S

S8 Mick

New Member
Hi

The wifes TD4 has lost all power. It has no engine light on and I can hear the turbo spin.

At a standstill in neutral if I put my foot down the pipes expand as if the turbo is boosting.

I have tried a few things so far.

New MAF.

Disconnect MAF.

New Boost Sensor (MAP)

All the above have made no difference.

Any tips on where to go next without spending money as I'm allready into a new MAF and MAP.

Thanks

Mick
​
 
Thanks for the reply.

According to the piping diagram for the solenoid I am getting a constant vacuum through the vent with the filter on. Is this right or is the solenoid piped wrong??
 
S8 Mick said:
Thanks for the reply.

According to the piping diagram for the solenoid I am getting a constant vacuum through the vent with the filter on. Is this right or is the solenoid piped wrong??
Click to expand...
Correct. . . . . .but ,i guess you've made sure there is no holes in the large rubber inlets [all three] ? and air filter is good, and egr is not totally blocked ? if you have then fine, another one is a weak lp pump [don't always kick in the mill light] if its just below the warning threshold. . . . . .just a thought :) :) :)
 
Thanks for the replies guys.

Slight update.

This morning I have tried

Removing the solenoid to turbo vac pipe

putting vac direct to the turbo

disconnecting the low pressure fuel sensor

checked the egr valve

none of these have made it any better. :doh:
 
Try cleaning the MAP sensor on the back of the inlet manifold. These can get clogged with carbon

EDIT: Just seen you have replaced the MAP sensor already, sorry
 
Just changed fuel filter and disconnected the low pressure feed under the bonnet to bleed it and fuel flowed out fine so I think the low pressure pump is ok.

Going to test it shortly but dont think the filter will improve it any but fingers crossed.
 
I'm putting my cash on a fuel pump problem. At the end of the day the principle is simple, the more fuel you throw in the pot, the more power is developed. You have tried the obvious things and all is suggesting the ECU is demanding high injection volume but is not getting it. Both the High and Low pressure pumps are known for their issues on the TD4. The low pressure pump goes weak which results in rough running and smoke. Then it fails, which causes an obvious engine failure with alarms. The High pressure pump is also known to fail but not so often. I'd say yours is weak and isn't getting the common rail pressure up high enough. Not cheap, if memory serves, I'm sorry to say.
 
After my fuel pump (in the tank under the back seat) was replaced the mechanic gave me the advise to avoid to run with less than 1/4 in the tank but fill it up when nearing that level. Apparently the downforce of the full tank helps the fuelpump(s) to run smoother and to avoid a little they f.... up.
 
We have the same problem with my partners TD4, we have replaced fuel pump (wheel arch) twice as thought first one might be suspect. Like you replaced map sensor also replaced fuel rail sensor. But no difference, we have put it on laptop and ran diagnostics but nothing really shows up. So we are little stumped as to what to do next. Injectors dont show up any faults the software showed that they were working within parrameters etc.

We do get a drop of pressure at low level fuel sensor on full throttle but only a slight drop. Its a new OEM pump so should be OK, we even ran a fuel line direct form pump to engine bay incase there was a blockage in delivery pipe. Next step is to run a pump with fuel can in to see if that makes a difference. When my mate spoke to bosch the technician did say they have problems with the injectors not having correct pattern and that would show in lack of power. So if seperate fuel supply does not work we will get injectors checked even though diagnostics showed they were working.

Will report back
 
We did check wastegate valve, it operates via solonoid when you rev it you can see actuator move two or three cm. However this may not mean it is working internally I guess? Anyone know if that could be the case?

Its funny you mwntion it because if you drive it with intercooler pipe off it drives no differently?
 
If when you tested with the turbo pipe off - it drove the same?
Could be there's no boost pressure from the turbo - hence low power.
Check to see if you are getting boost pressure when the turbo spins up. :der:
Has been known for a turbo shaft to break or waste gate to get stuck hence no boost - rare but nasty one. £££££

Would have expected black smoke tho' - no smoke and no power would point back to lack of fuel.

May be time to feed the stealer (or equipped independant) and connect up to a test book to check out the fuel system. If they can do the dynamic tests for low and high pressure systems while running it should give you something to work with.
 
The TD4 has a variable boost control on the Turbo wuch that it give good response performance at low engine speeds, without over boosting the engine at higher speeds, but is the wastegate also solenoid operated? They are normally mechanically pressure operated. I had a look at Haynes and its not clear. The Turbo performance can not be judge off-load. Sounds like an examination is in order here.
 
You can see the wastegate actuator moving when you floor throttle then let off. It moves two or three cm which suggets it is working correctly. We run diagnostics whilt driving and it showed there was boost but down maybe .3 of a bar. We assumed this was due to lack of fuelling. It points to fuelling as there is no smoke even under full throttle. But again the fuel pressures appear to be operatin within limits as shown on rave cd.

Really is baffling
 
No power anywhere in the rev range or just at a particular rpm??
Have you run with the maf disconnected?
 
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