Morning everyone from the Harz Mountains Germany! Newbie here with a question which hopefully somebody can help me with as It's driving me nuts!

I own a 2006 Natural Gas cargo van with only 80,000kms on the clock. It's in perfect conditionwith full servie historxy and until 2 weeks ago it ran perfectly on Gas and Benzine.

The engine management light came on, blinked a few times and then went out but it seemed to have lost all power when running on gas. I switched it on to Benzine and it ran perfectly. Two minutes later the EML came on again and stayed on. The next day I took it to my local Fiat dealer who plugged the old lap top in, got the light ot go off and sent me on my way telling me there was no problem found.

The next day it wouldn't run on gas at all! Off I trundled back to the same dealer and he then diagnosed a blocked fuel filter which he duly changed and the bloody thing sprang in to life and the EML stayed off.

On the way home it was clear that running on gas, it still had no power, was reluctant to rev and was jerky and generally feeling not right.

I took the van back the next day, he plugged in his diaognostic gear and found no problem depsite the fact I told him it wouldn't pull the skin off a rice pudding.

In desperation 2 days later I took it to the next nearest dealer, explained the problem and thexy duly plugged in their laptop to find ........... no surprise, no faults!

I'm an engineer myself, I know there's a problem but everyone tells me it's fine (which is ********). Fiat Germany only have a 'customer care' department and can't help:bang:

Could someone on here with experience of the natural gas Doblo please advise.... Is this a known problem? What the hell is going on?

Best regards from the Harz Mountains

PS. When I say filter change, I meant Gas filter and incidentaly there is a massive flat spot between 2 and 3 thousand rpm in 4th and 5th gear.

Hello everybody.
For my good or bad luck I have exactly the same problem with my fiat doblo van 1600cc,146000 km on the clock .Mr. Harz Mountains did you find what was wrong with your van?I have seen 3 differens garages and everyone change something ,but no results.The last one ,after pluging his laptop said that for a reason that he can not understand my van goes in safe mode(What he said)
Every advise is wellcome.Thank you .All the best from Greece,Keli.

This post applies only to the supercharged T-Jet 1400ccm engine with CNG and you will not believe it.

In my workshop I had the Doblo with T-Jet CNG. I had to do some work after a minor crash. The driver claimed engine problems like unstable idle, power loss and MIL lamp went on sporadically. In petrol mode everything was fine.

Fiat has not managed to improve it significantly. No DTC were recorded in the ECU. Becoming desperate a bit after having applied standard procedures, I tried to check the CNG and petrol ignition and gasoline injection timing. Surprisingly, CNG injection valves have not been synchronised with the engine rotation. The CNG injection sequence was 360 degree out of sync. Petrol injection worked properly.

This means, the injector for cylinder 4 was open when cylinder 1 was charging and vice versa, the same for cylinders 2 and 3. This had a huge influence on filling of the cylinder and caused warnings and torque drop, because the engine is programmed for correct sync of the crankshaft and injection. I even wondered that the engine could run for more than 30000 km.

To fix it, I simply rearranged the wire harness for CNG system. I´ve unplugged the cable from injector 4 and connected it to injector 1, 1 - 4, 2 - 3, 3 - 2. After that, the engine ran somewhat smoother and quietly. MIL indicator does not light anymore.

I think the engine has not assembled properly in the factory since there were no traces of disassembly or mishandling. Later on, I´ve found the same problem on other T-Jet engine with similar symptoms and I´ve fixed it in the same way. I think more cars are affected.

So guys, if you experience same symptoms (MIL on, idle jerky, engine vibrations, power loss) and there is no other explanation, let the FIAT people check the CNG injection valve timing.

You can just try to do the same as me - swap the injector cables as described. Go for a drive and if you see no improvement, simply put it back. It will make no harm.