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Discussion Starter · #1 ·
Haven't been on here in a while, but here's the latest story with my CDTi. The car refused to start about 3 weeks ago, and the problem was tracked to a failed in-tank fuel pump. No worries, got an MG specialist to replace the pump, and that was fine.

Except that I had the car tuned about 9 months ago, raising the power to somewhere around 170bhp. Now, with the new fuel pump, if I'm accelerating hard in 2nd, the car gives me a shudder around 3500 revs, and then comes to a halt, ignoring any input I make with the accelarator pedal. Once she stops, I just start it again after a few seconds and off we go, but I'm obviously worried about this new phenomenon - is it a feature of the new fuel pump? Has anybody else noticed this?

It only happens in 2nd, and only when under hard acceleration - if I'm accelerating gradually, there are no issues. Help!!
 

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not being a mechanic myself i would have guessed that it sounds like there isnt enough fuel getting through to the engine when you press hard on the accelorator it could be something to do with the modifications you have done but im sure somebody with more savvy will be along soon
 

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Discussion Starter · #3 ·
Ah, that tallies with another new feature, which is better mpg (ie car using less fuel).

So the new question is, is there a way to regulate the fuel being sent from the pump (ie can I get the pump to send slightly more?)

Or does my new ECU program need adjusting - does it have the ability to get the pump to send more fuel in response to a more open throttle? (My knowledge of the oily bits is vague at best).
 

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Does the engine completely cut out?

Mine does this

Total loss of power without any warning could be under maximum throttle or just after or between gear changes, not related to any cornering effects as it has happened at rounabouts and on the flat twice, it does it with any amount of fuel in the tank

The low oil pressure indicator come on but the engine is still going, with barely enough power to even crawl to a safe place to stop

If I rev it, it is completely gutless just sort of ticking over

Once I switch off the ignition it starts and runs perfectly, it never recovers on its own

This happens about once a month

It last did it coming back from Beaulieu as I changed up to fifth gear after a flat out blat on the M54 damned annoying whatever it is

In your case if it never did it before I would supspect the new pump
Does it happen with a full tank or only near empty?
 

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Discussion Starter · #5 ·
I get those very symptoms, but never after a gear change, and only in second under hard acceleration.

Fuel levels have no impact on this occurring. I get the oil pressure warning light and lack of power, very same as you, and I have to restart to fix it.

Once a month? My new fuel pump is in 5 days and it's happened 6 times already.
 

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I am thinking buggy OS!

BSOD anyone...................................

I have just been on the MGR web site and followed the link to the ClangPing FTP server but I can't find the latest drivers for my car.

Might have to revert back to an earlier driver as it never seemed to happen with wife MK2 driving it

:bgrin:

We really do need some homebrew diagnostics for these cars
 

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Thinks.

If yours only does it in second i.e about max thrust for this type of car then maybe you do still have a pump problem as all that G force! could be causing starvation.

Mine died the last time at shall we say somewhat higher speed so not much G force at that end of the spectrum.

Normaly it goes in second or third if I am going flat out

I have got into the habbit of doing a rolling restart with the ignition now!

Puts you off overtaking anywhere other than long empty straights doesn't it, just imagine it doing that alongside a lorry in busy traffic at night in the wet!
 

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Discussion Starter · #11 ·
Thanks for all the input, people. I am going back to the garage guy today, who will hook up the car to the diagnostic system and we'll see if the fuel pressure sensor is shot, or needs a clean, etc.

And as for overtaking, let's just say my journey home is 10 mins longer these days!
 

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I am thinking low fuel pressure..... the fuel demand is so great that the pump can't keep up and fuel pressure drops. This will momentary stop, but not stall, the engine.
 

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It may be neither. Maybe the pump can't cope with trying to flow enough fuel for 170 BHP?

I had this problem in my standard car about a year ago, would overtake and the engine would stop but not stall. It was like the ECU had stopped the throttle input.
 

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Turbo Vanes Sticking ?

Keith Alexander said:
Does the engine completely cut out?

Mine does this

Total loss of power without any warning could be under maximum throttle or just after or between gear changes, not related to any cornering effects as it has happened at rounabouts and on the flat twice, it does it with any amount of fuel in the tank

The low oil pressure indicator come on but the engine is still going, with barely enough power to even crawl to a safe place to stop

If I rev it, it is completely gutless just sort of ticking over

Once I switch off the ignition it starts and runs perfectly, it never recovers on its own

This happens about once a month

It last did it coming back from Beaulieu as I changed up to fifth gear after a flat out blat on the M54 damned annoying whatever it is

In your case if it never did it before I would supspect the new pump
Does it happen with a full tank or only near empty?


A friend of mine was having a problem with his Skoda TDI (80kmiles) with sudden losses in power, he tried changing the MAF
over, but there was no difference. The sudden loss of power would occur intermittently and at the most inopportune times.
He found that if he switched of the engine and then restarted it again normal power and running would return. Of course
switching off the engine in the middle of moving traffic is not always easy, so it became a real pain and safety hazard
a junctions etc.

A few days ago he ended up removing the complete turbo and inlet manifold to check this area out. It took about 10
hours start to finish. What he found in the turbo was stuck vanes which were seized solid, so with a little knowledge
sharing help from a friend in the trade he stripped the turbo down, freed up the vanes using some kind of caustic soda
solution. Rinsed the parts out again to remove any residue. Fitted the parts back on and has not had the problem
since, (the power ,losses occurred on numerous occasions daily) Quote from him " running like a new car"
With the turbo assy being exposed to hot exhaust gases I imagine it would be easy for these parts to seize up in no time
at all. The bottom line is that it cost him nothing to check this out, and take action, well nothing apart from his time.

If I start to get these symptoms like these at higher mileages this is going to be one of the areas that I would look at, and
maybe should be part of a regular maintenance at say 100k miles anyway, depending on how hard a life the turbo has had.
The overhaul of a turbo is not really as bad as it looks and certainly anyone with a bit of common sense will manage to do
this task I would think.

Regards.
 

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Good post Lovel but I think I would definately know if my Turbo was sticking
I also think the effect would not be as dramatic i.e you would at least have some rpm

When it happens to me I have absolutely no go at all
I think it is fuel starvation/pressure related and the High pressure pump is being disabled by the ECU why the car continues to sort of tickover rather than stop completely baffles me but I assume even with no high pressure pump running the low pressure pump can provide enough for a trickle to the injectors.

I do however have a different tuning box on mine to nearly everyone else
which is probably the culprit.

I don't want to, but probably will end up chucking it and getting one from Ron just to see if the problem goes away.
 

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Discussion Starter · #18 · (Edited)
ok, just wired up to the T4, and the symptoms were as follows

First fault code said

(1) problem with fuel supply, check blockage or failed pump
(2) low fuel pressure sensor

and another fault code revealed

(1) high fuel pressure regulator valve, maximum pressure exceeded

Bit confused - can't be both low pressure and high pressure together?

And the garage pointed out an official Xpower cd rom with a power upgrade for diesels, what sort of power does this result in?

BTW I also got a CAN BUS error to other ECUs, but I'm assuming this is a red herring?

Just to go through the symptoms again
(1) floor hammer in second gear, car always dies in the strange way as described by Keith at around 3200rpm
(2) can get to 4000 revs in second gear in a normal way with no problems
(3) can floor hammer in any other gear, no problems
(4) car is definitely using way less fuel than before.

Is it possible that the low fuel pressure sensor is mistakenly thinking there is not enough fuel pressure and is causing the EMS to shut the engine down? But then why do I have a message about a high fuel pressure regulator valve?
 

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Vinny

i had this problem before any tuning box was fitted (not had it since)

Get them to replace the low pressure sensor - that's what was wrong with mine.
 

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Ti Rich said:
Vinny

i had this problem before any tuning box was fitted (not had it since)

Get them to replace the low pressure sensor - that's what was wrong with mine.
I thought it was the HP sensor?
 
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