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Passat (BHW) Mis-fuel
Well, you did it, mis-fueled your Passat tdi b5.5. Bummer, me too : (
Below is my rescue procedure so you don’t have to ask anyone else and divulge your mishap : )

Fuel Lines Diagram:
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Not sure why my diagram text is not coming through:
  • Upper right blue box is 8a
  • Lower right blue box is 8d
  • Upper left blue box is 8b
  • Lower left blue box is 8c
  • Upper green box is Tee
  • Lower green box is Fuel Filter
  • Upper red box is Fire Wall
  • Lower red box is Front of Car

Tools Needed:
  • VAGCOM
  • Battery Charger – optional (see step 1 below)
  • Cardboard – to catch spills under gas cans, etc.
  • Paper towel – to catch dribbles and clean up
  • Gloves – do not do this without wearing gloves!
  • Gas can(s) – for draining tank of mixed fuel
  • Gas can – with 5 gallons fresh diesel
  • Hand transfer pump (I got mine from Harbor Freight for $6.99)
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  • Small hose clamps – for fuel lines
  • Mityvac (I have the MV8000; $33)
  • 10mm socket and extension – to loosen fuel filter clamp
  • Flathead screwdriver – to tighten spring clamps
  • Funnels – one larger and one small
*Fuel is flammable – take precautions!

Steps:

  1. If you think your battery is a little weak, hook it up to a charger now (Mine was not up to the task before charging for 1-2 hours)
  2. Put your gloves on before getting fuel on your skin!
  3. Insert tubing* into the fuel tank and hand pump as much mixed fuel into your empty gas can(s) (there will still be a gallon or more left). This worked really well – fast and easy. Try to jockey the tubing to get to the lowest spot in the tank.
    • *I removed the plastic strainer from the gas can spouts because if you just insert the output hose into the can with the strainer in place, and you do not have someone holding it or it taped in place, the fuel stream will cause it to shoot out of the spout and squirt fuel all over (don’t ask me how I know)
  4. Remove hose 8a from the fuel filter (have some paper towel under it to catch any dribbles). Pull hose 8a out of the clip on the plastic intake pipe. Insert a barbed Mityvac butt connector piece into hose 8a and clamp with small hose clamp. Hook up the other end of the connector to the longest clear tubing that comes with your Mityvac. Route the tubing to the front of the vehicle where you have a mixed fuel can propped up (you can also use longer tubing and have the can on the ground). Insert the tubing into the gas can spout (minus the strainer) and secure it in place with electrical tape.
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  5. Hook up your VAGCOM and open VCDS. Click Select --> 01-Engine --> Basic Settings - 04 --> enter group 035 --> Go --> On/Off/Next. This will turn on your lift pump* for 30 seconds. Repeat clicking “On/Off/Next” until no more mixed fuel is coming out. (This probably drained my battery a bit – see step one) RossTech Video for doing this (Yours is non-UDS)
    • * I read that this would actuate the tandem pump at the same time. The article I read was for a later model. It did not on mine. The same article stated that you could go into Output Tests - 03 (instead of Basic Settings – 04) and choose the lift pump individually, you cannot with this model vehicle. Again, article was for a later model.
    • ** The lift pump is inside the gas tank. It primes or pressurizes the fuel going to the fuel filter through 8a. You will be using this pump in 30 second bursts through VAGCOM to pump out your tank. How cool is that?
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  6. Remove the long clear tubing and hook your Mityvac up to the butt connector with a short clear tube, then the catch can and then another short tube to the Mityvac. Pump out the line, pour the fuel into the mixed fuel can.
  7. Remove 8b from the fuel filter and repeat the pump out using one of the cone shaped Mityvac connectors inserted into 8b (easier than setting up the barbed butt connector and hose clamp again)
  8. Remove both 8c and 8d from the fuel filter Tee and repeat the pump out procedure with them.
  9. Reattach hoses 8b and 8d to the Tee. Remove the Micky Mouse wire clamp from the Tee on the fuel filter and remove the Tee from the fuel filter.
  10. Loosen the fuel filter clamp (10mm) and remove the filter. Drain the filter into the mixed fuel can. You will want to use a funnel. Discard the fuel filter. (See Fuel filter change and interval in Passat B5.5 “how to” section for more detail and video)
  11. Fill new filter with diesel or Diesel Kleen (a small funnel is great here too) and install into the filter clamp.
  12. Remove the old O-rings from Tee (only if your new fuel filter came with replacements). Apply a finger dab of diesel to the new O-rings and install them on the Tee. Install the black one first and then the blue (furthest one).
  13. Hook up the fuel lines to the filter (8a, 8c, and the Tee with Micky Mouse wire clamp)
  14. Wipe up any spills
  15. Pour 5 gallons of diesel into the fuel tank (with the remaining Diesel Kleen if you used that)
  16. Remove the battery charger if you hooked it up and clean up the area
  17. Turn the key over to the pre-start position about 4 times to actuate the lift pump and fill up the supply fuel line (8a)
  18. Crank over the engine. It took me about 15-20 cranking attempts to get my engine going (I had to charge the battery ½ way through). It ran a little rough for about 5-10 seconds and then smooth.
  19. Let run for a while
  20. Clean up your tools
  21. Go out for a drive and fill up the tank when you are satisfied that it is working well
  22. Dispose of your mixed fuel appropriately (hazardous waste)
Well, I hope that you never do this rookie diesel mistake as I did in a hurry one day.

This is what worked for me. I have read about damage that can occur when your tdi is mis-fueled because of lack of lubrication (diesel fuel lubricates). I ran mine with about a 50:50 mix (diesel:gas) up to freeway speed for 2-3 miles before exiting and then the engine stopped working and I realized my mistake!

I have not had any problems since (fingers crossed). There are a million ways that you could do this. After reading lots of stuff this seemed like the least hassle and I just hoped everything would be ok and it has been.

Paul
 

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My wife 'misfuelled' her polo diesel many years ago. Filled it with 2-Stroke (petrol mixed with oil for motorbikes and some cars). I knew nothing about diesels then. She rang me, I telephoned a few mates and we were advised just use it like normal. The car ran like normal - it didn't bat an eyelid. people explained to me that 'cos diesels compress the fuel to ignite it, most fuels will burn in a diesel engine (not the other way around tho). We had that car for years and made the mistake of giving it away. Still drives around.
 

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My wife 'misfuelled' her polo diesel many years ago. Filled it with 2-Stroke (petrol mixed with oil for motorbikes and some cars). I knew nothing about diesels then. She rang me, I telephoned a few mates and we were advised just use it like normal. The car ran like normal - it didn't bat an eyelid. people explained to me that 'cos diesels compress the fuel to ignite it, most fuels will burn in a diesel engine (not the other way around tho). We had that car for years and made the mistake of giving it away. Still drives around.
2-stroke fuel worked because it has OIL in it. I'm no chemist, but the oil, aside from the fact that it provides lubrication to the fuel system (necessary), is going to alter the flashpoint of the gasoline. With just gasoline the ignition properties are going to be totally messed up: straight gasoline needs a spark rather than compression to ignite- no spark plugs in a diesel so gasoline ain't going to "see the light!"

Older mechanical fuel pumps and injectors are more tolerant and less likely to suffer permanent damage from improper fuel. Common Rail, on the other hand, is likely to get hammered: high pressure pumps aren't very forgiving, and if you piss them off they're going to send their guts down the fuel rails and into the injectors- BIG $$!

I would suggest treating all diesels as though they'd be destroyed if run on gasoline. Keep the fear lest you lose your wallet...
 

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That's worth knowing! Yes, that wasn't a common rail - it was some time ago now, longer than I like to think about.
It was lucky then that she realised when she paid - here diesel is much cheaper (still) - hasn't done it since (or hasn't told me).
But now her car is an over-engineered polo so probably it would blow up if she did it again - then I would have to drive her :rolleyes:
 
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