Hello This could be a lack of fuel pressure from the electrical pump at the tank. If the connections to this are corroded or damaged then the pump could stop at any time or could not be running at full speed. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubt and do the same for the fuse, Ideally measure the pressure at the inlet to the main engine fuel pump and if this is low check the pump as described
If both of these are OK then also check the connections to the EGR valve, if either the vacuum pipe of electrical connection are damaged / corroded then the EGR can be on all time which certainly will hurt performance. Its also possible that its a fault with the EGR valve so its worth removing the valve and cleaning it out with brake cleaner, if it looks particularly clogged then replace it.
If this is OK then check the small vacuum lines to the turbo and its connected control solenoid on the bulkhead, any cracks or leaks can give turbo issues and its best to have the boost pressure measured actually measured with a boost gauge to check that the turbo is healthy and that the sensor is reading correctly
If its a variable vane turbo (they’ll be an actuator on the turbo body - but not a wastegate) then check its vacuum pipework as above and check the connections to the diaphragm / solenoid valve
Also worth checking that the glow-plug relay is switching off as they can stick on and leave the glow plugs also on - on some cars this can force it into limp home
Also worth considering a bottle of injector cleaner into the tank as a clogged injector nozzle will reduce power and give poor combustion - the next stage on from this is to remove all the injectors and have them ultrasonically cleaned and flow checked
Also check all the high pressure hoses post turbo/s for any split hoses or cracked metal pipes, also check the ends of the intercooler as its not unheard of to pop the end caps off under high boost.
If the above are all OK then try checking for airleaks after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and leans the engine out causing rough running. As its a mechanical fault it tends not to turn on the fault light and you can sometime hear a 'hissing' noise with the engine running.
Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.
The best way to locate a leak is to have the engine running and warm and then spray lighter gas around each joint in turn. If the engine rev's up you've found your leak.
Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.
Might also be worth checking the wiring and connector to the airflow meter for any signs of corrosion or damage. you can do a quick fault find if you unplug the meter and run the engine without it.
if the engine condition is the same then chances are the meter or the connection to it is faulty
I'd also suggest inspecting the throttle pedal sensor for corroded contacts and damaged wiring
and finally its worth doing a compression test on all cylinders just to ensure the that the base engine is OK
I'll try to check on the unit again and I will apply your suggestions and technique on how to find leaks then I'll get back to you.
My Hi-lux does'nt have a fuel pump in the tank, the fuel pump is located at the front left side of the engine and is mechanically driven by gear. We tried replacing it with another but same kind of pump but it did'nt work, the engine stops after a few seconds, but if the accelerator is depressed it do not stop, and further acceleration, the engine power drops and can no longer be accelerated and engine check lights on. I hope we can work this out Matt.
We pulled down the tank twice already before and did not see any pump inside or outside of the tank, there were only two wires there for the floater resistor which transmit the capacity of fuel to the fuel gauge.
We checked the feed pump for blockage (since this is where the fuel pass thru a filter) and found no problem with it. But as i pumped fuel to the rail (also passing thru the main fuel pump), the pumps gets harder to pump that means the rail is full already. Is it normal that while the engine is running, the feed pump gets softer? I am asking this because; after starting the engine, it tends to stop and as we pump the feed pump it remains running but as soon as we stop pumping, the engine stops.
Try pumping up the fuel using the hand pump in the engine bay on the filter housing, then crack off / loosen each injector pipe in turn while cranking the engine and getting an assistant to operate the primer. This will expel air from the injection side and the engine should fire up. The problem will be cured by checking the supply pipe along its length for signs of leakage and repairing any you find.
If you daub each pipe joint with heavy grease and the issue goes away then wipe the grease away one at a time to highlight the problem joint
I'll check this out tomorrow and I'll get back to you as soon as I finish testing my unit.
I did what you told me to do with the tubes and hose fuel supply to check for leaks. I pumped the fuel to the rail with the feed pump and when it hardened up already, we started the engine. While engine is running, I pumped the feed pump again to check its hardness and it became soft again.
I tested it by supplying the rail with fuel thru the feed pump and filter by using a gallon as its tank, using new fuel hose. I pumped the feed pump again until it was hard then started the engine, still the feed pump becomes soft and the engine cannot increase its power, and once you step on the accelerator, the engine check lights on then engine power drops.
okey I'll have it check by Denso injector pump calibrator then I'll get back to you ASAP.
I just came from the calibrator and they said that the injectors and pump are normal so we tried and tested it again but the engine still stalls. The calibrator said it could be a problem with sensors. The hand pump still get soft when engine is running and as we increase the rpm, engin check lights up then no more power and it stops.