fuel pump only getting 7 volts ?!?!?!? - Page 2 - JeepForum.com
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post #16 of 42 Old 06-06-2019, 07:42 PM
Louie4
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Great responses guys. I appreciate them. I should have done some more testing earlier but ran out of daylight and figured this had been discussed before. So here are some responses and questions to answer questions.

-I used the ground in the plug as a point of ground reference. I stuck it to the frame but didn't get much of anything. However, I have never actually found a dedicated ground to the frame from the battery (nor any other path for that matter).

-I pulled the relay at the PDC and tested the relay. It tested good so I plugged it back in and tested for voltage with the key in the ON position and OFF. I got nothing in OFF and got the 7-8 volts in ON.

-I will run a wired directly from the battery ground and use it as the true ground. I'll also run a dedicated ground to the frame unless I just can't find it.

-When I tested the plug, I used terminals 1 and 2. I will have to confirm but I'm 95% sure those are the ones.

I found a wiring diagram on JF and Pirate.

BL/YL = GND
OR/BK = Pump Power
TAN/BK = Sending Unit


Lou

I have a jeep...and it is modified...I win.

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post #17 of 42 Old 06-06-2019, 09:01 PM
Awesome
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Sounds like a bad ground. For what it's worth, your frame is grounded to the battery through the body bolts and the ground strap on the firewall.

The 4th 5-seater YJ in the world.
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post #18 of 42 Old 06-06-2019, 10:23 PM
Louie4
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Quote:
Originally Posted by Awesome View Post
Sounds like a bad ground. For what it's worth, your frame is grounded to the battery through the body bolts and the ground strap on the firewall.
Which to me, is not directly grounded to the frame. I will remedy that so if I do add the ground to the fuel pump, it will actually be a ground.

I actually picked up some small ground straps from work that were for a $1 million dollar power transformer from Germany. Hopefully they are long enough.

The current grounds I have are:

Battery to body
Battery to engine block
Battery to winch
Cylinder head bolt to body (braid)

Lou

I have a jeep...and it is modified...I win.

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post #19 of 42 Old 06-09-2019, 03:17 PM
Boojo35
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How did you connect your meter to test for Amps? The circuit needs to be broken and the ammeter hooked in series.

If you cannot fix it with a hammer then it has to be an electrical problem.
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post #20 of 42 Old 06-09-2019, 03:44 PM
jtec
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post 15 had the information needed and WHICH wires to ck...

do not complicate this. It had the pinout. wire colors and circuit designation - ie power ground and sender...

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #21 of 42 Old 06-09-2019, 05:44 PM
Boojo35
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Quote:
Originally Posted by jtec View Post
post 15 had the information needed and WHICH wires to ck...

do not complicate this. It had the pinout. wire colors and circuit designation - ie power ground and sender...
Oops. Sorry your highness. I believe this was directed at me. Trying to remove some complication from his head if he incorrectly used a meter to test for amperage. He said his head was spinning.

Maybe.... No... certainly.... a voltage drop test is in order also.... both sides of the circuit.

Not denying your intelligence, experience and help on the forums. Sorry to step on your toes. I really believe though that his (without looking back to see his numbers) .09A reading on his fuel pump test is part of his confusion.

People do not always focus on the best post on the thread that leads them to the right direction. The dont know and dont always pick the most qualified answer as the next step and also get confused by something else that they are sure they did right.

People trying to help them may or may not read into the same things that the OP posted, thought or tried either. The OP may or may not have used his words correctly....

Anyways. Are we on the same team to help the guy or not? It is not like I told him to clean the throttle body or replace a bunch of sensors or something. I asked how he did a test that I think possibly in his own mind has him stuck.
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If you cannot fix it with a hammer then it has to be an electrical problem.
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post #22 of 42 Old 06-10-2019, 06:33 AM
Que89YJ
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No posts back. Is it fixed?

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post #23 of 42 Old 06-12-2019, 10:20 PM
Louie4
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Back on topic. I ran a dedicated ground from the battery and checked voltage at the plug. Same voltage. I need to run a new wire to the fuel pump and figure out where the old one terminates.




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Lou

I have a jeep...and it is modified...I win.

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post #24 of 42 Old 06-12-2019, 10:21 PM
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Oh and I pulled the tank, took the pump off and hooked it to the battery charger and it fired up. It would not do so with the plug.


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Lou

I have a jeep...and it is modified...I win.

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post #25 of 42 Old 06-13-2019, 07:26 AM
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Some pics.


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Lou

I have a jeep...and it is modified...I win.

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post #26 of 42 Old 06-13-2019, 03:56 PM
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Not that I'm saying you're doing something wrong but are you sure you are measuring the right wire. The fuel gauge will have power all the time key on and there's a voltage drop across the sender that will give you low voltage. The fuel pump will only show 12 volts for a couple seconds unless it starts or you jump the fuel pump relay. Its best if you check to chassis ground for the measurements.

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post #27 of 42 Old 06-13-2019, 05:40 PM
Louie4
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Quote:
Originally Posted by Que89YJ View Post
Not that I'm saying you're doing something wrong but are you sure you are measuring the right wire. The fuel gauge will have power all the time key on and there's a voltage drop across the sender that will give you low voltage. The fuel pump will only show 12 volts for a couple seconds unless it starts or you jump the fuel pump relay. Its best if you check to chassis ground for the measurements.

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Daryl, thanks for chiming in. I think you are on to something. I didnít think twice about that the source voltage for the gauge but it has to come from the battery (duh). I will jump the relay and test then, what terminals do I jump on the relay? Assuming you know off the top of your head.


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Lou

I have a jeep...and it is modified...I win.

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post #28 of 42 Old 06-13-2019, 05:45 PM
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30 to 87

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post #29 of 42 Old 06-14-2019, 01:46 PM
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Originally Posted by Que89YJ View Post
30 to 87

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Thank you, good sir.

Well, it appears I did not know what I was doing. I jumped the relay and tested and all was good. The bad part is I backfed 12 volts into the sending unit and scorched the little potentiometer before hand.

Thus, Iíve ordered a new sending unit that will be here in a week. I figured this is what should have been done anyway.

Thanks to those who have helped me determine that I am indeed...a dingus.


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Lou

I have a jeep...and it is modified...I win.

YJOTM July 2012
YJOTM February 2014


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post #30 of 42 Old 06-14-2019, 05:55 PM
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Glad its resolved.

My fuel pump is also from factory. What is the average life expectancy on these little suckers?

I have never had a fuel issue and am curious. I have to drop the tank soon because I want to reinforce my bumper/tire carrier for peace of mind (also want to put an access hatch in while there because why not?)

Stop whining about the 'ride' - If your YJ ain't wrangling your soul free, then might I suggest you buy a stationwagon... at least you can fit all your bull**** in the back.
~YJOTM MAY '16~
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