Jeep Enthusiast Forums banner
1 - 20 of 22 Posts

·
Registered
Joined
·
14 Posts
Discussion Starter · #1 ·
Hello to all. I replaced a failed in tank fuel pump on a 95 YJ now I have no power to the pump. I have run power to the tank portion of the harness and the pump will run and system will preasurize, but will not start. Have checked the relay @ Power box next to battery. Power to relay and relay checked, all ok but still no power to pump not even for the 3 seconds it should run before starting. Could the Autoshutdown relay/ circuit have something to do with it? where can I find a explanation of the function of this little item and caN i BYPASS IT?? THANKS IN ADVANCE FOR any HELP PROVIDED.
WHAT SHOULD HAVE BEEN A ONE DAY JOB HAS GONE ON A month. Rust & arthritic hands!
 

·
Registered
Joined
·
4,697 Posts
when you turn the key to on does the Check engine light come on for a few seconds?
 

·
Registered
Joined
·
966 Posts
Can you jump the power across the relay (30 to 87) and get the pump to run?? If you can jump the relay, its in the control side of the relay (something in that circuit is messed up, wire, connection, ecu). If not, its in the fuel pump circuit itself....

edit, check all fuses before you get to involved with stuff
 

·
Registered
Joined
·
14 Posts
Discussion Starter · #4 · (Edited)
Well the "edit' you posted was the '****' as they say these days.. A fuse for the dash lights was blown a 15 amp one now the relays click and the pump engages, primes and she STARTS!!:2thumbsup: but won't stay running. So today its a recheck of fuses. Plenty of fuel pressure despite sounding like she is 'out of gas' before she dies..
Should I start a new thread?? :drool:.
Off topic.but hows the weather in Naples??
 

·
Registered
Joined
·
966 Posts
Well the "edit' you posted was the '****' as they say these days.. A fuse for the dash lights was blown a 15 amp one now the relays click and the pump engages, primes and she STARTS!!:2thumbsup: but won't stay running. So today its a recheck of fuses. Plenty of fuel pressure despite sounding like she is 'out of gas' before she dies..
Should I start a new thread?? :drool:.
Off topic.but hows the weather in Naples??
Warm but dark and cloudy today....

Troubleshooting 101, check the cheapest, easiest stuff first. I just went through a 4 week episode with finding a problem with similar symptoms but I wasn't lucky enough to have a blown fuse.... connection problems in plug to ecu here
 

·
Premium Member
Joined
·
25,637 Posts

·
Registered
Joined
·
14 Posts
Discussion Starter · #7 ·
Fuel Press is @32 psi. no spark ended up to be a broken Ignition rotor. Replaced it but it won't stay running. It kicks over but will not continue to run.. will be doing TPS, Idel motor, Manifold Absolute Press and intake Manifold temp sensor.... I will advise on how that all turns out...
Thanks again guys!!
 

·
Premium Member
Joined
·
25,637 Posts
Wait! 32 is only part of it. You need to disconnect the vacuum line and see if pressure goes up. Then reconnect it and see if it hold pressure for 20 or more minutes. Each part is important. Check your fault codes next. I agree with the MAT sensor but you can check the sensors with a meter and save some $$$.
 

·
Registered
Joined
·
14 Posts
Discussion Starter · #9 ·
Codes came up with 13, and 33, and of course 55. here is where it gets crazy. Well NOW I have NO fuel press and with the key in the 'on' position: No fuel pump or press., no voltage at center post of Throttle Position Sensor, Vehicle Speed Serazynsor. Checked for a ground and it is GOOD. So today the washer bottle comes out to look at the computer so I can check continuity of mentioned sensors. As I look @ the schematic it sure looks like all these sensors are interdependent. Some weeks ago it started with the loss of my speedometer, I replaced the sending unit & it still did not work. That's when I learned to use my multi-meter. no power to unit and all downhill from there.
Thanks again for all the input...I will keep ya posted.
If you have any ideas I am all ears..and tools. LOL
 

·
Registered
Joined
·
14 Posts
Discussion Starter · #12 · (Edited)
The Saga Continues

Well a little back peddling, Under the dash After testing all the fuses @ PDU (next to battery) along with ALL the relays..all was well So I went to the ignition switch which had power from the red wire (heavy gauge) with key off and on. The other side of the connection is the Yellow wire which should be hot with the key on...dead as a ISIS fighter in Syria should be. lol Key on or off its D-E-A-D. So the ignition switch is defective, (I hope!!!) What this has to do with my VSS(Vehicle Speed Sensor) going out a few months ago is beyond me. Oh since the fuel pump will NOT energize it is not possible to further test the pressure @ the fuel Rail...sure am learning a boat load of stuff!!
 

·
Registered
Joined
·
966 Posts
I learned more than I ever wanted to know about that part of the system when I was trying to figure mine out....

If the ignition switch is bad, it would prevent the ECU from powering up and starting fuel system.... Don't feel bad about vs thing yet, still haven't got my speedo working yet either....
 

·
Premium Member
Joined
·
25,637 Posts

·
Registered
Joined
·
14 Posts
Discussion Starter · #16 · (Edited)
UpDate

Well after an Ignition Switch change I have all (2) relays going but still no fuel pump so into the computer harness I went and found power @ 3 and 9 and grounds on 11, 12, 13, and 14. So unless someone has another thought it's into the computer today for a 'look-see' for expanded diodes or obvious signs of problems
With the ignition key in the run position I still have no power to the Throttle Position Sensor (TPS), Manifold Absolute Pressure (MAP) or Vehicle Speed Sensor (VSS) and I think they all share a common feed from the computer.
And with power to pin 3 & 9 and solid continuity to ground on pins 11, 12, 13, and 14. it looks more & more like the Engine Control Unit (ECU)

PS all the 3 letter codes explained VSS, ECU, etc. were done for the benefit of people like me who, at one time had no idea what the letters stood for.:wave:
 

·
Premium Member
Joined
·
25,637 Posts

·
Registered
Joined
·
14 Posts
Discussion Starter · #18 · (Edited)
I checked it to the Battery (with cable attached), to the negative/ ground battery cable, and the connectors. Continuity to ground both negative battery & Body ground good.. Thanks
UPDATE::: After removal of the "computer" and inspection it was observed that two of the three diodes were 'popped' Sent it to Miami, Fl to be rebuilt. 5 day turnaround. NOW I have power to everything and she starts!!
As in life the more you learn, the more you realize how much you do NOT know.. As of this moment I know more about the 95 Jeep YJ than I ever thought I would with the help of ALL OF YOU GUYS & GALS and a few Valium. LOL

Special thanks to Que89Y....
 

·
Registered
Joined
·
1,886 Posts

·
Registered
Joined
·
966 Posts
You really deserve some kind of award for that much patience, but I'm not sure what. Mine is my only driver, no other way to get to work... I just wouldn't be able to do what you did :duhrock:
Que pointed me in the right direction with spread pins and eliminating other stuff....

Most proud of figuring out screwy cel thing myself to tell the truth..
 
1 - 20 of 22 Posts
Top