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Dirt / Blockage in fuel system

  • 04-07-2009 8:21pm
    #1
    aido 1976
    Registered Users Posts: 341 ✭✭


    How do you know if there dirt or a blockage in the fuel system of a diesel engine,

    Thanks /


Comments

  • #2
    Slidey
    Closed Accounts Posts: 12,811 ✭✭✭✭Slidey


    Well there is a couple of different ways to find out.

    Is the vehicle down on power or what?

    The 2 most common options are to either

    *Run a pipe back to the tank straight from the filter.
    *Take off the pipe and blow down it back into the tank. This should blow and debris out of the line/tank gauze.

    More details would be a help to be honest


  • #3
    aido 1976
    Registered Users Posts: 341 ✭✭aido 1976


    Thanks for the reply Slidey.
    Some more details.

    I have being having trouble with my 2006 VW Passat 1.9TDI, occasionally cutting out and then being a right pig to re-start. It makes no difference if the engine is hot or cold. The engine just shuts down without any warning, no warning light show up on the dash. The only way I can tell when it happens is no longer hearing the engine and the rev counter drops to zero.
    Have had it to a mechanic who hooked it up to the computer and can find no faults and wants to start replacing parts, that he is not sure really need replacing or not. I don't believe throwing money at the problem is going to resolve the issue.

    Mentioned it to the father (who has driven diesels for as long as I can remember) instantly said it is most likley dirt in the diesel/fuel system. Rang a mechanic mate who also suggests a blockage / starvation in the fuel system, possibly dirt, but cant look at it until next week.

    Are these the type of symptoms that can be expected with dirt in the fuel system, and if so would getting a bottle of fuel cleaning additive from the local motor factors fix the problem. And if it is another problem would using the additive if not needed create more problems.

    At this stage I feel like putting a fcuking match to the dam car.

    Thanks for your help.


  • #4
    Slidey
    Closed Accounts Posts: 12,811 ✭✭✭✭Slidey


    In an 06 car dirt is unlikely unless you have been filling from 5 gallon drums?? ;)

    I am going to assume that you have replaced the fuel filter?
    It could be a lot of things but power supply to the pump in the tank would need to be checked. Because it is an intermittent problem it is going to be hard to find.

    It could also be something on the engine side like rail pressure control..


  • #5
    slimjimmc
    Registered Users Posts: 7,787 ✭✭✭slimjimmc


    aido 1976 wrote: »
    The engine just shuts down without any warning, no warning light show up on the dash. The only way I can tell when it happens is no longer hearing the engine and the rev counter drops to zero.

    This bit would make me think it's not a fuelling problem but an electrical one. Fuel loss would not affect the instrument panel. Lights should still come on when engine stops.


  • #6
    aido 1976
    Registered Users Posts: 341 ✭✭aido 1976


    Slidey wrote: »
    In an 06 car dirt is unlikely unless you have been filling from 5 gallon drums?? ;)

    I am going to assume that you have replaced the fuel filter?
    It could be a lot of things but power supply to the pump in the tank would need to be checked. Because it is an intermittent problem it is going to be hard to find.

    It could also be something on the engine side like rail pressure control..

    The fuel filter was replaced a couple of weeks ago, and checked by the mechanic with the computer gear, he actually was the one who replaced it. What is a rail pressure control.
    slimjimmc wrote: »
    This bit would make me think it's not a fuelling problem but an electrical one. Fuel loss would not affect the instrument panel. Lights should still come on when engine stops.

    The mechanic checked the all of the electric system on the computers and said he got no fault readings. I get no change in the instrument panel, as if the electrical system still thinks the engine is running only thing that happens is the rev counter drops to zero.


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  • #7
    Slidey
    Closed Accounts Posts: 12,811 ✭✭✭✭Slidey


    Well something you could do is check the fuel filter the next time it knocks off.

    If it is something to do with the pump in the tank the fuel level should have dropped in the filter.

    I am not too sure of the VW common rail system but most of the systems I know have rail pressure monitoring valve that regulates fuel pressure. If that is faulty it may be causing problems. A faulty pressure sensor in the rail could also be sending faulty signals to the ECU


  • #8
    aido 1976
    Registered Users Posts: 341 ✭✭aido 1976


    Slidey wrote: »
    Well something you could do is check the fuel filter the next time it knocks off.

    If it is something to do with the pump in the tank the fuel level should have dropped in the filter.

    I am not too sure of the VW common rail system but most of the systems I know have rail pressure monitoring valve that regulates fuel pressure. If that is faulty it may be causing problems. A faulty pressure sensor in the rail could also be sending faulty signals to the ECU


    Think I am better of waiting for my mate to take a look,


  • #9
    Slidey
    Closed Accounts Posts: 12,811 ✭✭✭✭Slidey


    Then I would suggest saving yourself some wasted time and get him to look at it after it cuts out while the symptoms may still be present.

    It is time consuming looking for a problem while it is not present, so next time it cuts out tow it to him or get him to call out to it while it is not running.


  • #10
    slimjimmc
    Registered Users Posts: 7,787 ✭✭✭slimjimmc


    aido 1976 wrote: »
    The mechanic checked the all of the electric system on the computers and said he got no fault readings. I get no change in the instrument panel, as if the electrical system still thinks the engine is running only thing that happens is the rev counter drops to zero.

    I would have thought the ECU would have detected no charge from the alternator and at least show the battery light.

    If you intentionally stall the engine, what lights come on? Do you get the same lights when the engine stalls on it own?


  • #11
    Slidey
    Closed Accounts Posts: 12,811 ✭✭✭✭Slidey


    The wheels will still be turning the engine.

    If he dipped the clutch the charging light will come on.


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  • #12
    slimjimmc
    Registered Users Posts: 7,787 ✭✭✭slimjimmc


    Ok but why does the rev counter drop to zero if the engine is being pushed along?

    Faulty TDC sensor ?


  • #13
    aido 1976
    Registered Users Posts: 341 ✭✭aido 1976


    slimjimmc wrote: »
    I would have thought the ECU would have detected no charge from the alternator and at least show the battery light.

    If you intentionally stall the engine, what lights come on? Do you get the same lights when the engine stalls on it own?

    Just went out there and deliberatly stalled the engine, I get the usual engine, battery lights. When it stalls on it's own I get nothing.


  • #14
    slimjimmc
    Registered Users Posts: 7,787 ✭✭✭slimjimmc


    Sounds like you might have an electronic/electrical problem that kills your engine (unless its in the design of the ECU not to show warning lamps after a fuel-out).
    Sorry I can't be of any more help.


  • #15
    Row
    Registered Users Posts: 2,025 ✭✭✭Row


    I have heard of High pressure pumps giving trouble in the newer passats..:(
    I would say you will need to check the rail pressure in live data with a
    dealer diagnostic tool or from a good diagnostic Garage dia tool and
    compare the rail pressure to the default rail pressure.
    Not sure if the passats have got a in tank lift pump...:confused:
    Could be a difficult one to get to the bottom of...:rolleyes:
    Best of luck with it.


  • #16
    Slidey
    Closed Accounts Posts: 12,811 ✭✭✭✭Slidey


    The Golf has a tank pump.

    When you turn on the ignition you will hear the gurgle as is pressurises the system.

    I would assume the Passat is the same.

    It is strange that the rev drops.. could be the Crank TDC sensor alright. Might be an idea to have a look at this.


  • #17
    beachlife
    Closed Accounts Posts: 246 ✭✭beachlife


    aido 1976 wrote: »
    The fuel filter was replaced a couple of weeks ago, and checked by the mechanic with the computer gear, he actually was the one who replaced it. What is a rail pressure control.



    The mechanic checked the all of the electric system on the computers and said he got no fault readings. I get no change in the instrument panel, as if the electrical system still thinks the engine is running only thing that happens is the rev counter drops to zero.

    make sure there is not an air leak at the fuel filter,are all the "o" rings okay. if there is a slight leak here it will only cut out at idle or when coasting or slowing down.


  • #18
    slimjimmc
    Registered Users Posts: 7,787 ✭✭✭slimjimmc


    Just wondering if a dickey ignition switch or one of its connections could cause these symptoms. ECU might think you've turned the key hence no fault codes and warning lights.


  • #19
    anon11
    Closed Accounts Posts: 131 ✭✭anon11


    or could be the steering column electric control unit, they give trouble on these:)


  • #20
    beachlife
    Closed Accounts Posts: 246 ✭✭beachlife


    When you say it's a right pig to restart does that mean it cranks over for an age with out picking up or that you can't get it to crank? I re-read your OP and now see you said that the dash lights are not on when it happens,I think it is electrical in nature. The most common thing that could cause this is a failing main ing. relay.


  • #21
    Mr.Diagnostic
    Registered Users Posts: 937 ✭✭✭Mr.Diagnostic


    A point that is note worthy in this case is that there is no monitoring of fuel supply so a fault in this will not cause a fault code to be stored.


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  • #22
    beachlife
    Closed Accounts Posts: 246 ✭✭beachlife


    Mr.Diagnostic wrote: »
    A point that is note worthy in this case is that there is no monitoring of fuel supply so a fault in this will not cause a fault code to be stored.

    That's a good point,a simple check could be done.I think in the diagnostic reader you can activate the fuel pump for 30 secs. and the minimum flow rate for this engine is 1000ml for 30 secs delivery


  • #23
    aido 1976
    Registered Users Posts: 341 ✭✭aido 1976


    beachlife wrote: »
    make sure there is not an air leak at the fuel filter,are all the "o" rings okay. if there is a slight leak here it will only cut out at idle or when coasting or slowing down.

    You may have a good point there beachlife, the fuel filter was only replaced a couple of weeks ago, I will point your suggestion out to the mechanic.
    beachlife wrote: »
    When you say it's a right pig to restart does that mean it cranks over for an age with out picking up or that you can't get it to crank? I re-read your OP and now see you said that the dash lights are not on when it happens,I think it is electrical in nature. The most common thing that could cause this is a failing main ing. relay.

    I will also mention this to the mechanic, yes it cranks over for about 30-40 seconds before picking up.
    Mr.Diagnostic wrote: »
    A point that is note worthy in this case is that there is no monitoring of fuel supply so a fault in this will not cause a fault code to be stored.

    Mr.Diagnostic, This would explain why the computer showed no fault reading


  • #24
    R.O.R
    Registered Users Posts: 12,672 ✭✭✭✭R.O.R


    I think there has been a recall for the fuel pump on the 06 1.9Tdi Passat's. We've had a load from here with the pumps replaced under warranty.

    Try speaking to a VW service department. If you give them the chassis number they should be able to check if a recall has been issued and completed or not.

    ***EDIT**
    See thread - details on recall towards the end
    http://www.boards.ie/vbulletin/showthread.php?t=2055376880


  • #25
    martinr5232
    Registered Users Posts: 2,298 ✭✭✭martinr5232


    Sounds very like a low pressure lift pump to me the Citroen Xantias and C5s used to suffer from this problem.

    I thaught there was a thread on this somewhere on Passats.

    Next time it happens turn on the ignition and you should hear the lift pump in the tank working.

    If not the pump is sticking intermitently or there is a wiring fault to the pump.

    Not saying it is but its something to look at.


    Feck ya R.O.R Imay learn to type faster:D


  • #26
    aido 1976
    Registered Users Posts: 341 ✭✭aido 1976


    Thanks to everyone for their suggestions,

    I have to bring the car to my mate this evening, I will let you know what the outcome is...


  • #27
    aido 1976
    Registered Users Posts: 341 ✭✭aido 1976


    beachlife wrote: »
    make sure there is not an air leak at the fuel filter,are all the "o" rings okay. if there is a slight leak here it will only cut out at idle or when coasting or slowing down.

    Spot on beachlife,

    The mate took a look at the passat last tuesday (wanted to make sure before getting back) and the "o" ring was fitted wrong on the fuel filter, and obviously he corrected it.
    I will be having a word with the guy who serviced the car, when I get a chance to call into him........
    After all his computer checking of the electrics etc;
    My mate was spot on with the car being starved of fuel and had the problem sorted in a few minutes.

    Thanks all for your suggestions and help.
    I hope this is the end of the problems with this car !!!


  • #28
    Slidey
    Closed Accounts Posts: 12,811 ✭✭✭✭Slidey


    Thanks for the update. It is nice to read the solutions as well as the problems.


  • #29
    Mr.Diagnostic
    Registered Users Posts: 937 ✭✭✭Mr.Diagnostic


    Good to hear its fixed.

    I think this is a perfect example of the true meaning of diagnostics. If the man holding the scan tool had known there was no fuel supply pressure monitoring he would not have discounted it as a possibility when he was looking at it.
    Aside from a scan tool, knowledge and information are required. If even one is lacking it leads to inefficient diagnostics.


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