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How to build a Switch Relay Bridge for Fuel Line check

 
Old 03-20-2019, 10:58 AM
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frugal928
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Smile How to build a Switch Relay Bridge for Fuel Line check


As a newbie with my 88, I knew I had to change the Fuel Lines. I kept reading about Switch Jumpers which I saw them but Dr. Bob kept mentioning Switch Jumpers and I was intrigued, so I asked him about the Switch Jumpers what type of wire to use...thus making my own. (Thanks Dr. Bob regarding Lamp Wire information). I didn't want to use just a Jumper Wire. A jumper is needed because I was educated [on the forum] that the fuel pump doesn't come on like regular cards in Position 2 Ignition...It comes on when the car is cranking up. I wanted something with a switch, so after fuel lines installment, I could turn if ON and OFF whilst under the hood to check for fuel leaks. I hope someone finds it useful Cost to build about $12.00. I will always keep this in my Shark at all times. So, here you go...please bare with as this is the first write up on a How to:
Supplies: SECTION TO CONNECT TO MALE/ FEMALE DISCONNECTS: Measure out at 6ft ( or longer if desired) of lamp wire. Go to one end. Take both ends of wire and pull them about 2-3" apart and strip the ends of the wire about .5 inch. Bend end of wire about 1/8" and twist it. Place the twisted end into the Female Disconnect and crimp it very hard...pull the end to make sure its secure. Place RED Heat shrink to identify the HOT/LOAD Side. Do the same thing for the other side for another Female Disconnect. These two connections will go to Rocker Switch.

The side that you have identified as HOT/LOAD, cut the wire into and place heat shrink on both sides of wires and solder the Fuse Holder into place. Then shrink the RED heat shrink at the soldered joints. I know this is redundancy to run a 20A Fuse' but since this is a 928, I felt it was a MUST. Fuse Holder should always go on LOAD or hot side

Go to the other end of the wire and do the same procedure as you did for the Female Disconnect, but this time use the Male Disconnect. Place RED Heat shrink to identify the HOT/LOAD Side.. These two connections will go to the CE Panel for the Fuel Pump Relay.

CONNECTING THE WIRES to ROCKER SWITCH: Insert the Female (RED-shrink wrap) on the LOAD side into the Male Connect on the Rocker Switch( look at your Rocker Switch to determine the LOAD side). Place the other Female Connector on the other side of your Rocker Switch.

CONNECTING WIRES TO FP RELAY: (NOTE...BEFORE DOING THIS, it is SUGGESTED to DISCONNECT your battery strap from the back. This is to protect any electrical situations when pulling the FP Relay since the Relay Puller tongs are metal. IMPORTANT REGARDING RELAY (30 & 87). 30 on the relay is always BATTERY, HOT!!!!!... ). The leads that go into the FP Relay on the CE Panel are the 2 (two) MALE connectors. Go to CE Panel and identify your FP Relay ( on my 88, it was XX-53,-but verify). Use the Fuse Relay puller and pull it out. Mind came out very easily with this tool. Once you have pulled the Relay out, go back to the back and reconnect your Battery Lead. Place the wire you have marked HOT (RED heat shrink) into 30 FIRST- (REMEMBER-30 IS HOT). Then place your other MALE connector into 87. Take your chord (gingerly) and go back to the engine bay and turn if ON. You should hear the FP come on!!! Use your hand to check or a brown coffee filter to check for Fuel Line leaks...hopefully everything checks out. When you are finished go back at your CE Panel and unplug 87 1st then 30. Before replacing relay, I used some Deoxit100

*ROCKER SWITCH HOLDER (OPTIONAL): I wanted the Rocker Switch to be inserted into something because 1) I could hold on something round (rather than the rocker switch) and 2) I didn't like the wires dangling from the Rocker Switch even though the FEMALE connects were insulated. So, get a Plastic Aspirin (whatever) bottle and using an exacto knife and cut out a section from the bottom of bottle that would accommodate the switch. Once you have cut out the right size, take the cap off the bottle. Take your bottle cap and drill about a 1/4 hole into the cap. Run the two female Disconnects thru the bottle cap and end of cut out section. Insert the wires on the Rocker Switch. Push in the Rocker Switch so clicks into place. Take your bottle cap and screw it on. Mark it OFF & ON

Last edited by frugal928; 03-20-2019 at 07:40 PM. Reason: changed Title
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Old 03-20-2019, 12:52 PM
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dr bob
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Nice write-up!

I suspect that the clear sleeves on your crimp connections are heat-shrink. Try a little heat and see if they grab the wire.
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Old 03-20-2019, 12:58 PM
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Originally Posted by dr bob View Post
Nice write-up!

I suspect that the clear sleeves on your crimp connections are heat-shrink. Try a little heat and see if they grab the wire.
Well... they are insulated but don't know if they are heat shrink...I will check. I did add the black heat shrink opposite of the Load wire to make sure. Thanks Bob.
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Old 03-20-2019, 02:10 PM
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This is pretty timely as I just bought a SPST switch yesterday for this very purpose! The only significant difference between what I will be doing with my switch is using heavier gauge wire (probably 12 gauge or so). I used lamp cord before and noticed that the wires got pretty hot after awhile. Probably not an issue at all if you're just checking your fuel lines for a couple of minutes before startup, but in case I ever needed to use this for a longer time period for some reason I just thought I'd be extra safe. Great write up!
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Old 03-20-2019, 02:21 PM
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I hear yah Simon...Redundancy/ Overkill whatever you want to call it...is great vice.
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Old 03-20-2019, 06:43 PM
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Well done, frugal928!
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Old 03-20-2019, 06:59 PM
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Thanks Seth!
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Old 03-20-2019, 07:03 PM
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dr bob
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Originally Posted by Simon928 View Post
This is pretty timely as I just bought a SPST switch yesterday for this very purpose! The only significant difference between what I will be doing with my switch is using heavier gauge wire (probably 12 gauge or so). I used lamp cord before and noticed that the wires got pretty hot after awhile. Probably not an issue at all if you're just checking your fuel lines for a couple of minutes before startup, but in case I ever needed to use this for a longer time period for some reason I just thought I'd be extra safe. Great write up!
Simon brings up a good point. Prior to posting, the OP Frugal928 PM'd for some details on what he needed for the project. I need to go find the PM thread, but I'm almost positive (appropriate...) that I recommended 14ga lamp cord for the duty. Ten (total) feet of 14ga conductor will carry the max 20 amps of fuel pump current safely. The 18ga cord used by the OP is marginal for extended service. For those playing along at home, consider using 14ga lamp cord for this project. There's a reasonable chance that you will someday depend on this jumper to get you home from wherever your fuel pump relay no longer functions, so having adequate conductor size can be important.

Also, when you are out shopping for a switch, note the same DC current requirement on the switch. Hardware-store switches are typically rated for AC current flow. DC switches need a bigger gap between contacts when open so there's less tendency to arc-weld the contacts when you open the switch. Auto Parts stores are more likely to carry DC-rated switches, typically targeted towards auxiliary lights or other high-current accessories. This isn't critical bacause use of the switch will be intermittent at most, but if you are going shopping you have the chance to use the right part.
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Old 03-20-2019, 07:38 PM
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Bob...im pretty sure you told me to use 14 gauge... thus forgetting your recommendation. Thanks for the recommendations you stated. Btw the wires never got hot or warm since it was off and on within 10 sec or less. The purpose of this was testing fuel lines and to make changes according to what someone feels it's best for their set up ( a foundation How To). If I need to limp back home, I will use a jumper wire from 30 to 87 with the proper gauge. As far arching....i think a.fuse holder is good insurance
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Old 03-21-2019, 10:08 AM
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Good idea.

I built one of these a few years ago myself when troubleshooting a fuel pump relay problem and it now stays in the toolbox in the car along with 2 spare FP relays. I also labeled the wires with the terminal numbers where they should be plugged in so I wouldn't forget (#s are on the bottom of the removed relay).

Ill be using mine again as part of my engine R and R to check for leaks before firing anything up.


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Old 03-21-2019, 10:18 AM
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Originally Posted by Petza914 View Post
Good idea.

I also labeled the wires with the terminal numbers where they should be plugged in so I wouldn't forget (#s are on the bottom of the removed relay).
Great idea labeling the contacts that go to FP relay.
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