Dumb Relay Question

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Philtenn

Member - Posts: 3

Joined: September 10, 2004

Location: United States

Posted: September 10, 2004 at 5:47 PM / IP Logged

My son has been having problems with his 1994 Ford Ranger. Specifically it has failed to start on 2 occassions, both times when low (but not empty) on fuel. After putting fuel in the tank to 1/4+ tank, we find that there is no fuel pumping from the fuel pump. Assuming that it has a bad (weak) fuel pump and is losing the prime, we purchased a new pump.......but before installing we were told to check the fuel pump relay. Switching 2 identical relays (air conditioner and fuel pump) makes the car run smoothly, but now when i switch them back to their original positions, the pickup still runs....not as smoothly though.

My questions is: Can a relay get weak and fail to hold the switched position for a higher draw component, such as a fuel pump? Or will relays always just crap out all at once?

The puzzle is that no mater what relay is where, the A/C works fine......HELP!

Philteen

Teken

Gold - Posts: 1,492

Joined: August 04, 2002

Location: Aruba

Posted: September 10, 2004 at 5:56 PM / IP Logged

A relay upon terminal failure will exhibit what you have discribed.

The primary failure point is caused by contact arching. Each time the relay is energised (turned on) the act of opening and closing will leave a small amount of carbon build-up.

ie. corrosion / burnt oxidization debris

After many cycles, the contacts are simply too dirty, and the resistance within goes up, causing the relay to be internally insulated by the debris / corrosion.

Which at that time, will not allow sufficent current to be transferred.

The secondary fault is from the coil itself. Those who insist upon applying a under rated relay will simply burn out the coil, and the contacts.

Regards

EVIL Teken . . .

hotwaterwizard

Silver - Posts: 1,350

Joined: December 11, 2003

Location: California, United States

Posted: September 10, 2004 at 6:50 PM / IP Logged

I had the same thing happen to my Ford Ranger and the problem was the Fuel filter not the Relay.

Sediment settles in the bottom of the tank. When you let it run out of fuel the pump will pick up this sediment and plug up the fuel filter.

John DeRosa (Hotwaterwizard)

Stockton California

When in doubt, try it out !

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Philtenn

Member - Posts: 3

Joined: September 10, 2004

Location: United States

Posted: September 10, 2004 at 6:57 PM / IP Logged

Thanks Dudes......i think it's a combination of maybe both things....it's a full time job with an 18yo boy and his vehicle....i think i'll throw his tools away and have less trouble too,

Philteen

Teken

Gold - Posts: 1,492

Joined: August 04, 2002

Location: Aruba

Posted: September 10, 2004 at 7:09 PM / IP Logged

Philtenn wrote:

i think i'll throw his tools away and have less trouble too,

LMAO . . . Dumb Relay Question -- posted image.

Remember, you were once young as well. Dumb Relay Question -- posted image.

Regards

EVIL Teken . . .

Philtenn

Member - Posts: 3

Joined: September 10, 2004

Location: United States

Posted: September 10, 2004 at 7:22 PM / IP Logged

yea......but i didn't lose all my dad's tools....lol

Philteen

Teken

Gold - Posts: 1,492

Joined: August 04, 2002

Location: Aruba

Posted: September 10, 2004 at 7:27 PM / IP Logged

LOL, make him cut the grass NFL style. Cross cut boy !!

delphidoc

Copper - Posts: 53

Joined: June 13, 2004

Posted: September 12, 2004 at 5:05 PM / IP Logged

Philtenn wrote:

yea......but i didn't lose all my dad's tools....lol

Sure you didn't. Me neither. Dumb Relay Question -- posted image.

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Dumb Relay Question

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