fuel pump relay help

[jammin636]

hey can someone tell me where the fuel pump relay is? my explorer wont start, and i pulled a 543 code which is the secondary circuit fault. i wanted to check the relay first. can i get some help

 

[410Fortune]

in the power dist box under your hood.

 

[jammin636]

k thanks. ill take a look

 

[410Fortune]

You can also use the search function, the relay is a very very very common topic

 

[jammin636]

yea i can only read so much. everyone just talks about it and never says where it is. im still not sure. i looked in the box and all i see are fuses, am i missing something here? i still dont feel as if im getting anywhere with this problem. it wants to start but its just not taking. i kinda acts like its gonna then it just dies. am i looking in the wrong place?

 

[410Fortune]

if this is a really early model 93 then it may have the 91-92 style fuse box, the relays are directly underneath, there are 3, brown, green and black (AC WOT, Fuel, and EEC)

 

[marragtop]

Are you sure it's the FP relay? When you turn the key to the ON position, you should hear the fuel pump prime for a second or two. If you are hearing that, then your problem may not be the FP relay. If you don't hear it, then the relay is a good place to start.

 

[jammin636]

yea i has the old fuse box. i took it all apart before and i those might be relays, thanks for clearing it up. im not hearing anything, no priming or humming so im gonna replace the relay and see what happens.

 

[shamaal]

On the 91s, the fuel pump relay is the one nearest the firewall.

 

[jammin636]

crap!!!

:fire: i replaced the fuel and eec relay and it still doesnt wanna start. does anyone have any other ideas. im not hearing any sort of priming at all. i do hear a click in the back when i turn key to the start position though. could it maybe be the spark plugs or the coil pack? so what part should i replace next. fuel pump. if i had to do that i was thinking of just cutting a hole to get at it from above. any ideas?

 

[shamaal]

You want figure 19
http://www.autozone.com/servlet/UiB..._us/0900823d/80/0b/a9/c7/0900823d800ba9c7.jsp

The inertia switch is at the passenger's feet at the firewall. The most common thing that goes out is the fuel pump, with the aid of the diagram you can do some troubleshooting, reading voltage on a paperclip used to jumper the inertia switch connector should yield a +12 voltage for two seconds when the key is turned on. Further verification can be made by running +12 volts to the same jumper. Depends upon how certain you want to be.

Replacement involves dropping the tank, you'll need the special fuel connector tools from an autostore. The tank is plastic, I wouldn't recommend cuting holes above it, but I'm the cowardly type.

Feel free to ask questions or do a search. There has been a rash of these recently.

 

[DeRocha]

I have compiled some similiar threads to get you in the right direction..
Stuff like
Fuel pump low voltage (inertia switch pic)
Fuel pump problems
Fuel filter Replacement

 

[jammin636]

alright thanks everyone. i just got done checking the inertia switch and found a few things. i jumped the switch with piece of wire and found that after i put the key to the start position it would jump to 10 to 11 V. what does that mean? after the jump in voltage it would go down to 6.3V, shouldnt it go down to zero or am i doing something wrong?

 

[jammin636]

i also read through all of the threads above i just dont know where the best place to start is. anyone?

 

[shamaal]

It means you're going to be needing a new pump. There is also a chance that the pump connector is corroded, but you have the tank down anyway you might as well change it.

The 6.3 volts that you read is the sense bias voltage from the computer. Digital voltmeters have such a high impedance that these voltages are picked up. On mine it's +6.8 VDC.

With the jumper removed and reading the first pin to ground I have 2.5 ohms. This is the pump winding.

 

[jammin636]

k when i took the jumper out it read in the millions of ohms on the first pin. the second pin read in the 10s of thousands. so that means somewhere along wire to the pump theirs a short right? im guessing my next task would be to drop :thumbdwn: the tank and check out whats going on under there.

 

[shamaal]

No short, an open.

Reading open on the first pin (>Mohm) to ground indicates that there is an open between the inertia switch and the fuel pump ground. (see fig on schematic). The most likely problems are a corroded connector at the fuel pump or the fuel pump itself. Yes, you will have to drop the tank and use the special fuel line connector removal tools.

The reading on pin 2 is back through the computer and is meaningless.

 

[jammin636]

awesome thanks alot shamall. you have provided me with lots of good info. ill get right on this to see if it fixes the problem. i hate having to bring my vehicles to a shop to service them. i love doing all my own work, and it saves tons of money.

 

[jammin636]

i need some help. i replaced the fuel pump and fuel filter and the truck still wont start. what now???!!! i had a friend with me and he said he can hear a click coming from the fuel pump when i turn it to the start position. am i doing something wrong or do i need to start looking in another direction?

my gut tells me theirs no spark but who knows. was thinking of getting news plugs wires and coil. we can also smell fuel after trying to start it a couple times. anyone??

 

[410Fortune]

the fuel pump should prime when the key is tuirned to the on position, this means it runs for a few seconds, not clicks

If it does not and its a new pump then the issue is in the wiring to the pump.
I suspect first the plugs that relay attaches to, it is common for them to get corroded, so look deeper then just plugging in a new relay.

Also are you sure you replaced the correct relay?
I would check your fuse, relay, then trace the wiring....
if the fuel pump is not priming then that is the first thing to fix, dont move on to spark just yet.