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Thread: 3.4S Starting Problems

  1. #1
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    3.4S Starting Problems

    Good Morning.

    I have owned my 1966 3.4S for about ten years. I have enjoyed every mile.

    The car is becoming harder and harder to start. I'll list the progressive symptoms and perhaps the good folks of this forum can give me suggested repairs.

    After the car has been sitting for three weeks or more, the car will not start after cranking on-and-off for about half an hour. My mechanic thought that the carburetors weren't getting enough fuel, so he added a supplementary fuel pump. This attempt did not change the problem.

    For what it's worth. Once the cars starts after a multi day starting attempt, it runs perfectly. It idles great, accelerates properly, and shuts down immediately. Also, once the car has started once after heavy cranking, the car will start perfectly the next day, and the next few days. It's only after the car has been sitting for weeks that the starting problem reoccurs.

    I would be grateful for any suggestions about repairing this problem. I hope that the posted diagnosis and its cure may help others in my position.

    Thanks in advance for any help.

    Dan

  2. #2
    Senior Member rchiv's Avatar
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    Hi and welcome to the forum.
    Sounds to me as though the fuel in the fuel line is evaporating when left for any length of time. Could be an air leak in the fuel line or a vacuum is present in the fuel tank and sucking the fuel back into the tank. When you remove the filler cap after a run is there a release of pressure which will indicate the breather in the fuel cap at fault.

    Roger
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  3. #3
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    Hello Dan,

    assuming the float chambers are empty after an extended idle period, do you switch on and start cranking straight away? It can take a little time to fill them from empty so is better to wait for a minute or two. Did you mechanic actually do any fuel flow checks and determine if the floats were empty? The other thing to look at is the starting carburettor, is that working?

    Alec
    2004 2.5 X Type Estate, MK 2 3.8 (Long term restoration), 2.5 P.I. Triumph saloon, 564 Hymer motorhome.

  4. #4
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    Thanks!!

    Thanks for the warm welcome and quick responses.

    I have forwarded your comments to my mechanic and I will follow your suggestions. The only thing holding me back is the persistent rainy weather in the Pacific Northwest!

    I hope I will report back with a successful start.

    Dan

  5. #5
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    Success!

    Thanks for the advice. I let the fuel pump run for about five-minutes and after some heavy cranking, IT STARTED!

    Thanks again.

    Dan

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  7. #6
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    The float chambers should never be empty!
    Jaguar Keys & Remotes
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    SS7 2PD

    07792 552423
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    castle.locks@btinternet.com

  8. #7
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    Dan

    With the scarce information you have supplied, particularlya lack of servicing / repair history, it is almost impossible to advise you. Itwould be most helpful to know the recent (say last 6 month) repair / servicehistory.


    In the absence of that history the following may be helpful.


    You have an S type which is different from the MK 2, in thatthe S type has twin fuel tanks and pumps, but NO none return valves fitted tothe fuel line. When say the right hand pump is live any restriction upstream afterthe common line “T” piece can cause fuel to divert from the right hand tank tothe left and leave the carburettors partially starved. In this case theinternal none return valve in the left pump would be allowing fuel to by-passback into the left tank. This situation can eventually lead to enough fuelreaching the carburettors to action a start after the line has been primed.That is fuel has been lifted from the tank bottom vertically to the rear end ofthe chassis fuel line .A secondary fuel pump will make matters worse dependinghow it is plumbed into the system.


    If you study the system you will realise, the pumps are about as far away from the battery as you can get, and to ensure the leastvoltage drop the feed and ground connections need to be clean, including thefuse and fuse holder for the pump supply. The rear end of the fuel supply linedrains fuel back to the tanks when the ignition is off but full drain back cantake a few days, hence it will start for a few days.


    If the pumps are 8 to 10 years old the diaphragms will havehardened, (and so will the carburettor diaphragms) and the pumps will needrenewing or rebuilding. You need to be sure that the fuel tanks and tankfilters are clean, otherwise the pumps have no chance of drawing up fuel andpriming the fuel lines. The pumps on this car will have difficulty priming thechassis line if the pump diaphragms are hard or there is debris in any of thefilters or tanks.


    These cars are particularly easy to determine if fuel isreaching the carburettors, if you depress the tickler pin on the top of thefront carburettor with ignition ON you will be able to hear fuel flowing intothat front chamber. You will notice Jaguar skimped having S.U place a ticklerpin on the rear carb. Although you can convert the rear carburettor floatchamber lid and fit a tickler pin, or fit a new converted lid, (note the lidsare handed)


    It is very advantageous to convert the rear lid, as you canuse the pins to temporarily flood both carburettors to prove existence of fuelin each chamber and to enrich both cars for a really cold start when the autochoke may be purposely set weak.


    If the main fuel filter has been fitted with a filterelement (gauzes were original) ,beware that you cannot see debris on the paper elementas the fuel flow is reversed with the dirty side on the inside. You may find itpreferable to remove any filter turning it into a simple water separator onceagain and one more obstruction removed, considering the numbers of filters inthis system.


    Bottom line…..it is because you have left the pumps runningsome time, that you have obtained a start and all the evidence points to thepump valves and diaphragms needing attention. You need about 3 psi to 3.2 psiat the carburettor inlet with an S type installation.

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  10. #8
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    Quote Originally Posted by NWG View Post
    Dan

    With the scarce information you have supplied, particularlya lack of servicing / repair history, it is almost impossible to advise you. Itwould be most helpful to know the recent (say last 6 month) repair / servicehistory.


    In the absence of that history the following may be helpful.


    You have an S type which is different from the MK 2, in thatthe S type has twin fuel tanks and pumps, but NO none return valves fitted tothe fuel line. When say the right hand pump is live any restriction upstream afterthe common line “T” piece can cause fuel to divert from the right hand tank tothe left and leave the carburettors partially starved. In this case theinternal none return valve in the left pump would be allowing fuel to by-passback into the left tank. This situation can eventually lead to enough fuelreaching the carburettors to action a start after the line has been primed.That is fuel has been lifted from the tank bottom vertically to the rear end ofthe chassis fuel line .A secondary fuel pump will make matters worse dependinghow it is plumbed into the system.


    If you study the system you will realise, the pumps are about as far away from the battery as you can get, and to ensure the leastvoltage drop the feed and ground connections need to be clean, including thefuse and fuse holder for the pump supply. The rear end of the fuel supply linedrains fuel back to the tanks when the ignition is off but full drain back cantake a few days, hence it will start for a few days.


    If the pumps are 8 to 10 years old the diaphragms will havehardened, (and so will the carburettor diaphragms) and the pumps will needrenewing or rebuilding. You need to be sure that the fuel tanks and tankfilters are clean, otherwise the pumps have no chance of drawing up fuel andpriming the fuel lines. The pumps on this car will have difficulty priming thechassis line if the pump diaphragms are hard or there is debris in any of thefilters or tanks.


    These cars are particularly easy to determine if fuel isreaching the carburettors, if you depress the tickler pin on the top of thefront carburettor with ignition ON you will be able to hear fuel flowing intothat front chamber. You will notice Jaguar skimped having S.U place a ticklerpin on the rear carb. Although you can convert the rear carburettor floatchamber lid and fit a tickler pin, or fit a new converted lid, (note the lidsare handed)


    It is very advantageous to convert the rear lid, as you canuse the pins to temporarily flood both carburettors to prove existence of fuelin each chamber and to enrich both cars for a really cold start when the autochoke may be purposely set weak.


    If the main fuel filter has been fitted with a filterelement (gauzes were original) ,beware that you cannot see debris on the paper elementas the fuel flow is reversed with the dirty side on the inside. You may find itpreferable to remove any filter turning it into a simple water separator onceagain and one more obstruction removed, considering the numbers of filters inthis system.


    Bottom line…..it is because you have left the pumps runningsome time, that you have obtained a start and all the evidence points to thepump valves and diaphragms needing attention. You need about 3 psi to 3.2 psiat the carburettor inlet with an S type installation.
    I concur
    You are only masking the problem.
    In this case I would also empty and clean the glass bowl regularly.
    Jaguar Keys & Remotes
    Castle Locks
    196 London Rd
    Hadleigh
    Essex
    SS7 2PD

    07792 552423
    01702 555557
    castle.locks@btinternet.com

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