DIY Fuel Pump HotWire/ Concern

[87chrisss]

So for no apparent reason went under the car and checked the fuel pump voltage at plug. It was very low 8volts was present at plug ..So i decided to do a DIY hotwire, only concern is i think i might have wired some things incorrectly,

1st i had to cut both plugs, stock fuel wiring and the reds double pump..
then i introduced the relay 30 went to back of alternator with a 30 amp fuse inline, 85 ground also spliced another ground on chassis on same ground wire... 87 fuel pump 12v.. and finally 86 which is test for pump..

Now the car runs fine and hauls ass no problems. BUT researching a little, on vendors hotwire kits, i noticed that they merge the stock 12V feed to the test wire (fp prime) on the plug that attaches to fuel pump plug and seems it uses the 87 wire from relay to directly feed the fuel pump power. The issue is i think i might have wired incorrectly the stock FP wiring..Which i butt connected the POS wire from stock harness to the POS of fuel pump and it shares the same wire that is on the Relay that is supposed to power the pump 12v directly from relay.
I merged all the wires together should i have not done that?

What i mean is i did the wiring correctly but i would butt connect the old wiring in between the relay and pump wiring? Would you think its a problem??

 

[87chrisss]

ok well i decide to map out what i did here's a quick diagram of what i did..

Black is ground
red is 12v wiring
yellow is FP test wiring fp (prime when you turn key)

at the top of screen is the 3 stock wiring to the left is the fuel pump and to the right is the relay #30 being the lowest one that goes to alternator with a 30A inline fuse. Please let me know what i shouldnt have done.. or if its ok?

 

[TurboBuRick]

I might be able to help if I wasn't color blind.

The fuel pump only has 2 wires. The third wire on the tank harness is the fuel gauge sender circuit. In the diagram it appears you have the relay tied to it???

Tying all the wires together is crude. Ideally the new relay should only be tied to the signal wire. Power, ground and pump feed should be direct. Not tied to other wires where a previous and undetermined problem stemmed from. Yes, no?

RL

 

[87chrisss]

Received info

 

[87chrisss]

Sometimes i feel like i can do everything myself and dont feel like spending $$ on a hotwire kit from a vendor here then waiting for it in the mail... but sometimes it is good to just buy the nice and clean hotwire kit... BUT i had some spare 12gauge wire and thought to myself lets put it to use...

 

[TurboBuRick]

#30 Power feed tie to back of alternator.

#85 Relay coil ground and pump ground can be tied together and bolted to chassis.

#87 Goes direct to the pump.

#86 Ideally would be tied to the green and white wire on the factory fuel pump relay or at the ecm. Aftermarket hot wire kits use the old pump feed for this which stacks relays. It works but really shouldn't stack relays like that. Just adds confusion and another point to fail.

Hope this helps.

 

[87chrisss]

Thank You Sir!

 

[salvageV6]

Only two wires are used fron the stock connector.
Ground and fuel pump power.
Third wire is the fuel gauge and stays tied through if you cut the connector out and ties to nothing else.
Fuel pump and relay can share a good ground that cab support the fuel pump load and can be added to the factory ground.
Hot from alternator stud 10 or 12 gauge wire through a new fuse gies to one side of the relay contact pump load plus wire goed to the other contact terminal.
Relay coil trigger plus is the factory original pump feed wire.
Dont parallel the old plus feed with the new 12 gauge feex.

 

[TurboBuRick]

Received info

In this diagram the ground is being switched.

With our set up's 12vdc is switched by the ecm so the grounds just go direct to chassis.

 

[TurboBuRick]

Thank You Sir!

Glad to help..

 

[87chrisss]

In this diagram the ground is being switched.

With our set up's 12vdc is switched by the ecm so the grounds just go direct to chassis.

yea it was that diagram i pulled from google that kinda thru me off on the relay.. But i saved your's for future reference

 

[RmvBfrFlght]

Note that the factory relays have a diode across the coil. This makes the polarity of the coil important. Reverse the polarity and the diode fries.

I don't know for sure if the aftermarket relays have this diode, but it is required when driving the relay from the ECM.

Haven't found a simple DVM test to see if the diode is present. Can do it with a power supply (car battery will work), and a resistor.

RemoveBeforeFlight

 

[87chrisss]

Hey but im just running a hotwire outback im not touching stock FP relay, actually now that you say that.. i was wondering since i removed the stock oil pressure switch which helps take load of the FP relay.. i bought 5 different oil press sensor and after 15 miles they all started leaking. I got tired of it and just ran the oil pressure gauge. Is there any other way to take load off the FP relay? I was planning on trying to make something equivalent to what the sensor oil pressure does to help take load off FP relay.

 

[87chrisss]

Well after correcting the wiring checked the voltage still getting under 12V im seeing, 11.20 wire that feeds pump.. i ran two grounds to chassis really didnt see a change will the ground strap on tank to chassis make a better voltage to pump.. i do have a volt booster but i really want over 12V to pumps, im running e85 thru double pumps.. and 120's need that fuel to get to the front.. any other suggestion's? i was thinking of running a 8 gauge from Battery + to relay?

 

[TurboBuRick]

How much voltage drop are you getting between the alt lead to the relay feed?

Describe your grounds off the battery and the motor.

 

[87chrisss]

i just F**** everything up... why has this become so complicated??... i had it working but it looked incorrect. i have 3 wires that are found on stock plug. Tan/white Black and a Pink...

back of alternator to #30 terminal 'fused'

So i cut the tan/white wire on the stock plug which is what runs pump.. left it cut 'not used'

I ran #87 Terminal to the grey wire on PUMP SIDE which is what run's the pumps and was previously connected to the tan/white.

I then connected the black wires together Ground

i then took the pink wire connected it to the the purple FP wire which is fuel level sender.

I have #85 terminal as Ground to the chassis.

I have nothing on terminal #86 ? it doesnt prime nor FP turn on because i dont have anything switching the voltage on the relay to the #87 terminal

then i read to use the grey wire behind the alternator im assuming the oil pressure sensor wires that is grey to switch the #86 terminal on relay tried it doesnt work??? What do i do next?

 

[TurboBuRick]

Sorry. I didn't mean to confuse.

Just use the old pump feed for the relay switched signal #86.

Rick

 

[salvageV6]

The faded purple or pink wire is the fuel sender don't tie it to anything else.

Tan/wht. is the fuel pump old feed so use that to trigger the relay coil plus feed.

Other side of the relay coil goes to ground.

Not that it matters too much but is your hot wire relay in front near the alternator or located out back near the stock fuel pump wiring plug/socket?

 

[Chuck Leeper]

Have you looked at the hanger/wires/bulkhead connector thru the hanger base?? [GN FANATIC has a thread on his problems w/ a Red's dbl pump]
Are you attempting to run both pumps on 1 relay? [As in both on all the time?]
AIRC, a common 30A relay, is only continous rated at about 80%. [24A].
Are the "butt connectors" U R using, the plastic covered pieces? If so, forget that shyt.. solder and shrink wrap.
A volt loss at the pump can lower output as much as 15%. When checking volts, check the neg side, too.

 

[87chrisss]

Have you looked at the hanger/wires/bulkhead connector thru the hanger base?? [GN FANATIC has a thread on his problems w/ a Red's dbl pump]
Are you attempting to run both pumps on 1 relay? [As in both on all the time?]
AIRC, a common 30A relay, is only continous rated at about 80%. [24A].
Are the "butt connectors" U R using, the plastic covered pieces? If so, forget that shyt.. solder and shrink wrap.
A volt loss at the pump can lower output as much as 15%. When checking volts, check the neg side, too.

No im just hot wiring the first pump, the second is wired to the alternator, and engaged @ 12 psi? or 15psi?.. It's the first pump im worried about its only seeing 11.45 volts at plug with car on.. The connectors im using are regular plastic 12/10 butt connector's i do heat shrink them to keep the weather out as best as possible.