That is strange that the voltage did not change. When the fuel pump relay is activated, Pin 30 which is contant voltage from the fuel pump fuse, gets connected to pin 87 which feeds the pump. When you turn the key off, the relay deactivates and the pump should not have any power.

 

Another thing about voltage at the pump - when you turn the key, the pump should only be energized for two seconds before the computer shuts it off.

I was turning the key on then crawling back under the car to put the meter on it. Obviously...I can't get back under there in two seconds. I need to get a helper to be sure why I only show 6.3 volts. I'll report when I know.

 

I checked voltage this morning with Sun-Ra, my reliable 12 year-old key-turner and discovered the center wire on the three wire fuel pump harness - the harness plug right next to the fuel filter - carries 6.1 to 6.3 volts all the time the key is on like "ready to serve" voltage. I think it has voltage even when the key is off but forgot to check that.

The right wire spikes to 12.17 volts (or thereabouts) when the key is actuated but only momentarily (two seconds). After two seconds the computer shuts the voltage off unless the motor is running. Bear in mind, the right or left wire is a matter of plug orientation. If you have a queer plug, it will be the left wire. If you have a normal plug, it will be the right wire.

The leftmost wire seems to have no voltage at any time. It might if the engine was running, I don't know because the engine is not running because the fuel pump gods have decreed that it not run until a specified amount of money and time has been spent and I have not yet reached that point.

So I have concluded my pump is bad and I will R&R sometime today. Meanwhile I will summarize the diagnosis steps for future use.

If car won't start and you KNOW you have spark and it is occuring at the correct time, you know it must be fuel related. To find out the problem:

1. Remove Schrader valve cap and press the button - if fuel squirts out, you have pressure. It may not be ideal pressure but at least you know there is SOME pressure. If underpressurized, it might run poorly but should run some. If no pressure...no run. You should also be able to hear the fuel pump kick on for two seconds or so when you turn the key on. If no sound, go to step 2. If you have sound of pump and no gas squirting out, you probably have a plugged filter or gas is squirting out under the car someplace...but unless you have both nostrils plugged with your fingers, you probably know its the filter.

2. If no pressure and/or no sound of pump coming on, swap the fuel pump relay out for a known good relay. If this fixes it, buy a new relay for $11. If not, check all the fuses to make sure they are good. No joy? Goto step 3.

3. If relay test fails, crawl underneath and pull the wire harness plug apart and check voltage. One of the three wires should show 6.0+ volts when key is on and one should show a spike to 12+ volts MOMENTARILY when the key is activated, then zero after a couple seconds. If you have 12v, then the harness up to that point is probably good.

4. If the harness is good up to the plug but the pump makes no sound, either the wiring from the plug to the pump is bad or the pump is bad. In any case, you'll want to replace the fuel filter while you're down there so remove the OUT feed line and turn on the key. If gas squirts out, you are hard of hearing and the line from the filter to the fuel rail is plugged somewhere. If not, remove the IN feed line and turn the key. If gas squirts out, you are hard of hearing AND have a plugged filter. Buy a $6 filter and make an appointment.

5. If filter is new/unplugged, clean up the mess around the retaining ring that holds the pump in place and proceed to remove & replace pump. There are good instructions elsewhere on how to do this but I like these the best: http://www.allpar.com/SUVs/jeep/fuel-pump.html

 

caemi or anyone else, when you replaced your fuel pump, how hard was it to guide the return spout into the hole? I can't seem to get my fuel pump to seat right. Is there some trick to it? thanks for your info.

 

Pretty easy. Once you have the right angle it goes right in.

Seating it is a PITA. Seems you have to insert, remove, insert, remove a couple times before the Gas Tank God permits it. I have no explanation other than that.

The key is to center the pump assembly pretty well then put the locking ring into position. Hold the ring down with some pressure and star turning/driving it with a long handled screwdriver. I know, I know...use a brass punch. Righto...I couldn't get a punch up in there to save my life so I just babied it in with a long flat blade driver.

Mine didn't leak. I suggest an offering to the Gas Tank God before you start. He takes Paypal and I have his address...PM me.

 

Harbor Freight sells a fuel pressure gauge cheap,, everyone should have them,, I love mine,, used to make my own from cheap Ace hardware water pressure gauge and fuel line but the schrader valve has to be depressed, hence the Harbor Freight gauge.