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  1. #1
    michaelc291's Avatar
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    4.0l XJ starting problem

    Something has changed. I have two 4lit XJs and until recently they both started with the first flick of the key, winter or summer.
    Now one of them, the 1994 one, needs a lot more cranking than it used to, but it always starts. I have checked the usual things like plugs and distributor cap which seem OK. The check enging light is not on.
    Can anyone suggest what might be the cause and what else to look at.
    At the moment it is very hot with temps up to 35C (95F) but this has not been a problem before.
    Thanks in advance for your help.
    Mike

  2. #2
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    Re: 4.0l XJ starting problem

    Check timing. Check plugs and wires.

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    4.0l XJ starting problem

    Try this. Turn the key to the ON position but do not start. Wait 5 sec then turn the key off. Immediately turn the Key back on for 5 seconds then try to start. If the engine starts first time easily the cause is the check valve. The check valve is to keep the fuel from draining back into the tank. This is a common failure and could be lived with for some time without causing damage or fault. This valve is in the fuel pump and the pump would need to be changed to correct.


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    Re: 4.0l XJ starting problem

    I have done the check and there definitely seems to be a loss of pressure as it fires up quickly when doing the key thing. I will be borrowing a pressure gauge from a friend this week.
    What I need to know is how to pinpoint the leak as there seem to be two possible places. One is the pump check valve and the other a leaking injector.
    I can pinch off the return pipe after the regulator to check the pump non return valve but how do you find out if an injector is dripping?

    If the pump check valve is leaking I propose to put an in-line check valve near the fuel filter rather than rip the tank unit out. Past experience with these things (on my 1986 Range Rover) resulted in having to replace the tank!! The cause being that in the UK we use a lot of salt on the roads in winter and everything was rusted solid.

    Best regards

    Mike

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    4.0l XJ starting problem

    The fact the key trick works is a good sign it is only the check valve.
    If you have an injector that keeps flowing with engine off the engine will not start until all the gas is pushed out of that cylinder. A quick check is to start by fully depressing the skinny pedal to the floor when starting. This cuts off the fuel pump and no gas is delivered. You might crank a bit but experience a stumbling start, if it is a injector.

    As mentioned you could do the key trick until you need to replace the pump.

    And I suppose you could add a check valve.

    Regards,
    JPNinPA

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    Last edited by JPNinPA; 08-25-2018 at 03:05 PM.
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    Re: 4.0l XJ starting problem

    Quote Originally Posted by JPNinPA View Post
    The fact the key trick works is a good sign it is only the check valve.
    If you have an injector that keeps flowing with engine off the engine will not start until all the gas is pushed out of that cylinder. A quick check is to start by fully depressing the skinny pedal to the floor when starting. This cuts off the fuel pump and no gas is delivered. You might crank a bit but experience a stumbling start, if it is a injector.

    As mentioned you could do the key trick until you need to replace the pump.

    And I suppose you could add a check valve.

    Regards,
    JPNinPA

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    Thanks for the suggestions so far. Will keep you posted on the pressure checks.

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    Re: 4.0l XJ starting problem

    Quote Originally Posted by JPNinPA View Post
    The fact the key trick works is a good sign it is only the check valve.
    If you have an injector that keeps flowing with engine off the engine will not start until all the gas is pushed out of that cylinder. A quick check is to start by fully depressing the skinny pedal to the floor when starting. This cuts off the fuel pump and no gas is delivered. You might crank a bit but experience a stumbling start, if it is a injector.

    As mentioned you could do the key trick until you need to replace the pump.

    And I suppose you could add a check valve.

    Regards,
    JPNinPA

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    If push comes to shove and I need to replace an injector I think I should go the the 4 hole type. Can you advise which is a good replacement? Can you include Maker, part number etc?
    I have worked on many diesel injectors but never before on petrol (sorry gas) ones.

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    Re: 4.0l XJ starting problem

    Iirc,late 90's dodge neon injectors are what you want.someone correct me if im wrong.

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    Re: 4.0l XJ starting problem

    You could swap. I understand there are no performance gains from the injector alone only a smoother idle.


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    Re: 4.0l XJ starting problem

    Thanks for the latest info.
    I have done a pressure check today and your diagnosis is spot on Thanks.
    On turning the key to run I got 30 psi and on the second go got 37 psi.
    When I turned the key off it lost ALL pressure in about 3 or 4 seconds.
    Running at low idle it settled at 38 psi and 44 psi with the vacuum removed from the regulator.
    With a quick blip of the throttle it hit 40 then dropped to 36.

    I have been to get an in-line check valve to put in near the fuel filter but, this being Spain, they did not have much idea what I was talking about. I have resorted to Ebay, so there will be a delay until I can do anything else.
    I don't think it will be necessary to change any injectors. The info is good should it be needed.
    Best regards
    Mike

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    Re: 4.0l XJ starting problem

    Glad you solved it.


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    Re: 4.0l XJ starting problem

    Hello again,
    It's been a long time since I started this and I have finally managed to put a check valve in the pipe just after the tank. I was hoping that would cure the dramatic loss in fuel pressure when I switch off. Unfortunately nothing has changed, so it wasn't the pump check valve after all.
    My next suspect is the fuel pressure regulator. I have done the checks with and without the vacuum pipe and it's OK, but I cannot think of a way to check whether it's passing fuel back to the tank when I swiitch off. Can anyone recommend how to do this or would it be better just to change it?
    I can find a lot of replacements on Ebay varying in price from 17€ to 60€. They seem to be a pretty common part. Would a 3bar one be OK for the 4litre? What is the diffference between a 17€ one and a 60€ one if they both have a 2 year guarantee.?
    Sometimes the engine starts first flick like it used to and others it needs a bit more cranking but I have got used to it now.
    I hope someone can help.
    Mike

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    4.0l XJ starting problem

    What is your current symptoms?

    Slow starting?
    Does the key trick work after sitting all night?
    Do you need to do this after short stop?
    Rough running?
    Engine sounds like it is about to die at mid or high rpm or load?
    Running rich? Wet sooty plugs
    Running lean? Ashed melted plugs


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    Re: 4.0l XJ starting problem

    Quote Originally Posted by JPNinPA View Post
    What is your current symptoms?

    Slow starting?
    Does the key trick work after sitting all night?
    Do you need to do this after short stop?
    Rough running?
    Engine sounds like it is about to die at mid or high rpm or load?
    Running rich? Wet sooty plugs
    Running lean? Ashed melted plugs


    Sent from my iPhone using Jeepz.com mobile app
    Hello,
    When I do the key thing it starts quickly, every time after a short crank, even on a cold morning. Sometimes when I don't do the key trick it starts instantly, like it used to.
    It runs like a clock.
    Plugs are as they should be. Fuel consumption has not changed.

    Please bear in mind I only start on petrol (gasoline) then run on LPG (propane), so I am not doing a high mileage on petrol.
    When on LPG the pump still runs, so the fuel passes straight back to the tank. It's just that the injectors are switched off.

  15. #15
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    4.0l XJ starting problem

    Ok so you added a check valve and you still need to do the key thing. And that is the issue. Correct?
    To be honest, you may be the first person i read that is trying to add an external check valve. Most either eagerly replace the pump or wait until it dies to replace it.
    Ill have to look at a diagram to comment on external valving and what could go wrong.
    On TJ the check valve is in the pump.

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    Last edited by JPNinPA; 12-19-2018 at 02:03 AM.
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    Re: 4.0l XJ starting problem

    Thanks for the help. Look forward to your suggestions.
    I did think about changing the pump but two things came to mind. First a new check valve to replace the 'dodgy' one in the tank is a very cheap fix (less than $2) and second, having looked at the tank I thought that by the time I got the old one out I would need a new tank as well!!
    A Happy New Year to all Jeepers out there.
    Mike

  17. #17
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    Re: 4.0l XJ starting problem

    What side did you put the check valve on the feed to the rail or return? It should be on the feed just post the pump.


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    JPNinPA

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  18. #18
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    Re: 4.0l XJ starting problem

    Came across this surfing the web.
    https://youtu.be/0PrgUOAG-fU


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    Re: 4.0l XJ starting problem

    Quote Originally Posted by JPNinPA View Post
    Came across this surfing the web.
    https://youtu.be/0PrgUOAG-fU


    Sent from my iPhone using Jeepz.com mobile app


    Thanks for the link. It is a very good video and perfectly address my problem. The check valve he fitted is identical to the one I fitted.
    I don't fancy pulling the injectors until I have done his air pump checks at the tank. That will identify if I have got the check valve in the right line and whether the pressure loss is towards the engine.
    If I remove the return connection from the regulator it will verify that at the same time because if it leaks it will push the fuel out and eventually air will follow.

    Even though this is Spain, it is very cold with frosts overnight at the moment, so I'll have a go at the new checks if we get a warmer day. It only gets up to about 12 deg C (53F) in the afternoon. Not much fun for crawing under the car.

  20. #20
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    4.0l XJ starting problem

    I wish you luck though I believe it is the check valve. But go through the list so you know other parts are not at fault.

    Winter here in Dayton Ohio has been surprisingly warm in the 30-50 deg F. Yesterday I was troubleshooting an issue in the driveway with no jacket and lying on the concrete. Today is 27F up to 31F (-3C to -1C)



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