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Engine being starved of fuel


normsquared
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Good Day All,

I have a 1997 Disco 300 tdi automatic transmission that I imported from the UK to Canada. Basically, the problem is as follows:

While on a road trip I noticed a sudden drop off in power while on the highway. The tachometer never seemed to get beyond 2,000 rpm. Concurrent with that, I also noticed that I could no longer hear the turbo when going up hills or accelerating quickly. Naturally, I suspected the wastegate actuator arm and when I stopped to have a look at the engine, I noticed that the actuator arm would not move. I was able to wiggle it free and apply the only lubricant available to me at the time (WD40).

After I did this, I could hear the turbo engage while going up hills or accelerating quickly. However, there seemed to still be difficulty in achieving rpms in excess of 2,500. The next day the problem seemed to correct itself and I had full power.

Then after a couple of days, I noticed the problem again where the engine did not “want” to go beyond 2,000 rpm however I could still hear the turbo.

I took the vehicle to a diesel mechanic and he confirmed the functionality of the turbo by getting me to put the vehicle in Drive and revving the engine while applying the break.

When I open up the throttle (in any gear) the rpms go up smoothly (up until 2,000) and then the vehicle feels like it's being artificially starved of fuel. The engine will get to 2,000 and then I'll lose power; it'll get back to 2,000 and I'll lose power again. It's almost like the engine wants to go faster but something keeps preventing the increase in fuel going to the engine upon reaching 2,000rpm this me thinking ECU.

As I understand, when the vehicle "thinks" the wastegate actuator arm is jammed open, a similar fault occurs to prevent an excessive amount of air being forced into the engine.

To prevent damage to whatever mechanism seems to be artificially starving the engine of fuel by continuing this "engine starvation" process this, I kept the engine revving at just below 2,000. Of course when I encountered a hill, the transmission always wanted to shift down thus increasing my rpms and starving the engine until it got below 2,000 rpms. At a number of points in time I was going over hills at 18 km/h.

Interestingly, when I had sufficient momentum going downhill and began reaching speeds of 90-100 km/h, the rpms would be in the 2,000 region just from going downhill in top gear. Then I would again feel a stutter and some white (and a little bluish) smoke would come out of the tail pipe as if the engine was artificially being starved of fuel.

I've since replaced the turbo because, though the the old one was technically functioning, my mechanic noted that it was not providing sufficient pressure. However, there is still a problem with the engine being artificially starved of fuel leading to dodgy transmission shifting. My mechanic says the issue appears to be with the electronic adjusting of the injector pump. Mechanically the timing is fine. There is an error code that my mechanic's Bosch scanner comes up with that says "Start of Injection". We're both a bit puzzled by this.

Any ideas?

Norm

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Okay, The system is thus. The turbo pressure operates via a small hose from the waste gate supply to a diaphragm on the top of the Fuel Injection Pump. Check that this is not damaged (its under the cap located with four screws).

The diaphragm has, on its underside a concentric plunger, being concentric is had a "infinite" amount of angles to act upon a small plunger pin located in the inside of the diaphragm housing, this plunger operates on the internal fuel pump and allows more fuel to be injected in direct ratio to the turbo air pressure. The greater the concentric angle, the more fuel. Don't play with this angle until you have more experience.

So, and I'm assuming now that you have first :-

1.) Replaced and purged the fuel filter.

2.) Checked that there is no water/crud in the separator "filter" unit located on the chassis rail and under the tank.

3.) Checked that the fuel lift pump is working. (crack open the banjo union on the FIP while the engine is running, fuel should flow out)

4.) Under the above banjo connection to the FIP there is a micro mesh filter, check that this is clear. If crud is present clear it with an air hose.

5.) That the small hose from the "T" piece on the turbo waste gate line to the FIP has no cracks of air leaks.

If all of the above has been done then check the above FIP diaphragm and that the fuel operating pin in the FIP is free and not jamming. If you have to change the diaphragm ensure that the concentric pin is replaced in exactly the same position as it was before, this can be easily achieved as the concentric pin will have minute scratches on it were it has come in contact with the fuel pin.

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We haven't tried all of these suggestions yet. I'm admittedly a bit of an amateur here so I've passed these on to my mechanic. With the amount he's charging me though I'm tempted to fly an LR mechanic to Canada from the UK to have a look...not exactly an enticing prospect this time of year though...more to follow.

Cheers,

Norm

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My guess is that the fuel filter and or the sediment catch bowl at the fuel tank is the problem, this occurs when the vehicle hasn't been used for some time, if it's left for any length of time between runs it's good practice to open the drain on the fuel filter to allow any sediment to drain off. The other "villain" is the micro-mesh filter on the fuel banjo on the FIP. being very fine mesh this gets easily blocked causing fuel starvation.

If you are able to have the fuel injectors cleaned by ultrasonic vibration, DO NOT dismantle them, the injection pestle is ultra machined and even the natural acid on your fingers can damage the taper surface of it.

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