Injectors and max fuel screw

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Xantiargh
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Joined: 26 Feb 2003, 16:09
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Injectors and max fuel screw

Post by Xantiargh »

Hi all
Xantia 1.9TD LX 1995 M.
Recently posted to get identification of an adjustment on my Bosch pump that the previous owners had made.
Apparently its the max fuel adjustment screw and has been turned 1/4 turn clockwise, reducing fuelling.
The post also mentioned this might be done to disguise poor injectors.
Could that be the case, and would the symptoms of poor injectors be white smoke and stuttering on cold start?
I changed filters, glow plugs, found air leaks in the fuel lines and still can't shake the cold start problem. Wondering if it could be the injectors.
What sort of mileage should they do before needing a recon (assuming the car is unloved)?
Mike
jeremy
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Post by jeremy »

Yes its common to turn down the maximum fuelling to disguise injector problems. The aim is to prevent copious quantities of black smoke being emmitted on full throttle (which tends to be the mode diesels accelerate in.)
I had bad injectors on my TD BX and not having driven it with good ones had nothing to compare it with. Aparently when it was started up in the MOT testing station it fumed very badly at idle and they didn't go any further as something was obviously wrong.
By this time it was starting quite well if a bit lumpily but there was no discernable fast idle (despite having replaced the cold start thermostat) and it tended to hunt a bit at idle. It seemed to goOk but as I say I had nothing to compare it with. It always needed heat to start when hot and could be a bit reluctant when cold and did tend to produce white smoke.
I had the injectors cleaned by a diesel specialist who charged me £100 for doing the job. The results were amazing, instant starting, smooth acceleration, nice discernable fast idle, no smoke . . . - all amazing on an engine that had done 175,000 miles. (the head gasket gave up the unequal struggle afetr 18 miles but that's another story.)
Some people claim good results for cleaners, either as recommended or in overdose. What I would say is that they are not free and a cocktail of the more exotic ones could easily add up to 30 percent of the cost of getting them cleaned or replaced.
jeremy
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Post by RichardW »

Mike,
If it's done more than about 100k, it might benefit from having its injectors overhauled. Poor injection certainly could cause poor starting. Try using a diesel additive such as Millers to see if that helps. A new set of injectors is around £120 from GSF. Not sure how much your local diesel specialist would charge to overhaul them.
However, have you tried giving it a longer glowing period - try at least an extra 4 seconds after the glow light goes out, this seems to help on older diesels. Is the cold start device functioning correctly? It consists of a wax stat in the thermostat housing with a cable running to the back of the Bosch injection pump. It should be taut when the engine is cold pulling the cold start lever on the back of the pump to the LH (Flywheel) end of the engine. When warm it should go slack letting the lever move to the RH (cam belt) end of the engine. Idle should drop from 1000 rpm cold to about 850 rpm hot. Have you checked the valve clearances? This has been mooted as a cause of poor starting a few times, and often seems overlooked as it is a pain to reset them!
Xantiargh
Posts: 35
Joined: 26 Feb 2003, 16:09
Location: United Kingdom
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Post by Xantiargh »

I do run Redex through when I fill up, and have done 10,000 miles with no perceptible improvement.
Have tried increasing glow period, glowing twice, etc. no avail. Waxstat works, but similar to Jeremy it seems to struggle to raise the revs.
The car always starts so I've never been too worried, but it gets a bit embarassing when Auntie has to stop waving goodbye and flee indoors to escape the cloud of fumes the car belches on cold start!
Do I need to take the injectors out myself, or will these places do that themselves? They seem fairly straight forward to get at.
As for valve clearances, I'd have to leave that to an expert as well!
jeremy
Posts: 3959
Joined: 20 Oct 2002, 16:00
Location: Hampshire, UK
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Post by jeremy »

The specialists did the whole job for me - including leaving the turbo /intercooler pipe loose so that it fell off when I accelerated up hill.
Injectors are easy enough to get. What I'm not sure of is what washers etc come with them and should be replaced.
Why not contact a specialist and see how much he will charge?
jeremy
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