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Longie

V8i random starting problem.

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I apologise if this has been asked before!!!

I have a 1994 300 series 3.9 V8i and it has developed a random starting problem, it has now happened 5 times in the last 18 months.
After a short stop, say 15 – 20 minutes, the engine will turn over but not start. If left for 1 – 2 hours it will start of as if nothing had happened!!! On the occasions I have called the AA it has been recorded that there is a problem with the fuel.
About the only thing I have not tried is replacing the fuel pump relay but I am not sure how to test it to see if this is the problem.
Any help would be greatly appreciated. (especially by my long suffering wife.)
Cheers
Graham

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If you have the two button alarm fob, check out the Definitive Alarm Spider post in the technical archive forum on here. If it has the older one button alarm I don't think it will be that.

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The other common failure for V8's of that era is the ignition amplifier, but that's more commonly when hot, not cold.

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Replacing the fuel pump relay is cheap and would rule that as the issue out, certainly a relay coil that is failing could be not quite as efficient at closing the pair of contacts when hot as opposed to cold.

 

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Thanks guys, I think I will change the relay as they are fairly cheap.

I shall investigate the amplifier to see which type I have.

I don't think I have the dreaded spider as I have the single button fob.

Cheers

Graham

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Posted (edited)
On 3/5/2019 at 10:58 AM, Longie said:

I apologise if this has been asked before!!!

I have a 1994 300 series 3.9 V8i and it has developed a random starting problem, it has now happened 5 times in the last 18 months.
After a short stop, say 15 – 20 minutes, the engine will turn over but not start. If left for 1 – 2 hours it will start of as if nothing had happened!!! On the occasions I have called the AA it has been recorded that there is a problem with the fuel.
About the only thing I have not tried is replacing the fuel pump relay but I am not sure how to test it to see if this is the problem.
Any help would be greatly appreciated. (especially by my long suffering wife.)
Cheers
Graham

The symptoms that your disco has is very similar failing immobiliser. Fortunately as you have a1994 disco you don’t have the passive ‘spider’ immobiliser which was introduced with the 1996MY disco which is known to have issues, such as intermittent starting, it happened to me, but a single wire overcame that issue  so fortunately no need to remove the front of the dash.

Testing your pump relay is simple when remover, just a 12v supply and a multimeter is all that’s required, if you can hear it clicking your halfway there, or of course you could just replace it. Do you know where to find the relay?

The ignition amplifier on your vehicle is attached to the distributor so could fail intermittently due to the hot environment in that area. LR moved the amp to a new location with the 1996MY and positioned it near to the coil at the rear of the slam panel on it own heat sink and linked it back to the distributor with is own dedicated cable. So no heat issues.

 

That’s it and now back to work.

Edited by teabag

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Thanks teabag. I did think immobiliser but I have a dongle to wire out the alarm unit and have tried that but it still didn't start.

So I am still on the relay and amplifier track.

The trouble is this never happens at home and seems impossible to replicate!!!

Cheers

Graham

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I managed to find and remove the relay for testing at work today.

I noticed, when I picked it up that it rattled!!!!!

I don't think that is supposed to happen.

New relay on order!!!!

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I don't think it's that one but there's ONE relay in the EFI system that has two 87 terminals, quite a rare beastie and has caught more than a few people out!

Now I think of it that might be flapper-EFI only, not sure.

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I think that must be the one I have found, it has 5 terminals - two 87s.

It is on a blue base in the drivers footwell.

I have managed to test it now and it seems to work perfectly but will still replace it.

Just looked at the wiring diagram again and there is another 5 pin relay that controls the whole system, I will try that.

Many thanks.

Graham

 

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Posted (edited)

The correct relay for the V8 EFI system fitted to the D1 has terminal 87 and terminal 87a which is a change over relay, according to the disco’s EFI diagram. There another relay with a dual 87 terminals  are just in parallel,  plus theres the common relay with a single 87 terminal.

 

89B3E1A6-7A45-492C-AFEF-2F4C382A9E92.jpeg

BE48DF7A-EF2B-4287-9FE0-694E94F27272.jpeg

A513B141-FDA2-4E81-A62D-C442BB6F42F5.jpeg

Edited by teabag

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From distant memory the extra pin is used to feed the heaters in the oxygen sensors. You need to make sure you get the right one,I was called out to a Morgan Plus 8 with the RR3.9 v8. It had failed its MOT on high emissions,I found that the fuel pump relay had been replaced with one that powered the oxy heaters all the time the fuel pump was off...

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1 hour ago, Ally V8 said:

From distant memory the extra pin is used to feed the heaters in the oxygen sensors. You need to make sure you get the right one,I was called out to a Morgan Plus 8 with the RR3.9 v8. It had failed its MOT on high emissions,I found that the fuel pump relay had been replaced with one that powered the oxy heaters all the time the fuel pump was off...

That will be the Bosch  relay then  with the parallel terminals  😋 therefore the oxy heaters and fuel pump are working simultaneously ... so Ooops I made a error the relay is not the change over variety although the LR diagram shows it as 87 & 87a.

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I now have both relays out and tested. There are both the same type and in the parts manual they are the same part number.

The main relay also tested OK but this one doesn’t rattle, so really none the wiser.

I will still replace the first relay. If it happens again I think we will be off to the scrapyard.

Thanks for all the help.

Cheers

Graham

DC9DC507-5E31-4262-931D-A01FD4A69A7F.jpeg

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They are standard relays, no need to visit scrapyard, just buy a decent new one.

The twin-87 terminal can also be bought new.

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I did mean to take the disco and leave it there!!

Graham

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Oh :)I'd take it off your hands for scrap 😛

 

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Posted (edited)

Then  can I have your wheel centre caps Land V8 Rover ?😃

Edited by teabag

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The wheel caps cost me a lot to have made, most probably more than the car is worth!!!!!

New relay fitted and has started 3 or 4 times today but no idea if that has fixed it!

There was almost a year between the last two episodes of not starting.

I think I might buy a couple of spares as they seem quite reasonable.

I will keep the post updated.

Thanks for your help.

Graham

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13 hours ago, Longie said:

The wheel caps cost me a lot to have made, most probably more than the car is worth!!!!!

New relay fitted and has started 3 or 4 times today but no idea if that has fixed it!

There was almost a year between the last two episodes of not starting.

I think I might buy a couple of spares as they seem quite reasonable.

I will keep the post updated.

Thanks for your help.

Graham

At last it looks promising for you. 😎

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