T Drew Posted May 10, 2011 Share Posted May 10, 2011 hi, i'm new to this site and would really, really appreciate some help. i'm sure you guys have probably heard this all before but i've tried to search through older posts and even printed out the diagnostic tests out of the tech archives aswell as any other wiring diagrams i can find but i'm no further forward. i have a 94 m reg 3.9 efi discovery auto. its been working great until the other day when i went to start it and it did, for a second or 2 then just cut out. however, before this, a mate of mine borrowed it for a few days and before he parked it up he did say it was wanting to cut out at lights etc. anyway, now it just cranks over and makes no effort to try and start. there's no aftermarket alarm/imobiliser fitted. i haven't tampered or been messing around under the bonnet before this occurred. however since, i've checked all the plugs(NGK's with good leads)and watched for a spark on a couple of them, which i think is good enough, i even swapped the coil with another v8 i have and that starts with either coil. i've took the fuel pipe off at the rail and turned ignition on and fuel pump works. i couldn't check the pressure at the schrader valve on the rail as i don't have the equipment. i believe fuel is getting in the cylinders as the plugs do get wet and smell of petrol. i got a multimeter reading of some kind at an injector plug just for a quick check. i read on one post that someone had a similar problem and they finally diagnosed a faulty temp sensor so i took mine out and heated it with a lighter and got a reading on the dash, tried to start it then too, but with no luck. back to the diagnostic tests. i have a wabco ecu (big silver thing behind glove box) number 446 044 040 0, amr 1097,(i hope this is the right one as i cant see no other obvious one). this has a 35 pin plug, therefore this leaves only the one test on ecu fuel injectors from the archives. first step, pin 10 and ground. less than 11v check cables... done. this is a white wire with a grey trace and i have no volts. the one next to it, pin 9 (white wire with a red trace) has battery volts on ignition. all the other pins on the ecu plug have no power and i am unable to get hold of a wiring diagram that suits my disco, wire colours or anything (or blank spaces on the plug 2,3,20,28,29. or does this not matter??). i've seperated the ecu plug and there's no corrosion at all. i've made a few checks visually and with a multimeter around both foot-wells and i cant find any obvious problems with relays, even replaced what i think is the main relay with a new one. does anyone have a wiring diagram that might match my vehicle? am i looking at the ecu plug right? is it possible to have jumped a tooth on the timing when it was started up, or im a just talking silly?? i'll be able to check this with a light while cranking won't i? i hope this isn't too long winded and like i say, any help would be greatly appreciated. thanks. Tony Quote Link to comment Share on other sites More sharing options...
zardos Posted May 10, 2011 Share Posted May 10, 2011 i read on one post that someone had a similar problem and they finally diagnosed a faulty temp sensor so i took mine out and heated it with a lighter and got a reading on the dash, tried to start it then too, but with no luck. Yes a faulty temp sensor is a common problem but if you got a reading on the dash when heating it, then you have the wrong sensor. The ECU Sensor is separate to sensor for the dash gauge (usually it is next to the dash sensor Have a look at http://www.britishv8.org/Articles/Rover-14CUX-EFI.htm to see info and pic for the Temp Sensor as well as more info about ecu wiring. amr 1097 is the ABS ECU, not the engine ECU, so you are looking at the wrong ECU (see above link for what you should be looking for) Quote Link to comment Share on other sites More sharing options...
mickeyw Posted May 11, 2011 Share Posted May 11, 2011 Disco V8 ECU for your age of vehicle should be behind the driver's side footwell side trim panel. You mention no after-market immobilisers, but what about a factory fitted one? I'm sure a '94 model should have one. Quote Link to comment Share on other sites More sharing options...
Pwyll Posted May 11, 2011 Share Posted May 11, 2011 Sorry if this sounds a little basic, but is it getting fuel? There is a schraeder valve on the feeder rail for the injectors, with the ignition on give the valve a press with a screwdriver. You should get a spectacular squirt of fuel. If you don't, then either your fuel pump is fubbared or the ECU isn't giving it any power. This was the case with mine, all we ended up doing was running a direct feed to it through a switch and fused relay. Works a treat and it's one more thing for the local pikeys to figure out before they can drive it off. Another thing to consider is the amp on the side of the distributor. They fail for no apparent reason. If yours is the problem, my advice is to go straight to your local LR dealer and get one from them. The price is a bit scary, but if it fails within a week (entirely possible) you can take it back and they will give you a new one. Try that with a factored part and they will point to the label in the bag/box that says "This item cannot be returned once this packaging has been opened". And then they'll ask you for another £35. HTH, just my experience. Regards, Paul Quote Link to comment Share on other sites More sharing options...
mudmagnet Posted May 11, 2011 Share Posted May 11, 2011 i had a problem with the crankshaft sensor on my v8 d2 i know yours is an earlier car so i dont know if yours has a crank sensor but your symptons are similar to what i had Quote Link to comment Share on other sites More sharing options...
zardos Posted May 11, 2011 Share Posted May 11, 2011 i had a problem with the crankshaft sensor on my v8 d2 i know yours is an earlier car so i dont know if yours has a crank sensor but your symptons are similar to what i had No crankshaft sensor on the earlier v8's unless you megasuirt it Quote Link to comment Share on other sites More sharing options...
T Drew Posted May 11, 2011 Author Share Posted May 11, 2011 Cheers lads, ive found the right ecu now. Just working my way through the hotwire diagnostic test that i got from the tech archives. Everything seams to be as it should so far, got of few more tests to carry out still. It took me a while to figure things out at first, like which pin was number one and which relay was what. As for the fuel, i carried out the test on the fuel relay and injector resistances and everything seams ok. I had already checked to see if i was actually getting fuel to the rail, also had pressed the schrader valve. No doubt i'l be back to ask more questions when im bamboozlled again! Cheers Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted May 11, 2011 Share Posted May 11, 2011 Yes a faulty temp sensor is a common problem but if you got a reading on the dash when heating it, then you have the wrong sensor. The ECU Sensor is separate to sensor for the dash gauge (usually it is next to the dash sensor What he said. Quote Link to comment Share on other sites More sharing options...
T Drew Posted May 12, 2011 Author Share Posted May 12, 2011 Cheers lads, ive found the right ecu now. Just working my way through the hotwire diagnostic test that i got from the tech archives. Everything seams to be as it should so far, got of few more tests to carry out still. It took me a while to figure things out at first, like which pin was number one and which relay was what. As for the fuel, i carried out the test on the fuel relay and injector resistances and everything seams ok. I had already checked to see if i was actually getting fuel to the rail, also had pressed the schrader valve. No doubt i'l be back to ask more questions when im bamboozlled again! Cheers Quote Link to comment Share on other sites More sharing options...
vougese39 Posted May 14, 2011 Share Posted May 14, 2011 at a guess low fuel pressure, or the amp on the dissy or worn out cap leads and rotor arm Quote Link to comment Share on other sites More sharing options...
Range Rover Blues Posted May 16, 2011 Share Posted May 16, 2011 When mine started doing that it was the MAF. In the air pipe form airbox to engine theres a silver box, try unplugging it and start without it (if your car has lambdas it should try to fire). If it runs, even lumpily then suspect the MAF. Quote Link to comment Share on other sites More sharing options...
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