Pump-duese vs Common Rail and petrol in a diesel :-(

Alan_uk

Alan_uk

A2OC Donor
In another thread:
ULP said:
The diesel, being Pump-duese rather than common rail,
Click to expand...

That's interesting. Last Friday I did something really silly. I filled the TDi with petrol (blame it on excessive working hours - 60 hours the last few weeks). I put 30l petrol into a tank with about 7l diesel. Drove 1/2 km home. Next day realised I had checked the tyres (due to go to London on Sunday). So drove back to same garage - another 1/2 km. Then the car wouldn't start. Waiting for recovery I tried to think what was wrong and then the penny (of should it be £££££) dropped.

Recovery said they would do the job for £170 (which the recovery centre said was a good deal). Next day took car to London (100mls) and back without any problem - took it easy going (max 2k revs) but engine sounded fine.

Reading some web pages they say that common rail diesel are a right-off if they get a sniff of petrol, even opening the doors on some cars primes the engine and is sufficient to ruin the engine.

My question is: are the Pump-duese less sensitive.

In my favour was the fact that the engine was cold and the fuel was mostly petrol. So after using the diesel in the pipes and filter the car then refused to fire.

I read that VW abandoned Pump-duese in 2007 having maintained to then that it was better than common-rail. The article said Pump-duese was more complex, hence being abandoned for CR by other manufacturers.
 
''My question is: are the Pump-duese less sensitive''.

Hi Alan
I would say the PD fuel system is much less sensetive to fuel quality than common rail.
Injection pressure on the PD system is generated by a camshaft operating on the injector plungers and these have some tolerance to operation on fuel with zero lubricity for short periods.
The common rail high pressure pump relies totally on diesel for lubrication and can sieze up within minutes if the wrong fuel is used. In severe cases, debris from the pump can contaminate fuel lines and injectors, requiring the whole system to be replaced.

PD v Common Rail
The common rail system is much more versatile as the reservoir of high pressure fuel in the rail can be metered very precisely in multiple injection pulses to smoothe combustion. The injection points can also be advanced or retarded at will to suit all operating conditions from cold starting through part and full load running.
The PD system can generate high injection pressures for good fuel atomisation but the camshaft operation severly limits pulsed injection and wide timing swings - which is why it is being superseded

Cheers Spike
 
Last edited:
Brilliant reply Spike!

A friend of mine filled his Citroen C3 HDi 1.4 with petrol and used half a tank before conk out. Garage drained it and thus far (6 months on) the car stil runs well. Perhaps old HDi not so sensitive as newer commmon rails.
 
Hi Lukas, thanks for the comments
The overview is rather simplified (I did not want to write pages) but failure of a system is dependent on many factors - from how much diesel was in the tank, how much petrol was added, to mileage on car... a worn injection system is likely to well bedded in and have greater running clearances which lessens the risk if instant siezure.

Cheers Spike
 
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