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Thread: 4.6 EFI hard starting when cold

  1. 18th September 2011, 04:07 PM #1
    Lotz-A-Landies's Avatar
    Lotz-A-Landies
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    4.6 EFI hard starting when cold

    I'm having trouble with hard starting on petrol when cold (which is also start mode on gas) on my '85 RRc hybrid 4.6 Motec EFI dual fuel.

    If the vehicle has been sitting for anything more than 10 min I often have to crank the engine over for long bursts before it will start. It starts on petrol and switches to gas when the revs reach about 800RPM so if I can get the cranking speed high enough for the change over to hapen it will cough on the 2nd or 3rd crank and then start on the 3rd or 4th, but if it's on petrol only I may have to crank for 20 secs four or five times and when it starts it dies and I need to crank again.

    When it does start on petrol, it runs fine.

    Similarly if I switch over to petrol on the run, there is a momentary loss of power before the petrol kicks in, which is unusual for this vehicle.

    I'm thinking fuel starvation or blockage.

    Any ideas?

    What do I need to test?

    Diana

    You won't find me on: faceplant; Scipe; Infragam; LumpedIn; ShapCnat or Twitting. I'm just not that interesting.
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  2. 18th September 2011, 05:26 PM #2
    bee utey's Avatar
    bee utey
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    I suspect your fuel pump is leaking its pressure back into the tank. I suggest you cycle the ignition on 4-5 times without starting. Every time the ignition comes on the pump runs for 1-2 seconds. A new pump would be a possible answer. Have the fuel pressure checked to see how long it holds pressure after shut-down.
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  3. 18th September 2011, 05:49 PM #3
    Lotz-A-Landies's Avatar
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    I was worried you'd say that, the manifold LPG tanks are sitting above the hole in the floor where you get to the fuel pump!

    Diana

    You won't find me on: faceplant; Scipe; Infragam; LumpedIn; ShapCnat or Twitting. I'm just not that interesting.
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  4. 18th September 2011, 06:09 PM #4
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    bee utey
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    I face that job regularly. Just undo the LPG tank bolts, tilt the tank about 45 degrees with the plumbing still connected, hold it up with a lump of wood. Usually about 1/2 hour extra each way.
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  5. 18th September 2011, 06:59 PM #5
    victa125
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    Intresting, If the fuel pump cycles as normall. IE, phiizch, click, then the fuel rail is charged. Therfore the pump would be functional. Pull a plug lead shove a screwdriver in and check while trying to start. Carefull HEI an all. If this retuns the desired result, Remove an injector plug and check for pulse with multi metre on low scale dcv usually only at about 6v to trigger, Have heard that lLED plugged in should flash? Has to be one or the other.
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  6. 18th September 2011, 07:10 PM #6
    victa125
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    Intresting, If the fuel pump cycles as normall. IE, phiizch, click, then the fuel rail is charged. Therfore the pump would be functional. Pull a plug lead shove a screwdriver in and check while trying to start. Carefull HEI an all. If this retuns the desired result, Remove an injector plug and check for pulse with multi metre on low scale dcv usually only at about 6v to trigger, Have heard that lLED plugged in should flash? Has to be one or the other.
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  7. 23rd September 2011, 09:49 PM #7
    Lotz-A-Landies's Avatar
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    Quote Originally Posted by bee utey View Post
    I suspect your fuel pump is leaking its pressure back into the tank. I suggest you cycle the ignition on 4-5 times without starting. Every time the ignition comes on the pump runs for 1-2 seconds. A new pump would be a possible answer. Have the fuel pressure checked to see how long it holds pressure after shut-down.
    I've been following the procedure and the engine fires usually on the first start.

    But my crystal ball is indicating a new pump in my future!

    Cheers
    Diana

    You won't find me on: faceplant; Scipe; Infragam; LumpedIn; ShapCnat or Twitting. I'm just not that interesting.
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