[Matt corsa 1.4 auto]

Hi all

I have a corsa 1.4 that starts normally and runs well with no problems until the coolant temp reaches 90 degrees. At this point the engine cuts out. I have traced the fault to the fuel pump relay being told to turn the fuel pump off at that temperature. I can't understand why this would happen? I have checked for sparks etc, the only thing missing is the fuel supply. I have bypassed the fuel relay and the car works with no problem but want to sort it out correctly.
Does anyone have any suggestions?

 

[g4vvq1983]

Hi there sounds like a an April fool joke...but it's the wrong date......have you got any fault codes, be the first thing to do....possible the ecu is getting hot and breaking down and deactivating the relay....very weird...from Fred in Essex.

 

[Koicarpkeeper]

Faulty fuel temperature sensor.

 

[marks152]

Your ecu is defective by the sound of it.

 

[Matt corsa 1.4 auto]

Hi there sounds like a an April fool joke...but it's the wrong date......have you got any fault codes, be the first thing to do....possible the ecu is getting hot and breaking down and deactivating the relay....very weird...from Fred in Essex.

Not April fool I am afraid. I changed the crankshaft sensor but that wasn't the issue however i guess it maybe the ecu. No fault codes at all.

 

[Matt corsa 1.4 auto]

Faulty fuel temperature sensor.

Is there a fuel temp sensor?

 

[Matt corsa 1.4 auto]

Your ecu is defective by the sound of it.

Could be I guess. Sounds expensive!

 

[g4vvq1983]

I'm not sure if there is a fuel temperature sensor, there might be, i have heard of such things...i know its unlikely but i might be inclined to look at the earth on the ecu....sounds like something its getting hot and cutting it off...might even be the relay, if yours is like my C there are 2 pink relays in the fuse box, one is for ECU and the other is for fuel pump, and i think the ecu one has something to do with working the other one...but i believe they both trigger off the ecu...its not beyond the realms of possibility the something in the ecu is getting hot and breaking down, cutting the relay off...might be worth taking the plug off the ecu and looking at it see if its wet or corroded...from Fred in Essex.

 

[Koicarpkeeper]

Is there a fuel temp sensor?

Possibly not, just checked some live data for the Astra 1.4 and that doesn't, which is a bit of a surprise because I expected the system to use one and it did seem to fit in with one possible cause of your failure.

 

[Matt corsa 1.4 auto]

I'm not sure if there is a fuel temperature sensor, there might be, i have heard of such things...i know its unlikely but i might be inclined to look at the earth on the ecu....sounds like something its getting hot and cutting it off...might even be the relay, if yours is like my C there are 2 pink relays in the fuse box, one is for ECU and the other is for fuel pump, and i think the ecu one has something to do with working the other one...but i believe they both trigger off the ecu...its not beyond the realms of possibility the something in the ecu is getting hot and breaking down, cutting the relay off...might be worth taking the plug off the ecu and looking at it see if its wet or corroded...from Fred in Essex.

Thanks. I will give that a try.

I have basically connected the coil side of the ecu relay to the fuel pump relay at the moment. So the fuel pump just runs while the ignition is on.

The fuel pump relay coil side looses its earth connection. I believe the ecu switches the earth on and off to control the relays.

 

[Matt corsa 1.4 auto]

Possibly not, just checked some live data for the Astra 1.4 and that doesn't, which is a bit of a surprise because I expected the system to use one and it did seem to fit in with one possible cause of your failure.

Just checked the live data and can't see fuel temp on the system. But thanks for the idea definitely worth checking

 

[andyl]

Have you tried replacing the fuel pump relay with the ecu relay and see if the fault still occurs, maybe the relay is getting hot and failing.

 

[g4vvq1983]

Yes your sounding pretty good with it...i think it works something like this...see picture below i concocted....colours might be different....sound like an ecu problem to me....might be worth checking power both sides of those fuses...from Fred.

 

[g4vvq1983]

 

[Matt corsa 1.4 auto]

Yes your sounding pretty good with it...i think it works something like this...see picture below i concocted....colours might be different....sound like an ecu problem to me....might be worth checking power both sides of those fuses...from Fred.

View attachment 19073

Thanks Fred. I will check both fuses however it works fine at low temps then the pump cuts out. I think from everyone's posts it maybe an ecu issue. Thanks for the cct diagram.

 

[Matt corsa 1.4 auto]

Have you tried replacing the fuel pump relay with the ecu relay and see if the fault still occurs, maybe the relay is getting hot and failing.

I swapped and got the same pump problem. Relays checked and both work fine. No contact resistance when operated so they look good

 

[g4vvq1983]

I suppose what you could do is monitor the ground circuit with a voltmeter and see the difference between when its cold and when its hot, if you haven't already done that....just put multi meter lead to live battery and connect the other lead to the ecu /relay ground terminal(s) which ever relay you suspect...Fred.

 

[cav TD gls]

years ago I had a mk4 astra 1.6 that had the same problem , was a duff ECU . difference is that it was throwing a fault code for fuel pump relay open circuit .

 

[g4vvq1983]

Yes it sounds to me like an internal fault on the ECU, something like a dry joint on a PCB or a component that fails when it gets hot...there is a place in Kent called BBA i think it is, that test ECU's...........from Fred.

 

[Matt corsa 1.4 auto]

I suppose what you could do is monitor the ground circuit with a voltmeter and see the difference between when its cold and when its hot, if you haven't already done that....just put multi meter lead to live battery and connect the other lead to the ecu /relay ground terminal(s) which ever relay you suspect...Fred.

Will do thanks