Pug_Power_Dave 0 Posted April 5, 2008 Hi there, got the mi back in my pug last week and and can get it turning over but not firing! I've had a spark plug out and am getting sparks, and there is fuel in the rail under pressure, and if i pour abit of fuel straight into the throttle body then it will fire and run for about 10 secs. So im guess the injectors arnt firing! I've had to put a new CPS sensor on it and this came off a 1.8 citroen xantia, it looks differernt but the multiplug is the same to connect it, and it sits at the same height as the mi one. could this be causing the injectors not to fire? Its running an mi loom and the ecu temp sensor conector is attached firmly. how do i test the injectors are getting power? just take an conector off and get the mulit meter on it when its cranking? Any help would be appreciated! Cheers Dave Share this post Link to post Share on other sites
Pugnut 9 1 Cars Posted April 5, 2008 one of the two relays on the mi motronic loom are for the injectors . i'de be looking there first Share this post Link to post Share on other sites
Pug_Power_Dave 0 Posted April 6, 2008 Cool cheers pugnut, i'll have a look at them and go from there! It was suposidly running before and i havent moved / d/cd any of those relays, but i guess they could just get festered up if its been sat for a while! Share this post Link to post Share on other sites
Pug_Power_Dave 0 Posted April 7, 2008 I have power to the relays and can hear them click in and out when i connect them with the key on, also i have +12v at both the connectors on each injector, is this normal? What triggers the injectors to fire? does the excitor to the relay come from the cps? Cheers Dave Share this post Link to post Share on other sites
welshpug 1,626 Posted April 7, 2008 (edited) the ecu earths the wires from the injectors and coil pack when it receives a crank signal (i.e negative earth system) it determines when to do this dependent on AFM TPS and CTS inputs, as well as the Crank sensor signal frequency. Edited April 7, 2008 by welshpug Share this post Link to post Share on other sites
Pug_Power_Dave 0 Posted April 7, 2008 Ahh ok, I think then next on the list must be try a CTS like the one i took out of it (which was mashed), as even thou it can produce sparks mabe it works on a different frequency to the other one so not making the injectors fire! Sound logical? Cheers for the help! Dave Share this post Link to post Share on other sites
welshpug 1,626 Posted April 7, 2008 nope, if it has spark it should fire the injectors, unless there's no power to the injectors. Share this post Link to post Share on other sites
Pug_Power_Dave 0 Posted April 7, 2008 Hmmmm ok then, so as there's defo power to the injectors could it be not earthing through the ecu properly then? not making them fire? Share this post Link to post Share on other sites
Pugnut 9 1 Cars Posted April 7, 2008 Hmmmm ok then, so as there's defo power to the injectors could it be not earthing through the ecu properly then? not making them fire? possibly. try belling the wires out back to the ecu . you can get away with a fair bit and the car still starts due to the limp home mode. If possible try another ecu if you can borrow one for a test. are you getting 12v on both injector pins with the connectors disconnected? Al Share this post Link to post Share on other sites
Pug_Power_Dave 0 Posted April 7, 2008 I havent got a spare motronic ecu, how do you mean 'belling the wires out'? And yes im getting 12v to both pins on the injector connectors. I've had the engine out recently to replace the box, i labled all the wires up and cant see any that i might have missed, is there any ones i should be looking at to check with these symptons? what happend was the diff exploded into the bell housing and stalled the engine out, is there anything that might have burnt out with this happening i should be replacing? Cheers Dave Share this post Link to post Share on other sites
welshpug 1,626 Posted April 7, 2008 yes im getting 12v to both pins on the injector connectors. you shouldn't have, you should only have live to one pin and earth to the other when the ecu pulses. Share this post Link to post Share on other sites
Stu 18 Posted April 7, 2008 As above, there should be a live at one side of the injector plug with the ignition on and whilst cranking, and a 'pulsed' earth on the ohter when cranking. First thing id check is that the live is still on the injector plug whilst cranking, that says that both relays are working and wired correctly. Next, id put a bulb on the injector plug wire, crank it, and if it flashes then you've got a good supply, and more importantly the pulsed ground from the ECU is there, thus proving the CPS and relay supplies/switches are working. If the injector flashes the bulb, and you've got fuel pressure and a spark, then it should run. If not, crank it for a few seconds, then disconnect the injectors and try it again. If it fires and stops, then it may well be overfuelling due to a dead coolant temp sensor. Share this post Link to post Share on other sites
Pugnut 9 1 Cars Posted April 7, 2008 you shouldn't have, you should only have live to one pin and earth to the other when the ecu pulses. you will get 12v on both pins if all or even one of the injectors are still plugged in . since the injectors are all connected together the +12v will backfeed through the coil of a plugged in injector. the bulb test sounds a good one . also earth down the -12v side of the injectors and they should click open. belling out - just testing the continuity of the wiring with a multimeter or a bulb if need be . Share this post Link to post Share on other sites
Stu 18 Posted April 7, 2008 As above, forgot to say that, when testing the injector supplies make sure they are all disconnected! That had me confused for a minute or two! Let us know how you get on mate, have you got a copy of the CAPS software? I found it invaluable whilst faultfinding mine. Share this post Link to post Share on other sites
Pug_Power_Dave 0 Posted April 8, 2008 Cool cheers for the help guys, I'll give all those things a bash later on! Yea i only had one of the connectors disconnected, so will see what happens with them all d/cd Am i right in thinking pin 24 on the ecu is the ecu earth, to make sure thats got continuity to body earth or sumthing. Stu, no i dont have a copy of the CAPS software, what is it? a step by step checklist thing? Cheers Dave Share this post Link to post Share on other sites
Pug_Power_Dave 0 Posted April 8, 2008 Wooooooh manged to find the problem, 1st up like to thank everyone for their help, it's much appreciated! I disconnected all the injector connectors to check they had +12 one side and nothing the other, and the 1st one still had +12 both sides, so then i went to check the 2nd and the metal clips inside the plug werent there! they had been pushed back into the rubber waterproofing so must have been in contact with each other meaning the system couldnt earth so the injectors wouldnt fire! Put them back in place turned key and off it went!! I'm a very happy chap now! just need get it up to temp and check for leaks etc then go abusing! Thanks very much again everyone!! Dave Share this post Link to post Share on other sites
jackherer 543 Posted April 8, 2008 I've seen that a few times. Once the two pins short the ECU seems to totally shutdown until you turn the ignition off and on again to reset it. Share this post Link to post Share on other sites
Stu 18 Posted April 9, 2008 Coolio.. Glad you got it going mate! Share this post Link to post Share on other sites
