Fuel pump eating fuses

[m c]

Howdy. First timer, completely mechanically retarded but very ambitious. Sounds like I'm posting a classified ad. Sorry.

Anyway, 2003 325XiT has decided to not start. Cranks and cranks but will not fire. Did some fishing and found the fuse to be fried. Pulled the cigarette lighter fuse and put it in the fuel pump fuse's place. Engine cranked, sounded like it wanted to fire and then crapped out. Did this two more times before it decided to just crank and crank with no more sign of firing.

Pulled the replacement fuse out of the fuel pump socket (the one from the cigarette lighter) to find it fried as well. Did a little bit of research to find that one possible cause could be the relay. Took the glove box apart to find the relays but realized the relay are pretty tough to get to even though I can see them.

I'm a little apprehensive because they're tucked in there pretty well and I'm prone to break things and, like I mentioned, I'm mechanically retarded.

Now, I have absolutely no idea if the relay is the issue but I'm assuming that now that I've come up with two blown fuses it is likely NOT the fuel pump or filter but an electrical issue. I have altered nothing electrical in the car so I can't trace it to some modification I've made.

Any feedback, suggestions and/or preferably walk-throughs would be hugely appreciated.

Thanks,

Michael

[Jeron]

The relay panel may be held in place by a bolt or a tab. It should come free so you can get to the relays. Are you certain the relay inst in the engine bay? There are usually at least 3 location where various relays reside.

My guess is the fuel pump is bad, drawing too much current and blowing the fuse.

[m c]

Originally Posted by Jeron

The relay panel may be held in place by a bolt or a tab. It should come free so you can get to the relays. Are you certain the relay inst in the engine bay? There are usually at least 3 location where various relays reside.

My guess is the fuel pump is bad, drawing too much current and blowing the fuse.

Thanks Jeron.

From an electrical standpoint, is it a virtual certainty that the fuses are blowing because of the fuel pump and not as result of the relay having a problem? If there is a relay problem would it even effect the fuses other than to not provide current?

[Jeron]

I am not qualified to answer that but I can tell you what I know or at least what I "think" I know.

The fuse is sacrificial, meaning designed to heat up and "blow" so that the wire or components do not heat up and blow. This can be caused by excessive load on a motor such as a bad fuel pump or pumping through a clogged fuel filter. It can be caused by "dirty" contacts increasing the resistance of the circuit.

I dont know how much testing you are willing to do but you could hook up a fused direct line to the pump and connect the pump fuel output to a line into a bucket and see if the pump will pump fuel without blowing your fused circuit.

You could also pull the relay and check it general condition and condition of its contacts, same for the pump connector

[m c]

Originally Posted by Jeron

I am not qualified to answer that but I can tell you what I know or at least what I "think" I know.

The fuse is sacrificial, meaning designed to heat up and "blow" so that the wire or components do not heat up and blow. This can be caused by excessive load on a motor such as a bad fuel pump or pumping through a clogged fuel filter. It can be caused by "dirty" contacts increasing the resistance of the circuit.

I dont know how much testing you are willing to do but you could hook up a fused direct line to the pump and connect the pump fuel output to a line into a bucket and see if the pump will pump fuel without blowing your fused circuit.

You could also pull the relay and check it general condition and condition of its contacts, same for the pump connector

Thanks again Jeron.

I picked up some new fuses and replaced the fuel pump fuse. I removed the back seat and sound insulation to expose the fuel pump cover. Turned the ignition to 'on' to listen for the fuel pump priming but heard nothing. I assume that means it's toast. It's getting hauled to the shop on Monday morning.

Thanks for your input.

[Jeron]

I hate to hear you're giving up.

The pump only turns on for a split second to bring the system up to pressure, so you wont necessarily hear it when you turn the ignition on, if the system is pressurized. Pumps are not too expensive so if you aspire to be a do-it-yourselfer replacing the pump and filter are not really wasted money even if they are not the culprit.

Good luck either way.

[m c]

I'm hate to be giving up. Frankly I don't have the time to dedicate to replacing it or the know-how or time to fix any problem I might encounter and with my track record, problems are inevitable. It's definitely something that looks doable based on the Pelican article for the e36 but I'm lucky to get an hour of daylight and free time a day and with temps dipping into the twenties regularly now (Northern NH) and no garage, it's tough.

But thank you again for your help. Hopefully the shop is kind to me.