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SDi Stuttering/Stalling


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I've started to get a bit of a weird problem with my SDi that I can't get to the bottom of.

Basically, when being a bit generous with the accelerator pedal the car will attempt to stall. There's a bit of a bang and the car lurches forwards before picking up again and acting like nothing happened.

Also, at times when starting the car whilst warm (after waiting for the glow plug light to go off), it will cut out instantly. This feels very similar to when starting the car with a key that hasn't been programmed to the ECU.

The issues only started after changing the fuel filter but not purging the air from the system, however I have now done this so shouldn't be an issue.

No fault codes are logged on the ECU when either problem occurs. Everything seems to point towards fuel starvation but there isn't a massive amount of air in the lines, maybe a small flurry of air when revving to approx 3k RPM. The stalling on start also makes me think the immobiliser may be at fault.

I have a bottle of injector cleaner which I'm going to chuck into the tank and see what happens.

Anyone else had a similar issue?

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How did you purge the air? If the car is stalling on acceleration then simply put, the fuel isn't getting to the engine. So either there's air getting into the lines or you have a fuel strainer issue. I've tackled both and they're not big issues to overcome.

If it happened after changing the fuel filter, my first port of call would be the thermostatic valve. There's two rubber o-rings which you're supposed to replace every fuel filter change.

Me? I put a film of lithium grease with the tip of my finger round the rings and seemingly got away with it.

If that doesn't work (which it quite possibly won't), replace them. They're about 30p a pair with free delivery from CarParts4Less. Make sure you remember the order as the blue one is slightly different to the black one and they have to be on the right way round.

If that doesn't work, I'd replace the valve. Cheap enough part and they do wear out. 

If that doesn't work come back and we'll talk about the fuel strainer.

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1 minute ago, Skezza said:

How did you purge the air? If the car is stalling on acceleration then simply put, the fuel isn't getting to the engine. So either there's air getting into the lines or you have a fuel strainer issue. I've tackled both and they're not big issues to overcome.

If it happened after changing the fuel filter, my first port of call would be the thermostatic valve. There's two rubber o-rings which you're supposed to replace every fuel filter change.

Me? I put a film of lithium grease with the tip of my finger round the rings and seemingly got away with it.

If that doesn't work (which it quite possibly won't), replace them. They're about 30p a pair with free delivery from CarParts4Less. Make sure you remember the order as the blue one is slightly different to the black one and they have to be on the right way round.

If that doesn't work, I'd replace the valve. Cheap enough part and they do wear out. 

If that doesn't work come back and we'll talk about the fuel strainer.

Purged the air by removing the rubber cap on the end of the fuel rail and letting the car tick over with the fuel going into an empty bottle. Is that the correct way?

Thermostatic valve seems to be logical as the stalling on start issue only happens when warm, it starts first time every time when cold. I have a pair of o-rings that were given by a friend. The filter I bought from GSF didn't come with any unfortunately. Will try that next, do you know which order they go in as I seem to remember both of the originals being black when I looked at fitting them last time. 

Have discussed the fuel strainer already and it is a possibility as it does tend to happen when the tank has been run to near-empty.

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13 hours ago, DeanH said:

O-rings and or injector cleaner seems to have fixed it for now.

Just a wheel bearing to sort next, that's not going to be fun...

Maybe a bit of both, although to me injector cleaner is a bit snake oil'y, if you really want to clean your injectors properly, you should order some diesel purge ;) 

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  • 2 weeks later...
16 hours ago, DeanH said:

So, it's been much better since swapping the o-rings, but today the stutter came back. Just once, going uphill, approx 40mph in either 3rd or 4th gear. Ideas?

You changed the fuel filter? Did you run any additives?

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2 hours ago, JoeyEunos said:

Worth asking as well, when you did change the fuel filter last time round did you prime it, ie using a small funnel and topping up the filter with fresh diesel until no more air bubbles were coming up and the filter was completely full of fuel?

Joey, this isn't really necessary. If you prime the filter by removing the bleed valve that's enough. Something else is wrong here.

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31 minutes ago, Skezza said:

Joey, this isn't really necessary. If you prime the filter by removing the bleed valve that's enough. Something else is wrong here.

Conscious of that, none the less I followed that process purely as a 'belt and braces' exercise and all went well. Interestingly, I didn't use the bleed valve at all when doing mine -_-

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The filter was changed just before the stuttering started, I have only changed the o-rings since.

I ran a bottle of redex through it but I doubt that made much of a difference.

Hasn't done it again today, will keep an eye on it.

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1 minute ago, DeanH said:

The filter was changed just before the stuttering started, I have only changed the o-rings since.

I ran a bottle of redex through it but I doubt that made much of a difference.

Hasn't done it again today, will keep an eye on it.

The next thing I would be looking at is the fuel strainer.

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Look at the fuel return pipes on the injectors and if they are weeping or looking tired replace them as air gets in there if they arent up to snuff. If i had suspicions of air in the fuel then i'd also change the fuel lines from the filter to the pump for clear reinforced pvc so any air is visible.

If you have air in the fuel and nothing obvious as to where it is coming in then it is worth looking at the fuel strainer on the pickup in the tank. I had a mk1 Golf diesel with a blocked strainer in the tank many moons ago (oh the memories).

If this started after a filter change then double check all the pipes etc disturbed during that procedure, also make sure the pipes are on the right inlet / outlets.

Edited by Sausage
splelling
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Did it again today, had a quick look around and there's no evidence of weeping fuel lines.

One thing I did by accident when I changed the filter is crack open the banjo fitting on the side of the fuel pump. Did this by accident before I realised where the bleed nipple was! Could that have caused me some problems? 

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UPDATE: Swapped the fuel return valve on the fuel filter last weekend, problem went away until today. Any advice on what to try next?

 

Could it be the EGR valve? Tried to remove it and clean last weekend but struggled to remove the top bolt (the stud with the dipstick attached), anyone know how to get it out?

Edited by DeanH
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Is the fuel strainer the plastic mesh bit in the bottom of the fuel sender?

Opened that up, there was some brown dirt in the bottom so I've cleaned it out and given it a blast of carb cleaner before refitting.

Will see how it goes.

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Still happening but doesnt feel quite the same. Feels a bit less violent i suppose.

Anything else to check?

EDIT: Turned the car on after typing that. On came the engine management light. Rescanned this afternoon and have the following fault codes:

http://wiki.ross-tech.com/wiki/index.php/17978/P1570/005488

and

http://wiki.ross-tech.com/wiki/index.php/17654/P1246/004678

Still nonethewiser. 

 

 

Edited by DeanH
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Just been thinking about your symptoms...

The needle lift sensor works like a microphone and listens to the beginning and end points of the high pressure injector pulse, delivered by the injection pump.

At the beginning of the pressure stroke (when the diesel pump begins to push diesel down the injector pipe, a bit like a bicycle pump), the sensor will notice the start of the stroke, when the pin inside the injector begins to move. While the injector is open, the pin remains up while fuel is flowing through the injector nozzle.

As soon as the injection pump has completed its fuel stroke, the pressure in the injector drops, closing the nozzle which allows the pin to drop to its rest position again. The pin moving back to its rest position generates another reverse pulse which indicates the end of the fuel pulse to the ECU.

I dont get what use this is, since as far as i know there is no way to alter the injection timing on the SDI mechanical injection pump. I guess it is nothing more than an engine monitor to let the ECU know that everything is fine.

If you get air bubbles or cavitation in the pump, then it is possible to get unusual readings as the fuel flow will be erratic. So, I think the problem is either upstream of the injector, air in system or cavitation, OR the wiring from the sensor to the ECU is iffy. The injector with that sensor built-in is pretty tough and unlikely to fail. The sensor is no more than a tiny coil of wire which you can measure with an ohm meter.

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I have bought a multimeter to test the resistance when cold. Read it should be 80-120ohms, is that true?

If that all checks out okay I think my next port of call is all the fuel lines. I'd like to do it all clear so I can see where any air is getting in in the future. Could anyone give me some pointers as to what to use? I don't want my car going up in flames...

 

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