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Blown Fuse 37


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Hi all, I've had my RR 4.6 '98 for 6 months now and all had been fine, ahh ignorance is bliss! So a about a month ago the engine cuts out and she wont start, no crank, electrics work. AA came to the rescue and replaced blown fuse 37, all was well for 24hrs until the same thing happened again. Sent it to a stealer who said he had no clue what was wrong with her and i should junk it! Wan*er! This is where i began the glorious journey of being a proper LR owner! Fuse 37 was now blowing everytime the ignition was turned to position 2?? thanks to forums and the internet i came to the conclusion it was a duff fuse box. Replaced the fuse box and she started first time no warning lights! HAPPY DAYS... if only...

Since then fuse 37 has blown 5 or 6 times, twice today. It has mostly been on 'warm' starts on hot days. I've also had engine overheating problems starting around the same time, I got to drive slowly and with the heater on to avoid gauge going red. Also shes decided theres an EAS fault.

As far as i can figure out Fuse 37 protects the Main Relay (R19) which supplies the power feed to the ECM and also the fuel injectors and air flow meter. The Main Relay is controlled via the ignition switch in position 2. I've checked most of the earthing points, changed relays, fuses, all seem good. I'm thinking it's a short in the circuit somewhere, but where?.

Anyone got ideas or had the same problem?

Where should i be looking?

Could all these problems be related and caused by the same fault?

Thanks in advance

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Do you have a circuit diagram so you can trace everything fuse 37 supplies?

Switch on then get out and see if anything extra is on outside...someone may have wired spot lights to that circuit and you've unknowingly switched them on.

Next take all of those you can out of circuit and see if you still have the problem.

If you do then you know which routes it has to be in and run (temporary) new wires to bypass the ones in the loom.

Will take a while but stick with it.


PS I doubt any of the fuse37 problems are related to the overheating unless you have electric fans in which case it could have everything to do with it.

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ARGHHHHH So after tinkering around with earthing points and checking a few looms, shes decided it didnt like that, and is back to blowing fuse37 on turning the ignition again. Maybe a good thing though as it should be easier to find the fault? I've re-checked all the things i was checking before (cleaned earthing points around RH side of engine compartment, cut away some tape around big loom under coolant tank, checked a loom under engine in ribbed plastic tubing). She just blows instantly when in ignition postion 2.

HI Steve, Thanks for your quick reply, I have RAVE but i can barely make out wht the diagrams mean. I know it supplies Relay 19 which is linked to Relay 18( i know it's not this as ive tried with it removed and still blows) and comes out C508 and in to the ECM at C509 pin17, according to Rave this is the 'Main Control Relay' (output, switched to ground) I dont think theres anything extra been added to the circuit, I've taken apart the old fuse box to trace fuse to relays and out, all that fuse is linked to is the ECM. Good idea to run temporary wires i'll keep that in mind if i ever find the faulty bugger.

Does anyone know where it goes/what happens after it enters the ECM? What things should i try disconnecting to test? Is there a way to test without having a bag full of 20amp fuses! with a multimeter? Could it be a fualty ECM?

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FOUND THE MOTHER! Problem is solved, managed to trace the fault to a bad earth on one of the fuel injectors!

For anyone who might have the same fault in future here is how i found and corrected the problem:

Persistence in reading the ETM showed the relay was supplying the 8 FEUL INJECTORS and the air flow meter. The workshop manual also states this in plain english, as i'd written down here before, but the circuit drawings had me confused :wacko: and not able to see what was right in front of me!

So to testing, Firstly i pulled all 8 connectors for each injector (located above each cylinder) and tried starting, the fuse blew, so it was not a fault with the injectors themselves.

Then referencing the ETM and Workshop manual to trace each injector connector to the appropriate pin on the other end (ECM), Using a multimeter to test the resistance between the output pin (from ECM) to each of the two pins at the injector end. This was repeated for each of the 8 injectors. I found that all the readings were near identical except one injector would read 150 ohms on the ground pin (compared to the other ones not registering a value)

I could see that cable went to one of either two earthing points, I had previously moved all the cables from one of those points to another one after snapping the thread, and knew it was a now good connection, so it had to be the one (under fuse box behind ECM housing nearest to RH wing) I cut and extended the cable to another earth point and tested the resistance, it read like all the others.

Plugged all the connectors back in, put a new fuse in and gave it a go. Bingo!!!!!!!!!!!!!!!!

I have no previous auto mechanical knowledge (at all) so please only take this as reference to my experience. I only hope this helps somebody someday.

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I will say this very quietly so your car can't hear.

I don't think you have found the actual problem just disturbed the real culprit.

The reason I say this is because an earth is the end of the circuit so if it is not good nothing is connected so nothing can blow. For the fuse to blow then something is earthing earlier in the circuit. It may still be in the injector run where the injector supply cable is earthing before the injector.


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Yea an electrics genius i know wasnt convinced either. What you say makes sense, especially something earthing earlier in the circuit. When i tested for resistance between ECM output pin (for injector2) and the pin going to ground (from the injector end) it registered 150 ohms. This should be zero, right? In fact, it proves the two wires are contacting, when they shouldn't be???

Will look again tomo.

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This time i really think its fixed! I found 150 ohms resistence accross the two pins at the connector (input and ground) This proves there is a short. Poking a harness around i noticed a spark, so, disconected the battery negative and unwrapped the harness. I found two wires had been burnt and the copper exposed, presumably by heat from the engine. The colours matched input and ground from injector 2 but, to make sure, i tested for continuity by measuring for resistence at the exposed copper and corresponding pin. Then simply cut the wires and reconnected using a crimp on barrel connector.

Photos for those interested:



It's been driving great all day, still haven't got used to it!

LOVE my Range Rover!!!

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What condition is the wire insulation in?

The wiring for the injectors can get very brittle because of the engine heat. In your case the insulation may have cracked off and then shorted. If that were the case then others could go the same way.


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All the wires around there are not bad, still flexible, just the melted bits. The outer plastic conduit was toast, it just fell apart. Probably a good suggestion to check the other wires. Have just taped them back up and off the engine at moment, will super insulate them tomorrow.

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