craig sharp

hi i'm a new member and would like some technical advice about my non starting impreza please.
it's a 99 turbo. when i turn the key there is no pressurization noise from the fuel pump. i've disarmed my imobiliser but still no joy.
cheers
craig

mart360

check the fuse that feeds the fuel pump/ if ok check fuel pump relay , make sure you have a 12v feed.

and make sure you have disabled the immobiliser

if fuel pump relay & fuse ok you need then to check the fuel pump, / power feeds

and check the wiring at the ignition barrell / inductive loop for the key/ immobiliser transponder,

basically the fuel pump is waiting for

immobiliser to be turned off

12v feed from the ignition to ecu,

ecu to send power to the fuel pump

the ignition is waiting

just a thought,

you havnt had the key apart recently, or dropped it??


Mart

scoobyboy

if it's got a sigma alarm then they have a habit of burning out the fuel pump immobilization circuit i've changed quite a few for this exact problem.

craig sharp

cheers Mart
the imobiliser is working i think because the car want's to start. The fuel pump relay you mentioned, would that be found in the fuse box and if so which one is it?
I've cheked the fuses and there fine.
The car did this about a week ago but started after a few times of trying to re start it.

cheers
craig

mart360

the relay may be in the fuse box, i,ll have to check,

if you reckon its trying to start, then it could be faulty cam or crank sensor,

a common scooby fault..

i ll post details of how to diagnose in a min


Mart

Sigma Sam

Just to clarify...
The alarm unit only acts as a relay within the immobilisation circuits and so cannot cause the circuit to "burn out".
Excessive current draw from the fuel pump can cause the immobilisation circuit to overload and when this happens it generally does so at the alarm connector, which due to size of the terminals can only handle a limited current.
Just because the alarm unit is the nearest component does not put it at fault - I would look to your fuel supply and why the pump is drawing so much current.
SS

craig sharp

Cheers Mart
i've had the cam sensor off. All conections looked ok. Bit of a bad one really as i can't get it to a scooby specialist to check it out and i'm rubish with electrics.
Craig

mart360

Right ho,

to diagnose a cam or crank sensor fault..

when the car exhibits a non starting scenario, try the following.

with the ignition turned off, disconnect the plug from the back of the cam sensor. wait 5 seconds and replace.

try to start the car.

if it starts fine, this will give you a temporary fix,

if it dosent try the same for the crank sensor,

again if it works, its a temporary fix, and will work everytime the car will not start.


replacement sensors are as follows


£100+ +vat eah from the main stealers. £35 from grade A or similar.


now the difficult bit.


i had the same symptoms, and got it to start by the disconnection/ reconnection method on the cam sensor, so i replaced it, unfortunatly it was the crank sensor which was at fault, so i had to do that one too

best of luck

mart

mart360

its not the connections, it to do with the hall effect generated by the sensor,

over a period of time, the sensor looses its ability to find the pulse generated from the magnet on the cam pully

unplugging and replugging the connector for some reason gives a bit of a boost and it usually works.

try both and see what happens.


the fuel pump only energises when the ignition is turned on, once energised it turns off until given a cal from the ecu. the ecu is waiting for the pulses from the cam and crank sensors to start things off.

one way to further check is to whip out a plug, and to see if you have a spark.

no spark= ignitor pack u/s or not being given feed via ecu, which comes back to the immobiliser side of things


mart