Hard to start when cold
10-29-2006, 10:10 AM
#1
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Hard to start when cold
After my car sits overnight, it is real hard to start in the morning. But if the car is warm, or was just recently running it will start up no problem. If I turn the key to the on position, and let it sit for 10 second or so before I crank it over, it will start fine. I think it may be losing fuel pressure overnight? But I don't know what could be causing it to do that if that is the problem. Anybody else have any ideas?
10-29-2006, 11:05 AM
#2
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probably the fuel pump
pull the vac line at the FPR, see if it is wet with fuel(should not be)
get a hold of a fuel pressure gauge, see what the pressure is running, then see what it does when you shut it off
post back
pull the vac line at the FPR, see if it is wet with fuel(should not be)
get a hold of a fuel pressure gauge, see what the pressure is running, then see what it does when you shut it off
post back
10-29-2006, 01:08 PM
#3
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if you think your fuel lines arent holding pressure, then put a pressur gauge on the fuel line, start the car, take note of the fuel pressure while idling, then shut off the car and see how long the line holds that pressure, if it doesnt hold the pressure, that will cause your hard start problem after the car has been sititng a while
10-29-2006, 03:10 PM
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10-29-2006, 04:33 PM
#6
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Several things hold the pressure in the fuel line:
-the FPR closes off the return line.
-the check valve in the fuel pump closes off the supply line
-the injectors can't be leaking
-the fuel lines can't have any holes in them.
Any one of those fails, and the sytem won't hold pressure.
-the FPR closes off the return line.
-the check valve in the fuel pump closes off the supply line
-the injectors can't be leaking
-the fuel lines can't have any holes in them.
Any one of those fails, and the sytem won't hold pressure.
10-29-2006, 09:50 PM
#7
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Where can I get ahold of a fual pressure gauge at? Can you just rent one at Autozone? Also, where is the fuel pressure regulator located at on these cars. Never had to mess with it so I have no clue. I was planning on putting a new fuel pump in my car pretty soon anyway since I am getting ready to install a Comp 306 in it, so hopefully it is a problem with the pump.
Last edited by 69gto96z; 10-30-2006 at 10:55 AM.
10-30-2006, 11:38 AM
#9
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You need a "fuel pressure test gauge", about $30-35 at most auto parts stores. It needs to have a -4AN fitting on it, which is the standard Schrader valve connection.
Shoebox has a photo of the back of the intake manifold, where you will find the fuel pressure regulator and the Schrader valve:
http://shbox.com/1/fp_reg.jpg
Shoebox has a photo of the back of the intake manifold, where you will find the fuel pressure regulator and the Schrader valve:
http://shbox.com/1/fp_reg.jpg
10-30-2006, 08:22 PM
#10
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Well I went and bought me a fuel pressure gauge today, and hooked it up. When I turned the key to the on position, it immediately shot up to 45 lbs, but the car had only been off for about 20 minutes, so it was still warm. So I just have the gauge plugged up and am letting it sit for a couple of hours and I'm gonna go back out and check it again once its cooled off, and see if it gets good pressure. Also, I pulled my fuel pressure regulator vacuum line off and it was completely dry.
10-31-2006, 12:56 AM
#11
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I think I have ruled out loss of fuel pressure. I let the car sit for about 5 hrs with the gauge on it. When I went out to check on it, the gauge was sitting at 0, so i turned the key into the on position, and it immediately shot up to 45 lbs, i tried to start it, and same thing, the car still had trouble starting. Is it a safe bet to say that loss of fuel pressure is ruled out or is the car supposed to hold the pressure at all times, regardless of how long it sits for?
Also, when its running its at about 40 to 42 lbs, and when I shut it off it stays right around there.
Also, when its running its at about 40 to 42 lbs, and when I shut it off it stays right around there.
Last edited by 69gto96z; 10-31-2006 at 01:08 AM.
10-31-2006, 09:33 AM
#12
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Try holding the gas peddle to the floor (flood mode) while cranking the engine to see if it starts better. Your fuel pressure seems high (45 psi) if your vacuum line is attached to your fuel pressure regulator. With the vacuum line removed from the FPR your pressure should be 41 - 47 psi.
10-31-2006, 09:52 AM
#13
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Weirdest thing, I went outside this morning and it started fine. 
My chiltons manual said it should be between 42-47 lbs, but if you are saying that is what it should be with my vacuum line disconnected from the fpr, then what should it be with it connected?
My chiltons manual said it should be between 42-47 lbs, but if you are saying that is what it should be with my vacuum line disconnected from the fpr, then what should it be with it connected?
10-31-2006, 01:00 PM
#14
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The acceptable rail pressure WITHOUT the vacuum line connected is 41-47psi (43.5psi is "correct"). When you reconnect the vacuum line, the rail pressure will drop in proportion to your intake manifold vaccum. With a stock cam, it will drop 6-8psi. With a "lopey" cam, it will drop less. The rail pressure will continue to vary with intake manifold vacuum as you drive.