Technical fuel relay
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Technical fuel relay
hi mate and WELCOME TO THE FORUM :wave:
The LP fuel pump relay is R10 in the engine bay fuse box.
What problem are you having? If there is no power to the fuel pump have you checked the inertia fuel cut off switch?
Alan
The LP fuel pump relay is R10 in the engine bay fuse box.
What problem are you having? If there is no power to the fuel pump have you checked the inertia fuel cut off switch?
Alan
hi,
thanks for the quick reply.
only owned the car a month, first ever fiat and yesterday it wouldnt start.
was away from home so called out RAC and let him go through it for me.
turns over but wont fire.
all fuses fine
error code p0685 (fuel relay)
checked pump under rear seat and no power to it.
separate power source and pump works fine but still wont start
figure it is relay which is therefore cutting power to everything so even though pump is on separate power relay not allowing fuel to injectors.
had a look for the inertia cut off as guessed it was suppose to be drivers side in the fuse box area. no signs of the cut off switch what so ever so thought perhaps it doesnt have one?
next stage find the fuel relay, check the soldering in it and if necesarry replace it.
is there a like for like relay that i can remove and use to test in place of fuel relay to see if car then starts?
cheers
ash
thanks for the quick reply.
only owned the car a month, first ever fiat and yesterday it wouldnt start.
was away from home so called out RAC and let him go through it for me.
turns over but wont fire.
all fuses fine
error code p0685 (fuel relay)
checked pump under rear seat and no power to it.
separate power source and pump works fine but still wont start
figure it is relay which is therefore cutting power to everything so even though pump is on separate power relay not allowing fuel to injectors.
had a look for the inertia cut off as guessed it was suppose to be drivers side in the fuse box area. no signs of the cut off switch what so ever so thought perhaps it doesnt have one?
next stage find the fuel relay, check the soldering in it and if necesarry replace it.
is there a like for like relay that i can remove and use to test in place of fuel relay to see if car then starts?
cheers
ash
Hi mate,
The inertia switch is located in the passenger foot-well tucked up almost behind the glove box. Its cuts the negative to the fuel pump, so if you have no positive then its probably not your cause. Still worth checking though.
There is another relay you can swap it with, cant remember which one of the top of my head, look on the top of the relays for the one with the same spec.
Also check fuse f21 in the engine bay fuse box.
Is the CODE light going out on the dash when the key is turned to MAR?
Alan
The inertia switch is located in the passenger foot-well tucked up almost behind the glove box. Its cuts the negative to the fuel pump, so if you have no positive then its probably not your cause. Still worth checking though.
There is another relay you can swap it with, cant remember which one of the top of my head, look on the top of the relays for the one with the same spec.
Also check fuse f21 in the engine bay fuse box.
Is the CODE light going out on the dash when the key is turned to MAR?
Alan
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You have 5 stages on your key
Back 1 = Parking Lights
0 - Just key in
1 - Low power circuits
2 - Ignition Full
3 - Cranks (auto returns to 2)
Ie turn the key to just before cranking
All the Electronic gizmo's should light up and then go off
EXCEPT handbrake, Oil pressure and battery
Ziggy
Hi,
Yep, in ziggys description above MAR would be position 2. Ie so the EML light etc is on on the dash)
Alan
Yep, in ziggys description above MAR would be position 2. Ie so the EML light etc is on on the dash)
Alan
ok on MAR all lights come off then the following lights remain on:
handbrake
oil
battery
airbag
engine managment
little orange one next to aitbag that i am not sure what is flashes lots quickly then remains on still
f21 fine
swapped t10 with t02 (relays) still no luck. all the black relays have the same spec numbers on
inertia cut off is behind carpet down door pillar. rubber button.
when i press this it doesnt click on or off just more presses down and then comes back up like a primer pump more than a switch?
anyway still wont start even pressing it whilst turning over at same time
handbrake
oil
battery
airbag
engine managment
little orange one next to aitbag that i am not sure what is flashes lots quickly then remains on still
f21 fine
swapped t10 with t02 (relays) still no luck. all the black relays have the same spec numbers on
inertia cut off is behind carpet down door pillar. rubber button.
when i press this it doesnt click on or off just more presses down and then comes back up like a primer pump more than a switch?
anyway still wont start even pressing it whilst turning over at same time
Hi mate,
Yeah the inertia switch sounds fine.
In that case, next thing I would do would be to crack out the multi-meter and check the low current supply to the relay. That way you can determine which side the problems on.
Alan
Yeah the inertia switch sounds fine.
In that case, next thing I would do would be to crack out the multi-meter and check the low current supply to the relay. That way you can determine which side the problems on.
Alan
ok from testing it I am getting 72 ohms across the 2 connectors which i am guessing is right.
there is no resistance across the larger connectors and when i press the coil to complete the circuit the ohms meter jumps high for a second showing there must be a flow through the coil?
hope that makes sense.
so to me that says that the relay is fine
also connected to a battery you can hear the connection click closed when 12v goes through and then click off when you take the battery off
there is no resistance across the larger connectors and when i press the coil to complete the circuit the ohms meter jumps high for a second showing there must be a flow through the coil?
hope that makes sense.
so to me that says that the relay is fine
also connected to a battery you can hear the connection click closed when 12v goes through and then click off when you take the battery off
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Right - to understand a relay here are the basics
there 2 sides to a relay
A Low current and a high current
The low current is an electro magnet, this needs to be tested for resistance / continuity
if there is stupidly high resistance, then its dead / dying
Should remain low
When you give the low tension side 12v feed, you hear a click
That click is a switch that can handle a HIGH current feed
That high tension side will need to be resistance tested, so energise the coil and then check for resistance
A Click is NOT enough of a reason to suggest its okay
Ziggy
there 2 sides to a relay
A Low current and a high current
The low current is an electro magnet, this needs to be tested for resistance / continuity
if there is stupidly high resistance, then its dead / dying
Should remain low
When you give the low tension side 12v feed, you hear a click
That click is a switch that can handle a HIGH current feed
That high tension side will need to be resistance tested, so energise the coil and then check for resistance
A Click is NOT enough of a reason to suggest its okay
Ziggy
Hi mate,
Sorry probably didn't explain myself very well. It's unlikely that the relay is faulty if you have swapped it with others and the fault still occurs.
Take your multi-meter, set it to DC Volts. Remove the relay. Put the red probe in the + low current supply hole, put the black probe in the - low current supply hole. With the ignition off you should have 0v. Switch the ignition to MAR and the reading should go up to 12v.
Depending on your results to the above test, you will then be able to determine if the problem is on the low current side, or the high current side. Then you can do further tests from there. For example there are further fuses/ relays to test depending on what side it's on. One prime suspect being the ECU main relay etc if you don't get 12v
Alan
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thanks for all of your help by the way. it is appreciated.
test shows 12v both when ignition is off and on MAR so it is definitely getting power to the relay.
just tried swapping it out with another couple of relays just to be sure but still nothing.
plan to take the fuse box out and start checking wires maybe?
the electrics side is a bit above me but i have no money so cant really take it to a garage yet
test shows 12v both when ignition is off and on MAR so it is definitely getting power to the relay.
just tried swapping it out with another couple of relays just to be sure but still nothing.
plan to take the fuse box out and start checking wires maybe?
the electrics side is a bit above me but i have no money so cant really take it to a garage yet
ok so i have tried swapping over the other injector relay and no luck.
i have also bridged the relay and that gives power to the rear pump but still wont start this shows the wiring to the rear pump is fine though.
I have cars with ecu's and all this electric stuff.
i have also bridged the relay and that gives power to the rear pump but still wont start this shows the wiring to the rear pump is fine though.
I have cars with ecu's and all this electric stuff.
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You need to test the power feed from the relay to the postive feed to the pump
See if there is high resistance or no continuity
Ziggy
See if there is high resistance or no continuity
Ziggy
Hi mate,
Sorry Ive had no 3g all day so couldnt reply to your results from this morning. I was going to say your result if 12v when the ignition is both off AND at MAR points to the fault being further back on the low current side.
Remove and test R9 (and swap if your unsure). This is the main relay for the ECU. Its indicating that it is stuck shut. Thus the ECU is remaining powered when the ignition is off.
Another common source of electrical problems on the MJET is the multi-plug connectors on the top of the ECU. Its located at the back of the engine on the bulkhead. Bang in the middle (incase you cant find it)
Disconnect the battery and carefully remove the 2 ECU connectors. Check for any signs of water damage or corrosion and then replace them. Connect the battery and try again.
Failing that we need to start testing the specific wires from the ECU multi-connector and ECU will probably require further testing via Examiner or similar.
Alan
EDIT: Just some further quick test for you if you are still interested.
At the pump, you should have 4 wires. A white and black, A Grey and Red, A violet and A Violet and yellow. Ignore the white and black and gret and red.
With your multi-meter, set it to continuity. Put the black probe on a good earth point, like a seat belt bolt. Test that its making good contact by placing the red probe on another good earth point, such as another seatbelt bolt. If your multimeter beeps or says >2000 ohms or similar, then you know your black probe is earthed correctly. Then (whilst still leaving the black probe on the seatbelt bolt) put the red probe into the pin of the connector on the Violet wire. It should beep or show that you have continuity. This will prove the continuity of your earth supply to the pump, and test the inertia cut off switch at the same time.
Then, set your multimeter to DC volts, use the same seatbelt bolt for the black probe, but place the red probe in the violet and yellow cables pin. Then (with it still connected) ((might want to ask someone to help)) turn the key to MAR and see if you have 12v.
And just to CONFIRM you have checked fuses F16 and F21
Sorry Ive had no 3g all day so couldnt reply to your results from this morning. I was going to say your result if 12v when the ignition is both off AND at MAR points to the fault being further back on the low current side.
Remove and test R9 (and swap if your unsure). This is the main relay for the ECU. Its indicating that it is stuck shut. Thus the ECU is remaining powered when the ignition is off.
Another common source of electrical problems on the MJET is the multi-plug connectors on the top of the ECU. Its located at the back of the engine on the bulkhead. Bang in the middle (incase you cant find it)
Disconnect the battery and carefully remove the 2 ECU connectors. Check for any signs of water damage or corrosion and then replace them. Connect the battery and try again.
Failing that we need to start testing the specific wires from the ECU multi-connector and ECU will probably require further testing via Examiner or similar.
Alan
EDIT: Just some further quick test for you if you are still interested.
At the pump, you should have 4 wires. A white and black, A Grey and Red, A violet and A Violet and yellow. Ignore the white and black and gret and red.
With your multi-meter, set it to continuity. Put the black probe on a good earth point, like a seat belt bolt. Test that its making good contact by placing the red probe on another good earth point, such as another seatbelt bolt. If your multimeter beeps or says >2000 ohms or similar, then you know your black probe is earthed correctly. Then (whilst still leaving the black probe on the seatbelt bolt) put the red probe into the pin of the connector on the Violet wire. It should beep or show that you have continuity. This will prove the continuity of your earth supply to the pump, and test the inertia cut off switch at the same time.
Then, set your multimeter to DC volts, use the same seatbelt bolt for the black probe, but place the red probe in the violet and yellow cables pin. Then (with it still connected) ((might want to ask someone to help)) turn the key to MAR and see if you have 12v.
And just to CONFIRM you have checked fuses F16 and F21
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thanks al,
progress!!!
f21 and f16 fine.
swapped f9 out and no luck
shows resistance on violet.
no volts on violet and yellow, but if i bridge the relay i do get volts to violet and yellow.
opened ecu clips and tadar!!! left side (the bigger pin) is flooded with water and all rusty and gooey.
if i clean this and dry it with a hair dryer all could be good again?????
heres to hoping
progress!!!
f21 and f16 fine.
swapped f9 out and no luck
shows resistance on violet.
no volts on violet and yellow, but if i bridge the relay i do get volts to violet and yellow.
opened ecu clips and tadar!!! left side (the bigger pin) is flooded with water and all rusty and gooey.
if i clean this and dry it with a hair dryer all could be good again?????
heres to hoping
Hi mate,
Yep that could well be your problem! Fingers crossed.
Alan
Yep that could well be your problem! Fingers crossed.
Alan
