HELP! Car goes in to limp mode!!

[Rocco321]

I have been a member since 2014, however this is my first post on here. I'm not sure if I'm posting this topic in the right place though.

Ok, so I have a Scirocco 2.0 TDI (140) a few months ago I gave my girlfriend the car to borrow. On the way back to me she stopped at a Shell service station and put £40 of V Power unleaded fuel in the car. She drove the car on the motorway and realised the car wasn't driving right so she called me and told me what was going on. I asked her to take the next exit on the motorway and park somewhere safely until I get there. Around 20 mins later I got to her and I saw the receipt and realised what she had done. Unfortunately, she told me that before she could stop somewhere and park up, the car wouldn't go up the hill and it ended up cutting out. I got the car towed back to my local garage. After a load of reading online I decided to ask them to clean out the tank and fill it with V Power diesel. They did this, and the car took a while to start but eventually started. The car seemed perfectly fine at first, but then I realised there was a weird noise coming from the front. I thought maybe it would go if I put injector cleaner in the tank. I did that and it still didn't make a difference. On my way home, I got on the duel carriageway and floored it a little. The car ended up going in to limp mode, the glow plug light came on and the car lost power. I turned the engine off and then back on and the light went and the car was driving fine. I got home and parked the car in the drive.

The next day I went to start the car and it struggled to start. I booked the car in with VW and they had a look at the car. They said that because they found traces of petrol somewhere this problem is not covered under warranty. So I decided to get the car checked elsewhere just to save a bit of money. I had one of my mates stick in a diagnostic machine, The code P008700 came up, with the description 'Fuel Rail/System Pressure - Too Low'. I have since taken the car to several different garages. I have changed the electric fuel pump, the fuel rail and the fuel pressure sensor. But, none of the problems have been resolved.

I was hoping maybe theres someone that might know what could be the issue and could give me some advice on how it could be resolved.

Thank you in advance.
Shaz

[Roy_01]

Sounds like the high pressure fuel pump is damaged, i think because petrol doesn't lubricate it well and the sulfur in diesel does. Or there is air in the system because of the repairs. First check if the fuel filter contains any metal shavings and put a new one in it. If there aint any metal in it i would try to prime the fuel system a couple of times with vcds to let the air out and try to get her running.

[rpsmith79]

Not strictly related, but i had the same fault code thrown up on my 2.0 TSI, and it turned out to be a faulty/failed fuel injector as the petrol injectors fail wide open, so the pressure in the fuel rail drops as it is constantly throwing in fuel

[davidscirocco]

Have a look on these video of what happens if you put gasoline insted of diesel " onclick="window.open(this.href);return false;

[Rocco321]

Sounds like the high pressure fuel pump is damaged, i think because petrol doesn't lubricate it well and the sulfur in diesel does. Or there is air in the system because of the repairs. First check if the fuel filter contains any metal shavings and put a new one in it. If there aint any metal in it i would try to prime the fuel system a couple of times with vcds to let the air out and try to get her running.

Is the high pressure fuel pump located under the seat with the tank? I have been advised to change that but I haven't come round to doing it. Also, the fuel filter was changed and the fuel system was also primed. Unfortunately, it didn't make a difference at all. Thank you for getting back to me Roy.

[Rocco321]

Not strictly related, but i had the same fault code thrown up on my 2.0 TSI, and it turned out to be a faulty/failed fuel injector as the petrol injectors fail wide open, so the pressure in the fuel rail drops as it is constantly throwing in fuel

Would a mechanic be able to tell me which fuel injector is faulty, if one is? Also, were you having the same problems with your car, going in to limp mode and struggling to start etc? I think that's what I'm going to do next.
Thanks for the help rpsmith79.

[Rocco321]

Have a look on these video of what happens if you put gasoline insted of diesel " onclick="window.open(this.href);return false;

That video was extremely helpful. Thank you David. I think I might just get everything changed. I could see that fixing the problem definitely.

[Roy_01]

Here you have a picture of the high pressure fuel pump:

http://humblemechanic.com/2012/05/24/wh ... 33019-jpg/" onclick="window.open(this.href);return false;

This high pressure pump is on the front of the engine.
The fuel lift pump is in the fueltank under the rear seats.
The fuel boost pump is on the back of the engine, just follow the hose of the fuel filters.

Its smart to first get a diagnose, are there metal parts in the fuel filter or high pressure fuel pump.
" onclick="window.open(this.href);return false;
If there are then it will spread through the whole fuel system because the injectors return fuel to the filter and fuel tank without filtering. Then you have to take some drastic steps:

- Cleaning fuel tank
- Replace fuel lift pump
- Replace booster pump
- Replace filter insert
- Replace/clean fuel rail
- Replace high pressure fuel pump
- Replace/clean fuel injectors
- Clean all the fuel lines

This is a very expensive job but if you forget any part and there might be still metal in the system it will mess all up.
So first get a good diagnose. Is all the air out, is all the petrol out of the system. No water or anything else in the system. Is the pressure of the low pressure side of the fuel system ok. What is the high pressure during starting.
Don't cranck it for too long because it will damage the pump, air also damages the pump.
And work very clean on the fuel system its very sensitive for pollution. If there aint any metal parts in the system, diagnose the injectors.

[davidscirocco]

Have a look on these video of what happens if you put gasoline insted of diesel " onclick="window.open(this.href);return false;

That video was extremely helpful. Thank you David. I think I might just get everything changed. I could see that fixing the problem definitely.

No problem! Hope you get your car fixed soon

[Rocco321]

Here you have a picture of the high pressure fuel pump:

http://humblemechanic.com/2012/05/24/wh ... 33019-jpg/" onclick="window.open(this.href);return false;

This high pressure pump is on the front of the engine.
The fuel lift pump is in the fueltank under the rear seats.
The fuel boost pump is on the back of the engine, just follow the hose of the fuel filters.

Its smart to first get a diagnose, are there metal parts in the fuel filter or high pressure fuel pump.
" onclick="window.open(this.href);return false;
If there are then it will spread through the whole fuel system because the injectors return fuel to the filter and fuel tank without filtering. Then you have to take some drastic steps:

- Cleaning fuel tank
- Replace fuel lift pump
- Replace booster pump
- Replace filter insert
- Replace/clean fuel rail
- Replace high pressure fuel pump
- Replace/clean fuel injectors
- Clean all the fuel lines

This is a very expensive job but if you forget any part and there might be still metal in the system it will mess all up.
So first get a good diagnose. Is all the air out, is all the petrol out of the system. No water or anything else in the system. Is the pressure of the low pressure side of the fuel system ok. What is the high pressure during starting.
Don't cranck it for too long because it will damage the pump, air also damages the pump.
And work very clean on the fuel system its very sensitive for pollution. If there aint any metal parts in the system, diagnose the injectors.

Thank you very much for your help Roy. I've booked the car in at my local garage. They will be doing most of the checks, I've shown your post to my mechanic and he says it's very helpful. Hopefully the car should be back to normal soon. I will keep you updated. Once again thank you.

[Roy_01]

Your welcome! Hopefully there isn't any damage. Always something im afraid of with this engine.
The video link i added is a very clear explanation and describes the whole message i posted.

[Roy_01]

And any news yet?

[Kugaman1]

This sounds like an expensive error!

[Roy_01]

Any news yet?

[Rocco321]

Hello Roy,
The car is now running perfect. I had the car in and out of the garage from the high pressure pump being changed to the tank pump being changed, nothing cured the problem. It turns out that it was the fuel filter housing that needed to be changed. The top of the housing where all the rubber hoses go there's like a small piston that moves in and out, that was blocked and wouldn't move in. So every time I floored it the fuel filter wouldn't send the fuel with full pressure towards the electric pump, making the electric pump make a weird sound and making the car go in to limp mode. This somehow also affected the starting of the car. I'm happy I didn't go to VW as they were looking to charge me £415 just to get the injectors checked. Luckily I bought the car down to my cousin in France and he had a good look at it and finally found the problem.

Thank you for all your help guys. Luckily I didn't spend as much money as I thought I would've had to.

A very happy young man

[blower]

Hello Roy,
The car is now running perfect. I had the car in and out of the garage from the high pressure pump being changed to the tank pump being changed, nothing cured the problem.
It turns out that it was the fuel filter housing that needed to be changed.

There's one more part you may need to change to ensure the problem doesn't come back.......the girlfriend!