W210 E320 rough running >>>

[99E320LPG]

I have a 99 E320, about a month ago it began to develop starting problems as in running rough and misfiring. Having read up on similar issues I have replaced the MAF, got it from EPC the replacement model not the genuine, this did not cure the problem. In the meantime one of the CATs began to rattle like the baffles had gone if it had been a silencer, so I have replaced that. I have also replaced the fuel filter, to no avail.

As I have had the car converted to be dual fuel I can rule out the electrical side i.e. ignition etc. as once upto temperature and she switches on to LPG she runs sweet as nut with no power loss.

Once started the engine runs reasonably well and will rev freely, however as soon as you lift off say to put into gear the revs die right down around 500 revs and then you will be lucky to get 1500 rpm and if there is an incline (like driving off the drive) you will just about crawl up it.

Can anybody help me get my engine back to its purring happy self??

 

[diy_dan]

why wait for it to warm up before switching to gas? I know this doesnt fix your problem but you should get your lpg man to set it to start on gas, its better for the engine

 

[99E320LPG]

Testing Injectors

Not sure whether starting on LPG is a possibility as the evapourator for the LPG requires that the water in the engine reaches at least 21 degrees, before switch over occurs.

Having had a day to think about this more I think I need to test the Petrol injectors.

How do I do this ??

2 possible methods spring to mind, firstly run the engine on petrol for a while and then feel around the injectors the theory being that if a cylinder is not firing correctly then there will be a lack of heat, or secondly as each injector has an electrical connection to it I could disconnect each one in turn and any that make no difference to the running would be suspect.

On the first idea would there be a noticeable difference in temperature around the injector if a cylinder was not firing correctly?

On the second idea I am not sure whether disconnecting the injectors would cause more damage?

Please Help.

 

[Dieselman]

I doubt it's an injector they are pretty simple devices, although you could try a strong dose of injector cleaner.

The injectors can be disconnected but do it with the engine off then restart.

My money still goes on the MAF as you have used the hokey pokey version from ECP. Try disconnecting it and see if there is a difference.

The injectors can be tested out of the engine by providing a pressurised fuel source, such as a garden sprayer, tehn applying 12v to the connector to open the solenoid.
Try spraying them into glass jars and watch the spray pattern.

 

[99E320LPG]

I know.... I wish I had gone for the Bocsh part and have considered going back to EPC and getting one it is just the circa £200 for another possible solution ???

I will consult the Bank Manager (her who thinks she should be listened to) and may order the Bosch part ready for the weekend and another go at sorting it out.

I'm not sure how much longer I can stand driving her Hyundai Tragic.

 

[Dieselman]

It could be the lambda sensor. I suspect that isn't used for the LPG, is it?

 

[BlackC55]

Or lack of fuel pressure.

 

[99E320LPG]

Probable Blocked Injectors

Have just spoken to the people who did the LPG conversion for me, they have said that the LPG system uses the same sensors as the petrol injection, so an issue with the MAF and Lamda would also be reflected with running on LPG if to a lesser extent.

He has also said that because I had the conversion done after some 70K miles it is very possible that a petrol injector is failing. Something to do with the fact that during the summer the petrol injectors are only used for 1/4 mile or so until the heater water temp reaches 21 degrees then the LPG injectors take over. Recommend action a good dose of injector cleaner and force to run on petrol for a while.

As suggested by Deiselman, so will try this as first action Friday Night.

Has anyone else heard of this sort of thing??

 

[BenzComander]

I know.... I wish I had gone for the Bocsh part and have considered going back to EPC and getting one it is just the circa £200 for another possible solution ???

I will consult the Bank Manager (her who thinks she should be listened to) and may order the Bosch part ready for the weekend and another go at sorting it out.

I'm not sure how much longer I can stand driving her Hyundai Tragic.

Do not worry about the MAF from ECP, as long as you got the one already in the plastic housing, they are fine. Mine works a treat!

 

[Brabus3.6]

Not sure whether starting on LPG is a possibility as the evapourator for the LPG requires that the water in the engine reaches at least 21 degrees, before switch over occurs.

I'm sure you can. My uncle has a 140 series 500se which has no petrol tank, it starts and runs on lpg. He has a Prins system installed and you have to select the gas tanks by pressing a button in the cabin. I assume you have a similiar button which switches between . petrol and gas? It's worth a try.

 

[Dieselman]

I'm sure you can. My uncle has a 140 series 500se which has no petrol tank, it starts and runs on lpg.

In that case he should have the compression ratio and timing optimised for LPG, it will bring back some of the lost horses.

 

[Brabus3.6]

It doesn't feel like it's lost too many horses. Doesn't the ECU work out all the maps dynamically via anti-knock sensors and such? The Prins system runs piggy back on the back of the Mercedes ECU, so when a petrol injector should open the corresponding lpg injector does so.
Any recommendations on who could do such a job in or around the London area if I'm off the mark?

 

[Dieselman]

From memory an engine running purely LPG can run a higher compression ratio, which will give more bang for buck.

 

[99E320LPG]

Detail on the Lpg system fitted

Thanks to all those who have posted about the starting on LPG issue, however the system fitted to my car is a Romano 'N' Sequential Multi Point injection system. As far as I can tell it is pretty intelligent and there is no way of overiding it to force a start on LPG.

Below is a quote from Go-LPG's website >>

"Romano 'N' can truly be called 'Automated'. If the switch was left in the 'gas' mode when the engine was last stopped, it will automatically switch to gas operation when the correct engine temperature has been reached after any start. The changeover from petrol to gas (and vice versa) is absolutely seamless. At the other end of the scale, if the LPG tank contents are run low it will automatically switch back to petrol and sound an alarm to let you know this has happened. When the LPG tank is refilled this normal automatic operation will be resumed.

The Driver can also switch back to petrol whilst driving the car at any time, simply by pressing a button."


"In a little more detail............
The Romano 'N' system requires even more information from the engine but uses a lot of data from the vehicle's existing engine management instead of picking it up raw at source as the earlier system did.
Additional information required is -
Gas temperature
Gas pressure
Petrol injector pulse length
The system also has its own ECU but this works in conjunction with the Petrol ECU, instead of working alongside it like the earlier non sequential system. Even more benefit of performance and economy are delivered by the new Romano system, along one or two useful bonuses. The new system will 'sense' that gas pressure is low and switch back to petrol before the gas tank runs dry - A very useful trick. It will even give you an audible warning to tell you it has done this. A 'self check' protocol has been added to the changeover procedure so that the system will not move on to gas if a problem exists."

 

[Dieselman]

Does it use a seperate temperature sensor to detect the 21c threshold, if so that could be fooled.
If it uses the standard petrol sensor and ECU then you are in trouble.

Go for cleaning the injectors and see then.

 

[diy_dan]

Thanks to all those who have posted about the starting on LPG issue, however the system fitted to my car is a Romano 'N' Sequential Multi Point injection system. As far as I can tell it is pretty intelligent and there is no way of overiding it to force a start on LPG.

Below is a quote from Go-LPG's website >>

"Romano 'N' can truly be called 'Automated'. If the switch was left in the 'gas' mode when the engine was last stopped, it will automatically switch to gas operation when the correct engine temperature has been reached after any start. The changeover from petrol to gas (and vice versa) is absolutely seamless. At the other end of the scale, if the LPG tank contents are run low it will automatically switch back to petrol and sound an alarm to let you know this has happened. When the LPG tank is refilled this normal automatic operation will be resumed.

The Driver can also switch back to petrol whilst driving the car at any time, simply by pressing a button."


"In a little more detail............
The Romano 'N' system requires even more information from the engine but uses a lot of data from the vehicle's existing engine management instead of picking it up raw at source as the earlier system did.
Additional information required is -
Gas temperature
Gas pressure
Petrol injector pulse length
The system also has its own ECU but this works in conjunction with the Petrol ECU, instead of working alongside it like the earlier non sequential system. Even more benefit of performance and economy are delivered by the new Romano system, along one or two useful bonuses. The new system will 'sense' that gas pressure is low and switch back to petrol before the gas tank runs dry - A very useful trick. It will even give you an audible warning to tell you it has done this. A 'self check' protocol has been added to the changeover procedure so that the system will not move on to gas if a problem exists."

If its the Romano N the lpg chappy only have to plug his computer in and change it to start on lpg, it should take no more that 10 minutes if he isnt familiar with the menu system or 3 minutes if he knows what he is doing, I have the romano and bigas system. you can force it to start on gas by switching the ignition on then flicking the lpg switch to p and back to g then turn the ignition to start on gas

 

[diy_dan]

Does it use a seperate temperature sensor to detect the 21c threshold, if so that could be fooled.
If it uses the standard petrol sensor and ECU then you are in trouble.

Go for cleaning the injectors and see then.

It has a cts on the reducer, some romano claims not to use the lambda but cant see how that works, Its a nice system when its running properly

 

[99E320LPG]

She lives >>>>

Thanks to all the members who helped me with this issue.

A dose of STP in the petrol tank appears to have sorted the problem.

I have replaced the MAF with the original one and still works fine, so I suppose I have a spare now.

Once again thanks and anyone else using LPG should be made aware of the potential problem with petrol injectors.