Hi everyone, I been trying to figure out this problem with my z where it will crank but it won`t start for the last few months. I looked through pretty much everything and replaced few things like the CPU, Fuel pump relay (new), Ignition relay (new), E.C.C.S. relay (new) and PTU (new). the ECU is not sending out ground signal to the fuel pump relay PIN#18, Ignition relay and E.C.C.S. relay PIN#16 but the ECU has good ground. I would really appreciate if someone could really help me with this. THANK YOU!!!!..

Does the car have an aftermarket alarm/immobiliser?

Ok sounds like you have got some details of the problem but you are going too technical on it, this is a common problem that can often make you overlook something obvious.

 

So your saying there is no fuel pump run output from the ecu to the pump, if your checking this at the ecu connector then this can only be caused by either a faulty ecu or the ecu is not seeing the start signal from the cas unit (crank angle sensor)

 

So the best way forward is to get to the fuel pump via the boot floor access panel, now you can make an earth connection to the fuel pump, it should run constantly with the ignition switch on then, if not you will need to check the power supply, if this is ok then suspect the fuel pump.

 

If it does come down to the ecu output been the whole problem then that is usually causes by a fault that has shorted the ecu, be careful if the short still exists then fitting a new ecu will damage that one too, snip the output cable at the ecu connector first before fitting any new ecu and then you can test the output of the ecu without any danger of damaging it.

 

Good luck

 

Jeff TT

Edited October 3, 201312 yr by JeffTT

Does the car have an aftermarket alarm/immobiliser?

 

it doesn`t have a aftermarket alarm/immobiliser.

Ok sounds like you have got some details of the problem but you are going too technical on it, this is a common problem that can often make you overlook something obvious.

 

So your saying there is no fuel pump run output from the ecu to the pump, if your checking this at the ecu connector then this can only be caused by either a faulty ecu or the ecu is not seeing the start signal from the cas unit (crank angle sensor)

 

So the best way forward is to get to the fuel pump via the boot floor access panel, now you can make an earth connection to the fuel pump, it should run constantly with the ignition switch on then, if not you will need to check the power supply, if this is ok then suspect the fuel pump.

 

If it does come down to the ecu output been the whole problem then that is usually causes by a fault that has shorted the ecu, be careful if the short still exists then fitting a new ecu will damage that one too, snip the output cable at the ecu connector first before fitting any new ecu and then you can test the output of the ecu without any danger of damaging it.

 

Good luck

 

Jeff TT

 

the fuel pump is not the only problem im having:( its also not geting spark and injectors won`t turn on. when i turn the key on i notice the check engine light doesn`t go away but there is not code when i scan it.

I think you need to check all three fuse boxes first...

I think you need to check all three fuse boxes first...

 

i did check all of the fuse and pulled the fuse out to see if there were any damage or corrosion but its all good

the fuel pump is not the only problem im having:( its also not geting spark and injectors won`t turn on. when i turn the key on i notice the check engine light doesn`t go away but there is not code when i scan it.

 

 

In general no spark and no injector signal points to a cas unit fault, this will be why there is no fuel pump signal, if not the cam sensor or cable fault it could be a cambelt issue, unscrew the oil cap and make sure the cams are moving when cranking.

 

Jeff TT

and Jeff comes to the rescue again... :bow::biggrin:

In general no spark and no injector signal points to a cas unit fault, this will be why there is no fuel pump signal, if not the cam sensor or cable fault it could be a cambelt issue, unscrew the oil cap and make sure the cams are moving when cranking.

 

Jeff TT

 

the fuel pump should turn on before you start the car right? i just checked the cams and there moving.

the fuel pump should turn on before you start the car right? i just checked the cams and there moving.

 

The fuel pump gets a 3 second prime signal from the pump ecu when the ignition is switched on if there is no pressure in the rail, from there it waits for a start signal from the crank angle sensor, may be worth try running a test power supply to the fuel pump.

 

Jeff TT

The fuel pump gets a 3 second prime signal from the pump ecu when the ignition is switched on if there is no pressure in the rail, from there it waits for a start signal from the crank angle sensor, may be worth try running a test power supply to the fuel pump.

 

Jeff TT

 

i turned on the fuel pump by grounding the fuel pump relay and it does turn on but no change in starting

it sounds like the ECU isnt seeing the engine crank, if you have changed the CAS then there could be an issue with the wiring.

 

have you tried pulling pin 16 (at the ECU end) to earth to confirm the wiring bettween the ecu and the ECCS relay is pulling in? it would be interesting if you pulled the ECCS in with a link wire to earth and cranked the engine to see if the ing and injectors fired. but if its not pulling the FP relay in to prime either, then the ECU sounds like its a dead stick.

 

the ECCS relay should pull on with the Ign relay as the ign comes on and during cranking, if it doesnt, the CAS wont be powered and it will never see a trigger.

 

check that during cranking you have 12v on pin 43 as there is a fuse there that is only used when the key is on 'start'

 

the EML lamp is not fed from the ECU, but fed externally and pulled down to ground by the ECU. so just because the lamp is on, it doenst mean that the ECU has power.

 

if you havent done so already, check thers is power at the ecu during ign and during crank - diagrams below.

 

http://www.300zx.co.uk/tech/manual/manual/efec/104.gif

 

http://www.300zx.co.uk/tech/manual/manual/efec/105.gif

 

if you have checked all the above and have good ground connections as you say you have and pin 16 wont pull the ECCS relay in then it can really only be the ECU.

 

are you definitely getting 12v up to the coil side of each relay (FP/IGN/ECCS)? shorting pins 16+18 to ground at the ECU plug would prove this.

 

 

i've kinda jumped about a bit but i hope this helps a bit.