4.2 Will Not Start
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Junior User
Joined: Sep 2002
Posts: 81
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4.2 Will Not Start
Truck (97' F150 4.2) is acting up and I wanted to see if y'all had any ideas. I drove it on the freeway and back home for a 30 mile round trip. No problems. Got home and turned it off. Went back a few minutes later to move it and it wouldn't start. First it started and ran like crap. Rough idle and would stall. Now it just cranks and cranks.
No engine codes thrown. Battery is 12v when sitting and around 10 volts while cranking.
Any ideas?
TIA
No engine codes thrown. Battery is 12v when sitting and around 10 volts while cranking.
Any ideas?
TIA
Elder User
Joined: Oct 2005
Posts: 907
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From: Citrus Heights, CA
Had a similar symptom on my son's '95 T-Bird. In our case, it turned out to be something to do with the stock anti-theft electronics. I wish I could be more specific, but I was at a loss and had a shop track it down. I was chasing ghosts and couldn't find it.
We could work around it sometimes by unplugging the wiring harness from the engine and plug it back in again. We heard a crisp "click", the computer reset, and the car would more than likely start.
Hope it helps.
We could work around it sometimes by unplugging the wiring harness from the engine and plug it back in again. We heard a crisp "click", the computer reset, and the car would more than likely start.
Hope it helps.
New User
Joined: Apr 2007
Posts: 9
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Originally Posted by BlueOvalFitter
Is your coolant level low or have you had to add any coolant? 
We're leaning towards a bad fuel pump. Anyone know of a sure fire way to test if that's the case? The truck will start if I dump gas down the throttle body, but runs rough for a few seconds and then dies. Thanks for the help!
Senior User
Joined: Nov 2006
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We need more info. Did you have an SES light or anything previous to this condition?
Try putting the gas pedal to the floor while cranking, see if the truck will start.
Try putting the gas pedal at 50% while cranking, see if the truck will start.
When you first put in the key and turn it can you hear the fuel pump run for 2 seconds? Have someone stick their head down by the tank if you cant hear from the cab.
Those 3 things are going to get us a good starting point, i have further steps we can take after we have tried a few things and have more info.
Try putting the gas pedal to the floor while cranking, see if the truck will start.
Try putting the gas pedal at 50% while cranking, see if the truck will start.
When you first put in the key and turn it can you hear the fuel pump run for 2 seconds? Have someone stick their head down by the tank if you cant hear from the cab.
Those 3 things are going to get us a good starting point, i have further steps we can take after we have tried a few things and have more info.
Senior User
Joined: Mar 2007
Posts: 403
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From: Medina TN
I think you should go with the fuel pump "huntch". When they quit, they just quit. The fuel pump relay may be bad but they normally dont go bad. If it runs while spraying fuel in the plentum, its probally the fuel pump...
New User
Joined: Apr 2007
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Originally Posted by thehawk789
We need more info. Did you have an SES light or anything previous to this condition?
Try putting the gas pedal to the floor while cranking, see if the truck will start.
Try putting the gas pedal at 50% while cranking, see if the truck will start.
When you first put in the key and turn it can you hear the fuel pump run for 2 seconds? Have someone stick their head down by the tank if you cant hear from the cab.
Those 3 things are going to get us a good starting point, i have further steps we can take after we have tried a few things and have more info.
Try putting the gas pedal to the floor while cranking, see if the truck will start.
Try putting the gas pedal at 50% while cranking, see if the truck will start.
When you first put in the key and turn it can you hear the fuel pump run for 2 seconds? Have someone stick their head down by the tank if you cant hear from the cab.
Those 3 things are going to get us a good starting point, i have further steps we can take after we have tried a few things and have more info.
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Senior User
Joined: Nov 2006
Posts: 252
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Yeah, sounds like a bad fuel pump. If you want you can whack on the bottom of the fuel tank with a large rubber hammer while your buddy cranks it, it will probably start then, but still run like crap. I wouldnt replace the whole sending unit, just get a pump.
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New User
Joined: Apr 2007
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Originally Posted by thehawk789
I wouldnt replace the whole sending unit, just get a pump.
New User
Joined: Feb 2006
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i hace had this problem with my 4.2 once i found out that i had blown the fuse
for the pump it is a 30 amp fuse to check if that is the problem just turn the key
to the on spot and if the cel dose not come on try putting a fuse in
for the pump it is a 30 amp fuse to check if that is the problem just turn the key
to the on spot and if the cel dose not come on try putting a fuse in
Senior User
Joined: Nov 2006
Posts: 252
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good point, do check the fuse, and if you drop the tank check your power and ground at the fuel pump.
However usually when motors in general go bad they go high amp draw- which would blow a fuse. Starters and window motors are good examples of this but with a starter you would hvae to measure with a vat 40 or some type of ammmeter
However usually when motors in general go bad they go high amp draw- which would blow a fuse. Starters and window motors are good examples of this but with a starter you would hvae to measure with a vat 40 or some type of ammmeter
Senior User
Joined: Nov 2006
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couldnt have said it better myself. yes to all of the above. pretty much a matter of getting the jack in place, removing the straps that hold the tank in, lowering it carefully and unplugging anything thats holding it up- wires, hoses, etc.