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Hey all,
I’m having some problems with my Ranger. Yesterday as I was driving, it died on me suddenly. After verifying that I wasn’t getting any fuel pressure at the rail, and wasn’t hearing the fuel pump prime, I checked the fuses. I noticed that the 20A fuse for the fuel pump circuit was blown so I replaced it. Truck started right back up and ran fine for about 5-10 seconds before shutting off again. I check the same fuse to find it blown again.
I tested the fuel pump relay with a 12v source and measured it with my multimeter, and it checks out. I reset the inertia switch that my Ford has and it didn’t seem to help. I’m not sure if that’s the problem, but I’m going to try bypassing it just to rule it out. I’m kind of at a loss of what to do after that. I really don’t feel like pulling the bed off to get at the fuel pump if that’s not it. I feel like since the truck starts and runs fine with the fuse intact, that the pump itself is in good shape.
Any advice would be much appreciated.
Thanks
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Update: WOW. I jumped the inertia switch by unplugging the connector and inserting a thick paperclip between the input wire and output wire on the connector. I had a new fuse in at the time as well. Turned the key and it fired right up. About 10 seconds later the truck dies again and I smell smoke. I look over and the connector to the inertia switch is smoking. It’s now melted at the end so I don’t really have a choice but to bypass the switch now. I’m just concerned as to why that happened. It’s not my first time bypassing a switch, and from everything I’ve read online, people were jumping it with no issues.
Anyone have any ideas? If I had possibly let the paperclip touch the metal surrounding the switch, would that have caused it to spark? I feel like it would’ve disrupted the current to the pump and caused it to not run in that case.
If I had possibly let the paperclip touch the metal surrounding the switch, would that have caused it to spark?
Yes of course it would. The metal of the engine/frame are connected to battery ground. The paperclip is essentially bare wiring connected to battery positive. Paperclip touches the metal frame and you have short to ground = heat/sparks. You should have been able to simply set meter to Ohms and test switch. If it showed 0, switch is fine and didn’t need to be bypassed.
You most likely have a short to ground somewhere tripping fuse. ETCG has videos on tracking those down so you can search this forum or his youtube channel. And for sure don’t bypass fuse or put in a larger one. Fuse is there to protect wiring and provide a weak link in circuit. Bigger fuse could move weak link elsewhere and melt wiring / catch something on fire.
Fuses don’t just blow. They are circuit protection devices, an intentionally weak link to protect the valuable electronics of the car.
The obvious culprit is likely the fuel pump. As it runs, it gets warm and the resistance increases so it draws more current so it produces more heat. then POP! Goes the fuse. How much gas has been in your tank when this is happening? In-tank pumps are submerged and cooled by the fuel in the tank, so if the pump is on it’s way out a lesser amount of gas could realistically reduce the cooling effect of the gas in the tank.
If you had access to an amp probe it would be easy enough to stick it on the positive feed for the pump and see how much it’s drawing, as fuses may actually take a couple extra amps over time before they fail. I’m just not too sure how you would check that without one because most DMM are only rated to 10 amps.
You’re absolutely right. It ended up being the fuel pump. Replaced it a couple days ago and did the fuel filter at the same time for good measure. The pump that was in there wasn’t the OE Motorcraft one, looked to be an aftermarket one. Doesn’t surprise me as I hear they only last a year or two in a lot of cases.
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