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post #1 of 6 (permalink) Old 03-25-08, 01:29 PM Thread Starter
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89 F250 460 Won't start on first try

Just bought an 89 f250 with a 460. It wouldn't start on the first try when cold. The starter turns and its like it hits on one cylinder and then dies. You think it's gonna fire right up because the starter doesn't have to spin very long. I've changed plugs, wires, cap, rotor, fuel filter, air filter, cleaned the throttle body, pcv system and used in-tank fuel system cleaner. It still does the same thing. Sometimes it does it twice, when it fire up its runs fine. I've held the key in the on position for a few seconds to ensure fuel pressure is up, but that makes no difference. Any Ideas? Old gas? Dirty injectors?

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post #2 of 6 (permalink) Old 03-26-08, 12:26 PM
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Re: 89 F250 460 Won't start on first try

First thing I'd do is a fuel pressure static test. Most FI systems need to maintain some minimal pressure when the system is off, otherwise symptoms like you describe can occur. I don't know the spec for that system offhand, but it should be available with all the other pertinent data. What you need to do is attatch a fuel pressure gauge and allow the vehicle to sit for a while - or overnight. Before you attempt to start it check the pressure on the gauge - if it is below the spec then you need to determine why the system is leaking down. There are 3 places you can lose pressure - the regulator, the check valve (usually in the pump) or through the injectors. To determine which one you have to eliminate them - first close off the return line between the regulator and the tank. If the pressure stays up then the regulator is defective. If not, close off the line between the fuel rail inlet and the tank. If this makes the pressure stay up then the pump is probably the culprit. If neither of these prevents the pressure loss then one or more of the injectors is leaking down. At that point I would remove them and have a competent shop peform a flow/leakage test on all 8 and repair/replace them as needed.

It is possible something else is the source of your problem, but I'd start with an overnight pressure test....

Gregg
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post #3 of 6 (permalink) Old 03-27-08, 05:31 AM Thread Starter
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Re: 89 F250 460 Won't start on first try

That was my initial thought. So the next time I started the truck I held the key in the on position to let the fuel pump run a few seconds. This should build enough pressure to fire up on the first try, but it didn't.
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post #4 of 6 (permalink) Old 03-27-08, 07:32 AM
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Re: 89 F250 460 Won't start on first try

While the pump may run, if the system has bled down sufficiently you may not get full pressure, and in any event the system is now charged with air - not fuel.

The only way to properly test/diagnose this issue is with a fuel pressure gauge.

Of course I'm assuming that you have one, since you checked the fuel pressure before you started replacing parts in the first place, right?

Gregg
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post #5 of 6 (permalink) Old 03-27-08, 11:55 AM Thread Starter
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Re: 89 F250 460 Won't start on first try

Quote:
Originally Posted by Fire59Rescue View Post
While the pump may run, if the system has bled down sufficiently you may not get full pressure, and in any event the system is now charged with air - not fuel.

The only way to properly test/diagnose this issue is with a fuel pressure gauge.

Of course I'm assuming that you have one, since you checked the fuel pressure before you started replacing parts in the first place, right?

Gregg
Good point about air in the system. I did not check anything before replacing parts because all parts mentioned were the original (1989) parts. You should have seen those old motorcraft plugs! No sense in trying to diagnose problems when the basics are in desperate need of replacement.
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post #6 of 6 (permalink) Old 04-08-08, 05:26 AM Thread Starter
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Re: 89 F250 460 Won't start on first try

I have done a few tests and found that there is no fuel pressure after sitting overnight. It seems to be losing pressure on the supply hose. When messing around in the area of the fuel filter the fuel line connector separated from the filter, I hardly touched it. I reconnected it and all seems well, but still losing pressure. Does anybody know where the checkvalve is located. Is it in the pump? High pressure pump or in-tank pump? Haynes manual was unclear about it and the Chilton's is just an assembly guide.
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