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  View original topic: Should an Electric Fuel Pump be Fused?
donmac Mon Jul 16, 2007 3:30 pm

It seemed obvious at first but the more I think about it the less obvious it gets. The ignition circuit isn't fused. The warning light aren't. I don't know :oops: .

Jimmler Mon Jul 16, 2007 4:08 pm

I don't think it hurts to fuse it. More importantly, you probably want some type of oil pressure protection, tho, in case of an accident. If there's no oil pressure(it's assumed the engine will die in the case of an accident), the fuel pump will not be able to pump any fuel thru a ruptured fuel line on a hot exhaust manifold.

Letterman7 Mon Jul 16, 2007 4:13 pm

Jimmler wrote: I don't think it hurts to fuse it. More importantly, you probably want some type of oil pressure protection, tho, in case of an accident. If there's no oil pressure(it's assumed the engine will die in the case of an accident), the fuel pump will not be able to pump any fuel thru a ruptured fuel line on a hot exhaust manifold.

Huh? What's an oil pump (and pressure) got to do with an electric fuel pump?

donmac - a fuse never hurts on any circuit. I would route the circuit in with the coil, though, so if you do have an accident, or the motor shuts off for some reason, then the pump will shut off. Otherwise you might consider a manual emergency shut-off switch, but why make more work for yourself :wink: ?

Rick

Jimmler Mon Jul 16, 2007 4:18 pm

The coil would NOT be the place to put the pump connection if you want the pump to shut off with the engine. If you're in a bad accident, it's extremely likely the key will still be in the "on" position, powering the fuel pump. If you use a low oil pressure switch, the fuel pump will shut off if the engine is stopped for any reason.

MURZI Mon Jul 16, 2007 6:03 pm

You need one like this....for safety. It is called an iertia switch and will shut the pump off if you roll the car. Mount it out back where the ride is pretty good.



Almost every ford product has one.

jason8 Mon Jul 16, 2007 6:41 pm

I would agree with "jimmler". It's standard practice on boats with electric pumps. I'm not a fan of electric pumps, unless the stock vw pump won't keep up with a big motor. I would wire it in so it works when engine is cranking and when oil pressure is available, that way, even if you don't roll it in an accident and the key is on with a broken fuel line, it won't pump fuel all over the place.

jason

donmac Mon Jul 16, 2007 6:57 pm

Thanks guys. Doesn't wiring it to cut-off on low oil pressure create a chicken-and-egg problem? That is, you can't get fuel to start your engine util oil pressure is up and you can't get oil pressure up until you have fuel???

Dunebubby Mon Jul 16, 2007 7:04 pm

I agree with wanting the pump to shut off when the engine dies but i don't think the oil pressure switch is the way to go.It can take a second or two to loose oil pressure and with some systems that can be quite a bit of fuel sprayed all over.I'd go with one to the ignition system but I'd go with one like Volvo and a lot of other Bosch systems use that stop power to the fuel pump when the pulse signal from the negative side of the coil is no longer present. Easy enough to wire up and YES,fuse that puppy.I've seen pumps,(volvo 240 that pulled nearly 3 times the specified amperage which led to some pretty hot wires,(overfused). You can also recognize potential problems leading to a future pump failure if your popping fuses.

Edit due to the most recent post while I was posting: A lot of systems have provision to supply power during cranking.The volvo one does,I suspect you wire the oil switch with a similar relay/set up

I'll post a picture of the volvo wiring diagram

rterfert Mon Jul 16, 2007 8:47 pm

fuse everything electric.....

sturgeongeneral Mon Jul 16, 2007 10:41 pm

Add me to the agreement list. Fuse any electrical device that you can. Electrical fire is nasty and will destroy your fiberglass body. A fuse will pop and disable a component. An anoyance yes, but you will be able to drive the car home most of the time. Even a simple inline fuse will protect your investment.



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