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How do you rewire a relay?

Big Bertha

Big Bertha

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Michigan
I have a new Walbro Frc-10, the old lift pump wires have no power to them( at the lp harness) but there is power at the 12v pin on the relay, I already have a new ground ran from the pump to the frame rail, I just need to know how I take out the old wire to the relay and add a new??or would it be easier to get Kennedy's new lp harness?
 
A bit more info would be helpful.
What terminal(s) of the relay are you finding power?
Is the relay installed when you are testing?
Have you tried another relay-they can fail over time.
 
racer55 said:
A bit more info would be helpful.
What terminal(s) of the relay are you finding power?
Is the relay installed when you are testing?
Have you tried another relay-they can fail over time.
Click to expand...
with the relay out I have power at the pin closest to the driver fron turn signal I think it is pin 87, I did switch the relay with the starter relay and same thing, this testing is with the relay out of the terminal, I really need to get the pump working asap it has been below freezing every night this week and soon will be snow.
 
Ok I gave a better replay at the other site,I will re-post here,please excuse the off site link for information purposes:

Looks to me like you need power to pin 30 to energize the LP,try a jumper and check the condition of the LP power wire.

Then you will need to ensure power is supplied to the relay trigger,pins 85,86-one should be power with the key on during the prime cycle(and again once running)-the other should be ground-not sure which is which-look for continuity to ground first on those terminals or power with a test light.

Another quick test of the LP power wire would be to provide 12v to the red wire with the white insulator found near the underhood fusebox/master cylinder area.
When power is provided there it is routed through pin 87(a) directly to pin 30 of the relay to feed the LP.

We need to figure out what circuit of your relay has failed to diagnose this properly.

A relay diagram can be found here to help understand the circuits involved:
http://www.dieselplace.com/forum/showpost.php?p=4414689&postcount=11
 
Thanks Racer for the info, I will try to give 12v to the jumper wire near fuse box, if I have power to the pump the I will check the other circuits. Thanks Again.
 
Sounds like the terminal you have power at is just the one pulling the relay in. Basically you have a control wire that isn't meant to carry a lot of current. A relay is just an electrically operated switch, and that wire is what operates it. You need to check the power source to the relay.
 
Sparky8370 said:
Sounds like the terminal you have power at is just the one pulling the relay in. Basically you have a control wire that isn't meant to carry a lot of current. A relay is just an electrically operated switch, and that wire is what operates it. You need to check the power source to the relay.
Click to expand...

Really depends on which terminal of the socket has power?
The OP did not indicate if the terminal with power was active during the key on priming cycle or if it was powered independently of key power?

He needs to map out which terminal is which in the socket-often the relay will be marked like the diagram I posted above.
During the key on priming cycle there should be 2 terminals with power.
The pull in winding terminal of the relay should cycle off when the priming cycle ends-maybe 3 seconds?Terminal 85 or 86.
There should also be constant power on terminal 87.

If so,with the relay removed and a jumper between terminal 87 and terminal 30 should run the LP provided the wire is not broken,the same thing happens when power is applied to the priming wire with the relay in place.
 
Sparky8370 said:
Sounds like the terminal you have power at is just the one pulling the relay in. Basically you have a control wire that isn't meant to carry a lot of current. A relay is just an electrically operated switch, and that wire is what operates it. You need to check the power source to the relay.
Click to expand...
Nice to see you around Jay!
 
85, 86, and 87 are all coil wires. None are for the load being controlled. Unless it was wired in series with another relay, there should be another terminal with power. As long as memory is serving me correctly.

Thx BT, nice to be back.
 
85,86 are coil wires only.
87,is heavy gauge power and 30 is the load.
87a is an alternate power source-like the priming wire in this case.

relay_diagram.gif
 

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  • relay pinout.jpg
    relay pinout.jpg
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Not all relays have this pin-out however,some do not include pin 87a when used in other applications.
In that case pins 87 and 30 can be interchanged as far as load and power or load and ground are concerned-they could be using the relay to control the ground just as easily as power if required in the circuit.
 
Thx for the diagram. All coming back. 30, 87, and 87a are the dry contacts of the relay. All don't have 87a because that is a single pole double throw relay. 30 is common, 87a N.C. and 87 N.O. With power to the coil, 30 and 87 will be connected. Without, 30 and 87a will be. If 30 is used for *12v than yes absolutely could use 87a for priming as long as the circuit and devices used are capable or carrying the current draw of the connected load.
 
ok so I can jump the lift pump prime connector and the pump will run and I can jump from pin 30 to 87 and the pump will run, I checked all the fuses and all are good, whats next, speak slow I am an electrical idiot!! seems like with the wirs going to the ECM and to the ops I'm sure I have a broken wire or something just don;t know enough eletrical where to go next, and the diagrams don't help me.
 
If you jump 30 and 87 and lift pump works, either the relay is bad or you have no coltage to the coil. But check both 85 abd 86 for voltage. Ceck for both + and-. It may have constant + and switched- if controlled through another relay.
 
UPDATE: I put a new relay in and erased the code PO231, drove it, shut it off and I could hear the pump running a few seconds after shut down, I waited a couple of hours and restarted while I waited for the glow plugs there was no pump noise, the PO231 code is back( low pump circuit), now what?? new wire to ECM??
 
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