Urgent - voltages of injector plugs

[Craved]

Hey people, just finished changing my head gasket today.... but the engine wont fire.. comes down to the injectors not actually pulsing.. thus no fuel in the engine.

: got spark and fuel to rail, compression is ok and timing is where it was before the change!

just need to confirm voltage readings on the injector plugs to isolate the problem!

voltages

ignition off and on reads :

12.12V on 1st side

6.9V on 2nd side

engine turning over:

6.5V on 1st side

changes from 2V to 3V on second side

one of these should return to 0V to actuate a pulse.. is this correct?

have checked earthing points on this loom, are they only located at the front of the plenum (bolted next to the temp sensor unit)?

any ideas? all help welcome

Cheers

Chris

[Craved]

just in case this matters it's a 94 S1 r33 ..

cheers

[blind_elk]

If you only have 6.5V at the injector, then its likely you only have 6.5V at the ECU. 6.5V is not enough to inspire the ECU. Try a jumper battery to get a bit of juice happening.

The injectors earth back through the ECU (ECU pulls to earth).

[Craved]

i'll try jumping the car tonight, but the battery has a full 12V.. hmmmm wierd!

does anyone know the earthing point for the ECU? might need cleaning up!

[Craved]

tried to jumpstart to help, and made no change to the situation!! all dash lights and everything work ok (that dont work if low power)...

Has anyone checked theirs before so i can see what a car that is running OK shows at the injector plugs??

oh and does the ignition control the injectors as well as spark?? just incase it's an issue with the alarm!

[blind_elk]

Everything (just about) is controlled by the ECU.

So, there is no click,click,click of injectors while cranking?

Try checking voltage at the ECU. In the RB20DE / RB20DET / RB25DE, the injectors are connected to pins 101 / 105 / 103 / 112 / 110 / 114, so I'm guessing the RB25DET is the same. Check for continuity between each injector and its ECU pinout.

Have you got any error codes out of the ECU? (reset ECU before trying to crank so you know that the error is "real").

[Craved]

actually there was no clicking of the injectors come to think of it! the car hasn't been run for ages now so im recharging the battery now.. will have to check the ecu diagnostics in the morning... the injectors and plugs were not removed with the headgasket replacement but have unplugged and plugged them back in... will also test out the readings at the ECU...

this would only show the earth side of the injectors right? if the readings at the ecu match those at the injectors would that show an ecu problem? or does it just confirm that the loom is working ok and the issue is elsewhere?

[Craved]

Ran the ECU check, and it came up 55..... so that doesn't help me much.. still rather it have an issue that way i could fix it instead of have it there not knowing ..

will be getting a power fc next week, but if the ecu isn't the problem then i still have to fix it!!

anyone know where the ECU earths out?

[Craved]

hey people, think i may have just found the issue causing there to be no fuel... and it doesn't seem to be anything to do with the injectors at this stage...

we looked further into the issue of no fuel, SO we removed the fuel pressure regulator the one controled by vacuum and let the car prime and also tested while cranking the engine over.... no fuel came from that regulator.. so it looks like the vacuum switch is stuck closed and not allowing any fuel through...

SO..... i was wondering if that switch should be letting fuel through regardless of vacuum input??

where can i get a replacement one from?

is this actually required if you run and adjustable fuel pressure regulator?

any other sugestions welcome!!

oh and on a side note, we disconnected the CAS, AFM, and injector harness then ran the ecu diagnostics ... still came up as 55 ...?????? wierd?

[blind_elk]

You said in your first post that you had fuel!

You would still be getting fuel at the injectors, even if the regulator was bung.

Are you sure the fuel hoses are connected the right way round on the fuel rail?

Can you hear the fuel pump 1) priming for 5 sec after switch to IGN and 2) working during START ?

If you disconnect the hose (between the filter and the fuel rail) from the fuel rail, and switch to IGN, does fuel get pumped out?

oh and on a side note, we disconnected the CAS, AFM, and injector harness then ran the ecu diagnostics ... still came up as 55 ...?????? wierd?

Did you try and start the engine first? The ECU doesn't read a sensor until you do something like "start".

[Craved]

My BAD

well thanks blind_elk seems that the fuel lines were around the wrong way!!! LOL we had fuel up to the rail.... but none going through it

only confirmed that now, that the guy who helped me is here now and the marks he put on the fuel lines had been wiped off when we cleaned everything up... so i put em on the wrong way.... i even checked some photos i had and i couldn't see the lines properly!!

OH WELL,,, at least now it does run and it was a cheap/no cost thing causing it!! and we know that the voltages at the injectors when turning over are supposed to be 6.5V

not too bad an experience.. learnt heaps about the car and saved petrol while at absurd prices LOL thanks for your help man

and once again its the simple things in life that shit you up the wall wont be doing that again

[Sumo]

Craved man, you dont admit that on the net.. you just say some bloke came and fixed it

[blind_elk]

Yeah, the regulator RELEASES fuel from the rail, it doesn't control the ENTRY of fuel to the rail.

[Craved]

Nah thats cool Sumo, i dont mind admitting we made a mistake it's all good!!

yeah, actually figured that one out the hard way... i was getting confused as to why there was 2 regulators on the line... just wasn't thinking! oh well, time to put it all back together!! thanks again for your help blind_elk!!!