Wont' Start: Injectors Not Firing When Starter Is Engaged

[Steffen Hi-Speed 0 2 Cars]

Car: 205 Rallye 1.9 from 1993

 

Engine: 102 hp 1.9 with Bosch LU-Jectronic, O2 sensor and catalyst. So basically it should be like a pre-cat 1.9 with L-Jetronic, except for the O2 sensor and catalyst. It's quite different from the Motronic on later 122 hp 1.9 GTIs with a catalyst.

 

Symptoms:

The car had been sitting for two weeks, but the battery had been topped up with a CTEK charger which indicated that the battery was fully charged. It started and ran fine before being parked.

 

* Engine cranks when the starter is activated by the ignition key, but it doesn't even cough - so no combustion taking place.

Checked:

* Spark is ok, checked visually by removing a plug and looking at the spark. Ignition coil, distributor and rotor replaced less than 3000 miles ago.

* Fuel pump running, tried loosening the hose at the top of the fuel filter. Fuel came spraying out.

* Tachiometric relay next to the ECU replaced with a new one from Hella. Old one didn't click, new one does. Makes no difference.

* Fuel injectors checked by dismounting the fuel rail and looking for signs of them squirting fuel.

 

And here comes the part I don't get: The injectors are not firing, when the engine is cranked by the starter no fuel is squirted from the injectors like it normally would.

 

Instead, when the ignition key is turned counter-clockwise and the starter is switched off the four injectors all give one simultaneous squirt of fuel.

Has any one on here experienced a similar problem, and solved it, or have any ideas as to what causes this?

[Tom Fenton 1,541]

I am not that familiar with the ins and outs of that management system, does it use a crank sensor? Or the distrubutor to provide the engine speed signal?

[Steffen Hi-Speed 0 2 Cars]

According to Haynes (I know: The big book of lies), the signal for the injection system comes from the ignition, just like on the regular L-Jetronic. It has the same coil, distributor and everything as the normal L-Jetronic cars. I haven't been able to locate any TDC-sensor, it doesn't have one according to Haynes, unlike the Motronic cars.

[Anthony 1,003]

Tom - It's basically regular Jetronic with the addition of a lambda, so the timing signal for the ignition amp is from the dizzy and the fuel injection side of things is triggered from the coil along with the tacho.

 

Is there 12v to the injectors when cranking? If so, you can rule out the relay/power side and it has to be something relating to the timing signal or ECU as that's what grounds the injector to fire it.

 

If the car is in a position to do so, it might be worth trying to bump start it. In theory it shouldn't start, but there has been the odd case of defective starter motors creating huge amounts of electrical interference that has caused weird starting faults. I wouldn't expect it to be so much a problem on Jetronic compared to Motronic with its comparitively weak signal from the crank sensor, but worth ruling out

[Steffen Hi-Speed 0 2 Cars]

I'll have to check whether the injectors receive 12V while cranking, I'm not sure.

 

I still don't get why the injectors give one simultaneous shot of fuel when the starter is switched off, at that point they must get a 12V burst to operate?

But of course then the ignition key is in a different position.

 

Googling my problem, I found only one simular problem (on another forum), and the "victim" had solved it by replacing the fuel pressure regulator which surprised me. But before buying a new one, I'd like to make sure I'm not overlooking something.

[Anthony 1,003]

I don't know the exact reason, but the ignition amp will sometimes do a single pulse on ignition-on but engine not turning. I *think* this is what causes the fuel pump to prime on Jetronic cars, although I've never understood why some cars do it and others do not, and why those that do only seem to do so intermittently.

 

I would imagine that the pulse would also fire the injectors, although I've never checked to see whether it normally does so in the circumstance that you're seeing it.

 

Assuming I'm right, that suggests that the connection between the coil and ECU is fine and that something is stopping the injectors being pulsed under cranking. That's why I suggested trying to bump it to rule out starter related oddities (if you do a search I know Jackherer posted about this a while back)

 

Seems unlikely to be fuel pressure regulator related to me, as if it was the FPR there wouldn't be pressure there to squirt the injectors when you released the key like you're seeing. I'm pretty sure it'll be something electrical, but it's certainly an odd sounding one.

[DamirGTI 342]

Pinch the return fuel hose at the back of the regulator with vicegrips that'll create high pressure within the system and if there was low pressure issue before the injectors should start squirting .

 

D

[jackherer 543]

I don't know the exact reason, but the ignition amp will sometimes do a single pulse on ignition-on but engine not turning. I *think* this is what causes the fuel pump to prime on Jetronic cars, although I've never understood why some cars do it and others do not, and why those that do only seem to do so intermittently.

 

Yes, following a similar theme, I've had several non running (specifically non sparking) Mi16s that will spark once when you turn the ignition off following an attempt at starting, I'm not sure what but something in the ignition system charges then discharges independently.

[Steffen Hi-Speed 0 2 Cars]

I finally had time to do some more work on the 205 Rallye this week (it's not my everyday car anymore).

 

- Changed the ignition module and ignition coil. Makes no difference.

 

- Tried squeezing the return fuel hose from the fuel pressure regulator. Makes no difference.

 

- Checked that fuel is flowing back into the fuel tank on the return side, it does. So it's not just "old fuel" recirculating in the engine compartment.

 

- Took the fuel hose from the filter to the fuel rail off at the union on the fuel rail, fuel pours out = that hose is not blocked either.

 

- Tried swapping all the relays in the engine compartment around to see if one was dead. Makes no difference.

 

- Took off the cambelt cover, the cambelt is still on so the camshaft turns when the engine is cranked thus the ignition should signal the ECU through the wiring to the ignition coil that fuel is needed.

 

- Established that when the engine is cranked, the injectors do not fire. But when the ignition key is turned anti-clockwise to 'ignition' (like when the engine is running, and not being cranked by the starter) all the injectors fire one shot simultaneously.

 

And finally grabbed the multimeter and tried measuring the current to the individual injectors:

- Starting with the injector plug on the right hand side of the car (closest to the cambelt): 0 volts to the injector, and no spike when the key is returned to 'ignition'.

- Tried the injector plug on the left hand side of the car (closest to the distributor): 0 volts while cranking, a short spike of 12-14 volts when the key is returned to 'ignition'.

- Tried the next injector plug, number 3 from the right hand side of the car: 0 volts while cranking, a short spike of 12-14 volts when the key is returned to 'ignition'.

So it seems the injectors are not receiving a signal from the ECU to fire when the engine is cranked. Other than the ECU itself being fried, what could cause this?

[woodymi16 24 2 Cars]

Not sure if you've read this one but it may help

 

http://forum.205gtidrivers.com/index.php?showtopic=69751&hl=%26quot%3Binjector+firing%26quot%3B&do=findComment&comment=645128

 

[Tom Fenton 1,541]

The injectors receive a permanant 12v supply, the ECU earths them to switch them. I would check the positive supply to the injectors.

[205tunerke 4 1 Cars]

First try to fire when someone is spraying brakecleaner/deoderant/wd40 pulsed in the air intake(remove air filter).

If it fires up you can be shure it is the injection not working. I had a problem with the main ground of the ecu, so mine didn't squirt either..

[Steffen Hi-Speed 0 2 Cars]

Thanks for the suggestions guys! Much appreciated.

 

@Tom Fenton: I've tried unplugging the wiring from the injectors, and mesuring on each plug (see above). But I've measured between the two connectors inside the plug, should I connect the negative side of the multimeter to ground on the car instead?

 

@woodymi16: Thanks for the link, it looks like I need to hunt for a small, white plug somewhere under the AFM and over the gearbox. Presumably it ends at the ground connection on the gearbox?

 

@205tunerke: Stupid question maybe, but is the ground for the ECU close to it inside the glovebox?

[Dizzee stuff 33 1 Cars]

Thanks for the suggestions guys! Much appreciated.

 

@Tom Fenton: I've tried unplugging the wiring from the injectors, and mesuring on each plug (see above). But I've measured between the two connectors inside the plug, should I connect the negative side of the multimeter to ground on the car instead?

 

@woodymi16: Thanks for the link, it looks like I need to hunt for a small, white plug somewhere under the AFM and over the gearbox. Presumably it ends at the ground connection on the gearbox?

 

@205tunerke: Stupid question maybe, but is the ground for the ECU close to it inside the glovebox?

I think tom means use the battery or car body as earth and check for live feed to injector plug with ignition on, as the ecu pulse's the - to switch the injector the live feed come's from another supply.

[205tunerke 4 1 Cars]

The main ground ECU is near ECU connector above the glove box.

 

But did it fire up?

[Steffen Hi-Speed 0 2 Cars]

Sorry to resurrect an old thread, but I thought I would just share that I did finally get the car running again.

 

I'm not 100% sure what did the trick, my guess is that the problem was the white plug running from the injection wiring harness to the earth / ground on the gearbox (as pointed out in this thread: http://forum.205gtid...ng"#entry645128). In my case the little metal wire that's supposed to hold the male and female plugs together was missing and the plug slightly loose. There was no corrosion or dampness inside, but I gave it some contact cleaner spray and a zip tie just in case.

 

I also slightly loosened the earth / ground connection on the gearbox itself, and gave it some contact cleaner spray too. It wasn't corroded, but there was quite a lot of oil and dirt there. So cleaned that off and tightened the connector.

 

After that I tightened the connector at the end of the spark plug wire going from the ignition coil to the distributor, it felt loose at the coil end. I also unplugged the coil from the ECU wiring harness and gave that connector some contact cleaner spray. Then I unplugged the wiring from the ignition module on the RHS shock tower and gave that some contact cleaner spray as well.

 

Moving inside the interior I unplugged the ECU (having unplugged the battery first) and gave the male and female plug some contact cleaner spray. I also had a look at the earth / ground connector above ECU (at the bottom of the A-pillar more like) and gave that some contact cleaner spray for good measure.

 

I re-installed the ECU, re-attached the battery and hey presto it fired right up.

 

So, in conclusion. The only part I changed was the tachometric relay, and that made no difference what so ever. Even though none of the connectors I looked at were corroded, clearly one of them had a poor connection. My money is on the white plug from the injection harness to the gearbox, but I guess I'll never really know.

 

On a side note, I did try, before starting the engine, to measure the voltage in the injector plugs by earthing the multimeter to the engine and body but I couldn't get any voltage output from the injector plugs with the ignition switched on (this was right before the engine fired up, so what ever had been wrong before was already fixed).