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Fuel Pump Fuse Blows. Now wire may be fried. Where does that wire go?

Fuel Pump Fuse Blows. Now wire may be fried. Where does that wire go?
I replaced the burnt fuse and she fired right up.
Now the pumps are dead again the next day with a new fuse. Maybe the wire is fried.
Where does that wire go if I have to pull a new wire?
Thanks,
Glenn
Old 08-02-2011, 09:50 PM
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Remove the fuse panel bolts, move it away from the fender and follow the wire to see where it goes. Hard to know which one you're talking about. Top or bottom one.

Two small fender lag bolts and one phillips head screw hold it on. A voltmeter meter and 12 volt test light with sharp probe for penetrating wire insulation helps for tracing and checking voltage.

Those old 1960 technology German fuses have very little surface area to make electrical contact at the ends and often have corrosion and they totally suck... The resistance makes them hot and eventually cooks them.
One quick and easy upgrade for the fuel pump fuse is put in a blade fuse holder with thick wires and a rubber cap. Radio Shack sells them for about $6.

Strip and put the ends of the wires into the holes in the fuse panel that the wires going to the fuse go into and snug down the screws that hold them in place and put a 25 amp blade fuse in the fuse holder. If you installed one or two bosch 044 fuel pumps that draw a little more current than the stock ones then a 30 amp fuse may a good idea.
That one fuse supplies fuel pump power to both relays and both pumps. You can also use an ampmeter to check current draw across the fuse mount contacts.
Old 08-03-2011, 05:41 AM
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Wayah Road Warrior
 
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See this thread ....


930 Fuel Pump Fuse Overload - The Solution
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Old 08-03-2011, 06:02 AM
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Thats a good post with pictures for finding the jumper wire between fuel pump relays and installing a seperate fuse holder for each fuel pump relay but drilling holes in the top of the relay panel for the fuse holder wires to pass through especially without rubber grommets is totally unnessesary and just a bad idea that creates the chance for short circuts down the road.

There's more than plenty of room to safely run the 12 gauge wires from the blade fuse holders out from under the back edge of the relay panel closest to the windsheild.

I didn't know there were 2 phillips head screws and a plastic standoff spacer under the one closest to the windsheild. They must have been dropped and lost before I got the car.
Old 08-03-2011, 06:36 AM
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Glenn sorry to hear about your woes hope this works out for you at least that thread shows where all of the wires are located. Maybe you should do it if the wire is fried. Shadetree am I correct in assuming that with this mod you are sending constant power to the relays and not switched power? Is that the way it is done originally? Looks like a worthwile endeavor just want to make sure I am doing it right.
Old 08-03-2011, 06:52 AM
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Hi Mike,
After meeting you guys at Sunday's Car Meet at Oak Beach Inn - Long Island, my engine shuts down in 4th gear while cruising down the highway. I did replace a burnt fuse and she started right up. The next day she wouldn't start and the fuse looked fine. I'll keep searching.
Old 08-03-2011, 09:40 AM
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Quote:
Originally Posted by JFairman View Post
Thats a good post with pictures for finding the jumper wire between fuel pump relays and installing a seperate fuse holder for each fuel pump relay but drilling holes in the top of the relay panel for the fuse holder wires to pass through especially without rubber grommets is totally unnessesary and just a bad idea that creates the chance for short circuts down the road.

There's more than plenty of room to safely run the 12 gauge wires from the blade fuse holders out from under the back edge of the relay panel closest to the windsheild.

I didn't know there were 2 phillips head screws and a plastic standoff spacer under the one closest to the windsheild. They must have been dropped and lost before I got the car.
Quote:
Originally Posted by E-man930 View Post
Thanks for the write up - I would have placed the fuse holders closer to the battery, maybe zip tied them to the positive wire bundle, then fed the leads under the fuse tray to hide the modification... but it will owrk just fine either way, and + 1 on grommets.
The location of this wiring mod as well as the drilling and holes were specifically located where they were so that the state of the fuses could been seen by me without removing the cover and also so that the next owner or any mechanic working on the car (if there ever is one) would clearly see this mod had been done. These are the two fuses you quickly want to be able to see on a dark and stormy night as you poke under the hood in the middle of the mountains.

If I was working for NASA or Boeing, I would have put in grommets but really ... I am a SHADETREE mechanic ... we don't need no stinking grommets. (Edit) Truth is ... I subsequently used some 1/4 hose and made grommets/sleeves for the wires ... risk mitigated. [/B]
Quote:
Originally Posted by Mike80911 View Post
Shadetree am I correct in assuming that with this mod you are sending constant power to the relays and not switched power? Is that the way it is done originally? Looks like a worthwile endeavor just want to make sure I am doing it right.
Purpose is to take some load off the original equipment single wire/two relay design which was prone to blowing fuses due to overheating.

I am no electrical guru so don't know if relays are constantly powered. Someone much smarter about electrical will have to answer that question. This was just my interpretation of someone else's modification that I picked up from this excellent fuel pump wiring thread ...

930 fuel pump relay wiring - once and for all
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Last edited by Shadetree930; 08-04-2011 at 05:35 AM..
Old 08-03-2011, 10:16 AM
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Its been a while since I played with this wiring but I do believe that the fuel pump relays have a +12v lead to the battery that is hot at all times. Doesn't mean they are passing current at all times. There is also a switched 12v to the relays that closes the main contacts and sends power to the pumps when the key is in the run and start positions.

Every 930 will eventually need some variation of this fuel pump wiring mod.
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Old 08-03-2011, 10:58 AM
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"If I was working for NASA or Boeing, I would have put in grommets but really ... I am a SHADETREE mechanic ... we don't need no steekin grommets. Having said that, where would I get some grommets?"

The holes you drilled have sharp edges that can cut through the insulation on those fuse holder wires going through them. Vibration from driving and movement of the fuse holders like when someone unsnaps and pulls aside the trunk carpet away to do something underneath will do it eventually and if the 12 gauge wire that is on the side going directly to the battery eventually shorts out there you will definately have a fire about 1 foot away from the gas tank and rubber hose in the gas tank fill tube.

Rubber grommets? radio shack or any other electronics supply store will have bags of them. You don't even have to remove a wire from a hole. You could cleanly cut one side of a proper size rubber grommet for that hole with a razor blade and put it over the wire, slide it down and push it into the hole with your fingers and it will keep the wire insulation away from the sheet metal.
If grommets are a stretch you could do the same thing with short little pieces of vacuum line over those wires.

Shouldn't take longer than 2 minutes to do that.
Old 08-03-2011, 11:57 AM
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Thanks for the write up - I would have placed the fuse holders closer to the battery, maybe zip tied them to the positive wire bundle, then fed the leads under the fuse tray to hide the modification... but it will owrk just fine either way, and + 1 on grommets.
Old 08-03-2011, 02:58 PM
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