E30 Zone

Hi just wondered if anyone could help me out. I have recently bought the car in the title it came as a non starter. I found the
Fuel pump to be knackered when testing why. It had a signal and a spark also tried to start when easy start was used. I've now fitted a working fuel pump but it still will not start. Strange thing is it now has no feed to the pump and also no spark. I've had a look on the wiki and I'm assuming the crank sensors randomly gone down. Just making sure there is nothing else as I think it's a bit strange it working a few days ago and now nothing. Any advice would be greatly appreciated thanks.

There are two relays in the engine bay sitting under the long black plastic tray going along under the windscreen.
The relay on the far right (left as you look at from the front of the car) is the main relay which gets +12 volts on the one side of the coil at all times and gets ground on the other side from the ECU when the ECU picks up CPS pulses as the engine is turned over. This relay then supplies ground to the second relay which is for the fuel pump and the first relay also supplies +12 volts to the fuel injectors.
So the fuel pump, injectors and spark will only happen if CPS pulses are picked up by the ECU as the engine is turned over.
You need to have a look at both relays to see that they both energize as the engine is turned over and they should remain energized as the engine runs.

Also check all fuses...if it used to get a spark then maybe you blew something while fitting a new fuel pump.

I've checked all the fuses in te engine bay they all seem ok. These relays don't seem to be doing anything at the minute. Which has me thinking the CPS is not sending a signal to the Ecu. Is there a check I can do to power the relays up with a power probe? Thanks for the reply.

It should be possible to check the CPS at both the ECU plug and at it's connection to the engine loom.You should get a different resistance reading between engine cranking and engine not cranking.By checking at both places,you can eliminate potential engine loom problems.
I have only,ever,needed to check for continuity on the engine loom part of the CPS,though.

Hi wondering if you know if the vehicle has a inertia switch or fuel cut off switch?

Clarkey1988 wrote:Hi wondering if you know if the vehicle has a inertia switch or fuel cut off switch?

No,BMW relied on the engine not turning being detected by the ECU to cut the fuel supply.

Pump is fed by a green/violet wire,this passes through the main wiring duct into the cabin from the fusebox,this area is often molested by those fitting aftermarket alarms,so could have been attacked there!

I discovered a few weeks ago that it is possible for the fuel pump to be wired the wrong way around,so that it blows instead of sucking(as the actress said to the bishop)and still sound as if it's working normally...

Hmm I fitted a new crank sensor and I'm still getting no spark or fuel . I've also bridged terminal 30-87 and 87 on the dme relay like the wiki says to do and it still won't start does this mean the Ecu is knackered?

Check engine to body earth strap first.

Where is this located mate? I tried to put a jump lead from the battery to the engine and that did not seem to have any effect.

It will be underneath the front of the car, between the engine block and the chassis leg.

Nice one for all the help lads. Its really done my head in especially because it had a spark and feed to the pump originally. Since fitting the pump nothing...

Hi, i had a problem with my car not starting sounding similar to yours,check that the inline fuse on the secondary cable that runs from the battery to the main connecter in the bulkhead isnt blown,
Your car will not start if this fuse is blown,try running a cable from the battery to the main connector block and turn it over.
I hope this helps.

Mo

Where is this inline fuse mate? it runs from the battery to the main plug in the bulkhead? sounds like it could be a possibility! thanks.

Mine was located about 10 inches down the cable from the battery,It could be covered over with tape or insulation, dissconnect both ends and put a meter on it and check it, or just run new temporary cable and see what goes.
Fire away with questions,when my car had this problem it was totally fustrating,

Mo

Nice one mate ill go back the garage and check this tomorrow. Did not know they had an inline fuse. Hopefully this will cure it otheriwise testing resistances on the ecu pins etc which i cant say i enjoy doing!

No bother,

Mo

In line fuse is only fitted on cars with the battery mounted in the boot. No such fuse on cars with the battery in the front.

Ahh damn there's that idea out the window then. Back to square one. Thanks for the info saved me searching all over for an inline fuse that was never there! thanks for the help anyway mo.

Oops,did not know that, Tho it sounds very similar to what my problem was,hopefully it is easily sorted.

Mo

Check that power is reaching the ECU. According to this diagram, there should be an ignition switched live (+12V) on pin 37, and a ground on pin 19:

Nice one mate. I've got autodata with all the ecu pin locations in work so ill have to check that tomorrow. Is there any info anywhere on what readings i should expect at the CPS pins on the ecu?

See the E30 Zone Wiki:

http://www.e30zone.net/e30zonewiki/inde ... ion_Sensor

yeh ive seen it gives the resistance. I was wondering if there was any info on when the engines cranking. Our diagnostic machine in work doesn't seem to want to go into the vehicle must be software issues.

The resistance won't change when cranking, since the CPS is just a coil of wire, with a fixed impedance. However, a small change in the output voltage/current may be induced, in the order of microamps, as the toothed crank wheel passes it. This is what tells the ECU where the crank is.

I think that unfortunately is where i may need an oscilloscope going abit too far for a multi meter. Thanks for the info though ill try a few things tomorrow and see what happens. Am i right in thinking these don't have any sort of immobiliser?

They do have an immobiliser if you have an OBC fitted. Also check the green wire behind the glovebox - do a search on here; it's a well-known cause of non-starting on E30s!

I don't have that fitted nope. Green wire behind the glovebox ok ill try a little search. Again thanks for the help hopefully get it all sorted tomorrow

Green wire is the feed from the ign switch to the coil,terminal 15,I think.
There's a handy socket in the green wire behind the glovebox to allow an OBC unit to be plugged in,no OBC,then there should be a loop of green wire in this socket.
This is an aftermarket alarm fitters choice of place to create havoc.....

Clarkey1988 wrote:I think that unfortunately is where i may need an oscilloscope going abit too far for a multi meter. Thanks for the info though ill try a few things tomorrow and see what happens. Am i right in thinking these don't have any sort of immobiliser?

An oscilloscope would be perfect...wish I had one.

There is a very good chance that you either had a factory fitted or an aftermarket immobilisor fitted....as stated above this is the area that aftermarket immobilisors are usually interupting so have a look under the dash and on top of the glovebox for any strange looking plastic boxes.

Yeh will do thanks I'm going back to the garage soon. Don't you just love spending your days off working on cars especially being a mechanic!

Update it runs!!!! Had an aftermarket immobiliser button fitted in I'm made up thanks for all the help lads

Congratulations, dude!