Over the past few months, I've had an issue with starting the bus when it's been driven for a few hours. Initially I fitted a hot start relay, but this did nothing. The relay was fitted under the bus. It was kind of a temporary fixing place to see if it solved the issue. It was not protected in any way, despite being relatively well "out the way". I then fitted a new ignition switch, but this also did nothing. I left the hot start relay fitted anyway. I then embarked on a 2 week journey across France, hoping to get by with push starting the bus if needed. This was, until we drove into Paris... An hour of so of driving in the rain and then the bus started to stutter under acceleration. I started a thread and it was quickly diagnosed as being caused by the hot start relay getting wet, and causing issues with the fuel pump. The fuel pump would run when it wasn't meant to, and so was presumably not running when it should be. So, this thread is just a cautionary tale to suggest: 1) Do you really need a hot start relay? Can you fix your problem without one? Ignition switch, wiring, starter, solenoid, etc. 2) If you do need to fit one, or want to, be careful where you fit it. Have it well protected from the elements. In hindsight, I should have either fitted it in the engine bay from the beginning, or removed it once I knew it didn't solve the issue. 3) If you get the problems I had, remove the hot start relay if it's in a position where it could get wet!
Why would your hot start relay affect the fuel pump? It's only switching current to the starter solenoid.
I don't know, but it does! @pkrboo or @Paul Weeding can advise. I think (maybe just on a FI model) it also controls the fuel pump somehow!
Simplifying it: During cranking power goes from the starter to the dual relay which powers the fuel pump (fuel helps to start the engine) once started the dual relay switches over and the AFM takes over control of the fuel pump. I think @AndyC hot start relay shorted out and caused the power to be fed to the fuel pump permanently, overfuelling and causing his running issues
The ignition wire will be going to the starter solenoid via the hit start relay. The red/white wire goes from the starter solenoid to the fuel pump via the dual relay. Which will have been moved onto the hot start relay with all the other wires, during installation If the hot start relay was shorted out and it turned the solenoid on it will have given power to the red/white wire which should only have power during cranking. I am making some assumptions here on how @AndyC wired the relay.
Yep, that's how I wired it. However the relay shorted, it was allowing a current from the battery to the fuel pump with the ignition off.
