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Old 09-07-2018, 04:01 PM   #1 (permalink)
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Default Losing pressure long crank

I have a 2008 forenza 2.0L and past week I have been trying to pin point a starting issue. The car will start but it takes like 10 seconds of it cranking then it starts. Also when it does start sometimes it sputters for like 4-6 seconds and returns to normal running RPM's. My first idea was to check the fuel pressure. I understand that this car is kind of wonkey in the fact the fuel pump doesnt turn on until you actually crank or that is what I have read somewhere. When it does start the fuel pressure is at 60psi(which is a little high because the service manual says it should be at 55-57, is that bad?) then when I turn the vehicle off the pressure drops to like 5psi and continues to drop slowly(takes about 3min for it to drop to 0psi). Is it just a bad fuel pump? I mean because its an all in one pump it has all the bits (pressure regulator, check valve, ect...)


Thanks for any help!!
John

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Old 09-07-2018, 04:14 PM   #2 (permalink)
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key on, pump should prime for about 2 seconds to get pressure up, 60 is quite normal. pressure should stay up and only drop off slowly. When it cranks, and sees rotation, pump should then operate keeping pressure up.

You might have a non return valve issue letting pressure drop causing the hard starting and the symptoms you describe. As I'm not familiar with that model, this pressure drop of course may be normal. Just as easily, it may not.

I'm sure someone more knowledgeable on this model will either confirm or refute my diagnosis. i'm basing this on my experience with similar models of that age where they hold pressure for some time.

It may of course also be a leaky injector causing a cylinder to flood which won't help starting and will give rough running until it clears.

Have you cleaned and gapped the plugs etc, and checked the basic things? like air filter element etc. Hard starting could be from incorrect plug gap as well.
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Old 09-07-2018, 04:25 PM   #3 (permalink)
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thanks for your reply, yes gapping is pre gapped iridium plugs, has a new air filter. Ok I just reread the service manual you are correct in the on position I should be getting a prime and in return should be getting pressure at the rail correct? If that is the case then it is a bad fuel pump because when it is in the on position I get no pressure at the rail when it is suppose to be priming.

Also is it possible a bad fuel pressure damper could cause any of these issues?

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Old 09-07-2018, 05:36 PM   #4 (permalink)
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Quote:
Originally Posted by darknight66617 View Post
thanks for your reply, yes gapping is pre gapped iridium plugs, has a new air filter. Ok I just reread the service manual you are correct in the on position I should be getting a prime and in return should be getting pressure at the rail correct? If that is the case then it is a bad fuel pump because when it is in the on position I get no pressure at the rail when it is suppose to be priming.

Also is it possible a bad fuel pressure damper could cause any of these issues?
OR! You could have a FI stuck open... more relevant diagnosis in your future..

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Old 09-08-2018, 01:20 AM   #5 (permalink)
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doubt its a FI that is stuck open because the symptoms are different. My car runs fine once its started.
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Old 09-08-2018, 01:24 PM   #6 (permalink)
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I am trying to test the voltage coming from the wire harness for the fuel pump but there are so many connections does anyone know the positive and negative connections so I can test voltage at on position? I tested the blue and black wire and only got 5 volts but the black wire and the purple wire got 12 volts so yeah I guess it is a bad fuel pump.

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