Diesel injectors. Dilemma

Diesel injectors. Dilemma

Author
Discussion

fergus

Original Poster:

6,430 posts

282 months

Friday 22nd April 2005
quotequote all
Hi.

Wondering if someone could help me. On my shopping car (1.9 NA diesel clio), I occasionally have some hesitancy at light throttle openings, which is then followed by a jerk forwards in the car. If it was a petrol engine, I'd imagine it was fuel starvation or problems with the accelerator pump in the carb. However, I think one (or more) of my injectors is knackered. Questions is, do I clean/recondition them, or buy new ones from GSF at £35/injector. Spoke to renault garage yesterday and 3 injectors are 'normal', but one has a wire coming from it and is almost 3 times the price of the standard unit. Anyone got any idea what the wire could be there for? To the best of my knowledge, the injectors are all mechanically driven from a central fuel pump (and operate at standard (i.e. low ~ 200 bar) pressure).

Any help would be appreciated. Of course, I could just need the fuel system bleeding!?

Alpineandy

1,395 posts

250 months

Friday 22nd April 2005
quotequote all
Have you tried using an 'in fuel' injector cleaner?
It may save you a few quid...

or maybe not...

fergus

Original Poster:

6,430 posts

282 months

Friday 22nd April 2005
quotequote all
I've tried two 'redex' type injectors cleaners, and also put several half gallons of petrol in the tank so far - it does the same as lots of the more expensive 'cleaners'. Injectors are still sticking!

nighthawk

1,757 posts

251 months

Friday 22nd April 2005
quotequote all
The wire leads to a sensor within the injector body, it's quite important too as it determines the timing from that cylinder and applies the figure to the rest of the cylinders.

www.feather-diesel.co.uk might beable to give more advice or a cost of them being reconditioned

Annodomini2

6,914 posts

258 months

Friday 22nd April 2005
quotequote all
Its the knock sensor isn't it?

nighthawk

1,757 posts

251 months

Friday 22nd April 2005
quotequote all
No, Knock sensors are fitted to the engine block between cylinders, that is to say, between 1+2 and 3+4.

The sensor in the injector looks at the start of needle lift and the total lift, by using that data with that of the other sensors, the management system can work out the exact point of injection and the amount being delivered.

Zad

12,762 posts

243 months

Friday 22nd April 2005
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A knock sensor on a diesel? I thought that was pretty much the point of a diesel, to detonate.

nighthawk

1,757 posts

251 months

Saturday 23rd April 2005
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modern TDCi/common rails etc use knock sensors in much the same way as petrol engines do.

Instead of the pump line pressure injecting once into the firing cylinder they use multiple injections at the point of optimum effeicency. most of these systems open the injector 8 times per firing cycle at the moment, with both bosch and delphi systems being able to step up to 16 pulses per firing cycle. Thats fecking quick operation. only the very high pressure fuel and modern electronics make this possible, giving modern deisels high power and low emissions and more importantly low noise!

MattYorke

3,886 posts

260 months

Tuesday 26th April 2005
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35 quid for an injector - I wish.
Just had to pay 150+vat for genuine ones for my nissan patrol, can't find any aftermarket ones.

nighthawk

1,757 posts

251 months

Tuesday 26th April 2005
quotequote all
Think your self lucky that they were only 150 each, some of the modern injectors are around double that now.

Bills for a couple of K's for a repair after someones run them on petrol are not uncommon.