Backfires, won't start
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Elder User
Joined: Mar 2006
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From: Western, PA
Backfires, won't start
Just bought a '86 F-150 Thats not running. When you try to start it it runs rough for a second then backfires very loud then shuts off. It allso fouls out the spark plugs right away. I checked the timing with a light and it is right on.
Any ideas on what this could be causing this?
Any ideas on what this could be causing this?
Senior User
Joined: Dec 2007
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Compression test should be done first.
Timing chain or belt can be off leaving the intake valve open.
Burnt or stuck valve, valve spring broken, lifter.
Compression tells a lot.
Compression, spark and fuel and it has to run to some extent.
Timing chain or belt can be off leaving the intake valve open.
Burnt or stuck valve, valve spring broken, lifter.
Compression tells a lot.
Compression, spark and fuel and it has to run to some extent.
Posting Guru
Joined: Mar 2007
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I agree with CTUBUTIS, you should check to make sure those wires are arranged to the proper firing order and # 1 is where it should be. Keep in mind that all that timing light is telling you is where that crankshaft is when #1 plug fires. It has no idea where the cam is and neither do you. If it's jumped time or the cam wasn't degreed correctly after someone worked on it, it'll never be right. If it gets to the point that you suspect that that's the case, pull the valve cover and watch the rocker arms for #1 cylinder and make sure they are both closed at TDC. Unless you find a compression issue in which case just start tearing it apart.
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Elder User
Joined: Mar 2006
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From: Western, PA
Went out today checked for compression in all cylenders and they all checked out. Double checked the plug wires they were fine. So then I took off the timing cover and checked out the timing set it was fine. Then I pulled off the valve covers to see if a pushrod came off or a spring was broke ect evrything was fine.
Everything looks good to me but it still wont start it just runs rough for a few seconds then backfires and shuts off.
This is an EFI engine is there any sensors that might cause this if they were to go bad?
Everything looks good to me but it still wont start it just runs rough for a few seconds then backfires and shuts off.
This is an EFI engine is there any sensors that might cause this if they were to go bad?
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Junior User
Joined: Dec 2007
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does it have a tps, or throttle positioning sensor,map or manifold absolute pressure sensor, etc, the best way with efi engines, is to get a code reader, where are you located if close you can just use mine, if far away i will sell it to you cheap and you can have it shipped, it is small like a calculater saved me a million times, but got rid of my efi car, i think this one works on a number of different vehicles i will check and see if it works on yours, then if you want it its yours name your price im not here to rob nobody.
Moderator
Joined: Jan 2001
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From: Virginia
This is an EFI engine
. You do not need a code reader if you have a testlight or old voltmeter. This site tells you how to read the codes. www.fordfuelinjection.comFind the fuel regulator on the fuel rail. Pull the vacuum line off and make sure there is no fuel in the vacuum line. If there is, the regulator is bad.
Last edited by Franklin2; Jan 3, 2008 at 12:29 AM.
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