Misc. Maintenance issues - 70 series Prado

[UAHMAD]

Old 4x4 vehicles require extra attention. Their mechanical and electrical systems have to be in good working order (if not perfect) especially if their intended purpose is off road use (unlike most of the modern SUVs which are mostly being driven on paved city roads).

Like any other used vehicle owner, after buying this one I got changed all fluids, belts and worn out suspension parts. Then came addressing other mechanical/electrical problems that were diagnosed due to performance and functionality issues. Some of these are described in this thread. This shall however, not include body work and accessories etc:

• Cold start problem and knock in winters
• Engine noise and vibration
• 4x4 not functioning
• Miscellaneous problems

[UAHMAD]

In cold mornings (or evenings) of winters the engine would knock like anything for a few minutes. This was accompanied by smoke and check engine light. And power also lost substantially if I tried to move the vehicle. But everything would turn out to be normal a soon as the engine warmed up. No rattling, no smoke, no CEL, and no power drop.

One of the four glow plugs was changed along with injector nozzles some time ago. So these were ruled out.

So we started from valve lashes/tappet setting on the engine.

1kz-te uses shims for valve clearances between valves and camshaft lobes. The specified clearances (cold) are:
Intake valve - 0.25 - 0.30 mm (0.008 - 0.012 in)
Exhaust valve - 0.25 - 0.35 mm (0.010 - 0.014 in)

First a feeler gauge was used to check/feel the clearances. Two of the exhaust valves (3 & 4) were slightly out of range (loose). Accordingly, those two shims were replaced to bring clearances to 0.010 inch for intake and 0.012 inch for exhaust as per available formula:

Intake: N = T + (A - 0.010 in)
Exhaust: N = T + (A - 0.012 in)

N = Thickness of new shim
T = Thickness of removed shim
A = Measured valve clearance

Result was better cold start but engine rattling sound didn't go away.

[UAHMAD]

We then turned our attention to the Check engine light, which led us to DTC 14 (when TE1 and E1 of Data Link Connector - DLC1 were connected using a jumper cable).

Description of DTC 14 is 'Timing Control System malfunction'.

Trouble areas are:
Open or short in timing control valve circuit.
Fuel filter (Clogging).
Fuel (Freezing, Air in).
Injection pump (Internal pressure and timing control valve).
Engine ECU.

[UAHMAD]

To address the problem it is good to understand how fuel injection system of this engine works and how can we connect cause and effect.

Electronic control of Fuel Injection Pump:-

The high pressure distributor fuel pump (almost same as Bosch rotary) is part of the pre - common rail system, and runs with the engine by way of a drive shaft driven by the timing belt. For two rotations of engine this pump goes through one rotation.

This pump is responsible for mainly two functions:

1. Fuel injection Volume control:- Metering the fuel before sending it towards injectors for burning with air inside the combustion chamber. This is achieved through instructions sent by the ECU to Spill control valve of the pump.

2. Fuel injection Timing control:- Advancing or retarding the injection timing, depending upon driving conditions (speed and load). This is achieved through instructions sent by the ECU to Timing control valve of the pump.

ECU of this vehicle performs dual function of fuel injection as well as auto transmission control. It controls above mentioned fuel injection volume and timing through calculations based on inputs received from various sensors like:
Engine speed (sensor located on the pump, attached to its drive shaft)
Fuel temperature (sensor located on the pump)

Air Intake temp (sensor located on air intake pipe)

Engine temperature (sensor located on engine head)

Crankshaft position relative to TDC (sensor located on engine block, below starter motor)

Boost pressure of intake manifold (sensor located near intake manifold, connected to it with a vacuum hose)

Variations from intended volume and timing injection are corrected through two correction resistors located on the pump.

Main purpose of the complete diesel injection system is to ensure right quantity of fuel burnt at the right time for performance, fuel efficiency and less emissions.

This is a good article for understanding basics of diesel fuel injection (including types of injection systems):
https://dieseliq.com/how-diesel-fuel-injection-systems-work/

[UAHMAD]

Function of Timing control valve has been highlighted in the previous post; that it mainly controls injection timing, but more precisely it achieves it through regulating pressure on a hydraulic Timing piston located at bottom of the pump assembly.

What I've understood is, through this timing piston the timing valve maintains a standard injection timing setting at cold start and low speeds. But timing injection system malfunction can result in too much advance of injection timing (especially at cold start), this will be counterproductive and results in excessive knock and load on the engine.

This figure of a cross section of the fuel pump shows the difference between timing device piston position at idle and at high rpm. This is how injection timing gets advanced with speed:

An actual image of pump interior just to have an idea.

Since knocking, smoke and severe loss of power problems I was facing were at cold start and low speeds only (along with CEL) so there is more likelihood of a faulty timing control system. Other possible causes identified in trouble area (s) of DTC 14 were not very likely because Fuel filter was recently replaced and ECU was checked by using another similar unit of 1kz-te.

Faulty valve was confirmed once it was pulled off the pump to find out that its solenoid wasn't clicking upon applying 12v directly. So a used valve was sourced. May I mention that I couldn't find a new part, while Toyota recommends replacement of complete pump. And a new Denso pump was priced around Rs. 250,000/-.

Correction resistors also needed replacement.

While fitting back the pump it is necessary to align the mark on its front flange to a protrusion on back of the timing cover case.

This article gives a good overview of diesel injection timing:
https://highwayandheavyparts.com/n-12787-adjusting-diesel-engine-injection-timing.html

[UAHMAD]

Interestingly, an online search revealed that this timing control solenoid failure is a common problem with Bosch VP29/30 pumps in certain European vehicles and even some industrial engines like Perkins. This VP29/30 pump is quite similar to the Denso 1kz-te, both being axial plunger type injector pumps. The only difference is that VP29/30 have own PCU (Pump Control Unit) mounted on the pump unlike Denso.

[UAHMAD]

Engine noise similar to exhaust leaks was being felt along with vibrations inside cabin.

When exhaust system was inspected, a flex pipe was found to be in worst condition. Its outer metal mesh had fallen off and there were visible small holes and cracks on it. So it was replaced with a new one.

To find out cause of vibrations, prop shaft and engine mounts were checked. Prop shaft was taken off to see if it was bent, and secondly the condition of U joints. Everything turned out to be okay.

Then we checked engine mounts. Both were fine, however transmission mount had completed its life. It couldn't perform its function anymore i.e reducing the drivetrain vibrations. So it had to be replaced with a new part.

[Hassan1991]

[UAHMAD]

The eletronic locking hubs have a reputation for failing and are always considered less reliable compared to the manual hubs. But there are not many experts out there who can also give you the reason for e hubs failures.

These e hubs have a small dc motor. When the 'Hub Lock' button on dash is pushed this dc motor gets activated and engages the locking system of hubs. After this front shaft can be engaged with high or low range 4x4 gears.

But when carbon brushes inside these hubs break/wear out this dc motor doesn't get required voltage to function, hence the failure of electronic hubs.

The replacement e hubs with intact carbon brushes.

There is a way to avoid damage to the carbon brushes:

Before these e hubs are being fitted back after a solid axle repair job etc, a pin should be inserted in the middle hole out of three holes located on the opposite side of the dc motor. This shall push back/retract these carbon brushes, which will then be safe from breakage. Pin can be removed once the hubs are properly fitted in place.

It is illustrated in the picture. Arrow points towards the hole in which pin is to be inserted:

[UAHMAD]

4x4 was working perfectly fine when tested on a few trips.

[consigliori]

Excellent.

[UAHMAD]

Very kind of you.

[dani_kk]

Excellent thread

[UAHMAD]

Thanks for encouragement.

On a side note, the other day came across a pump of 3L from some Hiace model at the diesel shop. I was particularly inquisitive about this part of the pump, which turned out to be Automatic Cold Start timing device or ACSD.

Some 1HZ/1HD T/FT pumps of LCs and 5L of Hilux vehicles also come with ACSD. It works with thermo wax contracting (and expanding) with changing coolant temperatures and actually advances injection timing at cold start up by taking over the timing piston's standard setting.

Sharing it here because I thought it was interesting.

[capsat]

@sameerulhaq064 @imranmaskeen @agoodfriend @rajaatta @VCheng @ser_gtr @babarhyd @nnabeel @brownrose78 another interesting thread for knowledge

[VCheng]

First a feeler gauge was used to check/feel the clearances. Two of the exhaust valves (3 & 4) were slightly out of range (loose). Accordingly, those two shims were replaced to bring clearances to 0.010 inch for intake and 0.012 inch for exhaust as per available formula:

Shim-under-bucket designs tighten as they wear, and thus do NOT clatter as they wear, and it is better to keep them on the looser side of the specification rather than tighter.

[UAHMAD]

Thanks for inviting other senior members for their valuable inputs.

[UAHMAD]

Thanks for the pro tip. Duly noted for future.

[UAHMAD]

The other day I came across this lesser known version of 1KZ TE with factory water to air intercooler set up at a local scrap yard. Whereas most of the later versions of this engine came with air to air intercooler.

As can be seen, it has separate reservoir, heat exchanger, and pump. It doesn't need a hood scoop or a bonnet modification. According to the shopkeeper, it came in some Hiace model.

Can be considered as an alternative to top mounted or front mounted intercooler, if someone is interested in an engine swap.

[capsat]

Thats' correct this variant of 1KZ-TE is from JDM HIACE Vans year 1999 - 2002, (KCH46W & KCH 16W).

Few such vans were seen in MirPur Azad Kashmir, where mostly such vehicles arrive from Japan auction houses under Gift scheme by UK residents. Out there some of Ustaaz were unable to tackle why 2 radiator caps are visible and ultimate failure of engines.

You may find few of such engines somewhere in Mirpur car scrap yards with only intercooler failure.

However this engine variant can not be swapped in trucks / suvs, the water-intercooler can not be shoved beyond firewall. The Hiace vans engine hangs in middle, after driver & passenger seat in cabin there is no firewall and this engine variant ride over 6 mounts , 4 for engine 2 for transmission.

try locating english workshop manual for Hiace KCH46 you will understand via graphics why 6 mounts are required.