Check engine light....wont start when on
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Joined: Jun 2003
Posts: 12,341
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From: SW VA
Check engine light....wont start when on
I have a '91 4.0 Extended and when I turn the key, the Check Engine light will come on. I try to start the engine, but it wont start until that light goes off. Sometimes it will take 5-7, 10-second cranks before the light will go off and it will finally start. My brother suggested that the O2 sensor is clogged up. 
After its started and running, the light wont come on again untill the next start-up. It has completely baffled me and my dad who is a life-long mechanic. Do any of ya'll have any suggestions?
After its started and running, the light wont come on again untill the next start-up. It has completely baffled me and my dad who is a life-long mechanic. Do any of ya'll have any suggestions?
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Joined: Sep 2004
Posts: 391
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From: brooksville, florida
I would think that the fuel pump or fuel regulator are faulty or maybe the fuel pump relay is bad, funny think is with most of these faults the van would not start at all except maybe the fuel pump is not pumping at full pressure, test the fuel pressure it should be about 40-45psi before the engine starts and around 35-40psi when the engine is running, you can use a regular tire pressure gauge to test it.
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Joined: Jun 2003
Posts: 12,341
Likes: 4,366
From: SW VA
Originally Posted by bear2x2
The check engine light is supposed to come on when you turn the key. It is doing a self check. Just be patient and let it go out then start it up.
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Joined: Sep 2004
Posts: 391
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From: brooksville, florida
thats right ATC the check engine light should not go out untill the engine is running, but it really does not matter that much if it stay's on after the engine is running, unless the engine run's badly, it is just telling you that one or more of the sensors has picked up a fault that needs correcting at some time.
