I need to know how to put power directly to my fuel pump and I cannot find this information anywhere... Basically I want to bypass the fuel pump relay, and the oil pressure switch all in one so I can rule them out of my no start condition. Oh and if there is a way to test my oil pressure switch solely then that added info would be good aswell. Thanks

Car is a 91 Z28 with a 90-92 L98 tpi.

 

I cant remember which wire does what, but there's 3 wires that go into the rear bulkhead right between the rear seats. If you jack the car up you'll see above teh differential where there's an electrical fitting that is on the bulkhead and a plug going to it. One is a positive to the fuel pump, one is a ground, and one is a fuel gauge sender. I think the center wire is power, but Im not sure. Maybe find a wiring diagram? But anyway you'll see it above the axle and then it will go across and over the top of the tank. Just be sure before you start sending current into random wires up there. You're still dealing with fuel.

 

Yea I think I saw that plug yesterday, it was tucked up above axle area... Anyways so by putting 12volts directly to the pumps plug it wont like catch on fire or anything rite? Lol that'd be a bad spot to be if it did BUT more importantly the pump should run if it isn't the issue rite?

 

Okay. This coming out of my '91 service manual. There should be a test connector at the fuel pump relay on a red wire located behind the passenger side shock tower. Comes out of the relay from the "C" harness connection. You should also be able to use the direct wire from the fuel pump relay to the fuel pump at the "E" harness connection. Hope this helps a little.

 

Yea thanks man.

 

I forgot about this...

There's a ALDL port that you can provide power to to power the fuel pump. It will only activate the pump if the relay is switched OFF. So key in the OFF position. This assuming you still have all the stock wiring. When the relay switches it gets power from other sources and disconnects this terminal from the circuit. So you can bypass EVERYTHING on the power side of the relay. Fuel pump draws 10 amps max.



Remember, there's a fuel pump fuse beside the battery. So check that too. I ended up blowing that fuse several times. And then I had to finally cut the wire to the OPSU because I think that's where my short was. I think my headers melted something down there just enough to cause intermittent problems.

 

Yea thanks for the diagram but I looked yesterday for the ALDL and I cant find mine... You wouldn't happen to have a pic of what mine should look like would you? Thanks Infernalvortex

 

A little more iinfo. Fuel pump relay is located at number 3. Test connector is located at "C8".

 

Under the dash on the driver's side.

Will look like this, somewhere. You dont have to remove anything to see it but it may not be visible without getting down there to find it.



This is one from an early thirdgen firebird, but my car is a 92 and it doesnt ahve this panel or the ALDL port in the same location. It's farther back and more centrally located under the steering column.

 

Alright I think I got it. Now I just have to go out in this 90 degree heat and mess with it haha, thanks guys.

 

Yesss I know exactly where mine is then... But how do I know which one is plug G etc to test it? Mine wasn't labeled and that's why I thought it wasn't it lol.

 

This is where mine is. I've got some custom wiring in there, ignore it. You see the ALDL basically above the clutch pedal.

You know which pin is what because they're all oriented exactly the same. The fuel pump port will be on the lower left.

Note if you ever need to pull codes. You put a paperclip into pins A and B and the SES light will flash codes at you once you turn the key to the "ON" position.

 

Ok ignore my last post... so to jump terminal G do I put a wire from G terminal to 12volts?

 

If it were me I'd just run a wire from a battery somewhere... a medium thickness wire. Connect wire to 12v battery, connect wire to pin G.

 

Alright well I have a wire with inline fuse for my fan switch, ill just use it. Thanks very much agin.

 

Ok so I think my fuel pump test port is on the opposite side of your picture. It should be the solid orange wire coming from the back of the aldl that I put the 12 volts to rite? If so mine was on the bottom right side of aldl... and it did nothing and I made sure key was off.

 

Best way to check to make sure it's oriented the same as the diagram is to do the paperclip test and find pins A and B. Should be the upper two pins on the right side. You should get the ses light flashing at you when you flip the key to the on position. It should flash code 12 at you to verify that it worked. THat's one flash, then two flashes. That will tell you where pins A and B are. I dont know what colors the wires are supposed to be, but hte ALDL should be that orientiation as the diagram above. It should not be backwards, if it is it's upside down and pin G is going to be on the opposite corner.



You can see how the circuit works in the relay here. Note the relay is on the engine bay side of the C100 connector, which can sometimes get flaky. THat's the big giant wiring harness plug on the firewall. So if you've got a problem between the relay and the pump, then this wont cause the pump to prime. You may need to pull up the carpet under the rear seat and send a positive and negative wire through two of those terminals in that plug. Or under the car, whatever you prefer.

 

A '91 does not have a fuel pump "G: ALDL connection.

antares57
listen to what he said
That wire will have a black connector on it.
Put 12v there and the pump will run.

 

Which years got this? Did it get moved to the "test terminal C8" or whatever in the other diagram in the engine bay?

 

Word of caution, do not use a light up switch.

I wanted a back up bypass option to power it direct, "oh look a cool blue switch that lights up at night."

all it would do is pop the FP fuse on fender every time it was used. Use a reg toggle switch and all was well.

 

Well I honestly believe it's the fuel pump now... As of earlier I hooked 12volts power straight to the pump harness that connects above my axle, and even grounded the pumps negative side on harness, and it never came to life.
Now im not sure if this is how you test a fuel pump BUT it seems like the most reasonable way to do it, and this means it's the cause rite?

 

Check and see if you're getting voltage at the relay and at the power wire to the pump in various places along the signal chain. Unplug the pump, obviously, you might damage your voltmeter if you don't.

 

Well with the key to the ON position the fuel pumps harness will only get power for the 2 second of prime up, rite?

So what I did was put direct power to where the harness disconnects on the pumps side which should run the pump no matter what.
So it's gotta be my pump or the pumps side of the harness is bad... either or.

 

Before the last fuel pump change on my '88 I wanted the cause to be anything but the pump. But after checking relay, test port, and harness...it turned out to be the fuel pump. Point is, if you haven't changed out the fuel pump yet, it probably should be done. On both my '91 Base and '88 the strainer had disintergrated to the point that it was clogging the fuel pump. Don't forget to change out the fuel filter as well. Good luck.

 

The fuel pump its self doesn't have a filter that you had to buy seperatly though rite?

Because on the end of my new one it has a tag that said install new filter...

 

True, the pump does not have a filter. But, it does have a sock / strainer that does do some filtering.

There is a separate filter outside the tank... driver side, next to or just in front of the LCA.

 

Alright lol I just wanted to make sure. It seemed as if it meant I needed to buy something else, And I already replaced my in-line fuel filter awhile back.

But yea I bought a new strainer/Pump filter lol. Thanks

 

were you under the car doing this or in the back seat?

I had a problem that that whole bulk head harness and connector and had to wire around it on mine.

Since I cut the hole for access it was easy to do that.

Oh and do not use the quick connects that come in a fuel pump kit, I made that mistake after all that work and had to go back in later. The quick connect melted and the hot wire had metled back a good 1/2 in. meaning at some point the way the FP kept working was the juice was jumping the gap.

Why it didn't go off like a bomb, I dunno.......

 

What are the quick connects? Are you saying just to re-use my factory pumps wiring basically? Sorry but just don't wanna catch my car on fire and I suck with electrical stuff.

 

youll find out, the pump is hard wired once inside the tank, so you have to cut the old one out. So they supply those cheap quick connects that you just clamp on to reconnect the wires.

they often come in tach kits too, just as bad of a use.

 

My cousin has a 92 Ford S10 4.3, we replaced the fuel pump and checked it and it was pumping yet when we put the bed back on the fuel pump won't come on.. Does anyone know where the fuel pump relay is on this truck. I've searched under the hood and can't find it. Please help

 

Get lost.

 

Hi Tammy, Since this forum is exclusively for 1982-1992 Chevy Camaro / Pontiac Firebird cars only, it's not likely that anyone here is gonna know specifics about your Ford truck, your best bet will be to find a Ford forum and ask your question there. (BTW, as far as I know an "S-10" is a Chevy truck, not a Ford) . The one small bit of info I do know is that if this is a Ford vehicle, Fords often have a "crash switch" that will disable the fuel pump if the vehicle receives a hard jolt, once you've determined what kind of truck your cousin has, if it's a Ford, do a search on line for the inertia switch to see if that's been activated.

Good Luck in your search.....

 

what specific battery would you use for that set up? Currently dealing with the same setup.