Rewiring your fuel pump [Merged 9-6]

[xlMcMlx DsM]

what gauge wire would be good to re-wire the fuel pump with? thanks

 

[Spooling99]

10-12 gauge wire should be fine
-ADAM-

 

[flacopower]

i just did this yesterday and i used ten gauge.. i followed the vfaq instructions and it told me to use a certain fuse holder that used 16 gauge.. didn't really make to much sense to me but oh well i guess

 

[Birdoprey]

The V-Faq reccomends 8-12guage and that most use 10. I did mine a month ago with 10 guage and i had a fuse holder with 10guage as well. Works great...

 

[overdoseheroin]

10 gauge is the lucky number, better than the 18 or 16 gauge wire that the stock shit has. ive seen as big as 4 gauge wiring but thats bigtime overkill.

 

[wt71gas]

Now might be a good time to think about a Walbro aftermarket pump while you are in there. It comes with an increased wire size harness as well

 

[TJGoSurf]

Just wondering, why do people add a relay? Could a switch be used in their place?

 

[FORMONTOYA]

The relay is used to switch on the fp. You would use the stock feed wire as the 'switchleg' to activate the relay which in turn activates the pump as it normally should. Using a switch instead would not be the safest way to do it as you might forget to turn it off, plus in a rollover there is a safety switch to deactivate the fp, which would not happen if you just wired in a switch.

Jim

 

[RotaryRyan]

Just wondering, why do people add a relay? Could a switch be used in their place?

So that you don't have to flip a switch everytime you turn on/off your car. A relay is a switch, it's just that you don't have to switch it, it switches with your 12v power (the turn of your key) If you read the VFAQ, it will show you how to wire so that the relay switches on when you stock fuel pump would.

 

[TJGoSurf]

So that you don't have to flip a switch everytime you turn on/off your car. A relay is a switch, it's just that you don't have to switch it, it switches with your 12v power (the turn of your key) If you read the VFAQ, it will show you how to wire so that the relay switches on when you stock fuel pump would.

Mine is already done, part of that preventive maintence deal. I wired mine with a relay first, then added a switch later as a theft deterent.

 

[rustyoldsmoker]

I am rewiring a new relay into the Fuel pump, doesn't seem to have power or what not..
First the car died, added more gas, started first try.. ran 1/2 mile, died for good.. no fuel pressure... Tried to get a light test on the positive connection of the fuel pump connector that is in the trunk.. no light.. possible relay problem, choose to rewire.. got a 10 gauge wire to battery... Foglight rewire kit.. will it hurt if i just wire in the new kit when the wire harness previous had four wires and i am just adding power to the pump?? Will the car be okay running off a diff relay switch.. Does it matter..

 

[jepherz]

I'm confused by what you just posted. Sounds like you already did a rewire and it didn't work? If the car starts and runs, it doesn't sound like a wiring problem...

 

[rustyoldsmoker]

I am in the middle of the rewire, i have the power wire run. just wanted to know if when i put the new relay to work, if the old relay will give the car a problem or not?? I dont' understand what the four wires are for.. Power, Ground. then what.. still got two left?? does the other wires do anything that could hurt anything or are they just like fuel gauge setup..
I guess to be frank, I haven't tested it yet, fear of melting the computer..

 

[Drifter27_04]

Check this out and it should help find all your questions about rewiring the fuel pump. I general used this rewired method when I did mine.

http://www.plymouthlaser.com/rewire.htm

 

[travislaw]

I am in the middle of the rewire, i have the power wire run. just wanted to know if when i put the new relay to work, if the old relay will give the car a problem or not?? I dont' understand what the four wires are for.. Power, Ground. then what.. still got two left?? does the other wires do anything that could hurt anything or are they just like fuel gauge setup..
I guess to be frank, I haven't tested it yet, fear of melting the computer..

Make sure you are grounding out the relay. I had a problem similar to yours and it was because my relay wasn't grounded good enough. I forgot to get all the pait off of where I was grounding the relay too.

 

[KRAZYKOREAN]

IMO the fuel pump rewire is not needed. For some reason everyone thinks you need to do it.

 

[rustyoldsmoker]

As the IMo came out, and my pump isn't working right now.. what else in your opinion do you think i should do.. can't find a signal from normal relay coming to the pump. I cycle the ignition on and off trying to find power.. with the plug undone, maybe i should plug it in and bury the tester into the insulated wire? I am a beginer at this DSM stuff. but very willing to try. and by my name i mean rusty and old and used to smoke real bad.. turbo seal, now running NO turbo.. just cold air and tube exhaust manifold. Riged up system with like 12 clamps.

 

[Drifter27_04]

IMO the fuel pump rewire is not needed. For some reason everyone thinks you need to do it.

I am not really sure about the 2g fuel pumps making a difference but I could tell a difference in my rewire. It may not be much of one but every little bit is accounted for.

 

[steve]

IMO the fuel pump rewire is not needed.

IMO the stock wires for the fuel pump are undersized from the factory and should be bypassed. This becomes more important with aftermarket fuel pumps that draw more current than the stock pump.

Now, assuming each of our opinions are of equal value yours has just been nullified.

Rusty,
The fuel pump doesn't get power until the switch is in START, just turning the ignition on shouldn't activate it. Get the wiring diagram and check the two inputs to the MPI relay that are for the fuel pump side and check to make sure it's all working correctly.

Steve

 

[GTM]

...
can't find a signal from normal relay coming to the pump. I cycle the ignition on and off trying to find power.. with the plug undone, maybe i should plug it in and bury the tester into the insulated wire? I am a beginer at this DSM stuff. but very willing to try. and by my name i mean rusty and old and used to smoke real bad.. turbo seal, now running NO turbo.. just cold air and tube exhaust manifold. Riged up system with like 12 clamps.

Cycling the key won't do anything unless the pressure is too low. Brain fade here but the pump only will run when you are charging and/or you have oil pressure. (engine running) Not sure if DSM has a 5 second timer which will activate the pump when first turned on, but if proper pressure it may not allow power to relay and thus to the pump. In the cranking mode the pump will run continuously, if you pull the starter solenoid wire and hold the key in crank position the pump should be running. You can hot wire for testing to energize the relay and eleminate pulling the solenoid wire and key crank position. Alternately is to ground the oil pressure switch which will activate the pump relay when the key is switched on.

Any questions?

Cheers,
GTM

 

[femmeDSM]

OK, let's get this figured out

First of all, can you describe how you hooked up the relay? i.e. what wires run to which connectors on the relay? What kind of relay are you using? Did you follow the fuel pump rewire VFAQ linked above (or similar instructions)?

A few things, just FYI - Assuming you have a standard 30A auto relay, the positive wire from the battery needs to connect to pin 30 on the relay. The fuel pump wire needs to go to pin 87. The MPI wire goes to pin 86, and ground goes to 85. The wire going to 87 needs to be spliced to the black wire with white stripe. On a 1g, the fuel pump does not get power until the key is turned to START, not KOEO (either that, or via the fuel pump check connector behind the battery)

 

[femmeDSM]

Haha, look at all these Wisemen

 

[rustyoldsmoker]

As my technical knowledge of the whole electronic systems is very mute, i would say that i don't know what the MPI is.. and where to find it, the Hanynes book i have is great, except for what i want to know, i feel like a kid in a candy store with no money.. I didn't see anything that said where the plug is, and my electronics are minimal, lightbalbs and probs basically..
So i should find the relay under the middle console and charge it? I can try that i guess.
Also, if what your saying is correct, my oil pressure could be the cause of this, i believe my gauge is good, maybe i should put more oil??
So today is nice, i'll tear into it, Thanks for all the help, and if anyone thinks of anything feel free to keep um comin, this is my way of learning, conversation with the good guys..

 

[femmeDSM]

I'm not sure where you're getting that you're having a problem with oil pressure....That will not keep your fuel pump from turning on.

There are two ways you can check operation of the fuel pump. One is via the fuel pump test connector, located behind the battery. When you hook this up to the battery using jumper leads, the fuel pump should turn on.
The other way is, since you have a rewire, just bypass your 30A relay and connect the Battery wire directly to the Fuel Pump wire. I.E. connect the wire coming from Pin 30 to the wire coming from Pin 87. (Obviously, this is only to check operation. Don't try to actually run your car like this ) If this doesn't turn the fuel pump on, there's a problem with the way the wires/relay are set up, and your fuel pump isn't getting power.

Alternately, you can verify the voltage to the pump, but you'll need a friend to help you do this. Have a friend crank the car, and use a multimeter to check voltage at the wire coming from the battery (you can just touch the positive lead to the connector going onto the pin). You should be seeing approx. battery voltage here while cranking (usually 11.xx volts, or whatever your battery is putting out during cranking).

If no voltage shows up, you know you've hooked stuff up incorrectly.

 

[GTM]

...
Also, if what your saying is correct, my oil pressure could be the cause of this, i believe my gauge is good, maybe i should put more oil??
So today is nice, i'll tear into it, Thanks for all the help, and if anyone thinks of anything feel free to keep um comin, this is my way of learning, conversation with the good guys..

No no no. Not related. You have an oil sending unit for the gauge and that's all it does. You have another similar unit except it will have 2 or 3 wires, if 2 then it is the switch, one side will have power all the time when the key is on and the other is ground through a relay activation coil. (pump relay, or relay for other relays etc.)

If 3 wire then 1 is the sender and the other 2 will be as described in the above. With the key on and a test light to ground you can probe them, the sending unit will be less than battery voltage thus dim but becomes brighter as the gauge approaches full scale. Depending on gauge regulation this may pulse as it gets brighter. The other 2 will be as described above for a dual sending units rather than a combined unit but I'm fairly confident DSMs use 2 units. The reason behind this is Federal Law to prevent the pump from running should the car be in an accident. There are easy ways to test all this but I've forgotten them for the moment.

Rewire may not be an option if the wires have corroded or been overheated. It can't hurt anything if done correctly, without a schematic I cannot address where the pump ground terminates but you must determine if chassis or into yet another component.
.................

The reason for all the Wisemen showing up is because the notification emails for misinformation calls is now working again.

Cheers,
GTM