Caterham EU2 K Series fuel pump cutting out.
Discussion
1996 Caterham K Series 1600 EU2 fuel pump loses power and cuts out at seemingly random times.
Traced the fault (?) back to the trigger wire from ECU to FP relay in the MFRU. In the case of this EU2, it's the Black/ Purple (“BP”) that feeds into the MFRU Input plug on pin 3. (It goes to earth to energise the Fuel Pump "FP" relay.)
Probing this wire shows the following characteristics:
Ign on; BP goes to 2.4V, FP runs for a second or two as normal, BP goes to 12V
Starter initiated; BP goes to 2.4V engine starts and runs.
Engine running; BP at 2.4V (occasionally going to 13.4V very briefly.)
Engine warm; BP flicking between 2.4V and 0.7V
BP goes to 13.4V, engine falters and gradually dies. Tachometer follows RPM.
Starter initiated; BP sits at 12V
Ign cycled off-on, starter initiated; Engine starts and runs.
With my limited ideas about how the thing works:
It seems that the ECU itself is intending the engine to keep running: it's supplying sparks, the CPS is being read and the ECU is driving the tachometer. (AS far as the ECU is concerned: things that shut the Fuel Pump down are, Lack of rotation of the crankshaft (crash detectected ?), Immobiliser armed, anything else?
Traced the fault (?) back to the trigger wire from ECU to FP relay in the MFRU. In the case of this EU2, it's the Black/ Purple (“BP”) that feeds into the MFRU Input plug on pin 3. (It goes to earth to energise the Fuel Pump "FP" relay.)
Probing this wire shows the following characteristics:
Ign on; BP goes to 2.4V, FP runs for a second or two as normal, BP goes to 12V
Starter initiated; BP goes to 2.4V engine starts and runs.
Engine running; BP at 2.4V (occasionally going to 13.4V very briefly.)
Engine warm; BP flicking between 2.4V and 0.7V
BP goes to 13.4V, engine falters and gradually dies. Tachometer follows RPM.
Starter initiated; BP sits at 12V
Ign cycled off-on, starter initiated; Engine starts and runs.
With my limited ideas about how the thing works:
It seems that the ECU itself is intending the engine to keep running: it's supplying sparks, the CPS is being read and the ECU is driving the tachometer. (AS far as the ECU is concerned: things that shut the Fuel Pump down are, Lack of rotation of the crankshaft (crash detectected ?), Immobiliser armed, anything else?
Anthony
I seem to have resolved the problem by disconnecting and re-routing the loom in the area around the inlet manifold. I’m convinced that in my case, the HT from the coil was interfering with the wires connecting the CAS/ CPS to the ECU. I’m thinking that the induced Voltage in the CAS/CPS wire was causing the ECU the shut down the fuel pump: as a safety measure to prevent feeding a fire in the event of a crash. Reading Angus and Tessa’s My Caterham notes it all stacks up. Go and look at The Engine 2 Electrical page and check out the Red Herring alert. Thanks to Angus and Tessa for documenting all this.
I seem to have resolved the problem by disconnecting and re-routing the loom in the area around the inlet manifold. I’m convinced that in my case, the HT from the coil was interfering with the wires connecting the CAS/ CPS to the ECU. I’m thinking that the induced Voltage in the CAS/CPS wire was causing the ECU the shut down the fuel pump: as a safety measure to prevent feeding a fire in the event of a crash. Reading Angus and Tessa’s My Caterham notes it all stacks up. Go and look at The Engine 2 Electrical page and check out the Red Herring alert. Thanks to Angus and Tessa for documenting all this.
Edited by susser on Sunday 11th November 14:01
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