SERIOUS Overfuelling on boost

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philhoward

SERIOUS Overfuelling on boost

Post by philhoward »

Back to the Xantia, whilst its having a rest from the daily commute..
There can't be anything drastically wrong with it if it's returning 47-48mpg on the daily commute, but I daren't take it over 3000rpm with my foot more than a 1/4 way down, otherwise I do actually cause a total eclipse.
Tried injector cleaners, "Italian Decoke", checked all the turbo and I/C hoses for leaks, and nothing. Weak spring under the boost diaphragm? All the screws seem to have yellow paint on them on the pump (should they be yellow?) Or is it just a need to turn the max fuelling down?
Air filter is spotless, by the way (only 5000 miles on it)
Any ideas, chaps?
Richard Gallagher
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Post by Richard Gallagher »

The yellow paint is normal and should be taken as a good sign if it original, because it means the pump has not been 'messed' with.
If I remember correctly, you can remove the top of the pump to check the diaphragm without changing the settings by removing the four screws, but be careful of the large spring underneath.
Just a thought for you, I had a 94 TD VSX which did this, I checked everything, even swopped the pump the list went on and on but in the end it turned out to be the air filter intake pipe, the one underneath the air filter made out of a canvas type of material.
This had disintegrated which resulted in hot air being drawn into the engine from the radiator rather than the cold outside air. The car also lost power, basically the car was now being 'overfuelled' due to the intercooler now being less effective.
Worth a look and free to check!
philhoward

Post by philhoward »

I shall...Cheers Richard! I've got some Hi-temp brake ducting about the same size to swap if it's failing...
Could hold true as it isn't as bad when cold (-ish - would I dare thrash a cold engine?!?!)
bad driver
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Post by bad driver »

What fuel pump is it, the lucas or bosch?? Very straight forward to tweak the settings on either, but if they havent been done before its unlikely this is the problem. Whip the I/C off and check for oil in the I/C or inlet manifold, maybe too much oil in the sump and its coming up through breather, or another possibility is worn oil seals on the turbo itself. I had my 306 literally turning black every 8 miles and the car is white!! turned out to be too much oil.
philhoward

Post by philhoward »

It's the Bosch pump...There's turning the car black (it already is) and turning the sky black...mines the latter! It's very dark grey smoke, and a little clumpy if anything
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Post by RichardW »

Phil,
Assuming it is diesel smoke and not oil smoke (which would be white for failed exhaust side turbo seals, and blue for inlet side) - there are only a few causes.
1. Not enough air. Check the hoses as described, then try running the car (for a short time!) with the air filter out to see if there's any effect.
2. Fuelling - OK so there are several facets to this one! You are basically getting more diesel than you can burn, or diesel in a form than doesn't burn easily. So, assuming you have plenty of air (see 1!) the fault lies either with the pump or the injectors. Poor injector spray pattern can cause excessive smoke, as the diesel is not finely atomised. Poor injector shut off can cause problems with injecting too much fuel. Faulty pump timing can cause all sorts of odd symptoms.
So, where to go now? Um, your local diesel injection specialist? I would check the air side, then maybe 'whip' the timing covers off and check that the sprockets are all in the correct position (note this is NOT the same as ensuring the timing is spot on!). Then bung in some good injector cleaner - Miller's Diesel Clean of the Forte one is recommended I think. If these check out and no improvement, you have really exhausted the realms of DIY, and you need to take it to a diesel specialist, and explain the symptoms. I would expect them to go for the injectors first (I think your MPG is pointing towards blocked injectors, as mine never betters 42 MPG even if I only tickle the loud pedal - and that's a 'light' LX! - unless your calculation is off - how many miles do you get to the tank? I fill at about 500 miles when the light comes on, and that takes around 56 - 57 litres which is 39.8 MPG upwards). It's very unlikely the Bosch pump is at fault (unless it's been messed with), but if the injectors are OK (unlikely!) then checking the timing (properly with a Dial Gauge, not just by the sprocket position) will be first.
philhoward

Post by philhoward »

The 47-48mpg has been over 8 or 9 tankfuls (didn't get to the red light, but filled up somewhere around the 500-550 mile mark), only ever at 2 petrol stations and filling to the "click". Sounds like injectors, then...
Oops...just had a better look at the air filter and it's rather dark when you actually open the "fans"...we'll try a new filter first! [:I]
philhoward

Post by philhoward »

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Richard Gallagher</i>

Just a thought for you, I had a 94 TD VSX which did this, I checked everything, even swopped the pump the list went on and on but in the end it turned out to be the air filter intake pipe, the one underneath the air filter made out of a canvas type of material.
This had disintegrated which resulted in hot air being drawn into the engine from the radiator rather than the cold outside air. The car also lost power, basically the car was now being 'overfuelled' due to the intercooler now being less effective.
Worth a look and free to check!
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Checked the canvas pipe, and it's still very much intact...one to cross off the list [:(]
philhoward

Post by philhoward »

OK...new air filter (had a spare one for the BX - same) and a damn good thrashing...it's a heck of a lot better, but that may be down to the water temp going over 80 for the first time since I had it and the oil hitting 90 degrees!!
Still think it would benefit from some decent injector cleaner! Any harm in adding it in a higher dosage that stated for that "serious cleaning power" effect, or is it likely to do more harm than good?
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Post by blueboy2001 »

My Xantia was a bit smokey when I first got it. I got 2L of STP Diesel Fuel Treatment and Injector Cleaner, and put 1L in with less than a quarter of a tank of diesel. It made no end of difference - the smoke went, it pulled better through the gears and idled a lot better. Stated dose is 250ml in 50L of diesel, after the inital big dose I stuck roughly to that and it made the car run a lot better, in particular it was easier to start.
philhoward

Post by philhoward »

I have no starting problems (apart from an air leak on the fuel inlet side - different story), but will try a high strength cleaner dose to see what happens...I shall report back!
paranoid
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Post by paranoid »

Sounds like mine when I got it, 2 oil changes 3000 miles apart injector cleaner in full tank twice, And thrash the living daylights out of it for at least a mile, it was like a different car afterwards, As I only do a small mileage I have to do this a few times a year, Its not easy for a mechanicly sypathetic person like me to keep it on the governer though!!!!!!![V]
philhoward

Post by philhoward »

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by paranoid</i>

Its not easy for a mechanicly sypathetic person like me to keep it on the governer though!!!!!!![V]
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
Keep it on the governer? I had to wince to take it to 4000rpm! [:0]
DaveC
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Post by DaveC »

The XUD9 and a Bosch pump can take some thrashing.
I rev mine happily upto 4000rpm. The only problem is above 4000rpm, when the water temp seems to shoot up dramatically...
Just be aware that when you, or if you do pop the top of the fuel pump off using the four screws, the diagphram is attached to a rod, and the conical end is offset to the centre of the rod. Twisting that rod by 90 degrees is like turning the max fuel screw about 1 turn, so it makes it black smoke LOTS...
To make sure that is right, there is a groove run into the conical end of the rod attached to the diagphram. This groove must point towards the cam belt side of the engine, ie, looking from the front of the car into the engine bay, the groove must point straight to the left.
Adjusting this and the top screw is a good way to alter the fuelling if it's done right, but also a good way to end up with what you have (I did it to mine to see what it did and mine smoked hugely on boost)... Still, your economy seems really good... I only managed 38mpg out of my last tank. Weird...
Seya
Dave
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