Mi16, No Spark

[arwel 43 2 Cars]

Hi guys. Really annoying problem. Basically had an off whilst rallying in February and we re re shelling the car. Engine was running absolutely fine before the off and even was afterwards.

It's now in the new shell using the same Citroen BX ecu and loom as before. Today we finished wiring up and now we don't have a spark going from the coil to the distributer. We changed the coil, crank sensor and ignition amp module with no success.

Am I missing something or could it be for some reason the ecu is knackered? At a complete loss at th moment.

 

Cheers

Arwel

[welshpug 1,678]

got live to the coil?

[arwel 43 2 Cars]

Forgot to mention that. Yes we do and have live to the injectors. Appears we have live everywhere we need it apart from leaving the coil.

[Anthony 1,003]

Does the fuel pump run and is fuel being injected?

[arwel 43 2 Cars]

Yes Anthony. Fuel pump is brand new one and comes live through a switch on the dash panel.

[S@m 156]

Are the injectors actually firing though? If you have neither fuel nor spark then the crank sensor is a likely culprit.

[arwel 43 2 Cars]

Will have to double check that they are firing tonight. We did try a different crank sensor but still no joy. Could try a different one of them again later and see if that does anything different.

[arwel 43 2 Cars]

Possible daft question alert!!! Just reading through other threads with similar problems and a lot is mentioned about earth to th gearbox. We did have one previously but since the engine went in on this car we made a new one running from the strut top to the engine mount instead so we dont have an earth to the gearbox. Would the lack of earth to the gearbox directly be causing the problem?

[Anthony 1,003]

Yes Anthony. Fuel pump is brand new one and comes live through a switch on the dash panel.

Ah OK, that doesn't help then. Reason I asked is that if the fuel pump is running off the ECU switched relay, if the fuel pump runs during cranking then it's a pretty good sign that the ECU is powered up, working and seeing a signal from the crank sensor.

 

As above, check if fuel is being injected so as to narrow down whether it's an ignition only issue or both fuel and ignition.

 

If it all worked when removed and doesn't now, then assuming you don't have fuel being injected either I'd double check that you've got everything connected correctly (plugging the crank sensor into the TPS wiring and vice-versa is a common one!) and that the relays are working and the wiring on the back of the holders isn't damaged - they seem quite prone to corroding and snapping off! Management and ignition electronic parts don't tend to spontaneously fail when unplugging them from one car and plugging them into another in my experience - it's usually wiring related issues.

[Anthony 1,003]

Possible daft question alert!!! Just reading through other threads with similar problems and a lot is mentioned about earth to th gearbox. We did have one previously but since the engine went in on this car we made a new one running from the strut top to the engine mount instead so we dont have an earth to the gearbox. Would the lack of earth to the gearbox directly be causing the problem?

Providing that there is a good earth to the engine/gearbox unit somewhere, that should be fine - it's normally the gearbox as that's the closest point to the battery and what the starter motor (with the heaviest current draw) is bolted to. Typically, if it'll crank over strongly then there probably a good enough earth for it to run.

 

A heavy duty jump lead from the battery negative to the gearbox should rule it out.

 

If you've not got an earth strap on the gearbox though, you did remember to attach the Mi16 loom earths didn't you given that both typically get bolted to the same point?

[Tom Fenton 1,562]

 

Yes Anthony. Fuel pump is brand new one and comes live through a switch on the dash panel.

The standard ECU controlled fuel pump relay means that if the engine cuts out then the fuel pump also stops. God forbid if you have a big enough off and can't reach the cut off for whatever reason its nice to know that if the engine cuts out the fuel pump will also stop.

[arwel 43 2 Cars]

Cheers Anthony. Will get on the case of the injectors this evening to see what they are doing.

 

Its looking like a wiring issue rather than a component going down isnt it. We shall go back through the wiring and double check everything is as it should be.

All the earths are connected unless we've missed one but we shall double check all those aswell.

 

It does crank over very well so sounds like the main earth we have fitted is more than adequate.

 

Guess it'll be a long few hours double checking everything then.

 

Thanks for all the help people.

[arwel 43 2 Cars]

Just an update for you all. The future father in law found the fault. Pin no4 in the plug that supplies the feed to the ignition amp was loose and wasnt making a connection. We now have a spark. He checked the rest of the loom over and decided he didnt like a few things so has now also re wired pretty much everything and taken out any wires that arent being used. Everything has now been tested and is doing what it should be doing so tonight it should start.....fingers crossed haha

[jackherer 543]

I've seen that several times but with injector plugs rather than the ign amp. If the pins short together the ECU shuts down to protect itself and wont run again until the power has been cycled.

[Dglopez 0]

Check Spark amplifier ground...i Had this problem