Glow plug relay theory

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Rangie.lad

New Member
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64
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York
2.5 DSE auto
In theory could you replace the timed relay for the glow plugs with a standard relay wired to a switch on the dash?

Would this also eliminate the temp sensor for the glow plugs that stop them heating when the engine is hot, or is it on difference circuit?

I understand its a pointless exercise, but its theory at this stage, and my relay has failed.
 
Rangie.lad said:
2.5 DSE auto
In theory could you replace the timed relay for the glow plugs with a standard relay wired to a switch on the dash?

Would this also eliminate the temp sensor for the glow plugs that stop them heating when the engine is hot, or is it on difference circuit?

I understand its a pointless exercise, but its theory at this stage, and my relay has failed.
Click to expand...

Plug relay it direct coupled to battery. It is switched by the ECM. The ECM will only switch it with engine cold.
 
No reason why you couldn't run a seperate wire to the glowplug feed run off a seperate relay and switch. The only thing is that it will still be starting on hot fuel map and timing.

I actually have all the bits as I planned to do this 2 years ago, I'm pretty sure its a morris minor starter relay and a push button switch I picked up in an agricultural motor fctors but I fixed my hot start issues by adjusting the pump timing.
 
SpudH said:
No reason why you couldn't run a seperate wire to the glowplug feed run off a seperate relay and switch. The only thing is that it will still be starting on hot fuel map and timing.

I actually have all the bits as I planned to do this 2 years ago, I'm pretty sure its a morris minor starter relay and a push button switch I picked up in an agricultural motor fctors but I fixed my hot start issues by adjusting the pump timing.
Click to expand...

THe ECM sets the fuel map and timing not the plug relay. Plug relay is just switched by ECM when it detects a cold engine. But you would not get any fuel lift pump for start up.
 
Last edited:
wammers said:
THe ECM sets the fuel map and timing not the plug relay. Plug relay is just switched by ECM when it detects a cold engine. But you would not get any fuel lift pump for start up.
Click to expand...

My plan was to not touch the existing wiring so everything would be normal as far as EDC/BECM is concerned. I was going to run a seperate feed from the battery to the relay like you do with a winch. The switch would just kick in this seperate relay. This relay would then feed the output of plug relay to fire the plugs independant of the EDC.
 
SpudH said:
My plan was to not touch the existing wiring so everything would be normal as far as EDC/BECM is concerned. I was going to run a seperate feed from the battery to the relay like you do with a winch. The switch would just kick in this seperate relay. This relay would then feed the output of plug relay to fire the plugs independant of the EDC.
Click to expand...

When, on switch on, the ECM detects a cold engine via the ECM engine temp sensor. It automatically sets fast idle (increases fuelling) and switches glow relay on. This in turn switches fuel pump on and glow lamp. You need a serious relay 80 amps to run glow plugs. If the glow relay is not working you wont get the initial fuel pump run or the glow lamp.
 
wammers said:
Yeah John good question. If he is having hot start problems why not just fit the hot fix. Or if the relay has failed fit a new one. Only about £65.00 i think.
Click to expand...


good way to fec up a car,catch fire and burn insurance see mod then sol. But am sure the op will tell about the mod to the insurance
 
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