Electrical fuel pump help

[Markr]

Hi all, god it’s been a while since I’ve needed some assistance so hoping some one can help me out.
I’m loosing my marbles with this one, moved the car into a garage 5months ago. Go to move it today and engine cranking but no fuel delivery.
Checked on the white cable with red stripe (at pump) and 0v showing. working back through the front relay ( think it’s NF01) to the yellow relay to the green relay I’m showing only 5v on the blue cable with relay removed.
I’m assuming I should have 12v at this point which then gets switched down the blue with red stripe continuing down the sequence of remaining relays?

I’ve checked at the 15amp and 20amp fuses at the drivers side footwell and both showing 12v out fuses are intact.

Can anybody confirm these voltages for me please? I’ve attached a couple of images for clarity showing which pin goes to which color.

 

[JoeLanger]

You're right it should be 12v. I'd have to check the drawings, but have you looked at the fuel pump resistor

The low voltage is high resistance in the circuit so that's loose or corrode connections.
0v likely a break, but could also be very high resistance.

 

[Markr]

Thanks Joe, I was sure I was ment to have 12v here at the blue, but I just needed it confirming to carry on my fault tracing.

No I’ve been thinking about that all night, on the diagram the resistor seems to straddle the blue and red cable from the green relay holder and being I’ve only got 5v to the blue into the relay I can’t see how this could affect this problem?

Thanks for your help

 

[Ceylon]

From your findings the issue is between the joint box fuse and x02. The only joints in that length are jb03 and X10, I'd start with X10 and check for decent contact or corrosion.

Or alternatively, rewire your feed like this from post 7 onwards:

Thread 'Fuel pump rewire wire'

Nov 11, 2018

Making up a couple of these for mates, thought I'd offer it up here in case anyone else needs one? Can do them for £15 delivered. The terminals are brass and crimped on with a little solder dabbed into the terminal to make it more resistant to corrosion.

This will change the fuel pumps power source from the ignition circuit to its own dedicated direct feed that will not suffer great voltage drop like the ignition circuit does. I've seen cars with as low as 11v at the pump under load, this fixes that issue.

Install is simple, everything takes place in the X-02 fuse box like in...

• Ceylon
• Replies: 71
• Forum: Parts For Sale

• 

 

[JoeLanger]

So you have voltage on the outgoing of "20A fuel pump" fuse
But only 5v at the "circuit opening relay"

The 0v at the fuel pump is probably that 5v disappearing across the fuel pump resistor.

So your fault is somewhere between those two.
I'd check both the holders for the relay and the fuse.
And check that x10 connector.
Just keep checking the voltage until it's not 12v anymore

You could measure continuity / resistance from the fuse to the relay. That will confirm the fault

 

[Markr]

From your findings the issue is between the joint box fuse and x02. The only joints in that length are jb03 and X10, I'd start with X10 and check for decent contact or corrosion.

Thank you, this is my logic too, can I confirm please that X10 is the blue plug on the back of the fuse board (drivers footwell) and jb03 is the green plug in the front? Just to save me some time tracing them back pin by pin

 

[Markr]

So you have voltage on the outgoing of "20A fuel pump" fuse
But only 5v at the "circuit opening relay"

The 0v at the fuel pump is probably that 5v disappearing across the fuel pump resistor.

So your fault is somewhere between those two.
I'd check both the holders for the relay and the fuse.
And check that x10 connector.
Just keep checking the voltage until it's not 12v anymore

You could measure continuity / resistance from the fuse to the relay. That will confirm the fault

Correct, 12v at output side of 20amp fuse (drivers footwell) only 5v at blue cable on circuit relay (green relay).

Right that makes sense the resistors is absorbing the 5v hence not seeing this 5v at the pump (thanks, this was confusing me a lot)

Yep I’ll make up some long test leads to check continuity between those points.
Thank you for your help,

Unfortunately I’ve got a fun filled family day out today so will have to pick this up in the week again

 

[JoeLanger]

Huh I didn't see Tom's reply. Looks like we're both saying the same thing.

Tom probably knows which connector is X10 though.
I'd have to look it up in the drawing packs, pretty sure it does tell you where they all are

 

[Markr]

My god the saga continues, I’ve rewired the live in to the blue cable on the green relay (circuit relay) same as Ceylon’s guide which I now have a solid 12.5v into the relay.

My issue now is once the relay coil becomes energised from the black and green switched live cable the relay keeps dropping out (relay closes the contact then immediately reopens circuit) this is happening on both the fuel pump relay and circuit relay.

Ive checked continuity on the earth side of the relays coils and this appears to be the issue on both relays ( circuit relay - blue and black cable which goes back to 1T ecu plug) and ( fuel pump relay - blue and white goes back to 1K ecu plug)

Both are showing continuity between the ecu pins and the relay spades and they are complete circuits (perfect) but I have no earth continuity on the pins 1T and 1K to chassis ground.

Does the ecu switch the earth out down 1T and 1K? Or should these be permanently earth regardless of ignition switch position?


Thanks if you read all of that and can help because I’m like 25hours into this and now really loosing the will to live

 

[JoeLanger]

Have you measured continuity throught the ECU with is connected?

I was always train to avoid that. Putting voltage onto electronics which aren't expecting it is risking damage. I'm not saying you've damaged it but could be a possibility.

Does the ecu switch the earth out down 1T and 1K?

Yes the ECU is switching the relays depending on it software. Have you tried simply trying to start?

If its not starting and not holding those relays in it could be a broken ECU? - interested in ceylons thoughts

Could be another fault in the loom though. Or a dodgy earth, where was the faulty wire? It's not the loom above the front wheel arch is it? They are known to rub through

I'd have to look at the drawing to come up with some other possibilities

 

[Tangelos]

I would go ahead and check the connector on the inside of the fuel pump hanger as well. It's possible that the pump seized from sitting and is locked up, burning up a connector pin.

 

[Markr]

Thank you all for your input.

Sunday evening I’ve got it running, but this job isn’t completed. I’ll post up all my findings encase anyone else finds this post useful. Interestingly the green nfo2 relay dropping out instantly is normal it seems.
I can’t confirm this (theory based) but I’m lead to believe that 1T terminal from the ecu (blue cable white stripe) is actually both a earth and live cable hence finding it impossible to test the function of the coil staying energised on the relay. When the ignition is switched the white and blue gets sent a earth pulse followed by a live to close the relay contact (providing a fuel pump prime) then when engine is cranking and running it provides a constant earth energising the relay, thus switching the 12v feed to the fuel pump relay speed (nf01)

I checked this by connecting a light bulb between the black and green(12v live from 15amp fuse in drivers footwell fuse board) and white and blue from 1T this visually let me see the current.


The problem now lies with the fuel pump speed relay (NF01) if I link the red and white cable to the blue and red the car will fire and run fine.

Does any one have any understanding of terminal/cable 1k (from ecu) and how it operates as the description in the wiring book I can’t get my head round. I can’t keep this relay open (closed contact) but have the switched 12v present on the green and black cable?

I’ve tested Nf01 relay on a battery and the relay operates so I’m pressuming it’s the 1k wire

 

[Markr]

Have you measured continuity throught the ECU with is connected?

I was always train to avoid that. Putting voltage onto electronics which aren't expecting it is risking damage. I'm not saying you've damaged it but could be a possibility.



Yes the ECU is switching the relays depending on it software. Have you tried simply trying to start?

If its not starting and not holding those relays in it could be a broken ECU? - interested in ceylons thoughts

Could be another fault in the loom though. Or a dodgy earth, where was the faulty wire? It's not the loom above the front wheel arch is it? They are known to rub through

I'd have to look at the drawing to come up with some other possibilities

I too have been considering a knackered ecu but now it’s running I can forget that theory luckily (post above). The original knackered cable was the 12v blue from 20amp fuse (front footwell) to nf02 relay which was getting the duff voltage. I moved a lot of wires in the car about 8years ago but yes the cable used to go through the front horse shoe loom. Really appreciate your help Joe

 

[Markr]

Can anyone see an issue or adverse effects in doing this: to hugely simplify the fuel system and remove everything but the nf02 relay? As this is looking the obvious choice currently.

 

[Ferrox117]

lol this is sorta what I’ve been doing recently aswell, was getting no signs of voltage from white with red stripe intermittently, traced it back through the car, and nothing, fuses fine, relays find just missing a switched feed- reckon it could be down the the immobiliser tbh

 

[Markr]

lol this is sorta what I’ve been doing recently aswell, was getting no signs of voltage from white with red stripe intermittently, traced it back through the car, and nothing, fuses fine, relays find just missing a switched feed- reckon it could be down the the immobiliser tbh

It’s just so much fun isn’t it tbh I’ve got a aftermarket immobiliser but I can’t see its linked in to the fuel system (allthough could be but can’t see it) I think mines only really on there as a central locking controller and alarm but has the immobiliser function.

 

[Ferrox117]

It’s just so much fun isn’t it tbh I’ve got a aftermarket immobiliser but I can’t see its linked in to the fuel system (allthough could be but can’t see it) I think mines only really on there as a central locking controller and alarm but has the immobiliser function.

It’ll have to be in the spark or fuel system somehow mate