Sensors stop injectors?

[monkeynuts]

Hello all,

I'm new to this game and i'm having problems already. I've got a beautiful deep burgundy 1983 320i with cream leather seats and it's died on me.... Literally, I was driving along and the engine cut out without a fuss. I tried starting it again and it turned over easily but would'nt fire.

I'm getting a spark, battery's fine, airflow seem unimpeded, fuel is being pumped. So I'm wondering which sensors would stop the injectors and not just affect how much fuel is being injected.

I've got the AFM out and checked the resistance for the flap which seems ok and the air temp sensor which is down by a factor of ten but I don't know if this is the main issue and have'nt got a replacement to check.

Would anything like the idle control valve, cold start valve / air slide, cold start injector, other temp sensors, TDC etc. stop the injectors working suddenly if it failed.

As an addendum the car was idling like a yo-yo hot and cold before it died.

I was thinking of plugging the AFM back up but not attaching to the throttle body, opening the flap and squirting cold start in the thottle body to confirm a fuel injector problem as it should fire on the gas in the air not i'm not sure if this is wise.

Any advice would be massively appreciated.

Thanks in advance.

[Brianmoooore]

Don't know too much about early E30 wiring, but assuming this is L-Jetronic, check that you've 12V+ on the red/white wire going from the fuel pump relay to the injectors. If not, change the fuel pump relay.

[Templ8e30]

The yo-yo idle is a big clue, I had this on my 1990 320i and it was a knackered idle control valve. It wouldnt start after i turned it off whilst the idle was acting up.

Installed a spare ICV and it's been fine ever since.

Cheers,

Iain T

[monkeynuts]

Thanks for the ideas, i've been working on it when I can over the weekend.

There is a red and white wire from the fuel relay on the left wing. I've checked it and it's giving out at least 12v.

The ICV I was thinking about but on this early model it's not wired up to anything like on later models so all it does is bypass the throttle plate. I do think it needs changing but I can't see how it's inhibiting the injectors.

I've checked the cold start injector and that is squirting nicely, the thermotime is kicking out a voltage also. I also checked the plugs on the injectors for a voltage when turning over the engine and what they give out is negligable so it's something stopping all the normal injectors from squirting (The plugs are definately not smelling of fuel).

Does anyone have experience of these early models, is a sensor telling the ECU not to fire the injectors or is the ECU knackered? I'm having a hard time finding replacement bits for ths old lady.... I'm up poo creak without so much as a cocktail stick on this one.

[Brianmoooore]

There should be 12V+ on both sides of the injectors when the ignition is on and engine not running. One side of each injector is grounded by the ECU to inject fuel.
Do your voltage testing with a 12V lamp of at least 5W rather than a meter. Voltage readings from a multimetyer can be misleading on unloaded circuits.

[monkeynuts]

Wonderful I've managed to fry the charging circuit/alternator. All I need to do now is drop a tool through the windscreen and my life is complete.

I'll get onto checking the voltage on the injectors again tomorrow. But what could be the problem if I do/don't get a lit lamp? It's just taken me half an hour to understand the last post.

I'll go out on a limb... if it does'nt light then it's the ecu or a sensor suppying the ecu, if it does then really at least one injector should be squirting?!?

1983 cars should'nt be complicated!

[Brianmoooore]

If the light doen't light, then you're not getting 12V supply to the injectors.
If the light does light, then the ECU is faulty, or more likely not being triggered.

[monkeynuts]

ok I don't know if I'm testing it correctly but i'm getting a light and also 12v+ on a multimeter briefly when the ignition is turned and continuously when I'm turning the engine over.

Soooo, if i'm getting this the right way round then the ecu is faulty or not being triggered (I assume that would be some kind of sensor feedback fault).

But which could stop old girl mid-flow and not let her start up again?

:flummoxed:

[monkeynuts]

Right I've priced up some early model parts available at a local garage, But funds are low so I'm trying to work out what to go for first.

AFM Ԛ£50
ECU Ԛ£50
ICV Ԛ£20

Obviously it could be something else so maybe there's more I could check first.

Also I should have mentioned this earlier but there's a brown wire with a female blade connection coming from end of the injector wiring loom. Thing is it goes nowhere! Nothing to plug into, just hanging there. There's also a similar wire going into a bolt/plug on the engine coolant manifold type area but that one has a lilac stripe. Just wondering if anyone knows if thats important?

[Brianmoooore]

Looks like the injectors are getting their 12V supply OK, and not being switched by the ECU.
If this is L-Jetronic, then, as far as I can tell from the wiring diagram that I have, the injection control unit is triggered (along with the fuel pump relay) by a signal emerging from the ignition module on a pin marked TD. This wire appears to be yellow at the ignition module, but black/blue at the fuel relay and the injection module.
Are you sure the sparks are OK?

[monkeynuts]

Thanks Brianmooore, you seem to be a wiz with the electrics!

I'll check the spark plugs and dizzy again and make sure I'm getting repeated sparks - I think I read in another post somebody was only getting one spark and that was their problem.

I'll check the wiring you mentioned aswell cheers for that.

I think part of the problem in diagnosis is that the electrics are a bit different in the early models like mine (1983) so whenever I read a similar account in someone elses topic some of the electrics just don't match up. The ECU is very early and is I believe an LE-Jetronic 0 280 001 301 which controls only the injectors (I've read!)

Anyway if I end up replacing a few bits like AFM, ECU, ICV would I be better off or able to use a newer models and 'mod' the old girl?

Thanks again, I'll post more when I've checked those bits...

[monkeynuts]

Ok, i'm definately getting a regular spark, can't find those wires though. Then again I have trouble even finding the parts!!

I've included some pictures (I hope)....

Ignition Control Unit - Bosch 0 227 100 111


Injection Relay - Bosch 0 280 230 001


Injection Relay in place (note it has been tampered with and taped back up - not by me!); AFM 0 280 202 031; ICV no code


And finally loose brown wire!?!


Although I can't say I know where the injection control unit (is that the ECU? I know where that is) or ignition module are...

Sorry if i'm being thick, I've got a Haynes but it technically does'nt even cover this car!

[Saj]

Alright guys, i dont no if this is gonna be any help. Ive got a 87 325i which had a similar problems. First time my brother was drivin the car when it missed and cut out. i replaced the jetronic ecu which solved the problem.

A few months later it did the same thing, i had to replace the flywheel sensor, which apparantly controls the way the engine fires.