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Likely damage from mis-fuelling 2006 Fiesta 1.4TDCI ?

craig1410 - 20/7/15 at 03:29 PM

Hi,

A classic "asking for a friend" question for you guys, only this time it really is for a colleague at work who mis-fuelled his car on Friday.

It's a 2006 Fiesta 1.4 Zetec TDCi and he says he filled it up some time after the low fuel light came on. It's something like a 40 litre tank so I'm guessing it would be down to about 5 litres left and he put Ł20 (around 17 litres) of unleaded petrol in it and drove off. So that would be roughly 75% petrol and 25% diesel and yet he didn't notice initially. He says he drove to work (~30 miles) and part way home (~10 miles) before the car started to shudder at which point he realised his mistake. He also said it was a bit difficult to get to start before his journey home.

He called the RAC who got it transported away to a garage for draining and purging etc and he says it is running fine again. Apparently the fuel filter was changed too and the total cost was Ł250.

My question is whether you guys think this episode will have done any significant damage to the engine, especially to the common rail diesel pump. Frankly I'm amazed he managed to drive so far on 75% petrol! He did say that the temperature gauge was climbing at the point when he noticed it was shuddering.

Any thoughts?
Cheers,
Craig.

ian locostzx9rc2 - 20/7/15 at 06:07 PM

The fuel system will be damaged I'll give it 3 to 6 months until the hp pump gives up there be metal fillings in the fuel system for sure ,I'm afraid to say.

ICARUSTROOPER - 20/7/15 at 06:09 PM

Hi Craig,

It's impossible to say that it hasn't done any engine damage. The fuel pump may have some damage as the diesel also acts like a lubricant and the presence of petrol can wear some internal pump parts. May be worth replacing the fuel filter if not done and cut it open to check for metal dwarf. Some manufacturersa after fuel contamination replace all fuel lines pump etc.

Hope that helps.

ReMan - 20/7/15 at 07:16 PM

A friend of mine did this once, or more.

No technical finding but Id be disappointed if it has done any significant damage in that space of time

v8kid - 20/7/15 at 08:37 PM

I did the same on my Mondeo and it ran another 100k.

Cheers

big-vee-twin - 20/7/15 at 08:50 PM

Did the same on my Mercedes never had any issues after draining and refuelling.

joneh - 20/7/15 at 09:31 PM

Petrol floats on Diesel so 30-40 miles on reserve hence why he didn't initially notice. Normally with 10 or so litres of petrol it eventually will break down and sort of disolve into the diesel but this amount will need draining, filter replaced and as above checked for metal...

craig1410 - 20/7/15 at 10:15 PM

quote:
Originally posted by joneh
Petrol floats on Diesel so 30-40 miles on reserve hence why he didn't initially notice. Normally with 10 or so litres of petrol it eventually will break down and sort of disolve into the diesel but this amount will need draining, filter replaced and as above checked for metal...

Apparently petrol floating on diesel is an often quoted myth. A petrochemical engineer responded to this point on a forum thread I came across. He said the diesel and petrol mix together quite quickly. More here: http://www.petrolindieseluk.co.uk/faq/does-petrol-float-on-top-of-diesel/

As I expected the predicted outcome is mixed. Personally I think he will have taken a lot of life out of the high pressure pump but it might still run for years.

Thanks to all who offered an opinion. Much appreciated.

[Edited on 20/7/2015 by craig1410]

mark chandler - 20/7/15 at 10:20 PM

Modern diesel is so pure it has hardly any lubricatiin properties, I would be more worried that he partially seized it by overheating

r1_pete - 21/7/15 at 08:45 AM

I did it on an 02 Peugeot HDI Diesel, it was a company car, I had a similar mix of diesel / petrol, I hammered it on the 100 mile journey home to use as much fuel as possible, then brimmed it with Diesel.

No noticeable problems in the remaining year I had it. Its still taxed and tested, and certainly wasn't worth the cost of replacement fuel systems / engine when it went, so I assume its still on its original components.

MikeRJ - 21/7/15 at 11:21 AM

quote:
Originally posted by mark chandler
Modern diesel is so pure it has hardly any lubricatiin properties, I would be more worried that he partially seized it by overheating

Low sulphur diesel has additives to restore the lubricity. Modern diesel engines absolutely rely on the lubricity of diesel which is why running on petrol can cause significant damage to high pressure pumps.

scootz - 21/7/15 at 11:35 AM

Done something very similar years ago... system was purged, filter was changed, and there were no problems thereafter. Maybe got lucky!?

craig1410 - 21/7/15 at 03:48 PM

To be honest, if my colleague managed to drive over 40 miles without realising he was using the wrong fuel then he probably wouldn't notice if his engine was slightly damaged and running a bit rough as a result...

To be fair, he only passed his driving test a few weeks back and this is his first car. He also said the car was owned by his Granddad and had a full service history so perhaps all that will have happened is that he has partially undone the easy life the car had before he got his hands on it.

Also, this is the same guy who crashed on his first driving test and had a near miss on his second attempt before passing on the third attempt so it would seem likely that engine failure is the least of his worries for the future...