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krasuskyp's Avatar
 
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keep blowing fuel pump fueses - help?

Out of nowhere last week, I fried the 25A FP fuse in the front block. I mean, really fried it - the red wire going into it looks charred somewhat.

Replaced it, parked it. Was nearly out of gas at the time, hoped that 'may' have caused it?

10gal in this morning, 15mi into a really nice run - POOF - over I go again. Replaced it, got maybe a mile, POOF again. Towed it home. Awesome.

The replacement I put in had melted and the wire is more charred. The block in the engine compartment has the middle fuse looking 'somewhat' corroded, and the red wire into it has nominal blackening.

Is one of my FP's on the way out (at 50k miles!?)? Relay on way out? Shorting out somewhere else? Car's unfort been parked outside all summer/fall, def took it's toll on corroding that rear fuse block - yay.

Please edumucate my ignoramus on how to proceed w/ the troubleshootage.

Figures, too - the famous "last run of the season" syndrome. Parked until spring, sigh. I'll get to it some winter's eve...

TIA gentz.

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Old 11-12-2010, 01:11 PM
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I am actually doing this upgrade tonight ..... I will post pictures of my charred (and melted fuse holder later).
This circuit is a weak link in the 930 wiring design.
It is horribly overloaded and any resistance in the circuit sets up a scenario like you described.

930 fuel pump relay wiring - once and for all

Cliffs .....

There is a red wire running between Pin #30 on the two fuel pump relays. Find it. Cut it.
You are now going to install 2 blade fuses (one per relay) at the cut.
The other end of each fused wire runs directly to the battery.
Clean up the #16 fuse (OE fuse) wiring.

Photo credit goes to Jeff (Sand-Man) .....

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Last edited by Shadetree930; 11-12-2010 at 01:32 PM..
Old 11-12-2010, 01:22 PM
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It's a good upgrade. I used the spade type fuse holders.

Here's Lee Rice's write up on it.

Pelican Technical Article: Technical & Safety

http://www.pelicanparts.com/techarticles/rice_ramblings/rice-2.gif

Last edited by A930Rocket; 11-12-2010 at 03:14 PM..
Old 11-12-2010, 03:05 PM
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Is this an easier wiring diargram or do I have it wrong?

Old 11-12-2010, 03:16 PM
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Wayah Road Warrior
 
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I would tweak the diagram a bit to provide to separate and distinct leads from the battery otherwise you continue to overlaod the circuit until the 'Y'.

Instuctions say to use a 16 amp for pump one and a 25 amp for pump two.

Last edited by Shadetree930; 11-12-2010 at 07:25 PM..
Old 11-12-2010, 03:25 PM
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20 amp. Radio shack has wired, rubber spade type fuse holders with covers that work very nicely.
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Old 11-12-2010, 04:17 PM
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What's the original fuse rating? I would think that you could halve that since each pump is on it's own fuse.
Old 11-12-2010, 04:41 PM
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Quote:
Originally Posted by A930Rocket View Post
Is this an easier wiring diargram or do I have it wrong?


I would run EACH pump from the hot(+) lead, not one source(and then splitting off to each pump).

It may be overkill, but a 0.1uF/16Volt capacitor across each relay located between positive and negative will keep the pumps basically impervious to voltage spikes that may occur to the pumps from the alternator.
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Old 11-12-2010, 07:25 PM
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If you've upgraded your pumps to 044's it's probably a good idea to upgrade the wiring and both fuses to 25 amps.
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Old 11-12-2010, 07:34 PM
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Quote:
Originally Posted by krasuskyp View Post
Out of nowhere last week, I fried the 25A FP fuse in the front block. I mean, really fried it - the red wire going into it looks charred somewhat.

Replaced it, parked it. Was nearly out of gas at the time, hoped that 'may' have caused it?

10gal in this morning, 15mi into a really nice run - POOF - over I go again. Replaced it, got maybe a mile, POOF again. Towed it home. Awesome.

The replacement I put in had melted and the wire is more charred. The block in the engine compartment has the middle fuse looking 'somewhat' corroded, and the red wire into it has nominal blackening.

Is one of my FP's on the way out (at 50k miles!?)? Relay on way out? Shorting out somewhere else? Car's unfort been parked outside all summer/fall, def took it's toll on corroding that rear fuse block - yay.

Please edumucate my ignoramus on how to proceed w/ the troubleshootage.

Figures, too - the famous "last run of the season" syndrome. Parked until spring, sigh. I'll get to it some winter's eve...

TIA gentz.
Drawing some serious amps, dude. First, a person should amp-up with your favorite energy drink then dive in to this.

Two things come to mind: Dirty connections or a pump about to go south. Let's hit the dirty connections first. Only two wires that are screwed into each end of the fuel pump fuse block. Unscrew them, sand 'em/scrape 'em/hose 'em down with some nasty carcinogenic aerosol cleaner, then re-torque in place.

Worse case scenario is you've got an actual wire short to ground somewhere. It can be a real female dog to find. Get the car running, and tug and pull on any and all wires leading to the pumps. Maybe you'll cause the fuse to blow again and narrow down the offending member. TIP: I had a fantom fuse blowing thing in my old Toyota truck that stranded me in a snow storm (eventually had my 'bro save my sorry ass and tow me 50 miles back home which really sucked in the snow, no engine, no power brakes, headlights and wipers almost dead, 10 feet from his bumper going 40mph). Got her home and stuck a resetable breaker in place of the fuse (since I had already blown several) and figured hey....let the breaker blow all it wants, I'll just reset it. Ended up jiggling wires until the breaker blew. Found the fault, just a short.

Sorry for the short story, just brought back a fond memory. One of two pumps must be drawing too much juice. You could put an ampmeter across each one indivudually to see which is pulling more amps, and at least limit where you should be looking. There just aint an easy fix for this kind of thing. Check all connections on the pumps, clean and tighten as well.

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Last edited by mark houghton; 11-12-2010 at 08:36 PM..
Old 11-12-2010, 08:32 PM
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