key won't start car but it will run with bridged relay

[richieb]

Hi my p38 was given to me with a wire going from the ignition relay to a switch on the dash, it also has a button on the dash that goes to the starter, I took these wires out and put the ignition relay back in after cleaning up all the fuses and relay box, but it still won't start on the key but will if i bridge ignition relay back over with the switch,
at first I thought this had been done to bypass the immobiliser but after speaking to someone today it seems that this wire would not start it if the immob was on, so the key must be sending the code to becm etc, but somewhere along the line the ignition is not fully working,
when I put the key in and turn it the ignition lights on dash come on and mileage and warnings etc but the fuel pump does not run until I flick the switch which is connected to the ignition relay, the starter won't run off the key either so I have to press the button to start it,
has anyone had this problem before? I am finding it a real headache even laying in bed at night thinking of things it could be!! I've tried several relays etc still no good,
could this possibly be a dodgy inhibitor switch that's on the gearbox or something I know automatics have these to stop you being able to crank the starter in gear or reverse but i've never known one to cut out the fuel pump etc, does it on these? and if so where is it?
I spoke to a becm man today and he does not seem to think it's that (makes a change!!) someone must surely have had this problem before and cured it without the need for extra switches and push buttons on the dash!!!??
I really hope someone can help me.
thanks
Richie

 

[wammers]

You could try looking at the isolator cutout switch behind the panel to right of drivers footwell.

 

[richieb]

what do i need to do? thanks

 

[Saint.V8]

Just bress the button on top of the inertia switch...simples....picture attached

 

[richieb]

you got me excited then for a second but it says in my handbook that it turns off the heating fans as well as fuel pump but the heater fan still runs so it can't be that, shame as i thought for a second you had sorted my problem out and saved me a fortune!!!

 

[Saint.V8]

Not sure where you heard that...as it is a first for me...

I attach the circuit diagram for the inertia switch...no connection to the Heating system that I know of....

I goes from Fuel Pump Relay to Inertia Switch to Fuel Pump to Earth....

As Attached....

 

[richieb]

does it also stop the starter motor though as that won't crank with the key either!? it says in my manual that it stops fuel pump puts hazzard lights on and stops heating and aircon fans, I will try it in the morning in the hope it works but it's 10pm here and a bit late to tinker in my garage, thanks for your help,
Richie

 

[Saint.V8]

The BeCM may put hazards on, and stop fans....all the inertia switch does is stop the pump....It won't stop the starter....

If you aren't even getting the starter to turn over....that is a new ball game....

 

[wammers]

does it also stop the starter motor though as that won't crank with the key either!? it says in my manual that it stops fuel pump puts hazzard lights on and stops heating and aircon fans, I will try it in the morning in the hope it works but it's 10pm here and a bit late to tinker in my garage, thanks for your help,
Richie

Think you had better download RAVE and look at the wiring diagrams. That and a test meter should sort it out. Obviously someone has gone to a great deal of trouble to jury rig it for some reason. Looking at the start diagram it looks pretty straight forward, position III goes through the BECM, maybe that's what has been cut out.

 

[richieb]

where do I rave!!??? I have no idea how to read these diagrams to be honest!! I don't know why my mate did it but he passed away so i can't ask him and I just want to get it going properly in his honour, i was thinking the starter could be an inhibitor switch on gearbox but where would that be ??

 

[Saint.V8]

I attach below the Starter Circuit Diagram and also a couple of Troubleshooting tests rfom the P38 WSM....

Maybe worth giving it a go....

 

[roddy4]

Think you had better download RAVE and look at the wiring diagrams. That and a test meter should sort it out. Obviously someone has gone to a great deal of trouble to jury rig it for some reason.

maybe previous owner had ram raids in mind lol,have you got the log book? this sounds a real nightmare your a brave man to try and fix this,hats off to you.

 

[Saint.V8]

If you can start it by bridging...I would not think it was the Start inhibit switch...

 

[Saint.V8]

After having a quick think....

The Shift Inhibitor Switch on the gearbox, doesn't directly cut off power to the starter....it tells the BeCM it is still in gear, it is the BeCM that energies the start solenoid relay to fire up the starter....

By the sounds of your odd wiring, I think you are bridging the starter solenoid relay, then pressing a button to energise the solenoid to fire up the starter....

This would indicate a potential issue with the BeCM signal to the starter solenoid relay...this could be a broken wire, the gearshift inhibitor switch (as you suspect), a dodgy connection at either the BeCM or the Relay connection in the fuse board, or (God forbid) the BeCM itself......

If you can bridge the gearbox inhibitor switch out, insert the starter solenoid relay then give it ago and see what happens, if it starts then we know it is the inhibitor switch...if still nothing, then it is the BeCM not pulling in the Starter Solenoid Relay...

Anyone else got any thoughts??

 

[richieb]

Hi
thanks for your thoughts, the starter relay is still in the fuse box, but he has just put a wire from the battery to a switch on the dash then down to I presume the starter motor (have not crawled under but it goes downwards to the bottom of the engine somewhere!)
I have just pressed the inertia switch after putting the ignition relay back in but still no joy,
it's very hard to get to the inertia switch is it just a case of pressing it down, is it supposed to click or anything? I got the little bit open that you take off but can't get the plastic panel around it off it seems really tight.
it's strange because there is a click when you turn the key to the start position but it seems to be the fan relays clicking! the relay box looks like new now so can't understand it,, does anyone know which colour plug on the bottom of the fuse box is for the ignition and which one is for the starter as I may be able to test and see if it's all working properly at the plug, that way i'll know if i still have fuse box issues??
thanks so much for all the advice

After having a quick think....

The Shift Inhibitor Switch on the gearbox, doesn't directly cut off power to the starter....it tells the BeCM it is still in gear, it is the BeCM that energies the start solenoid relay to fire up the starter....

By the sounds of your odd wiring, I think you are bridging the starter solenoid relay, then pressing a button to energise the solenoid to fire up the starter....

This would indicate a potential issue with the BeCM signal to the starter solenoid relay...this could be a broken wire, the gearshift inhibitor switch (as you suspect), a dodgy connection at either the BeCM or the Relay connection in the fuse board, or (God forbid) the BeCM itself......

If you can bridge the gearbox inhibitor switch out, insert the starter solenoid relay then give it ago and see what happens, if it starts then we know it is the inhibitor switch...if still nothing, then it is the BeCM not pulling in the Starter Solenoid Relay...

Anyone else got any thoughts??

 

[richieb]

If you can start it by bridging...I would not think it was the Start inhibit switch...

are you local by any chance!!
I have been able to start other automatics in the past by going direct to the starter as inhibitor just cuts power to starter between the key and starter motor so a direct live should always bypass the switch, do you know where it is on these as I might be able to get under and join the wires to complete the circuit manually and see if that makes it turn over with the key? not that i'm any good at crawling under cars!!
www.youtube.com/amazingfeet :doh:

 

[The Mad Hat Man]

is it wise to post that on an open forum?

 

[richieb]

is it wise to post that on an open forum?

post what mate??

 

[Saint.V8]

Looking at the cicuit diagram, the Gear Selector Position Switch is the one it uses to see if it is in gear or not....

This is accessed from the inside the car by removing the gearbox tunnel trim and selector surround....

I would be reluctant to tell you take a look at this as its position on the gearbox is set in a particular place,as when you move the gear selector, it tells the BeCM, Gearbox ECU and the Engine ECU which gear selection has been made....and my knowledge of cars ends at the gearbox and starts again afterwards...I have no clue about these things...

I am not local to Chichester I am affraid, but no doubt someone one here is, who may be able to have a look for the extortionate price of a soggy bacon sandwich and posh biscuits.

 

[richieb]

I attach below the Starter Circuit Diagram and also a couple of Troubleshooting tests rfom the P38 WSM....

Maybe worth giving it a go....

Hi yes very handy, on the b1 one is that the plug in the bottom uf the fuse box? if so which colour one is it? and I presume wr is white and red but what would nr be?? sorry i'm not an electrical person!!