Fuel issue cause by wiring?

[Macthemechanic]

My XJ has the standard cooling setup I believe. One mechanical fan one electric.
When the electric fan comes on, the voltage drops a bit (The fuel pump is kind of noisy) and while cruising on the freeway will start to stumble if I go more than about 1/4 throttle. Is this a common issue? either resistance on the + side, or bad ground?

 

[Macthemechanic]

Checked out the pressure and volume. Volume seems to be right, but pressure is down 15-20 psi.

 

[DaveB]

I would check the voltage at the pump

 

[Trate D]

I would also check the ballast resistor on the driver side inner fender. You can even just jump the wires going to it and see if that makes an improvement. Looks like this...

 

[Macthemechanic]

Any problems bypassing the ballast completely?
Checking voltage at the pump is my next thing.
Seems like the voltage needle drops quite a bit when the fan comes on so I'm going to check it hot also.

 

[DaveB]

I would also check the voltage at the alternator and battery to make sure the main voltage supplies are staying up when the fan kicks on. You don't have to wait till its warm, just turn on the AC.

 

[Trate D]

Nope, it can be bypassed. It is there to more or less quiet down the fuel pump through slightly decreasing voltage.

 

[Macthemechanic]

Battery voltage is 14.6 or so. One side of the resistor is at 13.8 the other is about 9.8, so I am going to just get out my soldering gun this after noon.
There is some crappy wiring right next to it that is actually the fan. So it just comes on with the key, which seems to work ok for now, but it looks like I'll need to hit up a junk yard for a relay.

 

[Macthemechanic]

Well, after bypassing the resistor the issue remains. I haven't had a chance to recheck the voltage or pressure but the driveability issue is still there, so it must be a bad FP.

 

[bryson]

Bad alternator? If the aux fan kicking on is dropping alt output enough to dim your lights, you need to solve that issue before you start replacing fuel pumps I'd think. If the alternator isn't putting out enough amperage to keep your pump happy, then, well, the problem isn't your pump.

The voltage may read fine, but there's more than an alternator than just 14.6 volts output - amperage is at least as important. I'd pull the alternator off and have it bench tested. Check ALL of your battery/alternator connections for corrosion too - pull them off and clean them, as you can't always tell by just looking at them.

 

[Macthemechanic]

The aux fan is wired up so its on when the ignition is turned on. I'll probably go ahead and have the alternator tested. I may also disconnect the fan first and recheck fp pressure. Might be an easy way to tell? The wiring for the fan is... Sub par at best lol

 

[Macthemechanic]

Its kind of weird though cause it drives fine for 20 min, and then starts acting up. Fuel filter looks pretty fresh, and it is installed with the flow going the right way

 

[frieed]

sometimes the ugliest electrical gremlins to solve are ground related. Can you ohm out from the ground on the fuel pump to the negative battery lead?

 

[Macthemechanic]

I can certainly give it a shot.

 

[Macthemechanic]

So it seems something is wrong with the pick up in the tank.
I was concerned I would have to drop the tank so I never filled up beyond half a tank. I thought I'd fill it up, and its been running fine.
So it sounds like I need to pull that out and see what the HECK is going on with it.

 

[Macthemechanic]

Has anyone ever had a FP overheat? Someone having a similar issue said maybe a crank position sensor but i can hear the pitch of FP change when its struggling

 

[bryson]

Has anyone ever had a FP overheat? Someone having a similar issue said maybe a crank position sensor but i can hear the pitch of FP change when its struggling

That sounds more like the pump is struggling to pull fuel - maybe you have a fuel starvation issue rather than a pump voltage issue... The pump shouldn't ever overheat since it's in the tank - if it does, well then that's a bad day. Pull the pump and check the pickup filter. Is the bottom of your fuel tank dented?

 

[Macthemechanic]

I just picked up an in tank and in line filter. Never thought about the tank being dented, but the fuel level doesn't really affect it. Although if its having issues and put in a gallon of fuel it runs ok for about 5 min. Also if i shut it off and let the fuel pump prime 3-4 times it runs ok for 5 min. Really friggin weird and annoying.

 

[bryson]

I was asking about the bottom of the tank being dented because it could have damaged the pickup for the fuel pump. Just thinking out loud.

 

[Macthemechanic]

I understand. I'll have look at it in the morning. I really appreciate all the help. I'm Damn near driving it to the junk yard and starting over. Its got a blown head gasket too.