Just in case anyone has any suggestions to help me before I order some injectors.

 

So the morning of the AGM the car started up missing on the front two cylinders which were previously running fine.

 

First cleaned the injector plugs, no joy. Ive swapped coils and the problem persisted, checked spark and the spark is strong, pulled the plugs and they are dry and white leading me to believe it has indeed got no fuel.

So I checked the resistance of the injectors and they are within spec at 12-13.8 ohms. Voltage also checks out at 12.8V (early style injectors btw).

 

So although they are within spec the cylinder still has no fuel in it so may just put some new injectors in (hopefully before Simply Jap).

 

Any other suggestions?

Check the signal to the injectors with a Noid light

How did you measure the voltage supply at the plug Alic?

How did you measure the voltage supply at the plug Alic?

Voltmeter at the plug. I think it was the same voltage engine on and off although obviously a voltmeter isn't responsive enough to detect the voltage drop when the injectors supposed the open.

Voltmeter at the plug. I think it was the same voltage engine on and off although obviously a voltmeter isn't responsive enough to detect the voltage drop when the injectors supposed the open.

 

So you put the positive in the connector and negative to the battery neg or similar? You know the rail is constantly live, then ground is given by the ECU. Yeah?

So you put the positive in the connector and negative to the battery neg or similar? You know the rail is constantly live, then ground is given by the ECU. Yeah?

Yeah constantly live, I checked the voltage as they connectors have been spliced on, just checking that the connection was not broken or similar. Just did multi meter to each of the terminals on the plug, positive and negative (not proving much but just making sure no broken connections)

Ecu maybe. Could be worth swapping another one in if you have one.

Edited July 22, 20187 yr by bird

You need a noid like Pete suggested. If the injection ohms ok then I doubt they are the issue.

Little update, Im not really sure what I've found out.

 

Put an LED to the connector; on a working one it would flash as expected. On a non working connector, it would not flash. But tested with a multimeter again and they both show 12v.

 

So not really sure what that suggests.

After playing for a few minutes, itl think it may be flashing but very dimly. So I'm temporarily running a 12v feed to the positive

I suspect you have an issue with the ground return from the ECU.

 

But tested with a multimeter again and they both show 12v.

 

So not really sure what that suggests.

 

Hi Alic, where are you taking your earth from when checking with the multimeter for voltage?

Some posts seem quite spontanous as they were during testing, but here is the findings:

 

Cylinder 1 and 2 do not fire.

 

 

Cylinder 1 is what is described above, dry spark plug, multimeter showing 12v, but very dim led. I suspect weak signal with the ground? (may have been ground issues previously as it has a ground kit snakes around the engine bay everywhere.

 

Cylinder 2 ive just gone to test. Injector wiring working as intended, injector within spec, and black sparkplug. Little if not no spark. Not a coilpack issue. Should i start with testing another ptu for this issue?

 

 

What should I do about the suspected weak ground?

I'm going to suggest go round and clean the ptu connections on both sides. Also check the CAS ones. The injector issue could be the signal from the ecu. I'd try the noid/ light at the end and since you have a bunch of cars, perhaps swap the ecu out real quick to see if the issue is rectified. If your getting signal fine at the ecu, it could be a damaged wire between the ecu and injector maybe.

Just as short term test, can you add a good known second ground?

Say to the engine for example?

I take it you are using the harness ground when checking.

 

- - - Updated - - -

Just as short term test, can you add a good known second ground?

Say to the engine for example?

I take it you are using the harness ground when checking.

 

- - - Updated - - -

You cant ground it as it is a switched ground that opens the injector

I'm going to suggest go round and clean the ptu connections on both sides. Also check the CAS ones. The injector issue could be the signal from the ecu. I'd try the noid/ light at the end and since you have a bunch of cars, perhaps swap the ecu out real quick to see if the issue is rectified. If your getting signal fine at the ecu, it could be a damaged wire between the ecu and injector maybe.

Would have swapped PTUs and ecus by now if I had one with me, but all my cars are in wales at the moment.

 

Suppose I could noid light at the ecu side, or run a wire from ecu to injector. But I dont really want to splice into that wiring.

You could pop off the ECU plug and continuity test the wire. I had a similar issue which turned out the ECU plug wasn’t sat right.

What Stephen said.

 

But you might be able to test at the ECU by the back of the plug. I think Jeff TT did a write up years ago

Cylinder 1 is what is described above, dry spark plug, multimeter showing 12v, but very dim led. I suspect weak signal with the ground?.

 

Would 12 volts across the terminals of the connector suggest a good ground?

Or am I missing something?

Would 12 volts across the terminals of the connector suggest a good ground?

Or am I missing something?

Im guessing not because the light is very dim compared to the others and its not the positive. So the signal must be weak, It could be a low current, though im no physicist :lol:

though im no physicist :lol:

 

Fair enough, I'll leave it with you.

Hope you get it sorted.

Might be worth a look, although it sounds like you know the basics. I'm still thinking either poor connection or ecu

http://z32.wikispaces.com/Injector+Testing

Im guessing not because the light is very dim compared to the others and its not the positive. So the signal must be weak, It could be a low current, though im no physicist :lol:

 

The lamp is dim because there’s insufficient power, wether that’s due to high resistance or low current I couldn’t say.

The lamp is dim because there’s insufficient power, wether that’s due to high resistance or low current I couldn’t say.

Well it's the same 12v. So if it's a high resistance then it would be a low current hence v=ir. And power is current times voltage, so if current is low and voltage the same, then power is low.

 

I did do a level physics :D

Well it's the same 12v. So if it's a high resistance then it would be a low current hence v=ir. And power is current times voltage, so if current is low and voltage the same, then power is low.

 

I did do a level physics :D

 

Well stop being a bell end and fix it then. :lol: