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1987 - 1996 F150 & Larger F-Series Trucks 1987 - 1996 Ford F-150, F-250, F-350 and larger pickups - including the 1997 heavy-duty F250/F350+ trucks

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Old 10-22-2012, 01:49 PM
hackmoremam hackmoremam is offline
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Fuel pump does not come on with ignition switch

Hello, can anyone tell me if the fuel pump operation is controlled thru the ignition switch on a 93 f-150 - 4.9l?

While driving last week smoke started coming from under the D/S dash and then the engine quit.

When I got it home I noticed the fuel pump does not come on when the switch is turned on.

Fuel pump runs when jumped at the fuel relay socket.

Where do I go next? Help - Please.
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Old 10-22-2012, 02:32 PM
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Originally Posted by hackmoremam View Post
Hello, can anyone tell me if the fuel pump operation is controlled thru the ignition switch on a 93 f-150 - 4.9l?

While driving last week smoke started coming from under the D/S dash and then the engine quit.

When I got it home I noticed the fuel pump does not come on when the switch is turned on.

Fuel pump runs when jumped at the fuel relay socket.

Where do I go next? Help - Please.
Replace the PCM computer.
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Old 10-22-2012, 02:55 PM
hackmoremam hackmoremam is offline
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Hey, thanks subford. I was really trying all options to avoid that but I guess I'm going to have to bit the bullet.

Is that still the case if I have 12 volts at the "voltage-all-the-time" pin in the Fuel pump relay socket and when I turn the switch on I get 12 volts at relay-on pin - but it doesn't time out - it stays on.

Is that also a symptom of a bad PCM?
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Old 10-22-2012, 03:15 PM
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Originally Posted by hackmoremam View Post
Hey, thanks subford. I was really trying all options to avoid that but I guess I'm going to have to bit the bullet.

Is that still the case if I have 12 volts at the "voltage-all-the-time" pin in the Fuel pump relay socket and when I turn the switch on I get 12 volts at relay-on pin - but it doesn't time out - it stays on.

Is that also a symptom of a bad PCM?
Yes it is.
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83 F150 Flare Side 351W AOD
77 F250 351M-2V NP 435/4 Speed 4X4
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Old 10-22-2012, 03:29 PM
hackmoremam hackmoremam is offline
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How about smoke coming from under the D/S dash.

Could the PCM have beltched smoke?

I've taken the cluster and the fuse block out and haven't seen any damage at all. I can only see a small amount of the PCM cover and I can't see all the wires in that corner without pulling some major stuff out of the way.
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Old 10-22-2012, 03:34 PM
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Originally Posted by hackmoremam View Post
How about smoke coming from under the D/S dash.

Could the PCM have beltched smoke?
Yes that is where the smoke came from.
You will have to take the computer out and open it up to see the burnt item that let the smoke out.

The computer comes out from under the hood and is located in the drivers kick panel on your 93.

Click the image to open in full size.

Click the image to open in full size.

/
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83 F150 Flare Side 351W AOD
77 F250 351M-2V NP 435/4 Speed 4X4
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Old 10-22-2012, 03:54 PM
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By the way you have to take the small screws out that attach the fender to the inter fender and pry the inter fender back with a broom handle.
The center bolt in the plug is a 10mm and you back it out and wiggle the plug as you do. Then there are two small nuts one above and one below the computer plug to take off.
Pull the rubber retainer that is round the computer socket off that was being held on by the two small nuts.
Then just pull and wiggle the computer out.
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95 F150 302 4R70W EB EX-CAB
94 F53 460 E4OD COACHMEN SANTARA RV
83 F150 Flare Side 351W AOD
77 F250 351M-2V NP 435/4 Speed 4X4
subford@gmail.com
Bill K, Kansas Chapter
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Old 10-23-2012, 05:42 AM
hackmoremam hackmoremam is offline
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Thanks, you'all have been unbelievably helpfull. I won't be able to work on the truck again until this weekend. I'll follow-up and with the results.
Thanks Again!
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Old 10-29-2012, 08:38 AM
hackmoremam hackmoremam is offline
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Hey Subford, You were right on target. I put a new PCM in and it cranked and runs better than ever.

This is the first time I have ever used a forum but it won't be the last. I hope I will be able to return the favor someday.

Thanks again.
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Old 10-29-2012, 08:38 AM
 
 
 
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