Hilux Surf 3RZ-FE Engine

[Stallion]

Good Evening to all, and hope all well at your ends by the grace of the Almighty.

I refer to the above mentioned subject.

I've had this vehicle brought to our workshop, and has a hard start once engine reaches optimum operating temperature.

It fires up very well during cold starts, but becomes a hard start once engine is to it's normal operating temperature.

1. Spark Plugs checked and found no fault
2. Ignition Coil tested and found no fault.
3. Fuel pump tested and found no fault.
4. Vaccum hoses checked and found no fault
5. MAS Air Flow Sensor checked and found no fault.
6. Crankshaft Sensor checked and no fault.

What am I missing ? Also when in optimum temperature, when you switch off and wait for 2 minutes ( 120 seconds ) and start her up, she'll fire like clock work, but if you switch her off and start her after half a minute or less, she won't fire.

What could cause such a problem ?

Your assistance and cooperation on the above will highly be appreciated.

Looking forward to your responses on this by return.

Regards
Shermohamed

[Mud Dog]

Does the 3RZ have a CSV (cold start valve)? If so try starting with it disconnected once hot and the problem has manifested.

[Stallion]

Good morning Andy,

Thank you for your swift response.

I've not noticed the CSV, but will find out if it does have on Monday, as am off to the farm this morning.

Will let you know.

Thanks once again.

Regards
Shermohamed

[Stallion]

Good Morning Andy,

I Hope all well at your end by the Grace of the Almighty.

I returned from the Farm yesterday evening, and as soon as i entered town, i was called by one of the electricians at the Workshop who had a spare ECU for the 3RZ-FE engine, and asked me to come and test it if the replacement of the ECU solved the problem. I went, we replaced the ECU and went for a test drive to get her to the optimum temperature, returned to the workshop, switched the engine off, and fired it up in 60 seconds, and she fired up perfect. We did the cycle of firing thrice thereafter, 1st in 30 seconds, then again at 60 seconds and then again in 75 seconds, and all the time she fired perfect.

The old ECU was opened to check inside, and found 3 resistors kind of discolored, like heated, yet i haven't understood what the resitors were controlling, but looks like the replacement ECU did the job.

I'd appreciate if you could shed some light into this, as why the resistors found were kind of heated up, and would they be responsible for such a fault? As you may remember that i'm not that good in electrics, but am learing with these modern engines as they come along.

Your assistance and co-operation on the said will sincerely be appreciated.

Regards
Shermohamed

[Family_Dog]

Possible faulty sensor. Can you still make out the colour bands of the resistors?

Just be careful the new ECU doesn't get fried as well.


-F_D

[Mud Dog]

No idea why the resistors overheated, but there may be an underlying cause that is not the ECU itself. I would take a snapshot of the old unit and the new one as well and record the values of the ones that overheated in case you need to repair the old one. No guarantee that it will last though.

[Stallion]

Good Evening Eric & Andy,

Thank you for your responses.

I've not noticed the Color Bands of the Resistors, but will check tomorrow by the Grace of the Almighty.

Both of you are correct when you say that the replacement ECU may not be the actual problem, this is why I wanted to know what would cause the heating of the Resistors, as Eric mentioned, the replacement ECU may get fried if we don't know what caused the heating at the first place.

I'll check the Color Bands of the Resitors and get back accordingly.

Andy, your idea of getting the snap shots and the values is also splendid. I shall do that as well.

Your assistance and co-operation is sincerely been appreciated.

Regards
Shermohamed

[Family_Dog]

You need to take photos of the resistors if possible, the colour bands indicate the resistors' value. If the resistor overheats and discolours, these colours would be hard to identify. An orange band might become brown in such a case, resulting in an incorrect reading of value.


-F_D

[Stallion]

Good Evening Eric,

Thank you for your response on this.

It was my mistake that i didn't look at the ECU closely on Saturday Evening when i'd returned from the Farm and got a call from the Electrician. I took a closer look at the ECU today this Morning, and called the Electrician again to show me where he thinks the problem lied. When he showed me, they were actually four Capacitors, and not Resistors. Now looking at the Capacitors closely shown by the Electrician under proper light, i personally couldn't see any signs of heating on any of the four Capacitors the Electrician pointed out. I also looked closely on the Vanish that is used to waterproof the Electrical Circuit, and i couldn't see any signs of heating. I took the pictures on my phone and have them with me in my phone. I don't know how to transfer the pics here. The Capacitors are numbered as: C103; C107; C110 & C115 (pointed out by the Electrician, 4pcs).

As per the client's feedback of today, the vehicle is running great and starts up perfect all the time. I still don't know where on the ECU would the fault lie. I'll try and transfer the pics here for you guys to have a look at it, and maybe we could get to the bottom of why and where the previous ECU could have been faulty, and most importantly, what caused the ECU to be faulty.

Do ECU's wear out over time? Meaning any of the Electrical Circuits or Components inside them?

Regards
Shermohamed

[Stallion]

Trying to attach the Images here;

[Stallion]

Another set of pics for better understanding;

[Mud Dog]

Hmmmm ..... they don't appear to be burnt / overheated to me. But then I am not an electronic technician. Obviously the ECU has a fault since the replacement one is working OK. Nothing lasts forever, but those ECU's are pretty robust and last well under normal operating conditions, so I'm still not convinced that there isn't an underlying cause for it's failure. It may be as Eric suggested that one or more sensors are giving inaccurate input and the ECU is working overtime in one sector to compensate.

[Family_Dog]

Hi Shermohamed,

As Andy said, the caps look fine to me as well. Those are electrolytic capacitors and while they do not generally overheat, they can get "old" and dry up. If they began leaking electrolyte, you would generally see it at the bottom of the caps where they are connected to the board. If they suffer stress due to over-voltage, they generally tend to bulge, worst case scenario they explode. It's difficult to see from your photos but all those caps seem to be well-formed to me, no signs of leakage or swelling.

I would suggest something else is wrong, might be a leaky diode or transistor (if there are even any transistors in the ECU).

Is there not possibly any sign of water ingress into the ECU enclosure?

I believe that is the same engine fitted to my Prado, V6 3.5 litre, my vehicle is dated from 1998 and all is 100% electrically.


-F_D

[Bear]

Hi Stallion

I agree with Mud Dog and Family Dog.
I am not a qualified technician, however electronics was my hobby. Cannot see clearly from a picture but those components do not look damaged. There is a tool which can measure capacitance while the component is on the circuit board or by desoldering the components, discharging them and using a multi meter to test.
How did the technician come to the conclusion that those components are damaged?

[Stallion]

Good Evening Andy, Eric & Ricky,

I agree with all the three of you, i also couldn't rule out that those Capacitors have any sign of failure, same applies to me, am not an Electrician, but am learning through these processes and increasing my knowledge as I go on with Vehicle Repairs at my Friend's Workshop.

1. Andy, you sound correct, it is a very great possibility that one of the Sensors' ain't functioning correctly, hence letting the ECU work Overtime.
2. Eric, according to my visual inspection of the ECU and the Capacitors pointed out by the Electrician, i couldn't see any signs of swelling, discoloration or leaks, even the Varnish they use for water resisiting the Electricial Circuit, has no signs of discoloration, swelling or peeling out. No signs of any water penetration into the ECU.
3. Ricky, your advise on testing out the pointed Capacitors via a Multi Meter is a great way of making sure if really those Capacitors have malfunctioned. I'll keep this in mind to do on my spare time at the Workshop. Electrician pointed out on the color of the Capacitors having signs of overheating, but as i said, i wasn't satisfied with his conclusion, as he didn't test them with any tool, he just ruled out by physically looking at them, and he's a very well reputed Electrician in our Workshop Area. Therefore i didn't want to standup on him, but I'm inquisitive, I want to know why & how Therefore i thought of discussing it here, am comfortable discussing here and learing more.

Thanks for all your advises, once i get spare time at the Workshop, i'll look into it further as per Ricky's suggestion.

Regards
Shermohamed