Under Bonnet fuel pump and relays

BT@Home · 6th June 2012, 08:49

So I did a search and found these symptoms from a few other members but didn't really understand where the original problem is.

In the last 3 weeks the battery on the ZTT CDTi has drained overnight twice. The first time was a mystery, no idea what it could have been been and it worked fine as soon as it was charged. The second time I swapped out the battery with a fully charged spare, and immediately noticed the fuel pump running all the time even with ignition off. Some investigation results in finding diesel on the fuse board too. So after cleaning up the board and the relay the running on of the pump goes away. Problem is there was clearly a problem causing the diesel to be pumped up the wiring to flood the board/relay.

So is the pump at fault for overrunning and then pumping the diesel up the wiring, is it a leaky pump that is caused from the overrunning, or is the relay at fault for staying open and causing the pump to continue running?

Don't really want to drive the car without knowing the solution/problem and even though it appears fine at the moment I wonder what it is that is causing the fault to occur every so often.

FrenchMike · 6th June 2012, 09:07

Is your plenum chamber dry ????

BT@Home · 6th June 2012, 09:09

Bone dry plenums.

75 Ken · 6th June 2012, 09:50

The under bonnet pump is faulty. If you take out the connector on the top of the pump you will see that the pump main seal is letting diesel pass into the base of the connector. Diesel runs along the wire and fills up the relay which then jams on. Sounds unbelievable but happens. Need new pump and relay Takes a long time for diesel in wiring to clear. The relay will be full of diesel. You can swop with one of the similar adjacent ones until you obtain a replacement relay.

BT@Home · 6th June 2012, 09:55

Yeah, that connector was the first thing I unplugged, and noticed the fuel.

So it's the pump that leaks that then causes the wiring/relay to become flooded, causing the overrunning ... And so a never ending circle

Cheers

75 Ken · 6th June 2012, 10:18

That's my belief. Happened after 6 hour motorway drive. Changed pump and relay 10K latter still no problem.

6th June 2012, 08:49	#1
BT@Home Loves to post '99 Club CDT / '03 ZT-T + CDTi Join Date: Oct 2007 Location: Basingstoke, Hampshire Posts: 420 Thanks: 0 Thanked 0 Times in 0 Posts	Under Bonnet fuel pump and relays So I did a search and found these symptoms from a few other members but didn't really understand where the original problem is. In the last 3 weeks the battery on the ZTT CDTi has drained overnight twice. The first time was a mystery, no idea what it could have been been and it worked fine as soon as it was charged. The second time I swapped out the battery with a fully charged spare, and immediately noticed the fuel pump running all the time even with ignition off. Some investigation results in finding diesel on the fuse board too. So after cleaning up the board and the relay the running on of the pump goes away. Problem is there was clearly a problem causing the diesel to be pumped up the wiring to flood the board/relay. So is the pump at fault for overrunning and then pumping the diesel up the wiring, is it a leaky pump that is caused from the overrunning, or is the relay at fault for staying open and causing the pump to continue running? Don't really want to drive the car without knowing the solution/problem and even though it appears fine at the moment I wonder what it is that is causing the fault to occur every so often.

6th June 2012, 09:50	#4
75 Ken Newbie Rover 75 saloon Join Date: Jan 2009 Location: Guildford Posts: 16 Thanks: 11 Thanked 1 Time in 1 Post	The under bonnet pump is faulty. If you take out the connector on the top of the pump you will see that the pump main seal is letting diesel pass into the base of the connector. Diesel runs along the wire and fills up the relay which then jams on. Sounds unbelievable but happens. Need new pump and relay Takes a long time for diesel in wiring to clear. The relay will be full of diesel. You can swop with one of the similar adjacent ones until you obtain a replacement relay. Last edited by 75 Ken; 6th June 2012 at 10:15.. Reason: Error at end ditvise on replacement relay

6th June 2012, 09:07	#2
FrenchMike This is my second home Rover 75 Saloon Join Date: Aug 2007 Location: Avignon Posts: 4,466 Thanks: 94 Thanked 661 Times in 554 Posts	Is your plenum chamber dry ????

6th June 2012, 09:09	#3
BT@Home Loves to post '99 Club CDT / '03 ZT-T + CDTi Join Date: Oct 2007 Location: Basingstoke, Hampshire Posts: 420 Thanks: 0 Thanked 0 Times in 0 Posts	Bone dry plenums.

6th June 2012, 09:55	#5
BT@Home Loves to post '99 Club CDT / '03 ZT-T + CDTi Join Date: Oct 2007 Location: Basingstoke, Hampshire Posts: 420 Thanks: 0 Thanked 0 Times in 0 Posts	Yeah, that connector was the first thing I unplugged, and noticed the fuel. So it's the pump that leaks that then causes the wiring/relay to become flooded, causing the overrunning ... And so a never ending circle Cheers

6th June 2012, 10:18	#6
75 Ken Newbie Rover 75 saloon Join Date: Jan 2009 Location: Guildford Posts: 16 Thanks: 11 Thanked 1 Time in 1 Post	That's my belief. Happened after 6 hour motorway drive. Changed pump and relay 10K latter still no problem.