Fuel inertia switch problems.
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Senior User
Joined: Sep 2010
Posts: 189
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From: Jackson, NJ
Fuel inertia switch problems.
Has anyone had a fuel inertia switch cut power intermittently? I hit a deer on the driver side of my excursion and it caused enough damage to have to replace the radiator support and get a new clutch fan. I was driving on the highway last night to just have my truck die on me. I recently just replaced the fuel pump in my truck. There's a thread floating around here somewhere about it. Anyways, long story short, there was no fuses blown and the relay was working. But I wasn't getting any power to the pump. So I pushed on the fuel inertia switch and it didn't click and nothing happened. So I checked with a test light to see if power was going to it. It was getting power. So I jumped the wires and got power to the pump. Started the truck up and drive it home and drove it for about 5 minutes and nothing happened again. Anyone ever hear of an inertia switch going bad? That's the only thing I can think is wrong now. I've been through the whole fuel system! I know it like the back of my hand now. Lol
Elder User
Joined: Mar 2012
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If the power shorted when you hit the deer, the switch could have arced. That could cause problems with the contacts.
While the switch does not usually fail, it is possible. Test the switch with a continuity tester or DVM to see if it passes voltage or resistance.
While the switch does not usually fail, it is possible. Test the switch with a continuity tester or DVM to see if it passes voltage or resistance.
Elder User
Joined: Mar 2012
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Any voltage in should equal voltage out through the switch contacts, as close to 0 ohms as possible.
The inside circuit is just straight through switch, no resistors or other components other than a switch contact. It should ohm out as if it is a wire when closed. If the circuit doesn't close, or you have high resistance, there is a problem. High resistance could be burned contacts, possibly due to arcing.
The insides of the switch include a weight (usually a loose ball) in an inverted cone (or a pendulum setup) that trips a cutoff switch on impact. That is why the switch requires a certain orientation for the mount.
The inside circuit is just straight through switch, no resistors or other components other than a switch contact. It should ohm out as if it is a wire when closed. If the circuit doesn't close, or you have high resistance, there is a problem. High resistance could be burned contacts, possibly due to arcing.
The insides of the switch include a weight (usually a loose ball) in an inverted cone (or a pendulum setup) that trips a cutoff switch on impact. That is why the switch requires a certain orientation for the mount.
Last edited by srteach; Aug 15, 2012 at 09:55 AM. Reason: clarification
Junior User
Joined: Feb 2016
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From: Mckinleyville, Ca
Where is your Inertia valve?
I hit a large pot hole and my truck also dies in its tracks, I have also checked all the fuses and associated causes. my owners manual says the inertia valve is in the right side kick panel, I pulled the panel and found nothing there. I looked under the hood all around and found nothing that resembles this valve. so where was is it on 97 F250 7.3L that is dead in the driveway
i ain't rite
Joined: Mar 2005
Posts: 65,581
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From: Marlboro Mental Hospital.
I hit a large pot hole and my truck also dies in its tracks, I have also checked all the fuses and associated causes. my owners manual says the inertia valve is in the right side kick panel, I pulled the panel and found nothing there. I looked under the hood all around and found nothing that resembles this valve. so where was is it on 97 F250 7.3L that is dead in the driveway
your 97 still has the mechanical fuel pump on the engine.
also, your in the wrong forum, you want the 94.5 to 97 powerstroke forum, one down from this one in the diesel section.
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Junior User
Joined: Feb 2016
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From: Mckinleyville, Ca
Thank you for answering that. I am now on a new thread with this issue on the 94.5-97 7.3L forum.
again thanks so very much.
again thanks so very much.
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2nd Gear
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Inertia Switch Pre-94.5
Originally Posted by tjc transport;[url=tel:16009213
16009213[/url]]your 97 does not have an inertia switch, that is a 99 and newer thing on trucks with electric fuel pumps.
your 97 still has the mechanical fuel pump on the engine.
also, your in the wrong forum, you want the 94.5 to 97 powerstroke forum, one down from this one in the diesel section.
your 97 still has the mechanical fuel pump on the engine.
also, your in the wrong forum, you want the 94.5 to 97 powerstroke forum, one down from this one in the diesel section.
Fleet Owner
Joined: Jun 2004
Posts: 25,090
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From: Rio Rico, AZ.
Only time inertia switches are needed. Mechanical fuel pumps stop when the engine stops.
i ain't rite
Joined: Mar 2005
Posts: 65,581
Likes: 5,613
From: Marlboro Mental Hospital.
2nd Gear
Joined: Dec 2022
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Inertia Switches 2.0
I have 1 of each, in regards to gasoline and diesel. Electric fuel pumps, as they became more the norm, brought Inertia Switches as a safety measure.
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emboyd
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
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Aug 27, 2003 08:53 AM