Long crank time, fuel pump or injector? - TCCoA Forums
 
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post #1 of 5 (permalink) Old 07-07-2016, 04:20 PM Thread Starter
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Long crank time, fuel pump or injector?

I inherited my moms '97 4.6 thunderbird 8 years ago. She bought it back in 2000. As long as I can remember it always took excessive cranking before it starts.

I've been taking care of the car and did a full tune up last year, compression test, mustang wheel swap, vogtland lowering springs, trac-loc rear, etc. After all that I drove it about 800 miles and went back to driving something else. It's been driven maybe 3000 miles since 2008.

Recently I did some tests to see why it cranks so long.

After sitting overnight I connected a fuel pressure gauge, it read approx 5 psi.
One key cycle gave it 10 psi, another key cycle gave it 15 psi, another gave it 25 psi. It still cranked long before starting. It has 36 psi running, 45 psi with the fpr vac hose off. Turned the key off at 45 psi and it dropped to 35 and held for 15 minutes. I just assumed there was a problem and took the gauge off.

It runs fine though. I'm thinking either a check valve in the pump module is letting the fuel line drain back. Or one or more injectors are leaking.

What could the problem be?
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post #2 of 5 (permalink) Old 07-07-2016, 06:47 PM
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Did you check this thread Jay?

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post #3 of 5 (permalink) Old 07-07-2016, 07:50 PM Thread Starter
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I did read that.
I can get an ECU for fairly cheap, maybe I'll try that. Like I said cycling the key to prime it up to pressure doesn't seem to help.
Time to look at things other than fuel and go from there.
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post #4 of 5 (permalink) Old 07-10-2016, 01:54 PM Thread Starter
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Ok, today I flushed some few month old fuel out and put fresh gas in it.

Then I looked into the long crank problem. When cold, and a 100+ degree interior the check engine light doesn't come on at all from off to cranking, to running. Even after shutting it off I get no light and extended cranking.

I drove it 4 miles with the a/c on, shut it off, the check engine light comes on with the key and it starts with less cranking time.

Sound like a bad ECU?
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post #5 of 5 (permalink) Old 07-11-2016, 05:42 PM Thread Starter
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Interesting. When the interior is real hot the check engine light doesn't come on with the key and it cranks longer to start.
When the interior is cooler the check engine light comes on and it starts right up.
Doesn't matter when the engine last ran, it's very consistent with interior temperature. I'm assuming that effects the ecu since thats where its located.
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