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warthogdriver 06-27-2012 06:20 PM

fuel pump help
 
ok first off some background...

couple of weeks ago my wifes 05 grand cherokee (125k miles) starting acting up.

it would crank all day long but not start...so i checked the fuel pump relay by swapping it with the ac relay in next slot over...that worked.
but what i found strange was that the pump relay still worked when left in the ac slot...so i swapped it back. i thought maybe corrosion or a glitch.

then it happened again...so i used electronics cleaner on the relay and slots for the connectors. started working again.

then today...the cherokee wouldnt start again..this time though swapping the relay didnt work.

after some searching around here i checked the asd relay and other fuses...disconnected the battery for 20 min or so and checked for codes (no codes). i also listened for the pump...nothing at all. also no pressure at all at the fuel rail.

so at this point based on previous exp, i am thinking fuel pump.

so i went looking for some more info around here....my question is dropping the tank. i noticed that the skid plate is under the tank, is there straps holding the tank in place or just the skid plate?

i have mech skills (not a pro but i have some exp), i also know to ask when in doubt.

sorry for the long story, i just know more info can help.

any help or advice would be greatly appreciated, thank you.

Escape 06-27-2012 09:57 PM

Re: fuel pump help
 
Quote:

Originally Posted by warthogdriver (Post 648975)
after some searching around here i checked the asd relay and other fuses...disconnected the battery for 20 min or so and checked for codes (no codes). i also listened for the pump...nothing at all. also no pressure at all at the fuel rail.

so at this point based on previous exp, i am thinking fuel pump.

so i went looking for some more info around here....my question is dropping the tank. i noticed that the skid plate is under the tank, is there straps holding the tank in place or just the skid plate?

i have mech skills (not a pro but i have some exp), i also know to ask when in doubt.

sorry for the long story, i just know more info can help.

any help or advice would be greatly appreciated, thank you.

Disconnecting the battery will erase all codes and set a stored trans code saying the battery was disconnected. Read the codes first then disconnect.

There are 2 straps holding the tank in place plus the filler neck, electrical harness and some other stuff.

Before you go dropping the tank you might want to jump the fuel pump relay. This will send direct battery power to it and will verify if it is the pump or some other electrical issue. If you still have no fuel pressure with the relay jumped you will probably need a fuel pump.

If you have a friend with a scan tool the wave pattern of the pump can also be viewed.

Also inspect all wiring going to the pump. It runs right by the cat on the drivers side by the pinch rail and should be wrapped in aluminum with an aluminum shield.

http://i41.photobucket.com/albums/e2...F/IMG_0780.jpg

warthogdriver 06-27-2012 10:10 PM

Re: fuel pump help
 
yeah, my list was out of order a bit...i checked codes and disconnected the battery as the last resort.

thank you for the reply....i did see info on jumping the relay as i continued searching but i didnt know which pins to jump.

agreed on the wiring...i was going to check the connectors at the pump when i dropped it as well for corrosion or other issues.

i have had fuel pumps fail on me before and it has been without warning...the relay issue leading up to the failure is what threw me...i guess it may have been my warning.

thanks again for the reply.

Escape 06-27-2012 10:59 PM

Re: fuel pump help
 
For a 2005 WK JGC

Fuel pump relay jumper

Relay Pin 30 = Battery
to
Relay Pin 87 = Fuel pump

If still no pressure or no start. It's the wiring or pump.

warthogdriver 06-29-2012 01:35 PM

Re: fuel pump help
 
ok, so i guess i am on a hunt.
the new pump did not solve the problem...i inspected the wiring well enough i thought...the harness has power.
either that or i have other issues i will have to do more searching.
i still have no codes either. i tried a little starter fluid in intake...tried firing.
it ran for a split second then stalled...so i have spark and air...back to fuel issue.

edit:
ok, i checked the old pump by hooking it up to a 12 volt source...and it worked.
so now i am thinking it is the fuel pressure regulator, which (if i hadnt been such a cheap bastard) i would not have this problem if i had bought the assembly and not just the pump.

thank you for your help so far Escape.
the tank was held up by the skid plate though...6 bolts with what looked like three straps integrated into the skid plate. i have to say the over all job was simpler than i had expected...the quick connects on the tank were great. far better design then the quick connects from gm and ford i am used to.


edit #2
ok, i figured out the problem i think.

i am getting a voltage reading at the pump harness, that registers for the prime and while cranking to start the engine.
however, when i attach the pump harness to the pump the pump wont work...figured that out to.

i took the pump out of the tank and applied the harness to see why it wouldnt work esp since the pump would work under an independent power source. when i plug the harness into the pump the voltage reading was zero!! the jeep has been shutting down the pump the whole time.
i verified this by putting the pump back in the tank and wiring it directly to a 12 volt source while i had a helper turn the key....the jeep started and ran.
soooo, the pump seems to have been fine the whole time.

now from what reading i have done it looks like the first thing to check is the crankshaft position sensor...apparently if bad, the pcm will shut down the fuel system.

i am hoping somewhere down the line this little witch hunt of mine will help someone out.

i have to say i love the jeep, but i dont like all the electronics. i am used to less sensors and more direct cause and effect issues.

warthogdriver 07-02-2012 05:14 AM

Re: fuel pump help
 
ok,

on advice from others i did the crankshaft pos sensor.
still nothing.
at this point i am out of ideas and patience...so off to local shop.
i will report back what caused all of this.

kennzz05 07-02-2012 08:31 AM

Re: fuel pump help
 
did u try checking voltage to another ground source other than the harness when you were testing

curio 07-02-2012 08:51 AM

Re: fuel pump help
 
yep. try first all cables and connectors, maybe a corroded or broken filament only working at certain degrees of flexing an not visible from outside.

Good luck

Achim

warthogdriver 07-02-2012 09:04 PM

Re: fuel pump help
 
yes,
i checked the harness and even went and got another one for a couple bucks from local yard going from the connection above axle to the pump...still no power to the line once the pump was connected.

i had it towed to a local repair guy that specializes in auto elec. systems. i just cant spend anymore time on it or keep tossing parts into the fire.

i am hoping it is something stupid simple i overlooked...just to save expense.
i have had him do work on my mustang when i got in over my head.

i will report back what it is when i find out.

i want to say thanks to all who replied, your suggestions did help me look for the problem.

i just have to when to cry uncle i guess.

Escape 07-02-2012 11:26 PM

Re: fuel pump help
 
Swap out or jump your ASD relay and see if you have power at the pump harness.

You should be getting a code though.

warthogdriver 07-02-2012 11:52 PM

Re: fuel pump help
 
i swapped the asd relay with the adjacent one in the power block..still nothing.
i have been at it for 4 nights when i get outta work and have made no progress so it is time to call it.
believe me i hate tossing in the shop rag..but this one has me stumped.
i checked all over the net. i checked all the grounds, tried jumping it, and alot of other checks and such....all nothing.

the worst part is no code....i hate going in blind.

edit:

ok, so for 100.00 the problem is gone. the shop inspected the jeep and found that i must have burnt up a connection in a power block in the dash. so i was given two options:
tear the dash apart to find the issue = 300.00
or
run a bypass from relay to tank = 100.00

so my jeep went in for bypass surgery you could say. which in hind sight i probably could have done myself...but oh well.
i am just glad it is up and running again.


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