Help - Petrol in my Diesel tank!

[AMH]

I have a Mercedes C250 Turbo Diesel saloon (5 cylinder) 1998 model. I filled the tank with petrol by mistake - she got me home and then stopped - which was when I realised my error. Can someone please advise me on the easiest way to drain the tank? Any advice or diagrams (as I don't have a manual) would be gratefully received!

 

[type49]

Ideally you need to get the car in the air. The tank goes over the propshaft & so is like 2 sinks joined at the top. This makes it difficult to fully siphon out from the filler neck. Luckily, you car is pre-CDI, so is not as critical to run on 100% diesel. Once you have filled it back with diesel, it'll run like a pig for a while but should'nt do any damage, no guarantees though.

 

[Hibbo]

Hi mate, Unlucky!

Go to www.detali.ru and find your car on there, there are good exploded diagrams.

I'm not sure if there is a drain plug on the tank, if not just remove the supply pipe.
The supply pipe should exit underneath the tank through the floor. You should be able to see it if you get under the back of the car. Remove the filler cap and pull this pipe off. Make sure you've got a big container under it!

You could of course syphon it out, assuming there is no anti-syphon thing in the filler neck.

Good luck, let us know how you get on.

 

[television]

The worst that happens is the all of the diesel components are lubricated by the diesel fuel itself. Drain it out as Type 49 says. It will be impossible to say what if any damage has been caused.

With a CDI common rail it would have been a disaster.

Malcolm

 

[AMH]

Thanks everyone! It's actually my Dads car - I'm trying to help him out as he doesn't have a computer, etc. Can you explain why it would have been worse - had it been a CDI? Also, what problems/effects should he look out for when he gets the car going again? He does most of his own servicing, so would be interested to know any other info. Many thanks to you all. Adrian.

 

[hawk20]

Yes, Malcolm, I too would like to know why cdi diesels are so badly affected. Guy I know put petrol in a 320cdi E class and said it cost thousands to put right. Must be careful!

 

[maldon]

I got away with about 4% petrol/diesel in my first ML 270CDI by constantly refilling with diesel - there are others on here who deliberately use a far higher level of 'contamination' for winter use.

Did you actually fill the tank with petrol -ie what approximate ratio of petrol/diesel do you think the tank contained?

Others here will also give a far more detailed explanation of damage petrol can cause to common rail systems.

 

[dava]

Lets see if I can help. Firstly the reason CDI's dont like petrol is they are high pressure systems and the pumps poduce real high pressures to the common rail. These pumps by there nature need extreme tolerances to acheive theses pressures and are lubricated by the deisel, petrol is not a good lubricant and as such wear's the pumps rappidly, causing loss of high pressure. We run a large fleet of these and have petrol put into them by mistake weekly!!! It realy depends how much you put in and how you drove it, if it was a small amount it would probably be OK, if you totally filled it and ran it hard, Motor way etc till it stopped, chances are the high pressure pump and injectors will have took a pounding and will give up some time. This is only my experience, some may disagree and say they have done this and got away with it. As for draining the fuel, take the feed pipe off the fuel filter and pump/syphon from here and change the fuel filter at this time. Remember it is PETROL you are taking out, any sparks etc from electric fuel pumps/static etc can cause explosions!!!!!! Also you'll have a hell of a job disposing of it. It's no good for any thing, dont try to run your wife's corsa or even the lawn mower on it, it wont work.

 

[Hibbo]

I think Dava is right about the reason ultra high pressure common rail engines don't like petrol is due to the lack of lubricity. However I do think there is a fair amount of scaremongering done. I personally don't think that an engine would run for long enough on a concentration of petrol high enough to do any real damage. Just my opinion. (What I am trying to say is if you had put so much petrol in that it would reduce lubricity to such an extent as to damage to pump, then the engine would conk out pretty quickly - and vice versa if the concentration was low enough for the engine to keep running then there can't have been enough petrol in there to do any damage) As I say, just my own opinion, happy to be proved wrong, but with facts, not someone else's opinion!

Your (Dad's) engine will be absolutely fine. The IP doesn't rely on the fuel to keep it lubricated as it has it's own oil supply. Drain it, fill it with diesel, and live happily ever after.

 

[jberks]

I too agree that it's primarily scaremongering. Of the cases I know well enough to be certain of my facts, tanks filled entirely with petrol on CDI systems and run till they conked out, none have failed to be fixed by simply draining and refilling with diesel. I suspect long term petrol/diesel mixes as used to be done in colder climates may cause damage over time, but one a one off basis I agree with the comments above that the same conditions that cause damage (100% petrol) also cause it to stop running - hence no, or at least insignificant damage.

 

[television]

It is as Dava says, a total lack of lubrication. CDI engines run at 300Bar presure, think about that in relation to your tyres at 2,3 Bar, say max. The only lubrication comes from the diesel its self. As we all know we can use petrol for washing away oil, so the high presure pump and the injectors receive no lubrication what so ever. These pumps are of the high speed rotory type. You could not drive your car ½ amile without engine oil, The pump and the injectors would need replacing, at a cost of around £2k. Nothing else would be effected.

At a recent injection seminar it was pointed out that 6 liters of petrol would be the max that you could get away with, without damage in a full tank, anything over this and the life and performance of the above components will be shortend. it is doubtful if a CDI would get 1 mile before stopping on a full tank of petrol.

Malcolm

 

[Ultymate]

Before I retired from work with the AA I dealt with many CDI vehicles that had been wrongly fueled by their owners or their spouses and they were all horrified by the scaremongering tales that are around which talk of instant damage resulting in £ thousands damage. I took them all to local garage connections around N.Wales and N.W. England and the ALL restarted and ran perfectly ok after drainage and in some cases filter changes. Now obviously I cannot say if there were any longterm issues nor indeed could you say the same for a non CDI sample of wrongly fuelled cars. What I can tell you is it's nothing like as bad as some of the manufacturers and their dealers would have you believe.

 

[dava]

Sorry I should of made my self a bit clearer. I agree with all the above about it being scaremongering and it was not my intention to do that, however, I was just trying to answer the question, we keep extensive records and from looking at what has had HP pumps and injectors it is obvious that at some time in the past it has been filled with petrol and ran to the point of stopping. Usually this shows it self as bad starting etc and when tested shows an open injector and not holding or building pressure in the HP pump. This may be total co instance but it's my thought on the matter. Hope it helps.
Regards
Ray

 

[Hibbo]

Malcolm, the second generation CDIs run at 2000 bar, not 300.

Yes two thousand BAR! That's about 29,000psi! Don't go undoing any unions with that thing running, it'll literally cut you in half!

 

[psmart]

there are others on here who deliberately use a far higher level of 'contamination' for winter use.

Your getting at me maldon.... I can feel it

Try running your lovely cdi at sub -30 for a while on winter diesel..... most is rated to -23'c. Often Arctic diesel is delivered too late to service stations, and often they still have summer/early winter fuel in their tanks! Also, if you park your car up for 24 hours, the diesel cools down to these temperatures and thats when it waxes and gives you oh so many problems! All the additives are doing is trying to stop the diesel crystals from bonding (coagulating) together, petrol isnt the best substance to stop this, but it works and is obtainable (there are some good additives out there if you look on the web, but they arent where you need them, in the garage shop!).

I use the ML in sub -30 every winter, have done since time imamorial (2000) and have used a touch of petrol in the diesel regularly. Having CarSoft diagnostics now, I monitor items such as injector quantity and common rail pressure (1600 bar for mine Hibbo) and as yet, no problem. Should I have a problem, Ive already sourced the pressure pump and injectors and EUR600 will see me good, all new (self fitted). The advise to use petrol was from Austrians and Germans used to living in these temperatures with diesels, some with older non-CDI, some with CDI's. I've been as high as 33% mix for a short period, but normally ~ a gallon to a tank (1:15).

As Malcom and others have pointed out though, you lose the lubricity from petrol which I fully understand, but then you do when your fuel is ice crystals (blow snow crystals across your face and look how cut your skin becomes).

Fortunately England doesnt experience these extremes, so no need to add petrol in England, but it does put paid a little to the scaremongering stories.