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Old 16th November 2023, 10:45   #1
AkpoTek59
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Default POSSIBLE STARTING ISSUE WITH UNDER BONNET FUEL PUMP MGZTT 2.0 CDTi (Automatic)

Wanted to ask if any of you know the signs of a failing under bonnet fuel pump (UBP)? Or under bonnet fuel pump or starter motor? Sound from in tank pump indicates that is working well, so on the odd occasion I've noticed starting issues even after a decent length drive so am a bit concerned and want to sort it before it gets worse?

My cars a ZTT Automatic diesel 04 model but very well cared for and when the issue comes up I've had to floor throttle before attempting to start otherwise it just won't turn over? Silent or very quiet click till throttle pedal floored then revs up. Hope I don't flood engine when having to do that to start? Jeez

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Old 16th November 2023, 13:36   #2
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check the wires that plug into it.. sign's of green or white powder

sign's of a bad fuel pump would be weak start

if u set the key into position 2 the fuel pump should switch on for 60 seconds so gives u time to put your hand on the fuel pump to see if it's working

also check the fuel lines under the fuel pump as the rubber is 20 odd years old and might need replacing
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Old 16th November 2023, 15:06   #3
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i think it's more likely to be leaking injectors or high pressure pump needs new seals
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Old 16th November 2023, 20:52   #4
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The only time my diesel 75 has ever failed to start was caused by a poor electrical connection at the under bonnet pump.

It was intermittently not starting easily and cutting out whilst driving for a couple of weeks, until one morning I drove about 1 mile into the village and it refused to start. I had to get the butcher to give me a lift home - he was a kind man and fellow Rover fan.

On the lead-up to the final failure, I could always get it going again by tapping it with a block of wood - I thought this was unjamming the pump, but I found out (after replacing the pump and experiencing the same issue) that all this was doing was shaking the electrics and re-making the connection.

The repair, that has lasted for the past 5 years and 50k miles, was to unplug the connector on the top of the pump, clean the contacts in the plug with a bit of wire wool and then reassembling with a blob of Vaseline

I hope your problem is as easy to fix!
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Old 17th November 2023, 18:10   #5
Mike Noc
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Quote:
Originally Posted by AkpoTek59 View Post
My cars a ZTT Automatic diesel 04 model but very well cared for and when the issue comes up I've had to floor throttle before attempting to start otherwise it just won't turn over? Silent or very quiet click till throttle pedal floored then revs up. Hope I don't flood engine when having to do that to start? Jeez
Nothing to do with you flooring the pedal and you can't flood it as they are drive by wire. If it is only turning over after a couple of attempts then either a bad connection at the starter motor solenoid cable or the solenoid contacts are worn. Plenty of info on here on how to replace them and you can buy a kit which has the parts you'll need.

If you have an auto then good luck with undoing the bolts holding the starter motor to the bellhousing - one of them is very cunningly hidden!
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Old 17th November 2023, 18:36   #6
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If it fails to turn over being a auto could be a dodgy inhibitor switch on the gear selector, try it in neutral and park
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Old 18th November 2023, 09:24   #7
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Default Re: Thanks fellas

Morning all and thanks for those who've taken time to reply my post on starting issues MGZTT 2.0 CDTi (Auto). Some scary responses mind PHEW!! Hopefully as another friend of mine who knows these cars very well suggests I change the FUEL & OIL FILTERS (as they might be clogged up?) and complete OIL change while I'm about it would not do any harm. Still think it may be the UNDER BONNET PUMP as the In tank seems to be working well. Will get those suggestions looked at and let you know the outcome.

Thanks folks
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Old 20th November 2023, 09:34   #8
Mike Noc
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My cars a ZTT Automatic diesel 04 model but very well cared for and when the issue comes up I've had to floor throttle before attempting to start otherwise it just won't turn over? Silent or very quiet click till throttle pedal floored then revs up. Jeez

You say it isn't turning over - if that is the case then it is nothing to do with fuel, oil or the respective filters.
If the engine is turning over then it could well be fuel related but it could also be a few other things.
So just to clarify does the engine turn over but not start or or does nothing happen when you turn the key, and if so can you hear a single click?
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