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fazzrallye

voltage drop on injector rail

24 posts in this topic

Hi the wire from ecu pin 12 ignition on starts about 8 v and drops to 0v quickly. Live has 12v. Any ideas.

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take it its not one of them there switched earths, that starts high then drops for an instandt when it wants the injectors to fire?

am i right in thinking the injectors all fire at the same time?

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Yeah it's a switched earth but it shouldn't have voltage on it, you can't put voltage down both sides of something.

Yeah injectors fire together even of cylinder doesn't

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Sorry with a volt meter across the connector for injector rail starts reading 9V then drops down to 0 real quick. New fuel rail and bigger injectors 3.5fpr. Got spark got fuel to rail. Will start with easy start. If fuel low pressure will injectors fire?. Bbm injectors and rail. Put another battery on but still nothing. Continuity ok. Reads 5 ohms for injector. Live has 12v.

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Bear with me no little about electrics.Ok. With ignition off. Tester connected to +'ve I have a circuit when pin 12 is touched but also have circuit to the red wire from injector. Then with ignition on no circuit the current switches from being ground to live on both. Should pin 12 not stay ground. Can understand red going live on ignition but not pin 12 as meant to be earth.

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if we're talking about a factory G60 the red wire to injectors comes from Z1 on fusebox, ignition live.

pin 12 at ECU shouldn't have a circuit to battery positive, it should be open circuit then with ignition on switch to an earth.

sounds like you've got short somewhere

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Yeah it's not switching to earth it's switching to live. The red goes to fusebox. I have put a direct earth to injectors and they firing but no starting. Will have open all up and check all the connections

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[quote name='fazzrallye' timestamp='1344520424' post='155268']
Sorry with a volt meter across the connector for injector rail starts reading 9V then drops down to 0 real quick. [/quote]

Just so you know, that's correct. You'll get power at the rail with ignition on briefly whilst the fuel pump primes, then it goes off until you crank.

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[quote name='chunkymunkey003' timestamp='1344516012' post='155266']
Yeah it's a switched earth but it shouldn't have voltage on it, you can't put voltage down both sides of something.
[/quote]

right, im no electrician by any standards but im pretty sure you can.

12v on two lines either side of a bulb. the PD is then 0. when you switch one of those two lines to earth (relay), you create a PD and cause current to flow.
pretty sure thats how half the electrics on the G work.

someone tell me if im wrong.

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I might be wrong but I'm sure it's not, you have an earth and normally a switched live.

Injector is switched earth so if the ECU fails you cant keep pumping fuel in for safety reasons.

Yeah Simeon is right it primes with pump then takes power then brings it back when cranking/running.

So if you've got injectors firing and still no start something else is missing? Got spark? Timing ok? Decent compression?

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With direct earth to injector bypassing ecu it tried to start. Have spark have 10.8v on hall sender pin 1 and 3. Have fuel to rail. Have not touched timing so should not be out. Only diff from before bigger injectors 3.5 fpr bbm. All wiring that was replaced was put back and continuity checked. All earths ok. I am going to go through the fusebox up check all wirngs. Let's see

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Have you disturbed the wiring loom then? Old wires do go a bit brittle so you may have accidentally created a break somewhere..

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New injector loom new wires from bay to ecu. Apart from that nothing. New earths in bay. Continuity on all wires. Only problem I had was fuel pumps no earth I had this before and simply wired an earth to G1/3 . this gave me fuel pump but it did not switch off after 5 secs they stay on. The relay was new. I am now gonna go through all wires linked to fuel pump and injectors checking earth and relay. Have ce 2 wiring breakdown so will start from the bottom and work up.

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Oh, why is it not even cranking now? Is the battery ok, had it before where the gearbox earth becomes poor, used to replace the cable and ensure it was tightened to the box

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Losing my mind on this. Engine still turns by hand so not seized thank god. Checked timing marks they are all lined up. Battery ok even have jump cables on to boost it. All the earth new. Gonna get the relays 90 and 80 to see if that sorts out why fuel pump not coming on. Then gonna figure out why injectors not getting earth from ecu. Done all checks gone through all what's been posted on the forums

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this is where i stand. ignition on fuel pump not priming. ( new fuel pump relay). checked the fuel pump relay even though new its not earthing the fuel pump. ( i have ignition live) because fuel pump not priming Z1 not sending out live to injectors. to bypass this i earth the wire to pin 3 on ecu in the fuel pump relay, fuel pumps come on and i have live coming out of Z1.
now when i check injector rail with ignition on it starts at 9v and drops down. when i crank no voltage is registering.
i took out the injectors and cranked it, injectors were not firing fuel.

any ideas why no voltage when cranking on the other posts it says voltage should return when cranking. as i have ingnition live off the key is cranking live of the key different?
dont want to give up but just in case any electricians herts/ london area that might be able to help

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ok 12V live into rail but when I put multimeter across connector it staits 9v and drops down to zero. so I earth the rail and the injectors fired but not starting as I think it's flooding. with injectors switched off car starts for 2 secs while it burns fuel in chambers. connecting earth back up to fire injectors does not start it. going to replace ecu cos I have checked everything so leaves ecu which is not sending out correct signal to pin 12 which goes to injector rail. any help most welcome. fuel pump still not priming on ignition so have earthed it direct.

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got another g60 ecu. started first time. it came with sns chip. will but new 1.5 bar map sensor from bar tek. is there anything else to mimic the rallye ecu. thanks for all help this matter.

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ok new ecu worked for one day. good news the fuel pump now powers up on ignition but injectors still not firing. is their a cranking live which will continue power to the injectors. I have 12v live from Z1 I have initial voltage to injectors of 9v which goes to 0v. in an earlier post someone spoke about cranking live continuing power after fuel.pump has finished priming. everything else has been checked and changed.

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I think they're ment to yes, my conversion never has had it, just prime and then ignition live.

That never caused me any issues unless I didn't let the rail pressure first

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Hi, was this ever fixed in the end?  

I'm having literally the exact same voltage issues with my mk1 g60 conversion 

Cheers 

 

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