Technical Fiat stilo 1.9 jtd can start only with spay

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Technical Fiat stilo 1.9 jtd can start only with spay

chris3234

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If it is smooth at higher revs, it can still be low compression, years ago I had a Ford V6 that I hammered down the motorway and the next day it wouldn't tickover, I had broken the compression rings on two cylinders. It turned out the engine had not been driven hard before and there was a wear ridge on the top of the cylinder bore where the pistons usually stopped before going back down, my higher revving made the pistons go a fraction higher causing the piston rings to touch the ridge. In those days I was able to borrow a "ridge cutter" to grind away the ridge. It was also possible to buy ridge dodger piston rings that had a step to miss the ridge. Nowadays the proper course would be a rebore and a set of new pistons.
You may be able to detect a weak compression the way I suggested. Another sign of low compression on a diesel is poor starting from cold accompanied with white smoke, although usually once running for a bit they tickover OK.
If you have tried everything else a proper compression test would eliminate that.
Erm what?


The travel of the position is set by the length of the rods and Pistons

It should have no difference on if it's at 50 rpm or 2000 how could the piston travel any further up the bore at higher rpm
 

bugsymike

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Erm what?


The travel of the position is set by the length of the rods and Pistons

It should have no difference on if it's at 50 rpm or 2000 how could the piston travel any further up the bore at higher rpm
If that was the case why were ridge dodging piston rings invented, I take it you haven't heard of wear. Have you never felt a wear ridge down the bore when stripping down a worn engine? I have rebuilt many 100s of engines over 50 years in the motortrade. A few thousands of an inch of wear in big end shells and piston gudgeon pin bushes is all it takes.
 
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Ever watched the rear tyres on Drag Race cars appear to double in circumference as they 'burnout'..?

Thats inertia

Consider the metres per second difference between a cruising 2500 rpm and a really shifting 7,000 on a piston crown

(One of our LeMans 'motors' had calculated forces in multiples of a tonne) :)

Image a human cannonball..with a rope around his ankles.. I would anticipate some 'flexing' !! As that motion was arrested :cool:
 
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Back to a poor starting JTD:

 

bugsymike

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Ever watched the rear tyres on Drag Race cars appear to double in circumference as they 'burnout'..?

Thats inertia

Consider the metres per second difference between a cruising 2500 rpm and a really shifting 7,000 on a piston crown

(One of our LeMans 'motors' had calculated forces in multiples of a tonne) :)

Image a human cannonball..with a rope around his ankles.. I would anticipate some 'flexing' !! As that motion was arrested :cool:
Not being very PC can I imagine a big lady on a trampoline;)
 
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stilo192

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If it is smooth at higher revs, it can still be low compression, years ago I had a Ford V6 that I hammered down the motorway and the next day it wouldn't tickover, I had broken the compression rings on two cylinders. It turned out the engine had not been driven hard before and there was a wear ridge on the top of the cylinder bore where the pistons usually stopped before going back down, my higher revving made the pistons go a fraction higher causing the piston rings to touch the ridge. In those days I was able to borrow a "ridge cutter" to grind away the ridge. It was also possible to buy ridge dodger piston rings that had a step to miss the ridge. Nowadays the proper course would be a rebore and a set of new pistons.
You may be able to detect a weak compression the way I suggested. Another sign of low compression on a diesel is poor starting from cold accompanied with white smoke, although usually once running for a bit they tickover OK.
If you have tried everything else a proper compression test would eliminate that.
Hello bugsymike,
Before this problems appear i did not drive hard (usually i drive quietly), in the highway last trip was about 300 km and drove at 80-90 kmh at around 2000-2200 rpm, car running really quietky and smothly and low fuel consumption too 4.8- 5 L ,in the city no hard acceleration too.
Is there any option that the fuel pressure might be fault too?
 

Ralf S.

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Hello bugsymike,
With the spray it fires directly and and the rev seems fine regular above 2000 rmp.
If it falls down 2000 rpm it looks hard to rev and in couple of sec the engine dies.
Today i could not make the test you suggested as i spent some times with the fuel filter and the other tests.I will make a try on monday for what you suggested.

After it starts (using the spray) does it run without spray? If it only runs with spray then the next thing to look at is the crank/TCD sensor, since that would imply there's nothing telling the injectors to fire.

If it runs without spray then the crank sensor is likely okay, otherwise the injectors would not be firing.

You can verify whether the injectors are firing by connecting one of them up to a voltmeter (one of the glass-bottomed bulbs with the wire tangs, will fit into the injector plug too). If you have volts or a "flash" when the engine is turning (whether it starts or not) then the injector is doing its thing and the TDC sensor must also be okay.

Check whether the injectors "fire" when the car is just cranking. I don't know what that would mean.. but I'm curious if they fire at 2000 rpm but not when trying to start.

If you have injection at the right time/a good crank sensor then I would look at whether the pump is giving you enough pressure. It doesn't sound like you have enough fuel going in..

I'm not surprised about the filter.. my old one I forgot managed 60,000kms without problems and no hint of dirt or water in it... but we had to check.



Ralf S.
 
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