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Old 06-03-2013, 02:41 PM   #1
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98 TJ died Fuel Pump?

Hello had my TJ die on me today.It turns over but wont start.Its been tuned up recently.Well I poured a little gas down the throttle body and it then acts like it was going to start it did but rough for a sec then died.Do you think its the fuel pump?If so what type of pump does it need a link would be great.Ive never done this and will be doing myself if this is my problem.Just want to make sure I get the rite parst and get it all done in one trip.Thanks for any help.

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Old 06-03-2013, 02:44 PM   #2
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In a quiet area, listen for the fuel pump mounted inside the gas tank to cycle on then off 1-2 seconds later each time you turn the ignition switch from Off to On (not to Start). Does the fuel pump cycle on then off each time you do that?

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Old 06-03-2013, 03:17 PM   #3
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Originally Posted by Jerry Bransford View Post
In a quiet area, listen for the fuel pump mounted inside the gas tank to cycle on then off 1-2 seconds later each time you turn the ignition switch from Off to On (not to Start). Does the fuel pump cycle on then off each time you do that?
If I hear it does that mean its ok?Im waiting on a ride my jeep is about 5 miles from here at my moms and the jeep is my only ride.I know sucks but Im hoping its not the pump just curious what else it would be if its not that.My ride is on its way Ill let you know here in awhile.Thanks for your help Jerry.
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Old 06-03-2013, 03:30 PM   #4
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Being able to hear it or not will just help to isolate the problem, it won't necessarily indicate that the fuel pump is good or bad.
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Old 06-03-2013, 03:57 PM   #5
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OK 3 of us couldn't hear it.
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Old 06-03-2013, 04:00 PM   #6
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Well that helps, that is a simpler problem to diagnose than if the fuel pump runs.

I'd first swap the fuel pump relay inside the Power Distribution Center with a different relay of the same size, like the horn relay which is the same exact type of relay. I would also listen to that relay for a faint on-off clicking when the ignition switch is turned on. If the fuel pump relay audibly clicks but the fuel pump doesn't turn on along with the fuel pump relay, that's a pretty good indication the fuel pump is probably bad.

Also check fuse #23, a 20 amp fuse, inside the Power Distribution Center. That fuse provides power to the fuel pump via the fuel pump relay.
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Old 06-03-2013, 04:23 PM   #7
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Well we can here the relay click and still can't hear the pump.
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Old 06-03-2013, 04:24 PM   #8
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Dang I didn't see your last part about the fuse.I'll try to get back over there.
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Old 06-03-2013, 05:06 PM   #9
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*EDIT* only do this after you've checked the fuses Jerry mentioned.

Did you switch the relays as suggested by Jerry? I like to use the horn relay. The horn uses the same relay and it's easy to find out if your fuel pump relay is bad by honking the horn with the fuel pump relay in place of the horn relay.

If still nothing, it's time to diagnose further. You can go ahead and drop the tank and install a new fuel pump now if you want, but I would diagnose and be sure of the problem. Failure to diagnose caused me to buy a new fuel pump last year when I didn't have to.

Here is from the FSM about the relays:

Quote:
ASD AND FUEL PUMP RELAYS
The following description of operation and
tests apply only to the Automatic Shutdown
(ASD) and fuel pump relays. The terminals on the
bottom of each relay are numbered (Fig. 24).




OPERATION
" Terminal numbeis 30 is connected to battery voltage.
For both the ASD and fuel pump relays, terminal
30 is connected to battery voltage at all times.

" The PCM grounds the coil side of the relay
through terminal number 85.
" Terminal number 86 supplies voltage to the coil
side of the relay.
" When the PCM de-energizes the ASD and fuel
pump relays, terminal number 87A connects to terminal
30. This is the Off position . In the off position,
voltage is not supplied to the rest of the circuit . Terminal
87A is the center terminal on the relay.
" When the PCM energizes the ASD and fuel
pump relays, terminal 87 connects to terminal 30.
This is the On position . Terminal 87 supplies voltage
to the rest of the circuit .
The following will be done at the PDC (power distribution center)
With a multimeter, or test light, check for voltage at the socket for terminal 30. If it shows voltage, place a jumper wire between the sockets for terminal 30 and terminal 87. The fuel pump should run continuously as long as the jumper is in place. If the fuel pump doesn't run, there is one more check you can do to rule out whether the fuel pump is bad or you have a problem in the wiring between the PDC and the pump.

On the driver's side, at the top edge of the fuel tank, is a connector. Unplug it and check for voltage on the vehicle side of the harness. I recommend using the ground in the harness, rather than grounding at the frame, to rule out a bad ground to the pump. At the harness, the black wire is the ground and the dark green and white wire is the positive for the pump. To make it easier to test, use the jumper in place of the relay as I posted above.

If you get voltage at the harness, look at both halves of that connection for any corrosion or other indication a proper connection wasn't being made.

If everything tests good to that point, it's probably the fuel pump. There are a few more things you can test to be sure, but first things first. Do the tests I've laid out to see what's going on.

I hope this post isn't too confusing. I'm better at just doing it then typing it out lol.
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Old 06-03-2013, 05:06 PM   #10
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I don't see a number 23?
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Old 06-03-2013, 05:18 PM   #11
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Sorry for asking dumb question but what would I use as a jumper wire?Never done this but sounds easy enough.
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Old 06-03-2013, 05:24 PM   #12
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Both relays do work
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Old 06-03-2013, 06:02 PM   #13
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The fuse labels are also on a label under the PDC cover, maybe they changed the fuel pump fuse number from what my documentation indicated. If you give me your model year, I can confirm the fuel pump's fuse # and location tonight after I get home.
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Old 06-03-2013, 06:04 PM   #14
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98 jeep TJ Sahara
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Old 06-03-2013, 06:08 PM   #15
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I didn't see one labeled for fuel pump just the relay I swapped relays they both do the same.
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Old 06-03-2013, 06:51 PM   #16
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Quote:
Originally Posted by s14sh3r View Post
*EDIT* only do this after you've checked the fuses Jerry mentioned.

Did you switch the relays as suggested by Jerry? I like to use the horn relay. The horn uses the same relay and it's easy to find out if your fuel pump relay is bad by honking the horn with the fuel pump relay in place of the horn relay.

If still nothing, it's time to diagnose further. You can go ahead and drop the tank and install a new fuel pump now if you want, but I would diagnose and be sure of the problem. Failure to diagnose caused me to buy a new fuel pump last year when I didn't have to.

Here is from the FSM about the relays:

The following will be done at the PDC (power distribution center)
With a multimeter, or test light, check for voltage at the socket for terminal 30. If it shows voltage, place a jumper wire between the sockets for terminal 30 and terminal 87. The fuel pump should run continuously as long as the jumper is in place. If the fuel pump doesn't run, there is one more check you can do to rule out whether the fuel pump is bad or you have a problem in the wiring between the PDC and the pump.

On the driver's side, at the top edge of the fuel tank, is a connector. Unplug it and check for voltage on the vehicle side of the harness. I recommend using the ground in the harness, rather than grounding at the frame, to rule out a bad ground to the pump. At the harness, the black wire is the ground and the dark green and white wire is the positive for the pump. To make it easier to test, use the jumper in place of the relay as I posted above.

If you get voltage at the harness, look at both halves of that connection for any corrosion or other indication a proper connection wasn't being made.

If everything tests good to that point, it's probably the fuel pump. There are a few more things you can test to be sure, but first things first. Do the tests I've laid out to see what's going on.

I hope this post isn't too confusing. I'm better at just doing it then typing it out lol.
I have a multimeter but honestly never used it and have no clue how too lol I'm a fabricating mig welder so not experienced with any of that stuff.
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Old 06-03-2013, 06:56 PM   #17
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A multimeter is pretty simple. Set it to DC Volts (not Ohms, not AC Volts, not MA) and the switch setting just above 12 volts, whatever setting it has that is for more than 12 volts. The same switch likely selects both DC Volts and the range of volts you will be measuring. Just select the DC range of voltages that is next higher over 12 volts.

Attach the meter's ground clip to something that is bare metal in the engine compartment so it is grounded. Turn the ignition switch on.

Each fuse has a little bare metal spot on top, which is there so you can measure what is there with a volt meter. Take the meter's red lead and touch it to both of those contact points on each fuse, one side then the other. Not every fuse will have 12 volts DC on it but those that do, they must have 12 volts on both sides... at both of the fuse's two exposed test points in other words.

If you measure 12 volts on one side of a fuse and nothing on the other side, that fuse is blown. Measuring 12 volts on both sides of the fuse means it is good.
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Old 06-03-2013, 07:15 PM   #18
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anyone ever put a fuel pressure gauge on it?
if the psi is below 45 its the pump. if it's above 54 its the regulator
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Old 06-03-2013, 07:26 PM   #19
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anyone ever put a fuel pressure gauge on it?
if the psi is below 45 its the pump. if it's above 54 its the regulator
His fuel pump isn't turning on.
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Old 06-03-2013, 07:39 PM   #20
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Originally Posted by Jerry Bransford View Post
His fuel pump isn't turning on.
Yeah I wouldn't know how to test anyways.Just trying to pin point the problem money is tight and being only ride is rough.I'll have to wait till tomorrow now to get back over to try anything else.
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Old 06-03-2013, 07:41 PM   #21
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Thanks for all your help I figured coming here would be my best bet for answers.
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Old 06-03-2013, 07:57 PM   #22
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You don't have to go out and buy a 300 Fluke multimeter (although it would be nice). You can pick up a basic one for 20 bucks or sometimes even a little less. I recommend getting a digital meter instead of an analog. If you get ready to do this, I'll help walk you through it, jumper and all.
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Old 06-03-2013, 08:00 PM   #23
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Anything elves you can think of for me to check before I jump into a pump?
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Old 06-03-2013, 08:02 PM   #24
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Originally Posted by s14sh3r View Post
You don't have to go out and buy a 300 Fluke multimeter (although it would be nice). You can pick up a basic one for 20 bucks or sometimes even a little less. I recommend getting a digital meter instead of an analog. If you get ready to do this, I'll help walk you through it, jumper and all.
I have a cheap digital one picked up at a flea market years ago just never used one.I'll sure use it tomorrow.
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Old 06-03-2013, 08:05 PM   #25
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Anything elves you can think of for me to check before I jump into a pump?
Quote:
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I have a cheap digital one picked up at a flea market years ago just never used one.I'll sure use it tomorrow.
The tests with the multimeter will help rule out several things.
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Old 06-03-2013, 08:35 PM   #26
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You don't have to go out and buy a 300 Fluke multimeter (although it would be nice). You can pick up a basic one for 20 bucks or sometimes even a little less. I recommend getting a digital meter instead of an analog.
I have extensive experience with digital multimeters and electronic test equipment but for basic automotive work, I will always go to my analog multimeter. Analog meters (the kind with a moving pointer/indicator/needle) are proven easier to interpret & faster to use by far. You can see an analog's meter swinging up & down out of the corner of your eye to indicate voltage/lack of voltage, continuity/no continuity, etc. far more easily than with a digital meter where you actually have to read & interpret the numbers.

Which is why aircraft & space craft cockpits quickly went back to analog displays (digitally driven) after an ill-fated short-lived introduction of all digital displays so the pilots can more quickly & easily interpret what the data is. The pilots bitched & complained so vociferously about all digital displays that the aircraft manufacturers were forced to develop new replacement analog displays for them.

Digital meters have their place but at least in my opinion, analog meters are a LOT easier & faster to use in basic automotive troubleshooting uses.
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Old 06-03-2013, 08:47 PM   #27
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I have extensive experience with digital multimeters and electronic test equipment but for basic automotive work, I will always go to my analog multimeter. Analog meters (the kind with a moving pointer/indicator/needle) are proven easier to interpret & faster to use by far. You can see an analog's meter swinging up & down out of the corner of your eye to indicate voltage/lack of voltage, continuity/no continuity, etc. far more easily than with a digital meter where you actually have to read & interpret the numbers.

Which is why aircraft & space craft cockpits quickly went back to analog displays (digitally driven) after an ill-fated short-lived introduction of all digital displays so the pilots can more quickly & easily interpret what the data is. The pilots bitched & complained so vociferously about all digital displays that the aircraft manufacturers were forced to develop new replacement analog displays for them.

Digital meters have their place but at least in my opinion, analog meters are a LOT easier & faster to use in basic automotive troubleshooting uses.
I've used both, I use mine mostly for electronics and I prefer a digital for that. Either will work in this instance. A test light will also work for most of what he'll be testing.
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Old 06-03-2013, 08:49 PM   #28
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A test light will also work for most of what he'll be testing.
Exactly. It is such a simple circuit that using a digital multimeter just isn't needed for this level of troubleshooting. I only carry an analog multimeter (and a test light) with me in my Jeep, one or the other will troubleshoot anything likely to go wrong. No digital meter needed. Digital meters are only so common now because they cost next to nothing to make. I wish I had a dollar for every time I showed an electronics tech the beauty of an analog meter vs. a digital meter... the usual response was that it was an eye opener for them.
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Old 06-04-2013, 09:41 AM   #29
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ok, this is a stupid one, but still very valid.
Have you checked the plug that wires into the sending unit?
Is it plugged in?
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Old 06-04-2013, 10:29 AM   #30
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OK call me dumb but where is it?I've always had others work on my vehicles so I'm clueless but am going to do this myself money us tight. Its a 98 with 70,000 on it I figured it was getting close for things to start going wrong.

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