Engine cranks but does not start - Holden Colorado

Also forgot to mention that the mechanic tried a noid light test @ injector connector with engine cranking. There was no illumination. This was also done in the very beginning with the original ECU; no illumination.

Because there is a small voltage reading (1.1V & 2.3V) @ ECU for injector power supplies, I'm going to say that they are ground side switched.

Ecms are reprogramable and cheaper than having to replace all modules.
You will need vin number, mileage, tire size, rim size, transmission type (4L80e etc). I will reccomend to take the original ecu with you if you have the 2nd hand one reprogrammed as they might be able to get the antitheft info from the ee prom of the ecu.
There are some cases where other modules can only be programmed once. So do your research with a shop that can program/reprogram modules to see if you would be better off getting a module preprogramed.

@Hardtopdr

Had a different Holden Colorado, exact same model/year/engine, come in for an oil change.

Back probed the injectors with a DMM to see what power supply reading was:

1. 5.3V KOEO
2. 6.0V with engine running

Correct me if I'm wrong but aren't injectors supposed to receive a power supply equal to battery (12V)?

It varies between manufacturers. 12v is common for all gas engines, with diesel engines some are 12v some are 48v volt(ford powerstroke 7.3 and 6.0 for example).

But i think your dmm is averaging the voltage when its running i haven't seen one run on that low of voltage. Use a scope to see the wave form set in volts and it will show what it really is.

Hardtopdr2 wrote: It varies between manufacturers. 12v is common for all gas engines, with diesel engines some are 12v some are 48v volt(ford powerstroke 7.3 and 6.0 for example).

But i think your dmm is averaging the voltage when its running i haven't seen one run on that low of voltage. Use a scope to see the wave form set in volts and it will show what it really is.

Using a scope I still get a reading of 6V at the injector connector. The wires to these injectors are thicker than normal. I'm assuming it's low voltage but high current.

So I asked the tech to go over all his previous checks. Turns out he did not use the wiring diagram to check the CKP sensor signal @ the computer. He probed a random terminal and saw a digital square wave while cranking, assumed it was the CKP sensor signal (CKP sensor is a three wire hall type).

We went back today and used the wiring diagram to locate the CKP sensor signal terminal at the computer. Using a scope, KOEO there is 5V at the signal terminal. When cranking the engine, the signal voltage stays @ 5V. Suspected a signal wire shorted to 5V reference/supply wire.

1. We probed the signal wire at the sensor, there is a digital square wave as expected.
2. Using DMM, checked continuity on 5V reference, signal & ground wires (from sensor to ECU). All okay
3. Checked for continuity with one DMM probe on ECU signal terminal & other probe on sensor reference terminal. There is no continuity which means wires are not shorted together?
4. Visually inspected wiring @ sensor end. The harness protector is in good shape. Removed harness protector & wires are good.
5. Have still yet to check the rest of the length of the wiring between the ECU & sensor but from where I was the harness protector looked in good shape.

Does anyone else know might be happening here?

If the injectors are not firing, I'm thinking that this CKP sensor signal is the most likely reason.

Wow 6 volts on injector feed that is a surprise. If you have access to service info i would see what it says but since that was off of a running vehicle i guess you might be right with what your thinking.

As for the ckp issue that is perplexing you have a square wave at one end at the sensor but not at ecm. This tells me with the info found about injector feed voltage to check your injector wires that run next to your ckp sensor signal wire and any other independent 5 v ref circuit that runs next to it as well. You should have a squarewave at both ends. Also double check the ckp sensor signal wire to see if it changes color throughout harness back to ecm to verify its not a mislabeling of the diagram (I've been there).

Would it be worth a try to probe @ the CKP sensor signal terminal & connect a wire from there to the signal terminal @ the ECU?
The jumper wire would just be connected in parallel to the original signal wire.

That would be worth a shot. Also de pin the wire at ecm and see if it still has 5v at that pin from ecm as that might be your 5v ref feed to ckp. Some diagrams will say ckp low ref or ckp sens ref. What i have found ckp low ref can be the ckp signal to ecm in some cases. If you have the pinout of ecm handy post it up for both conectors at ecm may save you some headaches.

Firstly merry Xmas to all.
My appologies for re-opening this thread but it is the closest I have found that describes my problem. If the issue was resolved then I'd love to hear what the final outcome was. My conversion is a Colorado/Dmax 4JJ1 motor, Mtr harness and ECM into 1996 HZJ75 Toyota troop carrier. ECM has had all immobiliser functions disabled so as to run as an engine only installation. So the problem I have is "Engine cranks but does not start". I have been through the service manual fault processes both section 1 and 2. The only thing I have been able to find is the ECM pulse and power to the injectors is missing. This tread covers the injector wiring and power question in detail and I have done checks as well. Injectors are -ve switched so I power is on at injector once ign is on. Wiring diagram confirms this. Power is provided from 2 internal sources to Inj 1 & 3 and 2 & 4. Each injector is then wired back to an individual -ve ECM switching terminal.

1. No power to injector when ignition is on or during cranking
2. No -ve pulse (ie Test lamp from bat +ve to injector -ve wire) with ign on or during cranking.
3. Continuity tested wiring harness from Inj plug to ECM plug. All good.

I don't have the ability to internally try to pulse the injector with a scanning tool. But intend to do this to prove the ECM was Ok or faulty.

I don't know what conditions need to be met for the ECM power and pulse to be provided to the injectors so am open to any thoughts and feedback.

Car ended up being taken to another workshop.

To this day I don't think it was ever fixed.

ok thanks, that's a pity.

So it seems we now have 3 ECU's displaying the same symptoms. I appreciate my ECU is not the same as the Colorado but it suggests the condition that needs to exist for power and pulse to occur at the injectors is likely/possibly to be the same.

I will pickup the fault finding at the CKP sensor, something I haven't done yet and also get a tech with a scanner that can manually pulse the injectors to confirm the ECU is ok. If anyone knows what conditions need to exist for the ECU to pulse the injectors then would appreciate your input.

It is worth commenting that because this is a motor conversion, I also did an intake and EGR clean so all the fuel lines were removed and required bleeding.
This was a considerable effort but I did get the engine to run for short periods (2-3 sec) quite consistently but wouldn't continue to run. The car then sat for a few days and here I am today. So something has changed or the fault has developed further.

Are you 100% positive the immobilizer function is off?

Cut out/missing injector pulse is a prominent mean to immobilize the engine on many MMY.

No I can't be absolutely 100% sure but am assuming it is. I sent the ECU to a tuning company who also has been providing the immobiliser delete service for many years so am taking their word for it that they have done the job. I will contact them after xmas and have a chat. Good suggestion tks.

As with the comments earlier about Injector charge voltage, I also assumed it would be 12v and as such could test with a low wattage test lamp. Novice mistake. Actual voltage (DVM) at injectors is 4.53vdc and test lamp won't glow at these voltages. Also found one of my test leads was open circuit, another NM. DVM showed injector coil ohms to be 0.5 as per service manual. So will put my CRO on the injector signal and see it there is a pulse when cracking. CKP and CMP cables and supply volts are Ok 5v solid.

Made a set of breakout leads for injectors 1 so that I have access to the connections. Tested again with DVM and found 4.53v on both sides of the injector as expected. Signal cable only synch to ground during the pulse cycle. Connected the CRO neg lead to ground (bat -ve) and input lead to signal lead to Injector 1. Turned on ignition and CRO read 4.53, same as the DVM. Cranking the engine the CRO showed pulse to 0v each time engine got to No 1 cyl then back to 4,53v for the rest of the cycle. So now I'm back thinking either the injectors are not triggering (physically stuck) or I have a HP fuel delivery problem to the injectors. I tested all the fuel systems earlier (both low pressure from the tank, HP to injectors and the return flow) and was happy there was no air and SCAN Kpa was as expected at the HP sensor.

If anyone has any thoughts on what I'm missing then please jump in.

Decided to go over the air bleeding checks again.
1. Removed the return flow from the low pressure lift pump. No return bubbles.
2. Cracked open the HP supply to injectors at fuel rail. Each showed fuel present.
3. Checked FRP reading. 162540kpa
4. Removed the leak-off pipe from each injector. Leak-off from each was the same.

So from what I can see there is fuel at the injectors, fuel pressure and ECM injector pulse 4.53v DC and injector coils all 0.5 ohms. Only thing left that I can think of is to do a "Force Trigger" from the ECM to see if the injector is actually operating via the pulse from the ECM. Unfortunately I don't have a SCAN tool I can use but do have a regulated power supply so can manually trigger them. Not quite the same but will prove the injectors are not stuck.

Injectors are not stuck and can hear them operate when voltage is applied. Last thing is to ""Force trigger" the injectors through the ECM module. Have this booked in for the 9th. Xmas/New year break and everyone is away.

Had a similar problem in 2012. After much expense etc found the problem was a burnt earth pin in the engine compartment loom to body loom plug located on the firewall LHS.

Thanks for your input and yes it could be a very simple fix at the end of the day. I'm looking at the obvious things that are most likely directly related to the engine starting and because there is an ECM involved, invariably it all gets very complicated. But one things is for sure, it will get solved.