I have had an intermittent fuel pump electrical problem, which has now become permanent. I have printed off the electrical diagram and traced the wires, earths etc. I have checked the relay and fuel cut off switch and they are fine. However, when we put a power probe on connection 4 of the terminal block on the fuel pump, we get an earth signal, same as connection 3, which is what one would expect with connection 3. If we then use the power probe to power up connection 4 the pump works? I see from the wiring diagram that the fuel pump relay requires a earth control signal from connection 30 of the ignition ecu, would this be affecting the power to the fuel pump?

when we put a power probe on connection 4 of the terminal block on the fuel pump, we get an earth signal, same as connection 3, which is what one would expect with connection 3.
resistance through an electrical motor like the fuel pump will be very low so it would appear as if the power pin 4 is connected directly to earth. That is normal. To test pin 4 properly you would need to disconnect the connector to isolate it from the pump

If we then use the power probe to power up connection 4 the pump works?
That's good then and shows nothing wrong with the pump. You now need to find out why no power is supplied to pump

I see from the wiring diagram that the fuel pump relay requires a earth control signal from connection 30 of the ignition ecu, would this be affecting the power to the fuel pump?

1.6 system shown here. You don't say what engine you have and each one is different but yes, ECU powers relay T9 here which then supplies power to pump via fuse. Then it goes through D4 - ho ho- and then there are a straight through connections on panel B2 in engine bay. Lots of places where power could be lost. I'd check power on each side of fuse F22 (might be different for your engine) then you know ecu is putting out and relay T9 is energising and the fuse holder is good

Back probe the relative D4 connection pins and check for continuity across the B2 connections.

JTD system

You don't say what engine you have and each one is different but yes

Thanks for the reply, the engine is the 2.4 20V.

Ha! Different again then. Quite a few places where a poor connection would cause problems


Think I'd check the voltages in and out of relay T10 as that's in the middle of it all then you'd know which side of it is at fault

I have tested connection 4 of the fuel pump connection whilst disconnected from the pump and confirm, it is dead!

I have tested T10 relay off the fuse board and can confirm that works.

I have tested F21 both sides and can confirm that works.

I have tested terminal 30 of T10 relay to earth and can confirm power is there.

I have tested terminal 87 of T10 relay to earth and can confirm it is dead

I carried out the same procedure on T9, which is the main ECU relay and can confirm that terminal 30 and 87 have power.

Therefore if T9 is working and getting its earth reference from pin 31 of the ECU, one could assume that T10 is not getting its earth reference from pin 30of the ECU?

What then would make the ECU not give this earth reference to T10 relay?

Just a thought, the car has been standing for months and the battery went flat. I charged the battery up and works fine now, but I did have problems with the immobiliser in that the remote keys would not operate it. I have since rectified this, but could it still be either the key or immobiliser?

Ok, well if you want to, you could connect relay T10 pin 85 to earth and the relay should energise, and fuel pump work. That would prove ECU not putting out an earth for the relay as you suspect
Do a continuity check between relay T10 pin 85 and ECU pin 30

I would expect a CODE warning light if there were immobiliser problems

Tried what you said, I took the cover off the relay as it is easier to get the probe on the terminal, applied power but still wont power-up the pump!!

I have just noticed that when I turn the alarm on now, it bleeps once and the lights flash once as normal, but then about 3 seconds later, it bleeps again with no lights flashing? Its never done this before?

Not apply power- put an earth onto pin 85 of the relay
Connect a wire from an earth point somewhere nerby to the terminal 85

Listen if relay clicks, if it doesn't then there's something up with relay or relay contact points as you've already found a 12v supply there to it at terminal 30

Can't help you with alarm

Deckchair5 said:

Not apply power- put an earth onto pin 85 of the relay
Connect a wire from an earth point somewhere nerby to the terminal 85

Listen if relay clicks, if it doesn't then there's something up with relay or relay contact points as you've already found a 12v supply there to it at terminal 30

Can't help you with alarm

Click to expand...

Sorry, getting confused with the pin numbers, I powered up pin 87 in the assumption that its a simple switch that breaks with pin 30. I will try what you said tonight.

No problem. Hopefully it'll fire up straight away once that relay is energised

Deckchair5 said:

No problem. Hopefully it'll fire up straight away once that relay is energised

Click to expand...

OK, turned the ignition on and tested all connection on T10. pin 30, pin 86 and pin 85 are all showing live on the probe, pin 87 is still dead. swapped over with another relay of the same and got the same reading. With ignition off pin 30 is live, pin 86 and 85 are earth with pin 87 dead.

What does this all mean???

turned the ignition on and tested all connection on T10. pin 30, pin 86 and pin 85 are all showing live on the probe, pin 87 is still dead
pin 85 should be getting an earth from the ECU in this statewhich would energise the relay but your ECU isn't supplying an earth. Pin 85 will show live because that's all its energising coil is connected to so there is no current flowing through it and the relay coil isn't being energised. Pin 85 should be showing earth but it's not getting connected to earth and that's the problem

With ignition off pin 30 is live, pin 86 and 85 are earth with pin 87 dead.
That's fine

It sounds like you haven't followed my suggestion of putting your own earth supply on pin 85 to see if that gives power to the fuel pump. Once you know that is all that is required and all the rest of the circuit acts properly then you need to find out why the ECU isn't supplying an earth to pin 85. A poor contact at ECU pin 30 would cause your problem for instance

It sounds like you haven't followed my suggestion of putting your own earth supply on pin 85 to see if that gives power to the fuel pump.

I did what you suggested with the ignition on and it blew a fuse, as I said, all the terminals are +12v with the ignition on, so connecting it to earth would just short it out, which is why the fuse blew?

With the ignition off, it's already connected to earth.

You should have said
There's the problem then, the relay requires 12v and earth across the coil for it to work. If applying an earth to the relay earth terminal blows a fuse then you have a short circuit at the relay holder. Rather than power going through the coil to energise it, you have a short circuit between pins 85 and 86.
Look for corrosion or bridged contacts there at the relay circuit board B1

Deckchair5 said:

You should have said
There's the problem then, the relay requires 12v and earth across the coil for it to work. If applying an earth to the relay earth terminal blows a fuse then you have a short circuit at the relay holder. Rather than power going through the coil to energise it, you have a short circuit between pins 85 and 86.
Look for corrosion or bridged contacts there at the relay circuit board B1

Click to expand...

Change the complete fuse board with a new one, still the same problem!

I cant even use my Fiat Examiner on the vehicle as it cant connect the the body computer!

Alarm issues still, as I said before, the alarm is making an additional bleep and I'm now getting a warning prompt on the dash saying alarm failure!!

Any ideas?

Still the same problem as in it still blows a fuse?
Which fuse is blowing?
Are you sure you are earthing relay T10 pin 85?

If you put 12v power on t10 pin 87 the fuel pump runs yes?
But if you earth t10 pin 85 a fuse goes? What fuse F16?


I cant even use my Fiat Examiner on the vehicle as it cant connect the the body computer!
Why not? Do you still have that problem of no 12v power at the BC?

Are you sure the inertia cut off switch I30 is working as it should and supplying a signal to the ecu to supply power to the fuel pump?

Just a thought, the car has been standing for months and the battery went flat. I charged the battery up and works fine now, but I did have problems with the immobiliser in that the remote keys would not operate it. I have since rectified this, but could it still be either the key or immobiliser?

What did you do and are there any problems with the immobiliser now? Is dashboard code warning light off when it should be?

Pull out relay T10 and just check that 12v is still being supplied by the ECU at empty relay socket pin 85 with ignition on. This should be earth with ignition on but i just want to be sure that the ECU is not supplying earth rather than 12v coming through the relay. Your problems all seem to relate to earth not being supplied on T10 so it's just working out why

Still the same problem as in it still blows a fuse?
Which fuse is blowing? F16 when T10 85 earthed

If you put 12v power on t10 pin 87 the fuel pump runs yes? No, but if I measure the voltage between pin 87 and live, I get a +12v


I cant even use my Fiat Examiner on the vehicle as it cant connect the the body computer!
Why not? Do you still have that problem of no 12v power at the BC? My Examiner is faulty

Are you sure the inertia cut off switch I30 is working as it should and supplying a signal to the ecu to supply power to the fuel pump? Replace inertia switch some time ago. However, have tested the following - Pin 1 is showing earth, and pin 3 is showing 6.42v with ignition off and 6.19v with ignition on?

I have done a check list and this is the result, it may help?

Pin 30 of T10 is +12v
Pin 85 of T10 is earth when ignition off and +12v when ignition on
Pin 1 of the inertia switch is earth
Pin 3 of the inertia switch is +6.42v with ignition off and 6.19v with ignition on
Pin 30 of fuse board connector block C is +12v
Pin 11 of fuse board connector block C is +12v
Pin 31 of fuse board connector block C is dead

I did some other tests

T10 relay out, pin 86 with ignition off +0.05v, with ignition on 3.62v

T9 relay out, pin 87 with ignition off +12v, with ignition on +12v
T9 relay out, pin 85 with ignition off +12v, with ignition on +12v
T9 relay out, pin 30 with ignition off dead, with ignition on 0.02v
T9 relay out, pin 86 with ignition off +12v, with ignition on +12v

T9 relay in, all pins +12v

I have bought the retail version of fiatecuscan, I looked for stored errors and there were loads, P1653, P0520, P0201, P0202, P0204, P0205, U1600, P0571, P0230, B1027, B1028, B1029 and B100E. A lot of these may be that I have disconnected a sensor and then turned the ignition on?

I am going to give up on the car soon, what would start of intermittently and then be permanent?

Oh, I forgot to say, the ignition ECU, with the ignition on, makes all kind of buzzing sounds ranging in pitch. Is that normal?

A lot of stuff there but the first thing I'd attend to is U1600- key not recognised as you're stuffed if that's happening. I'd find out if this is still happening by erasing codes and see what comes up again

but I did have problems with the immobiliser in that the remote keys would not operate it. I have since rectified this, but could it still be either the key or immobiliser?

What did you do and are there any problems with the immobiliser now? Is dashboard code warning light off when it should be?

B codes are your air con

P0230 is a fuel pump primary circuit failure

but you need to find out first if these are just history or present codes

What did you do and are there any problems with the immobiliser now?

I plugged some old diagnostic software in, which would not work, but afterwards, the remote locking and alarm started to work. I'm not getting any alarm failure warning at the moment, but am getting the oil pressure sensor warning. I know there is nothing wrong with the sensor, as it's new. I had this problem message before, so the I changed both oil sensors.

Is dashboard code warning light off when it should be?

What warning light, the engine management light is on?

but you need to find out first if these are just history or present codes

These are all historic fault codes, as not only does it tell you this, I cancelled them all and the only one that came back was the oil pressure sensor.

Fiats have tried in the past to try and sort this problem out, and when they put the vehicle on their examiner, they said it was low oil pressure and put some oil in, the vehicle then started. This, I think, was just pure luck, as I know the oil was at its correct level, as I had only just changed it, and this remedy never worked in the future!

U1600- key not recognised as you're stuffed if that's happening

I don't think it would be the key as if I put 12v direct to the fuel pump and turn the engine over, the car starts, and continues to run until I cut the power to the fuel pump. I have also renewed the aerial around the ignition.