hi
yeah if you mean the lambda sensor, then you can see it switching high and low and it does show lean with foot off the acclerator. I have a plan to prove this when I see my installer...... so ill let you guys know


Another question if I may... I, m paraoid that the car is runni g lean ancd will do damage. What iz the normal procedure for setting the RC on a prins VSI system. We went for a pong set up test drive were my installed was watching the graphical representztion of the petrol and gas injectors and was tryivng to get them looking the same. He said they were when finished and he set the RC to 93.... but laxt week I thought the car was down on power and without a text drive he increased the RC to 98.... I suppose the quextion is how do I really know if the car os running lean and how would you guys re ommend setting up the RC


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