Tbi

[J Cooper]

yeah

[mark]

From your description, it sounds like Holley made the fuel pump setup needlessly complicated. I have no idea why you would need four wires to the fuel pump. There is nothing "digital" about a fuel pump and no need for anything more than power and ground (although they may have simply doubled up the power and ground wires.) I am inquiring about all this because I am condidering a similar setup when it comes time for a V8.

-Mark

[J Cooper]

ill go check again, ive heard its a real good set up, it just says in big bold letters that it has to be mounted below the fuel tank because it pushes and does not suck. the only thing below my tank is my axles. it says it is gravity fed and that is the reason is says to do this. it has a wiring harness the plugs into and goes to the computer.... i guess to regulate fuel flow into the TBI, everything is adjusted on the computer... i dont know... only problem ive seen with it so far is the pump. but im sure a jeep is the only vehicle that would have this problem

[mark]

All electric fuel pumps work better pushing than pulling. But they can pull to some extent. The big problem is getting the thing to prime. You can imagine how tough it would be to get the pump to prime if it were at a high point in the fuel ine. That combined with heat can give you a wicked case of vapor lock.

To keep that to a minimum, it has to be lower than the top of the fuel pickup. The idea is to have any remaining fuel in the line pool at the pump, not just drain back into the tank. This is why most vehicles have at least one pump in the tank. The pump will never loose prime because it is partially submerged and as a bonus, the fuel keeps the pump cool.

-Mark

[J Cooper]

so what do you think i should do with it? get another tank? where its at on the frame rail now, there is about 4" to the top of the tank

[mark]

I think it will be fine. After all, they have sold millions of those kits. The pump just looks vunerable to trail damage. Usually the pump ends up on the inside of one of the frame rails near the tank. But that's a bit high. Greg's jeep has an earlier projection setup (or used to) and the fuel pump was on the outside of the right frame rail. It was well armored though. It also had a little resivoir next to it as I recall. I don't think he had any issues with the pump.

-Mark

[stinger7401]

my pump is off of an 80's model ford. It is mounted on the crossmember that is just in front of the tank. I haven't had a problem with it yet, I think they recomend mounting it below the tank due to the fact that the pump is a pusher and not a puller. They prolly just didnt want you to mount it somewhere near the engine that way its not pulling the entire length of the vehicle.

[J Cooper]

well i put in on the frame, so i should put it back on the tank?

[mark]

Leave it on the frame. Here's why:

TAMOR Wrenching Rule #1:
Once you've installed something, if it works at all, its perfect.

-Mark

[J Cooper]

ok damnit, what the ****.... everything is hooked up the way it is suppost to, all wiring, fuel lines, and pump.... turn the key, injectors fire, pump does nothing, check the wires all good.... nothing.... take it off and put ground and power to it... turns on.. hook it back up and not a damn thing.... check the power coming through the harness and a bunch of wack signals, what the ****...
if anyone has any ideas, suggestions... please let me know, i need this damn thing running like yesterday... i cant miss anymore school, if its not working by the end of the week im trading it in for a bike.
ill be here all day tomorrow if anyone can think of anything

[bburris]

don't you have to prime external fuel pumps or something?

[J Cooper]

thats what i thought but in the instructions it just says turn key to on and let pump prime. so i dont know, the pump does work though and the wires are getting power to it. .... but shouldnt the power still kick on.

[aggielr]

through the hot wire, we're gettin 12 volts with a direct ground through the frame, with the ground and hot wire both from the plug connecting the pump, the voltage jumps around randomly
when a direct sourse is hooked to the pump it runs, so it's good, and the grounds in the wiring harness are good because there is 0 resistance between them and the battery ground

could this possibly be a bad ecu or should we try hooking the ground directly to the frame at the pump?

[stinger7401]

I'd try grounding it to the frame and see what happens. The 12v feed is only hot during key on or run right? If it is i would most definately ground it to the frame. It would also be good to trace the ground in the harness and see where it goes or call Holley and ask them.

[J Cooper]

i emailed holley at fuelpumps@holley.com and told them the situation, so waiting for the reply... yeah it only turns on when the key is at run or crank so i dont see why it would hurt it. the red wire(hot wire) is the one that sends the signal to turn on and off im assuming so making a ground doesnt change the performence..... and sorry mark yes it is 2 wires not 4.... im a retard. i guess ill try it out when i get home from school.