Engine runs while cranking but then dies

Strangest thing happened to me this morning. Started car as normal, then just as I was going to put it in drive it cuts out. Strange I think, cranks it over and starts again sounds fine but the moment I back the key off from the cranking position it dies. Tried it a few times and exactly the same each time, cranks, starts and then dies as soon as I back the key off. However, I did notice that the EM light now is not lighting up, I imediately thought imobiliser but realised then its letting me crank and when the imobiliser on mine cuts in it wont crank. I also noticed the Orange low oil light has lit up, but briefly checked the oil and thats fine. I had a train to catch so abandoned it and used my van to get to the station. Maybe it's a faulty sensor, but if it's that surely it doesnt stop the engine from running does it? The red oil pressure light goes out as soon as you start to crank so its not lack of oil pressure and that side of the sensor must be ok. Will delve a bit more tonight when I get home, but any ideas in the meantime welcome. Thanks.

OK I have had another look at this tonight and now am even more confused.

When I crank the engine starts finbe and sounds ok, but as soon as I back off the key from the starting position it stops. My EML is not lighting up at all. If I try to look for fault codes my OD light flashes constantly. If I let the imobiliser activate by waiting a minute after unlocking the car, it doesnt let me turn the engine over which of course is right and as it should be. But, where as normally at this point if I press the button on my fob briefly the EML light comes on and I hear a relay click, now I hear the click, the battery light comes on as it should and I can crank the engine, BUT the EML light does not come on like it normally does.

I have checked all the fuses, unplugged the ecu plug and then pushed it back in again. Tried leaving the batt disconnected for a while but still no EML light and still not running when I back off the key from starting position. I am guessing that there is a direct feed to the fuel pump when cranking and once the engine fires up the fuel pump is fed via the ECU and that this isnt happening now for some reason. I guess there must be a fuel pump relay somewhere and that is not getting the supply from the ecu, any suggestions? Also what could have happened to my EML??

Am desperate to get to the bottom of this now and get my car running again so any ideas welcome, ta.

Anyone? Where is that Ian C when you need him?

Get a multimeter and in the diagnostic plug check that the b+ pin is getting 12v when you turn the ignition on. Then get someone to crank it over and see if it drops out when you turn the key back from cranking to ign.

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Is there any water (coolant) on any of the electrical connectors in the engine bay? It's a really long shot, but I had a similar-ish problem with a non-supra car: it turned out to be caused by a slight coolant leak onto an electrical connector.

Get a multimeter and in the diagnostic plug check that the b+ pin is getting 12v when you turn the ignition on. Then get someone to crank it over and see if it drops out when you turn the key back from cranking to ign.

 

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OK thanks, I will post back the outcome as soon as. Am at work now so won't be until tonight so long as it is still daylight when I get home.

Is there a mode of operation description anywhere I could look at to get a better idea of how it all works? Had a quick search but couldnt really find much, although have just printed the ecu pin out so that may help.

Is there any water (coolant) on any of the electrical connectors in the engine bay? It's a really long shot, but I had a similar-ish problem with a non-supra car: it turned out to be caused by a slight coolant leak onto an electrical connector.

Hi mate, I don't think so, well in fact I am pretty sure. Last time I drove it was on Saturday and it was a 70 mile journey, been parked up since then and we have not had a lot of rain. Opened up most of the plug sockets under the bonnet and all looks ok. It's the no eml bit that is strange and also the OD light flashing when looking for fault codes.

When you say it runs do you mean the engine is actually at idle until you let the key off? Mine was turning over on start up but would never actually go to idle... turned out to be the crank timing star which had come loose and damaged the timing sensor. Just an idea.

Could be ignition barrel contacts,as mine did that,just before i let you down on those injectors chap.Reason being,my getrag 160 looked like something from aliens film.things flying out.hence i bit the bullet and found a fresh one.It didnt leave any spare for tuning.

What alarm system do you have?

CAT 1 alarms have to immobilise the car with a minimum of 2 points. Usually, ignition and fuel. Sounds like it's allowing the fuel, but not the ignition.

I would check the alarm out.

Get a multimeter and in the diagnostic plug check that the b+ pin is getting 12v when you turn the ignition on. Then get someone to crank it over and see if it drops out when you turn the key back from cranking to ign.

 

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OK just got in and tried it. I have 12 volts between earth and B+ when ignition is on, it's there when cranking/running and there when you back off from cranking too. Obviously it takes a very small dip when cranking but you would expect that.

OK just got in and tried it. I have 12 volts between earth and B+ when ignition is on, it's there when cranking/running and there when you back off from cranking too. Obviously it takes a very small dip when cranking but you would expect that.

Had another look tonight and I have about 11 volts on pin 24 of plug E10 of the ECU and full B+ on pin 31 of E10 and this is dependent on the immobiliser status. Any other suggestions as to what I should be checking?

Id say dont waste your time, sounds electrical? Get an auto electrician out to look at it they will prob fix it in 10 mins Cost you about 40 quid. You could be there for days!

OK just got in and tried it. I have 12 volts between earth and B+ when ignition is on, it's there when cranking/running and there when you back off from cranking too. Obviously it takes a very small dip when cranking but you would expect that.

Ok so its not a power issue for the EFI system or a problem with the Ignition barrel output to the ecu (IGSW) as this is how the main relay is trigger by the ecu when it gets 12v.

Doubt its a fuel pump issue either but if you bridge B+ and FP in the diagnostic port that will tell you if the fuel pump is being turned off when you come back off the start position.

Check that the ignitor in the engine is getting a constant 12v when you have the key in start and when going back to IGN. This 12v system is on a different circuit see to the B+ system in the Diagnostic port.

On the ignitor the wire you want to check is on the smaller plug and its Black and orange.

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Is this guy a star or what ?

Meh He's OK

Is this guy a star or what ?

He sure is! But in fairness, over the years I have owned, messed around with and broke my Supra it has always been good to know that there are a few really good guys on here with great knowledge of the car and always more than happy to help. And Chris you and Ian are among those few people.

Have to be honest though this prob is really getting on my tits. I have just spent the best part of 3 weekends fixing a whole load of man made ECU and wiring problems on Frontera I bought for my GF where someone had tried to splice in half of a wiring loom after a fire and made a real mess of it. Just got that on the road and this has happened to the supra, difference is that the Motronic ECU in the Frontera is a lot simpler than the toyota one! Find the fact the EML light is not up and when I check for fault codes the OD light is flashing very worrying as both these lights are run from the ECU.

I found this thread mate,

http://www.mkivsupra.net/vbb/showthread.php?t=180116&highlight=light+flashing

Someone mentions about 6 posts down about the exact problem. No EML light and not starting. I know you say you've checked the fuses, but check the ignition one again.

I found this thread mate,

 

http://www.mkivsupra.net/vbb/showthread.php?t=180116&highlight=light+flashing

 

Someone mentions about 6 posts down about the exact problem. No EML light and not starting. I know you say you've checked the fuses, but check the ignition one again.

Thanks mate. Yes I found this thread also when it first happened and that was was led me to check the fuses in the first place as it sounded very much like mine. But sadly I am 100% sure on all the fuses. Thanks though.

If it's got an FCD try bypassing it, just an idea

If it's got an FCD try bypassing it, just an idea

Thanks Chris, but I think from memory mine doesn't as it's a NA. When I was messing around with the Supercharger some time ago I seem to recall I established it didnt have one.

Just flicked through this, hadn't realised it was an N/A, sorry. Good luck!

Are you getting any petrol smell after trying to start it?

Are you getting any petrol smell after trying to start it?

No but tonight's test will explain why, I hope!

OK so checked for voltage on the black/Or feed to the ignitor, its there in both ignition and cranking and remains when I back off from cranking, as it should I guess?

Linked Fp and B+ at the diagnostic socket and it started and stayed running perfectly, which was great as I managed to move it to where I need it to work on it properly, rather than parked outside a neighbour (who hates me) house.

One other thing though:( and this is something very new and I don't think it is connected but you may tell me different, the starter motor seemed to jam on me. its never done that before, but twice when I first turned the key to start it I got a click as though the starter jammed. On both occasions backing off and trying it again it was ok. I am thinking the starter solenoid is on it's way out maybe. Coincedence or connected?

Still no EML light so now I am thinking maybe that as someone suggested previously it might be one of the immobiliser functions not coming off and the supply to the fueling is being cut and this circuit is somehow connected to the EML side of things. On the other hand I am just guessing as I don't know the actual sequence of events on a supra.

Thanks to everyone for the help so far.

First , it sounds like your starter motor is wearing (probably where you've been trying to start it excessively recently with this problem). You're not the first to have starter issues on the supra, so don't worry to much about it, a new starter will cure the issue.

What alram system do you have. If you have a model that has a key mechanism on the alarm unit itself, where you actually insert a key and turn it to disable it completely, then this is certainly worth a try. Failing that, find out where the 'brain' part of the alarm system is and basically disconnect it. See where you stand then.

At least you know it's the fuel pump is not running for whatever reason, but the fuel pump itself works when fed a live, so it narrows it down alot.