No power to fuel pump
- Thread starter glenn
- Start date
greg92jeepxj
Official Supporter
Just as SUPERJ has advised , you will have to verify power actually reaching the fuel pump.
Its good you checked the fuse and relay , but ultimately , is power reaching the fuel pump ?
As SUPERJ stated , it is essential to own the proper wiring diagram for your jeep as we do not now know if an electrical problem exists. It is likely as he stated that the pump has just failed, but we must always be prepared for diagnostics. In general , it's just difficult to sort out electrical checks without a schematics , but you can try the AUTOZONE website for the wiring diagram.
First , when you turn on the ignition before cranking , do you hear the fuel pump engaging ?
If not , time to climb under neath . Disconnect the wiring harness connector to,the fuel pump . You should find this close to the fuel tank , usually near the fuel lines on the fuel filter.
incidently , do we know if the filter has been changed frequently ? Clogged filters will kill a pump
faster than running the fuel down below 1/4 of a tank (bad habit) . With a test light , ign. on , you are looking for power at the power wire. There is a ground and sending unit wires , should be an orange wire . When the key is turned on , you should be able to read voltage at this wire as the pump goes on to pressurize the system for starting. If power is found and you do not hear the pump turning on , line and/or filter badly clogged and/or pump bit the dust. Verify if there is fuel line pressure at the fuel rail to,the injectors first before dropping the tank . I wish the YJ has a similar tank design as the XJ (tank need not be dropped) , but body design did not permit.
In summary , first check fuel line pressure at the rail , if not found or weak , check power wire at harness disconnect near tank , if not found , investigate electrical with the aid of the WIRING DIAGRAM. If found , check fuel filter and lines for restrictions (clogs) . If all previous checks has determined the pump is shot , time to drain and drop the fuel tank. Best of luck to you , post back when you can the results and if further assistance is needed to changing pump. Greg92jeepxj
Its good you checked the fuse and relay , but ultimately , is power reaching the fuel pump ?
As SUPERJ stated , it is essential to own the proper wiring diagram for your jeep as we do not now know if an electrical problem exists. It is likely as he stated that the pump has just failed, but we must always be prepared for diagnostics. In general , it's just difficult to sort out electrical checks without a schematics , but you can try the AUTOZONE website for the wiring diagram.
First , when you turn on the ignition before cranking , do you hear the fuel pump engaging ?
If not , time to climb under neath . Disconnect the wiring harness connector to,the fuel pump . You should find this close to the fuel tank , usually near the fuel lines on the fuel filter.
incidently , do we know if the filter has been changed frequently ? Clogged filters will kill a pump
faster than running the fuel down below 1/4 of a tank (bad habit) . With a test light , ign. on , you are looking for power at the power wire. There is a ground and sending unit wires , should be an orange wire . When the key is turned on , you should be able to read voltage at this wire as the pump goes on to pressurize the system for starting. If power is found and you do not hear the pump turning on , line and/or filter badly clogged and/or pump bit the dust. Verify if there is fuel line pressure at the fuel rail to,the injectors first before dropping the tank . I wish the YJ has a similar tank design as the XJ (tank need not be dropped) , but body design did not permit.
In summary , first check fuel line pressure at the rail , if not found or weak , check power wire at harness disconnect near tank , if not found , investigate electrical with the aid of the WIRING DIAGRAM. If found , check fuel filter and lines for restrictions (clogs) . If all previous checks has determined the pump is shot , time to drain and drop the fuel tank. Best of luck to you , post back when you can the results and if further assistance is needed to changing pump. Greg92jeepxj
greg92jeepxj
Official Supporter
greg92jeepxj
Official Supporter
Hey that's great ! Bet you feel better knowing you don't have to pull a tank out ! I would , hate pulling tanks down , always get gas on me ! That's because I get lazy and don't drain the tank .
thats a no -no ! If you can make a fused jumper wire , after you change the filter , see if you can get a fuel pressure reading at the fuel rail . If you don't own a fuel,pressure gauge , maybe someone like AUTOZONE can rent you one . I feel better already for you ! Let us know how it goes , if all it is , is just electrical , it will be that much easier. Could be a dead relay . But I think you said the relay was ok ? Try swapping in one that is good . Let us know what you get .
best of luck to you and happy Father's Day !
thats a no -no ! If you can make a fused jumper wire , after you change the filter , see if you can get a fuel pressure reading at the fuel rail . If you don't own a fuel,pressure gauge , maybe someone like AUTOZONE can rent you one . I feel better already for you ! Let us know how it goes , if all it is , is just electrical , it will be that much easier. Could be a dead relay . But I think you said the relay was ok ? Try swapping in one that is good . Let us know what you get .
best of luck to you and happy Father's Day !
greg92jeepxj
Official Supporter
I don't like to use the word failure , so I won't . Since you did not yet achieve your goal of getting your jeep running , I will state you did not as of yet complete your task . So far , you jumped a power wire to get the fuel pump to run to find out if the fuel,pump is working. It's working , so that part is eliminated . No need to change a fuel pump . You will have to go back to the power distribution center and verify that current is ACTUALLY flowing from fuse , to relay to fuel pump harness . Obviously , current is not making to fuel pump harness at tank or engine would start .
Use a computer safe test light ( so you don't spike any wiring to computer) and immediately as key is turned to RUN position , check that current is going across fuse . I'm working from a diagram from a '92 wrangler since I don't have a '95 , but it will be similar if not the same.
If current is making it across fuse , now check terminal 85 in fuel pump relay . Check the same way , key in RUN and immediately check for current . Incidentally , keep in mind the AUTO SHUTDOWN RELAY is tied in with the fuel pump relay , so it may have to be checked as well . Check terminal 30 in fuel pump relay this way to. Check all fuses as well since this '92 diagram is showing an ign. Lps fuse to supply power to the fuel pump relay. Your goal is to find where is power and where it isn't . We will not readily blame the power train control module , or PCM (computer) , you would only do that if all checks are complete and wiring and components found to be in working order. If you can get a copy of the wiring diagram for this circuit for this jeep from AUTOZONE, it would help you immensely . This is where current is delivered from and ends up at fuel pump. I would tell you to just jump terminal 30 to terminal 87 , but you must find current first . Since some of these wires feed back to the PCM , you must use care , and a computer safe test light. They are not expensive and should be at your parts store. If you do find power at terminal 30 , you may try to jump it , but again , a fused jumper is to be used . You are better to invest in a TEST relay , as they are safe to check in these procedures. To cut to chase ( I know you want to get this done ) , see if a buddy has a couple of known good relays lying around , to avoid having having to buy some until you know for sure if one or both are bad.
Replace one relay in fuel pump relay socket and the other in the auto shutdown relay. Replace ANY bad fuses with one of the correct value as well . Turn on key and listen for fuel pump . Hopefully you got it . Try to crank . Hopefully it will start . A fuel pressure gauge is helpful to have at this Point . Your not just looking for current . You want fuel to, but , no current , no fuel.
please try these checks and let us know what you find. If there is anything you may not understand for any reason , post back for our help. Best of luck , greg92jeepxj
Use a computer safe test light ( so you don't spike any wiring to computer) and immediately as key is turned to RUN position , check that current is going across fuse . I'm working from a diagram from a '92 wrangler since I don't have a '95 , but it will be similar if not the same.
If current is making it across fuse , now check terminal 85 in fuel pump relay . Check the same way , key in RUN and immediately check for current . Incidentally , keep in mind the AUTO SHUTDOWN RELAY is tied in with the fuel pump relay , so it may have to be checked as well . Check terminal 30 in fuel pump relay this way to. Check all fuses as well since this '92 diagram is showing an ign. Lps fuse to supply power to the fuel pump relay. Your goal is to find where is power and where it isn't . We will not readily blame the power train control module , or PCM (computer) , you would only do that if all checks are complete and wiring and components found to be in working order. If you can get a copy of the wiring diagram for this circuit for this jeep from AUTOZONE, it would help you immensely . This is where current is delivered from and ends up at fuel pump. I would tell you to just jump terminal 30 to terminal 87 , but you must find current first . Since some of these wires feed back to the PCM , you must use care , and a computer safe test light. They are not expensive and should be at your parts store. If you do find power at terminal 30 , you may try to jump it , but again , a fused jumper is to be used . You are better to invest in a TEST relay , as they are safe to check in these procedures. To cut to chase ( I know you want to get this done ) , see if a buddy has a couple of known good relays lying around , to avoid having having to buy some until you know for sure if one or both are bad.
Replace one relay in fuel pump relay socket and the other in the auto shutdown relay. Replace ANY bad fuses with one of the correct value as well . Turn on key and listen for fuel pump . Hopefully you got it . Try to crank . Hopefully it will start . A fuel pressure gauge is helpful to have at this Point . Your not just looking for current . You want fuel to, but , no current , no fuel.
please try these checks and let us know what you find. If there is anything you may not understand for any reason , post back for our help. Best of luck , greg92jeepxj
greg92jeepxj
Official Supporter
Glad you got a relay to work with , any luck with fuel pump ? Did you hear pump ?
if jeep did not start yet , more investigation needs to be done . Sorry , but I got to return to work , post when you can and I will do what I can when I return . Really , best of luck .
Hope good news will be coming soonest !
if jeep did not start yet , more investigation needs to be done . Sorry , but I got to return to work , post when you can and I will do what I can when I return . Really , best of luck .
Hope good news will be coming soonest !
greg92jeepxj
Official Supporter
I got a minute to post , when I return home , I want to see wiring diagram for terminal 85 & 86 , I think that was in line with the auto shutdown relay , try swapping auto shutdown relay with horn relay to see if that works . Will take a look again tonite . Post when you can ? Your getting warmer ! Almost there , I think .
greg92jeepxj
Official Supporter
I must hit the books , we are close , but mist find where else to look . Must find what else powers the 86 circuit , will have to do with the auto shutdown relay , to start with . Will post soonest . Thank you .
greg92jeepxj
Official Supporter
I apologize , but I cannot research tonite , I will start again in the morning . As far as trying to start engine with fuel pump harness jumped , as long as it is disconnected and jumper is on fuel pump side of harness (you may need a ground ) so no damage risk to harness back to PCM , you may try. But first , with everything assembled , fuel pump harness ,etc. , did you get spark from the ignition ? I am curious to know . Food for thought in my diagnostics. I must figure if PCM is working.
