Hello all

Been hovering around the forum for a little while but thought it was time to join as it is a mine of knowledge!

I was hoping someone will be able to help me with this problem...

My 2003 Ducato 2.8JTD Rohill Minibus was intermittently cutting out, with the red injector light coming on. When the AA chap came out he read a fault code of P0191 (Low Pressure in the Common Rail).

I wired an LED to the Low Pressure Pump in the tank as I could hear it was not working once the red injector light came on and determined that the pump was functioning, but once the pressure sensor logged too low pressure the ECU was cutting the signal to the Low Pressure Pump, hence the van stopping.

I replaced the fuel filter, cleaned the lines, removed and cleaned the Pressure Regulator, but still the fault persisted intermittently. I then performed a leak back test on the injectors which seemed fine.

Next I removed the injectors and sent them to a local diesel specialist for professional testing and they came back with no fault found.

Then I took the whole bus to the diesel specialist who determined that the Low Pressure Pump was faulty and drawing in air. The van was just below half a tank of diesel at this point and when turning the ignition on you could clearly hear gurgling as the pump drew in air.

I took the bus away and filled it up, and it drove home without fault.

I replaced the Low Pressure Pump, which comes complete with the fuel level sender unit, and carried on my way.

Once the bus got to around half way on the fuel gauge, the van cut out again with the red light coming on! It continued to do that until it was filled up again. Then it ran perfectly again!

So, this has got me really stumped. Between full and around half a tank it runs perfectly. Below that, it cuts out as it draws in air, even though there is plenty of fuel in the tank when you pull the pump out.

I hope someone can help... :bang:

Many thanks

Blocked breather causing massive vacuum in the tank? You will hear a big inrush of air when you take the fuel cap off.

Thanks for the response.

I thought that so ran it without the fuel cap and it still cut out.

I'm not familiar with the set-up so forgive me for taking a stab at it (and if you've already thought of this)

Is it a submersible pump hanging on the cable and delivery tube? If so is it actually in the bottom of the tank?

Or is the pump part of the fuel level sender assembly and the suction pipe hangs down into the bottom of the tank? If so I would expect there to be a weight of some sort on the end of the suction tube to keep it down; maybe a coarse filter, has this come off?

Good thinking to run without the fuel cap - that eliminates any tank vacuum problems.
The only thing that I can think of that changes as fuel is used by the engine is that the fuel temperature rises in the tank due to the hot returned diesel from the injectors. This is very noticeable to users of vegetable oil like me (not in my Ducato, by the way!). It could be that the low pressure pump reduces pressure slighly due to the thinner fuel when the fuel temperature rises. If your pressure regulator is regulating a bit on the low side, the slight pressure drop from the low pressure pump when the fuel gets hot might be just enough to set off the error reading. I would try another known good low pressure regulator if you can get your hands on one or just replace it. At least they are a lot cheaper than the low pressure pump.

Sorry for the very slow response - work has been so hectic!!

So... The bus now cuts out if you put your foot hard down and take it off again - doesn't even need to rev past 2000, or it is always in limp mode and runs VERY slowly.

Tank quantity does not matter anymore.

I've got MultiECUScan and graphed it, so if anyone is au fait with figuring out if something is not right the Excel spreadsheet is in the next post.

Thanks

Theres only one reading when you floored it so can't tell much. try and drive it and gradually increase the load until it goes into limp mode. Like driving up a long incline. That way you'll get lots of reading and can see how the requested and actual pressure correspond.

Thanks. I'll give that a go later and post back.

Assuming there isn't a restriction in your fuel filter (you did replace it, didn't you?), the next pressure regulator up the line is on the high pressure fuel pump. I've got no idea if it is adjustable or repairable or if a new HP pump is the only cure. It still fits my theory of the diesel warming up due to the hot returned diesel lowering the viscosity of the fuel.
Maybe a good set of MultuECUscan results will show up the rail pressure varying.

This sound like the same problem that I am getting with my Fiat Ducato 2.0 jtd based motorhome. The diesel specialists at Halls in Swindon could find nothing wrong but it still cuts out under strain once the fuel warms up.
https://www.fiatforum.com/ducato/342543-ducato-motorhome-cutting-out-2.html

hi there . i have the same 1/2 full tank problem with my 2002 2.8jtd that you had in 2013 . did yo fnd a fix for it .many thanks. andy

Anyone had any ideas here, I have the same problem on a Hymer 464 motorhome (Ducato 244 Base) 2.0 JTD. Deffinitly worse as the fuel warms up and is below 1/2 tank. Local diesel specialist convinced it was the injectors and replaced them but the van still cuts out at around 3K rpm if under any load, Error code P0191. Can avoid cutting out by dropping to 4th gear as soon as revs fall near 3K. Have suggested HP pump but various experts say that when they go, they pack up completeley and van will not start. Also, even when cool, if I increas revs whilst in nuteral the van hesitates around 3K rpm and then picks up again. Any ideas?

Maff172 said:

Have suggested HP pump but various experts say that when they go, they pack up completeley and van will not start.

Click to expand...

They can packup completely if you lose lubricity e.g. water/petrol/alcohol they can also wear / leak / poorly regulate due to seals, cam /piston / bore wear / bad regulator regulator seat. The regulator can compensate for reduced pump performance / injector leaking by increasing duty cycle but once this falls outside prescribed percentages you will get a code.