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300tdi lack of power and grunt. Help?


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Hi there,

Yesterday i had to tow a small quad trailer around some country lanes, the total weight of everything on the trailer would have been no more than 650kg. I expected the 300tdi to not even notice pulling that weight, but to tell the truth, it struggled. Hense posting this thread! I was having to drop down into second gear and thrash it, just so it would even slightly pull in 3rd gear.

Then i came to pull the trailer offroad up a slight hill. And i had to use 1st gear low range. Which despite low range probs being the best thing, really indicated to me how down on power it was.

There is not a chance it would successfully pull a heavy farm trailer!

The power loss has come to my attention recently, and i thought the lift pump was suspect (another post), but ive checked the outlet pipe to the filter housing and diesel is present.

Its got all new filters on 500 miles ago and a service.

I dont think there any intake leaks as it stalled when sealing up the snorkel head.

The turbo can be heard spooling up or sucking. (Safari snorkel). Its fairly significant sound

It doesnt smoke much at all, theres a big puff of black smoke on start up, and thats it really. Ive been told by someone behind that it never smokes. All though in headlights ive noticed smoke when accelerating hard. But not bad!

No brakes are binding

Any help would be greatly appreciated. Thanks

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I would definitely be checking the turbo - when my 300tdi lost power it was a buggered turbo. If the hoses are all good, check for any excessive play in the turbine wheel. Other wise you may have to adjust the wastegate. If you don't have one, may be worth fitting a boost gauge so you can see exactly what the turbo is doing. Not sure on the cost in the UK, but I picked one up here in Oz for about $80, took all of 10 mins to install it.

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The hose between air cleaner and turbo can look fine, but try running the engine with this hose disconnected from the turbo, or better still, totally removed. If the engine gives normal power then the hose is the problem. When reconnecting, don't forget to connect the line from the rocker cover breather. If you do forget, you'll end up with a very messy engine bay.

Mike

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If you had a lack of air but full fuel delivery, yo'd have plenty of black smoke on full throttle. The lack of any smoke at all suggests the opposite - good air delivery but poor fuel metering. The boost diaphragm is a good suspect, as Mav said - I have just had exactly this on my 200 and a 1-2mm split resulted in no fuel response to turbo pressure. It drove smoothly and reliably, but down on performance and with no smoke at all, even at full load. I have to fit the new diaphragm (£20 from DieselBob Tuning, incl post), but the temporary Tiger Seal repair on the damaged diaphragm is holding after two weeks, so as a short temporary measure you can do that id the split is small.

I also had a very similar issue with my 300 RRC before I took it off the road. It was the horizontal pin that the cone on the bottom of the diaphragm plunger acts on - these sometimes dry out and stick in the pump case. To free it off, remove the throttle quadrants and the circular plug in the front face of the tower just behind the quadrants, and open the top cover of the tower, note the position of the spot on the diaphragm's silver disc, and remove the plunger and diaphragm complete (can be difficult if the plunger is seized in position against the plunger's cone), then use a soft drift and a very light tool like a toffee hammer to tap the pin free. Lubricate with grease and reassemble, reinserting the plunger and diaphragm in the original positions (if you have disturbed the disc relative to the plunger or forget its position, then the cone at the bottom usually has a witness mark from running on that pin).

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  • 2 months later...

Hi All

Im back again with the same problem. Ive tried a few things now. Firstly i replaced the lift pump with a delphi pump, checked intercooler hoses and checked boost diaphragm. I have no induction leaks at all. Intercooler pipes look fine (inside/out), and the diaphragm was free of splits.

I passengered in a friends 300tdi earlier this week, and i couldnt beleive the torque and low range power the 300tdi has. Which mine doesnt!

Before the turbo boosts up, there doesn't seem much power/torque to me. I have to thrash the engine to get any power out of it, which is on boost. It doesnt smoke at all either.

When the engine is cold, its considerably worse, its really down on power.

Ive turned the torx screw ontop of the fuel pump 1 and half turns, and its slightly better. Debatable i suppose.

Can anyone help please? 300tdi 1995 131000miles

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