My monster truck is a diesel guzzling snail.

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I've just picked up a 150,000km 120 GX diesel. It's sooo gutless; my friend reckons his 90 series (diesel) would blow it into the weeds. Mine wheezes its way past 120km/h up to a about 130, provided there are now hills. It struggles to get past 3,000rpm in 3rd & 4th gear and wont do it in 5th at all.

It also drinks like a fish. On highway runs, I'm getting about 1,100kms per tank. I get the same economy in my 78 series work ute & I drive that flat out like a rally driver with a good dose of your average tour de france competitor's little helpers....

I think either: My timing belt was just replaced & (very hopefully) they got it wrong by a toof, or: my turbo is stuffed.

In the morning I'm going to whip off the timing belt cover, so will most likely eliminate the first scenario, next I'll have a go at testing pressure in the inlet manifold.

Any clues from anyone as to where to look? Also, any easiest way to check boost pressure?

[Blokeman Member Find all posts View Profile Close Blokeman]

Can't help I'm afraid, just a sympathy post. My GX is at 150k too and goes as well as it ever did. Don't suppose a simple fix, some injector cleaner would help? Obvious stuff, air cleaner, fuel filter?

[mav Addicted PP Member Find all posts View Profile Close mav]

Sounds as though there is something mightily wrong with your donk, I think if it were me I would be taking it in to the nearest diesel shop and get a thorough going over. Might cost a bit but at least you will have a good time with the result.

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Also make sure the catalyst isnt blocked.

Tap a boost gauge into an inlet manifold feed, that should tell you the boost.

[robn Member Find all posts View Profile Close robn]

mmm Sounds like the diesel pump

Rob

[Fazza Senior Member Find all posts View Profile Close Fazza]

wildmangordo,
Did you manage to check the cam timing? As you mentioned it was using a lot of fuel & won't rev.
As Pradogxlv6 mentioned, no quick fix but blocked air cleaner or intake sounds a clue?
Also is it getting full throttle?

Again good luck.
Fazza

[Jacto Senior Member Find all posts View Profile Close Jacto]

Hey all you mechanics, does the diesel have an O2 sensor like the petrols? as this could also account for the high fuel use

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Thanks everyone so far... I've checked the cam timing and it's spot on. I've yet to check properly for leaks (haven't found a bucket big enough to put my car into... have to wait for the next flood, then stand back and look for bubbles).

Pradogxlv6, is point 6 on your list just the cam belt, or is there another way I can check the injector pump timing against the valves? Given that it's guzzling fuel, is it likely to be a restrictive fault in the fuel system? btw the air filter is new, albeit non-genuine. I did suspect the newly fitted snorkel (I had it fitted before I took delivery) but have removed the airbox lid to test this and it performed no differently. Clutch doesn't seem to be slipping, I can stall it like any other idiot in the sand. Do you really think it's unlikely to be a worn out turbo? A pressure test should rule this out anyway, but I'm a fair way off that at the moment...

Thanks so far... I'll report back in when I make some more progress.

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Great, I'll suss that. I am a bit far from a dealer. I'll be consulting with Mr Ellery (who I'm not a great fan of) and our local mechanic here (who I am a fan of) to try to transform my snotty tortoise into a leaping lizard myself. I will let you know the outcome.

Ta again.

[Strahan Advanced Member Find all posts View Profile Close Strahan]

My guess is go with obvious- you had the timing belt done so its a good chance your problem is there somewhere.

Check the pump timing as well as the cam timing would be my first look. I'm not sure if there are any connectors that could have been left undone after it was put back together?

I think also with those new electronic pumps the OBD might log a fault code? Get paper clip and see if you can T to E1 as this will bring up any fault codes.

[Drew Advanced Member Find all posts View Profile Close Drew]

Great, I'll suss that. I am a bit far from a dealer. I'll be consulting with Mr Ellery (who I'm not a great fan of)

Mate, if you need any info from the Toyota documentation - just let me know and I can extract it for you.

Good luck,
Drew.

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Wow. Thanks, Drew. I'm just about to do a 2,000km run (to the pub rtn) after having removed the roof rack, maybe it'll affect at least the economy a little... dunno, I'll keep you posted.

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btw changed the diesel filter & no change. Gave the inlet system a look for leaks (soapy water at this stage - no pressure test kit yet). No leaks by the look.

[Mark Smith Junior Member Find all posts View Profile Close Mark Smith]

Just another thought. If you are running BIG tyres on a GX model 120, you will have geared the beast up a fair whack compared to the standard 225/65 R17's. In the 95 series RV prados ( which I own) the final drive ratio's are taller than in the GXL's due to the smaller wheel diameter. If the same is true of the 120 series prados ( just guessing here) the taller gearing will cause you to use more fuel as you will have to work the engine a lot harder to get the thing up and rolling.

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Thanks Mark, interesting thought about the RV gearing perhaps relating to the GX and I take that on board re expectations of performance and fuel economy in top gear. However, even in 4th gear she runs like a good leatherwood in it's Tasmanian motherland, so there's no mistaking that it's well down on power. Today I drove from Warburton to Alice, a neat 1000kms, at roughly 100km/h and am down to my last dregs, 10 - 20l (by the gauge which has been fairly accurate so far), so certainly fuel economy is a major issue here as well.

I have to leave Alice on Sunday, so wont get to see a dealer, so will continue to phaph about with various diagnostic checks, guesses and trials for the time being.....

Cheese (& good red wine)
Gordon.