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Discussion Starter · #1 ·
All,

I have had a problem with my 05 MGZT 135 Diesel, I would be grateful for any comments to guide me to the next step...... first some history.
I have had the car for about a year, it now has 128K on the clock but is an excellent drive, the previous owner replaced the clutch and this is a later car so the major pump issues should be designed out, so in theory I did not expect any significant work to be done for sometime.

Last Sunday driving away from some traffic lights the car started to slow with lack of power, I pulled over to check it out and could not see any direct issues. I managed to the get the car home (just over a mile) but it lacked so much power it crawled along at 20 MPH. I called out the recovery service to check it and they said it was the "Injection or something" so I had it taken to my local mechanic.
So.... the car starts and ticks over fine, there is no smoke or leaks, there is no engine management light on the dash. It won't rev pass 2,600 rpm, it has very limited power so will stall under load at 2000 rpm.

The mechanic used his scan tool and managed to fine a code (P1260, I think) which he said was low fuel pressure, the ITP could be heard running. We decided to replace the pump (which was a lot of hassle) and replaced the fuel filter. The car was unchanged.

Hopefully you can help eliminate some other possible causes.
So somebody suggested that the injector might be at fault (leaking or not responding to signals), I don't think applies because you would see more smoke, or it would run rough at tickover.

The MAF sensor has been disconnected and it made no difference.

The ECU says the Throttle pedal pot is working fine.

The Mechanic says that the vacuum pipes to EGR valve has been closed off (apparently this a common mod)
I now plan to bring the car home from the garage (to limit the costs) and try to resolve it myself.
Is there any other component which I should consider replacing?

Is there another high pressure pump somewhere?

And can anyone recommend a diesel specialist who might have experience of MG Rover (or BMW) in the Southampton area?
Thanks in advance for your help.

Sean Flood
 

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Discussion Starter · #3 ·
High Pressure Diesel Pump

Hi Thanks for the quick reply.

Is that a mechanical pump?

Do you know if it is an easy job to replace?

Regards Sean
 

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Unlikely to be the HP pump. Try unplugging the LP fuel pressure sensor - it is in the top of the fuel filter. If the car then revs freely the fault is with the low pressure fuel delivery.
 

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Check the plenums first, then check the O-rings, also even though you have had the EGR by pass done check the PCV filter and the air filter, and get back to us
 

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Unfortunately the mechanic tried this, it made no difference.

I guess it could actually be low pressure and the sensor works as expected

Sent from AutoGuide.com Free App
Yes it could be a low pressure fault but, from what I have seen, with the sensor unplugged the the ECM won't put the car into limp mode so it will rev freely on idle.

If there isn't enough fuel to supply the HP pump and it can't maintain the pressure in the fuel rail then the ECM will shut the engine down when the reading from the HP sensor gets too low.

You seem to have both limp mode and cutting out so, to try and narrow down the cause, is your mechanic sure the engine won't rev past 3k with the LP sensor unplugged?

Before you replace any more parts - especially the HP pump, which is normally very reliable, it would be worth plugging the car into T4 diagnostics.
 

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You would have thought the MIL would light up with the engine in limp mode.

Funnily enough it doesn't, but does come on when you unplug the LP fuel pressure sensor.

Messenger (Corin) on the other side is based in Crowthorne, has a T4.

If you do a search French Mike has some multimeter tests you can carry out to check the signal voltages for both HP and LP fuel pressure sensors.
 

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Discussion Starter · #13 ·
05 ZT diesel problem - Update

I thought it was time to update you guys on my lack of power problem with my CDTi.

It went to a local mechanic who has done servicing and MOT's on our cars for a few years now. He connected his code reader and got back P1260 (low fuel pressure), the old pump still runs but we replaced the intank pump (ITP). This was a challenge because the replacement pump seem to have too many connections. Finally we got the pump installed and the problem remaining. We both agreed that it should go to a local Bosch diesel specialist in Southampton. At this time the car could barely do 30 Mph, so moving to another location required planning (sunday morning)

The diesel specialist went through the cars injection system and found a leaky injector, this was refurbished and replaced.... no difference. We looked at the MAF sensor, they had a spare BMW 320 Maf to try .... no difference. I still had the old ITP, it was fitted back in the car.... no difference. The fuel lines were blown through. The ECU was inspected and there was some water damage, it was tested and was found to be working well. The filter head (including the low pressure sensor) was replaced with a new unit from Rimmer Bros..... some improvement but the fault code keeps coming back. Unplugging the low pressure sensor makes no difference to the running.

Definitely sounds like fuel starvation/fuel pressure problem, we just can't find the cause. We are running out of options (and components for that matter).

I have asked them to test the fuel pump output pressure (should be 2.5 Bar I believe) to prove whether it is physical low pressure or a bad signal (loom issue or bad voltages). The only other thing it could be is a bad replacement pump (both old and new show the same problem).

Any suggestions would be welcome, I am beginning to think I will never get the MG running again.

Do you think that a T4 will show more detail of where the fault might be? There s only a low pressure sensor and some information from the High pressure side. There is a T4 in Southampton (Viking garage at west end) but they want £70+Vat to run it on the car and I need to get it there. If they can only say that the fuel pressure is low then I have no benefit.

Thanks in advance

Regards Sean
 

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does the car have a synergy fitted ? ours did this then died - it was the wiring in the plug on the fuel rail pressure sensor (it was actually the plug on the synergy harness that failed - wire soldered back in and all good )

the HP pump may not be present on an 05 car - its behind the battery box slightly to the left ( a silver cylinder vertically mounted) - did you fit the correct in tank pump - from a single pump car - not from an earlyier 2 pump car ?

2 pump car WFX 100 933 £ £236.84 (rimmers price)
1 pump car WFX 000 350 £459.68 (rimmers Price )

Hell of a price difference - page on rimmers here Item 4
 

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Carl the HP fuel pump is present in all the diesels - it is engine driven. The LP under bonnet fuel pump was deleted in later cars.

Sean if you unplug the inlet pipe to the fuel filter and place it in a large jar then with key to position 2 you should get a good strong flow of diesel into the jar. Anything less or with air then the problem is on the LP side.

You mentioned that the garage blew though the fuel lines - I've seen a partial blockage caused by one of the protective clear plastic covers for the open pipes on the LP fuel pump not being removed prior to fitting.

This dropped down into the pipe and caused the engine to run in limp mode. Long shot but worth a look.

Regarding T4 it will show what is happening with all the sensors in real time, and flag up anything that is outside the parameters, but as you say if all you have is a drop in fuel pressure on the LP side then I don't think it will be of much help. So worth checking the fuel pressure first.

It's easy enough to rig up a pressure gauge with a T piece into the low pressure side and check the pressure with the engine running. I did this with my car when having stalling problems. LP fuel pressure was fine and then a quick plug in to a T4 diagnosed a faulty MAF.
 

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oh right Mike whats the purpose of 2 pumps then if there both LP - just seen there is a mechanical pump as well - never knew that
 

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oh right Mike whats the purpose of 2 pumps then if there both LP - just seen there is a mechanical pump as well - never knew that
Lift pump in the tank to shunt the goo to the front, under bonnet to raise it to just over 3 bar ready for the HP pump, and HP pump to give it the several thousand PSI needed for the 'jectors.

In the later cars the design was simplified, the in tank pump did the 'just over 3 bar' bit.
 

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The fuel delivery system is quite sophisticated. It has to cope with equalisation of the fuel levels in both sides of the saddle tank, temperature regulation of the fuel and be able to self prime if the car runs out of fuel.
 

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The fuel delivery system is quite sophisticated. It has to cope with equalisation of the fuel levels in both sides of the saddle tank, temperature regulation of the fuel and be able to self prime if the car runs out of fuel.
I guess I should get my in tank pump replaced - it's totally dead. Luckily I have a spare under bonnet pump :)
 
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