Mi16 Wont Start

[AndyJ 1]

Right I have been sat out in the pouring rain trying to get my MI16 going since it decided not to start at lunchtime.

 

I dont know if my alarm has an immobiliser or not, but from what i have worked out, shouldnt be stopping the engine running.

 

I feel like i am missing a piece of the puzzle here:

 

1. Fuel pump has no power when cranking, but comes on for a second when you stop cranking. I have hotwired it so that it is running.

 

2. I have a spark but only with 1 of 2 ignition amps that i carry around. the one i drove to work with this morning doesnt give a spark but the spare does. Voltage at the amp and continuity to the ecu pin are all OK.

 

3. Injectors are not firing, engine coughs when i manually blipped the injectors, so i believe it will work if it wasnt for this.

 

4. There is +12v at the injectors and continuity back to the ecu pin, so to me that says the ecu is not firing the injectors. I have tested this by sticking a 12v LED in the injector socket, I would expect to see it blink when cranking but there is nothing.

 

5. There is a signal from the CAS at the ECU pin, bang on at +-4v max while cranking.

IIRC the spark/injectors will not fire without a good CAS signal, but the spark is firing so i dont think this is the problem.

 

Any thoughts on my predicament? At least i'm at work so theres plenty of coffee

[wracing 19]

What management are you running??

 

Thanks

 

James

[AndyJ 1]

What management are you running??

 

Thanks

 

James

 

Sorry, its motronic 4.1 (2 row)

[wracing 19]

Stupid question but have you lost and earth or 12v to the ecu?? Have you tested the crank sensor with a oscilloscope?

 

Thanks

 

James

[hothatch 2]

Right I have been sat out in the pouring rain trying to get my MI16 going since it decided not to start at lunchtime.

 

I dont know if my alarm has an immobiliser or not, but from what i have worked out, shouldnt be stopping the engine running.

 

I feel like i am missing a piece of the puzzle here:

 

1. Fuel pump has no power when cranking, but comes on for a second when you stop cranking. I have hotwired it so that it is running.

 

2. I have a spark but only with 1 of 2 ignition amps that i carry around. the one i drove to work with this morning doesnt give a spark but the spare does. Voltage at the amp and continuity to the ecu pin are all OK.

 

3. Injectors are not firing, engine coughs when i manually blipped the injectors, so i believe it will work if it wasnt for this.

 

4. There is +12v at the injectors and continuity back to the ecu pin, so to me that says the ecu is not firing the injectors. I have tested this by sticking a 12v LED in the injector socket, I would expect to see it blink when cranking but there is nothing.

 

5. There is a signal from the CAS at the ECU pin, bang on at +-4v max while cranking.

IIRC the spark/injectors will not fire without a good CAS signal, but the spark is firing so i dont think this is the problem.

 

Any thoughts on my predicament? At least i'm at work so theres plenty of coffee

 

 

The ecu opens the injectors by switching to earth so it shouldn't pulse at the injector . (I think)

 

Also just look at the fuel pump relay by the ecu to see if your imobiliser is wired into it . Could be the problem.

 

Let me know thanks

 

Ben

 

I've stripped many alaarms and imobilisers off 205s as they do more harm thsan good.

[mr_exe 1]

There is an injector supply relay, and fuse, perhaps check that they are ok or the associated wiring for power and earths etc.

[hothatch 2]

There is an injector supply relay, and fuse, perhaps check that they are ok or the associated wiring for power and earths etc.

 

I agree the problem should be pretty simple (hopfully)

 

Let us know how you get on.

 

I didn't know there was a supply relay to the injector, I thought there's a constant voltage anf the ecu switchs it to earth to open and close the injector.

 

Ben

[Cloverleaf 1]

As I understand it when cranking the CAS triggers the spark (via the coil and the ign amp) and the coil triggers the fuel pump relay.

 

On a two row ecu all the injectors have a common live (via a relay) and are switched in a batch to earth by the ECU.

 

So it sounds like there is a problem with the wiring around your fuel pump relay. Now you've wired the fuel pump directly I can't think why it wouldn't work. There must be something we're missing.

[AndyJ 1]

Having pulled it all apart today I now understand what happened: It turned out to be the alarm after all.

 

Basically, the alarm had died and shorted internally. Due to how it was wired, this had blown the fuel pump relay fuse, which I had forgotten to check as its hidden away in the engine bay. When I replaced the fuse it blew the fuse on the alarm instead, and the engine started (on my last attempt before the battery died!).

 

But the knackered alarm was also feeding 12v into the accessory circuit, so when I took the key out, everything bar the engine stayed on, so i ended up having to disconnect the battery whenever I left the car for the last couple of days...

 

Big thanks to mr_exe for jogging my memory about that stupid little relay box.

[hothatch 2]

JACKPOT ! Knew it was somthing to do with the fuel pump relay.

 

Like I said alarms and imobilisers to more bad than good on 205s, big old steering lock or a garage lol !

[AndyJ 1]

JACKPOT ! Knew it was somthing to do with the fuel pump relay.

 

Like I said alarms and imobilisers to more bad than good on 205s, big old steering lock or a garage lol !

 

I've got a clamp, but its more fun to use it on other people

[hothatch 2]

Hahaha ! Like my mrs hehe !

[mr_exe 1]

Big thanks to mr_exe for jogging my memory about that stupid little relay box.

 

Glad to be of service, and so pleased that you have got in running.