Hi, I have recently bought a 2000 model 2.0litre coupe, from ebay with only 2 cylinders firing. Obviuosly I have checked plugs cables and coils and they are all fine. By earthing the plugs I have worked out that it is electrical. (i can see a spark on 1 & 4).

So I checked for grounding on the cables to the ignition coil from the ecm (which is somewhat tricky to get to!!) they seem fine. The ECM is letting 6v through to 1 & 4 but only 1.5v to 2 & 3, i dont want to change the ecm until i know its definitly at fault and it wont happen again!

Any ideas? How do I check the CKP/CMP Sensors? CMP seems to go short circuit on all three feeding pins when ignition turned on is this right? (2 pins constant continuity the middle pin continuity when on with 8kohms resistance to the others?)

Please help as I would love to get her running!!

P.Courcoux

It sounds like it could have started out as a coil problem. You car is fitted with a waste spark ignition system, which means that each coil fires 2 plugs at the same time (1 & 4 - 2 & 3). Therefore if you have a spark at 1 & 4 it means that the coil for 2 & 3 has possibly failed. The CKP provides engine speed/position data to the ECM, relating to 2 pistons being at TDC, but the ECM doesn't know which 2 so the CMP provides number 1 cylinder TDC - firing data. If either of these fail the whole thing stops working. You should have battery voltage at pin 3 of the coil with the ignition on. The other 2 pins are the trigger wires which go via transistors in the ECM to ground. DO NOT put an ohm meter or power probe up these as you can damage the transistors. Disconnect the 3 pin coil connector and measure the primary resistance at coil pins 3 & 1 and 3 & 2, this should be about 1 ohm. Measure the secondary resistance at the plug lead terminals 1 & 4 and 2 & 3, these should be between 10.3 and 13.9 kilo ohms.
Hopefully it's the coil and not the ECM - best of luck.

Hi, I tested the coil as the first thing I did, it had also recently been changed by the previous owner for that of a 1.6 lantra, it appears to be ok.

The CMP Sensor is the bit that confuses me at the moment, I removed the CKP Sensor and obvioulsy the car wouldnt start! But when I disconnected the CMP Sensor it did start and it carried on firing cylinders 1 & 4 as before with nothing on 2 & 3. You have said before that if either fail it shouldn't work, but it appears to have no effect?

If either of the sensors were up the creak would the ECM not realise and show an engine fault light on the dash?

All help very welcome, I am a bit of a novice mechanic so I feel a bit up against it at the moment!

Thanks

P.Courcoux

Now we know why he sold it then. If another coil pack has been fitted (even if it is the wrong one) it can be narrowed down to: leads, plugs, or ECM. Because the ECM appears to be triggering at least one of the coils you can rule out crank (CKP) and cam (CMP) sensors. From what you've said it sounds like ECM and they are expensive. Your man may have already had this diagnosed and decided to flog the car rather than fork out for a new one.

You're welcome, any time.

If the ECM is faulty, then replacing it would cure your problem. As a rule Hyundai ECMs are pretty bullet proof and faults are external - loss of earths or power, or down to sticking meters or probes into wires without disconnecting the ECM first. Coils and injectors, etc are negatively triggered by the ECM and using an ohmmeter with a 9V battery in it on the trigger side of a component will blow a transistor. A Hyundai ECM forms part of the immobiliser system and is coded to the car. Therefore any recon or salvage units MUST be neutralised before they are removed from the vehicle, or they wont work when fitted to another Hyundai. So beware before buying one.

If you need any more advice either PM me or call me on the number that can be found on my website.