Vapor lock on my 365 gt 2+2 ?? | FerrariChat

Vapor lock on my 365 gt 2+2 ??

Discussion in 'Vintage (thru 365 GTC4)' started by bazooka joe, Aug 14, 2006.

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  1. bazooka joe

    bazooka joe Rookie

    Dec 29, 2003
    29
    #1 bazooka joe, Aug 14, 2006
    This past June on a run thru the green/ white mountains one warm day after about 150 miles the engine died ... rolled to the side of the road, had power but car would not re-start .. was not getting fuel, opened fuel tank, could hear pump clicking, closed tight, engine started.

    Car has been great since until this past Thursday .. similar scenario as above, long run, pulled over opened, closed cap .. started up fine. Over the past five years I have not had this problem until this past June .. suggestions, solutions ?
     
  2. ArtS

    ArtS F1 Veteran
    Owner Silver Subscribed

    Nov 11, 2003
    9,004
    Central NJ
    #2 ArtS, Aug 14, 2006
    Turn on the autoflux.

    When my car gets vaporlock, I turn on the electric fuel pump and the problem is solved. I drive with the electroc fuel pump on continuously on hot days.

    Regards,

    Art S.
     
  3. afwrench

    afwrench Formula Junior

    Nov 24, 2004
    593
    NY
    Full Name:
    Mike
    #3 afwrench, Aug 14, 2006
    Possibly the vent in the cap is not working.Tank must vent in some way. The fact that you remove the cap and then the fuel flows seems to indicate this. Vapor lock is the boiling of fuel in the line or carb and the vapor cant be pumped. I would look carefully at the tank venting.
     
  4. Bryanp

    Bryanp F1 Rookie

    Aug 13, 2002
    3,800
    Santa Fe, NM
    #4 Bryanp, Aug 14, 2006
    it sounds like vapor lock, but I am mystified by the fact that you "can hear the pump clicking" - the clicking would be the electric fuel pump at the back of the car, and if it is actually moving fuel, you would not have vapor lock. have you checked either of the fuel filters lately? I don't know why the pump, if it is working, would suddenly start delivering fuel when the gas cap is opened; the system is a loop - there is a return line back to the tank from the carbs - so you should not have a scenario where negative pressure in the tank itself would prohibit the flow of fuel from the tank into the pump . . .
     
  5. bazooka joe

    bazooka joe Rookie

    Dec 29, 2003
    29
    #5 bazooka joe, Aug 14, 2006
    I believe that the fuel pump will consistantly "click". I originally thought it was a weak connection to the fuel pump, but we checked all connectors, and made sure pump was secure to. We also checked fuel filters. It seems to be effected by the warm weather, and long runs.

    That being said, I just checked the fuel cap and it looks like the inner rubber gasket is seperated about 1/4 inch +. I assume that the spring mechanism in the cap needs to be working well ?
     
  6. yale

    yale Formula Junior

    May 2, 2004
    744
    New York City
    #6 yale, Aug 14, 2006
    B Joe,

    I'm not any kind of expert it's just that my car seems intent on gathering any sort of malady which I have come to look at as more of a professorial exercise then a testing one.

    So as for vapour lock, just to start at the beginning: Sorry if you know this but your car has two fuel pumps, one is mechanical and with the engine. It has a replaceable membrane that can be fixed without taking the engine out though these parts are quite scarce at the moment. At times other parts of this item can wear, like on my car where the cam that pushes the plunger in and out has worn enough to not able to pump enough fuel. This fix would require removing the engine from the car.

    And the other is a Fispa electric pump which is the one that clicks and is back near the gas tank. If we knew your car to be as delivered from the factory, we would expect that upon getting in to drive you would switch the second switch on from the left -marked A-, turn the key, listen for the chattering of the electric fuel pump to slow down and then push your key in to start the car. This electric fuel pump, according to the manual, should also be used in traffic and from experience also on super hot days and on the track.

    If you have to always use the electric fuel pump or if some previous owner has wired the electric fuel pump to always be on, (as has been known to happen), then you have a problem that has not come to your attention until now with some more strenuous use. (And you can read the second paragraph again for a guess).

    Yale
     
  7. TLKIZER660

    TLKIZER660 Formula Junior

    Jul 30, 2004
    315
    Québec
    #7 TLKIZER660, Aug 14, 2006
    Last edited by a moderator: Sep 7, 2017
    I assume you have a late model 365, with two electric pumps, otherwise you would have to turn on the electric pump with a dash switch.
    The attached sketch shows the fuel system, including the tank vent line. If that line is not plugged or kinked, there is no way that removing and replacing the cap would affect the fuel pump's ability to pump fuel. The tank vent line is supposed to keep the tank at atmospheric pressure all the time. If there was no vent line, then the tank pressure could vary, initially increasing the pressure when fuel that gets heated passing through the hot engine compartment is returned to mix with and heat the tank fuel. Also, as fuel is eventually used up, the lack of a vent line would cause the pressure in the tank to decrease, resulting in a vacuum in the tank. The combination of hot fuel (higher volatility) and low pressure (low vapor pressure) would result in the fuel being much easier to boil in the pump (cavitation) and cause what most people call vapor lock. If this scenario occurs, then removing the cap would definitely improve the pump's ability to deliver fuel. I don't know where the green/white mountains are or how high they are, but high altitude (lower pressure) aggrevates vapor lock tendencies.
    I doubt that the vent line just suddenly kinked or plugged so it's most likely a combination of high fuel tank temperature occurring after a long continuous drive, in combination with high altitude and perhaps fuel in the tank being left over from early spring (winter fuel is higher volatility and easier to vapor lock). One cannot always trust the fuel that is purchased during transition seasons.
    This is probably confusing but if you need more details (masochist) please PM me.
    Good Luck!
    Tom Kizer
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