Help - car won't start. Starter Relay Q

[Krismuss]

Not at home at the moment so limited to iPhone investigation.

 

Car won't start, little if any noise not even a click!

 

So far traced it to no voltage on start at 2nd starter relay coil (having carried out the mod last year). Shorting the output terminals of said relay starts car fine!

 

Only other work on it last year was big red starter button.

 

So where to start and silly Q but where is the original starter relay sited? Can't find it for looking!

 

Also need to check output from new starter to see if 12v there?

 

To add insult to injury just been shat on by a seagull whilst sat in traffic queuing for the car park in Brighton!

 

Thanks

 

Chris

[revilla]

Isn't it one of the four relays inside the MFRU (Multi Function Relay Unit) on top of the ECU?

[Jonathan Kay]

Quoting sforshaw: 

Martin, basically the Rover MFRU (multi function relay unit) which is mounted underneath the ecu is not up to the job of driving the starter solenoid. It needs a secondary relay ....

Firstly (as I mentioned in the text you've copied) is to break into the feed (brown/red) from the MFRU to the solenoid and insert a 30A relay.

Take the brown/red coming from the MFRU and connect it to the coil side of the relay together with an earth from the battery to the other side of the coil - use black cable for this connection.

Turning the ignition key to the starter position will now cause the MFRU to activate the coil in your new relay, closing the switch across the other half of the relay. This will put minimal load on the MFRU which is where the problem probably is.

Now, take a new feed from the positive side of the battery (4.0mm red) and connect to the switch side of your new relay, then connect the other side of the switch to the remaining brown/red which runs to the starter solenoid.

 

What happened previously ... turn key, relay in the MFRU closes to send high current to the starter solenoid, but in doing so overloads the MFRU and not enough current gets through.

Now .... turn key, relay in the MFRU closes to send low current to the new (beefier 30A) relay, which in turn allows a high current feed to the starter solenoid directly from the battery

 

If this fails then bypass the MFRU completely and take the feed from the ignition switch (one of the other wires going in to the MFRU but can't remember which).

[Jonathan Kay]

Advice from Stu in the preceding post.

 

Do you have a battery master switch?

 

Do you have an immobiliser?

 

Jonathan

 

 

[Krismuss]

My relay mod was exactly as described above I.e. not bypassing the mfru. So tonight I will try and bypass the mfru relay.

 

It doesn't have an imobiliser but does have the battery master switch. What's the issue with these?

[Stationary M25 Traveller]

The wire from key or starter button to the relay is white and red.

[Krismuss]

No output voltage from big red button...

 

Ignition switch next?

 

Just popping out again!

[Stationary M25 Traveller]

The feed is to the ignition switch, then to the button. Button only live when ignition on.

[Krismuss]

Sorted!

 

'twas a loose connection on the back of the big red button (not my wiring I hasten to add!).

 

I do hate crimped connections 🙆🏻

 

Though I shall go to the ball (or sosiges at least!).

 

Chris