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Old 08-30-2010, 17:40   #1 (permalink)
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Maybe Fuel Problem? f150 4.9L FI 1990

1990 Ford f150 pickup truck with a 4.9L fuel injected 6 cylinder engine.,

I'm at a loss now. I don't know the history because the person giving me the truck doesn't know either. (I did some work that's not relevant here). Relevant here, I changed the fuel pump with a junkyard one. It took a lot of work, particularly removing the one in the junkyard.

Now I need to get it running properly. I can't get it to respond the the throttle. that is, when I get it to start, it's hard to "gun" the engine; in may cough and die. But after it warms, it seems to respond to the throttle better.

I tried the self test (Ford Fuel Injection How To Run a Self-Test self-test, with "ST in" grounded ) and with the engine off I got 556 meaning fuel pump circuit. I didn't do the test while the engine running because I did't know how then. But I just learned you start the engine, then ground the wire ST1.

And where is the Schrader valve to do a fuel pump pressure test? I found the fuel rail but where is the valve? Is it in the back? Anybody have a diagram?

And what's my next step? I think it's a pressure test, right?

Any suggestions at all will be appreciated.

~~ Nehmo
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Old 08-30-2010, 17:45   #2 (permalink)
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Re: Maybe Fuel Problem? f150 4.9L FI 1990

Welcome Nehmo!

The Schrader valve looks just like the one used in the valve stems of your tires. There may be a plastic cap over it that needs to be unscrewed to expose it.
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Old 09-01-2010, 17:39   #3 (permalink)
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Re: Maybe Fuel Problem? f150 4.9L FI 1990

Well, I know it's supposed to look like something with a cap on it and it's on the fuel rail, but where is it? It doesn't appear to be in the front of the engine, so is it in the back? I know this sounds stupid, but I haven't found it yet.
~ Nehmo
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Old 09-04-2010, 17:29   #4 (permalink)
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Re: Maybe Fuel Problem? f150 4.9L FI 1990

Ok, I found the valve. It's in the rear, and it's covered by everything.
I'm waiting for a ride to get the tester.
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Old 09-07-2010, 11:52   #5 (permalink)
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Re: Maybe Fuel Problem? f150 4.9L FI 1990

I got a fuel pressure gauge and connected it. The pressure was plenty high. Apparently, the fuel pump is OK. (At least that part it done.) When I started the engine, this time the engine ran better. But the idle was very high, and I tried to lower it by backing off on a screw that goes vertically and the bottom of which limits the turning of a shaft of the throttle.
But I didn't have a battery jump available, and couldn't restart the engine after I turned it off.
When I start it cold, it's hard to start, and the idle position of the throttle isn't high enough to keep the engine running. But then after it warms a bit, the engine runs way too fast at idle. It seems there is something wrong here.
So I guess the problem now is to get it to consistently run well. And I need to do something to make it run at the proper idle speed.

~~ Nehmo
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