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-   -   Help! no power to fuel pump or coil!!! (http://www.jeepforum.com/forum/f12/help-no-power-fuel-pump-coil-1547325/)

beefers92 07-10-2013 12:10 PM

Help! no power to fuel pump or coil!!!
 
Hey guys i'm in need of some electrical expertise. I have a 93 yj 2.5l. While driving the other day it just shut off as if the key was turned off. all fuses and relays check out to be fine. when I turn the key to the ON position my check engine light, seat belt light, and shift light all come on. I can not hear the fuel pump kick on and from what I have tested there is no power going into the coil. Any help on this would be most helpful.

Thanks in advance!

Inzano 07-10-2013 12:37 PM

Check for any codes or stored codes that might not cause ce light. Could be a possible crank sensor. Seen them go bad with some odd kind of symptoms beside not starting

kingcat400 07-10-2013 01:27 PM

sounds like it is time for a dose a brain suregry.(computer cap replacement.) look in the sticky's there is a write up on it with diagnoses procedure.

good news is this is begining to look like a 93 yj fest to me :)

Siva283 07-10-2013 01:38 PM

Quote:

Originally Posted by kingcat400 (Post 15662349)
sounds like it is time for a dose a brain suregry.(computer cap replacement.) look in the sticky's there is a write up on it with diagnoses procedure.

good news is this is begining to look like a 93 yj fest to me :)

He has a cel. So he ahouldnt need to replqce the caps.

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kingcat400 07-10-2013 02:08 PM

true but my cel worked when it started to go.

op leave the key on for a while and see if it will start after sitting on for say 10min.

Firefyter-Emt 07-10-2013 05:03 PM

95 Attachment(s)
Yea, it does have all those symptoms of the CPU failure. Odd about the lights coming on though, but I don't think the crank sensor would kill the fuel pump. The good thing is that it's a very cheap and easy job to replace them. And lets face it, sooner or later they are going to act up!

I know I have posted this a hundred times, but it is very worth the download!
http://pdfcast.org/pdf/1995-jeep-wra...ctrical-system

laybackman 07-11-2013 12:06 PM

Quote:

Originally Posted by beefers92 (Post 15662109)
Hey guys i'm in need of some electrical expertise. I have a 93 yj 2.5l. While driving the other day it just shut off as if the key was turned off. all fuses and relays check out to be fine. when I turn the key to the ON position my check engine light, seat belt light, and shift light all come on. I can not hear the fuel pump kick on and from what I have tested there is no power going into the coil. Any help on this would be most helpful.

Thanks in advance!

Check for the ground wire attached near the drivers door/ hinge strap holder. If you broke it with your one of your big clodhoppers :) it shuts the engine down and it will not start back up. It is the fuel pump ground wire IIRC.

If that don't work then pull the VSS plug on the VSS sensor on the transfer case and hit the key again does it start? Bad VSS switch. If the VSS dies your crank and cam sensor got no voltage. You will get no fuel or no spark.

Siva283 07-11-2013 12:59 PM

Quote:

Originally Posted by laybackman (Post 15665933)

Check for the ground wire attached near the drivers door/ hinge strap holder. If you broke it with your one of your big clodhoppers :) it shuts the engine down and it will not start back up. It is the fuel pump ground wire IIRC.

If that don't work then pull the VSS plug on the VSS sensor on the transfer case and hit the key again does it start? Bad VSS switch. If the VSS dies your crank and cam sensor got no voltage. You will get no fuel or no spark.

He should still have fuel if its the vss. Cam and crank only shut down spark. The only thing the should **** down fuel is an interal fault in the pcm. I would def check that ground though

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laybackman 07-11-2013 01:53 PM

Quote:

Originally Posted by Siva283 (Post 15666124)
He should still have fuel if its the vss. Cam and crank only shut down spark. The only thing the should **** down fuel is an interal fault in the pcm. I would def check that ground though

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IF the crank sensor gets no power because of a short in it's circuitry which is part of the crank, cam, & VSS 8 volt circuit then the ECM does not get a report of engine movement. After several seconds of cranking if no engine movement is reported to the ECM you get no fuel.

Siva283 07-11-2013 02:06 PM

Quote:

Originally Posted by laybackman (Post 15666312)
IF the crank sensor gets no power because of a short in it's circuitry which is part of the crank, cam, & VSS 8 volt circuit then the ECM does not get a report of engine movement. After several seconds of cranking if no engine movement is reported to the ECM you get no fuel.

I stand corrected you are right about that. He should still read pressure at the rail though and for a few seconds at key on he should even get correct pressure. After it shuts the pump back off he should still read correct pressure or close to it if he is checking it with a gauge.

laybackman 07-11-2013 03:44 PM

Quote:

Originally Posted by Siva283 (Post 15666362)
I stand corrected you are right about that. He should still read pressure at the rail though and for a few seconds at key on he should even get correct pressure. After it shuts the pump back off he should still read correct pressure or close to it if he is checking it with a gauge.

That was my first thoughts also BUT if he has a short in that circuit does the ASD relay send power to the fuel pump relay etc etc etc IF the 8 volts going to these three sensors is not there?????

My first thoughts are yes until the ECM see no movement at the flywheel.

My head hurts already.....:facepalm:

Siva283 07-11-2013 06:34 PM

Quote:

Originally Posted by laybackman (Post 15666677)

That was my first thoughts also BUT if he has a short in that circuit does the ASD relay send power to the fuel pump relay etc etc etc IF the 8 volts going to these three sensors is not there?????

My first thoughts are yes until the ECM see no movement at the flywheel.

My head hurts already.....:facepalm:

Yes the asd should still come on even if those sensors are bad. Atleast mine did when my crank sensor was shot. I also got code 11 when that sensor went. The coil I thought was not controlled by the asd. Am I wrong about that part.

You know we make a decent team sometimes.

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laybackman 07-11-2013 08:21 PM

Quote:

Originally Posted by Siva283 (Post 15667236)
Yes the asd should still come on even if those sensors are bad. Atleast mine did when my crank sensor was shot. I also got code 11 when that sensor went. The coil I thought was not controlled by the asd. Am I wrong about that part.

You know we make a decent team sometimes.

Sent from my SPH-L300 using JeepForum

All the time my friend!

All of us together try to help each other out and that is what makes this forum so valuable. I would be the first one to admit to not knowing everything. As I get older I cannot retain all that I once had stored in memory....actually that is incorrect my memory is perfect. I have trouble with recollection!! :p

I retyped this is from the FSM for a '95 YJ. I think I made no mistakes.

When the ASD relay contacts close they connect circuits A14 & A142. Circuit A142 splices to supply voltage to the ignition coil. The PCM controls the ground path for the ignition coil on circuit K19. Circuit K19 connects to cavity 19 of the PCM.

Circuit A12 also supplies voltage to the fuel injectors, ignition coil, PCM, generator, and heated oxygen sensor.
The fuel pump gets its power from fuse 4 in the PDC to fuse 5 in the fuse block. It then supplies power to coil side of the fuel pump relay. The PCM provides ground for the relay and connects to cavity 51 of the PCM.

When the PCM grounds the fuel pump relay, contacts inside the relay close & connect circuit A14 from fuse 1 in the PDC to circuit A141. Circuit A141 supplies voltage to the fuel pump motor which is art of the fuel pump module.

These damn YJ's are complicated!!!

I gotta soak my 2 index fingers...I swear they are starting to swell up!

Siva283 07-12-2013 06:26 AM

Wow, If I read the right it looks like the fuel pump problem could also be causing the coil to lose power. Thats kinda strange. When my CPS went I still had power to the fuel pump. So here is what I am thinking. He needs to use 2 jumper wires and should jump the ASD relay and the fuel pump relay and then check for power to both the fuel pump and coil. Its early so my thinking may be wrong. While doing this he should just dissconnect the VSS. Once its running he can reconnect it. That way its taken out of the equation. He should also check all the above mention fuses. Also this may have been asked already but maybe he should do it again just to be safe. Are there any stored CEL codes. DOes the check engine light come on at key on and go off after 30ish seconds. This sounds like it may be the Brain surgery issue(2 bad capaciters in the ECM). If it is not the cap issue even if the sensors are bad it sounds like the fuel pump should still prime at key on but stay off after that. Also with the key on shouldnt there be 5 volts at the 02 sensor. It looks like if bad sensors the 02 should still get power but if it is a bad wire the 02 would not get power. Hopefully I am not making this more complicated than it needs to be. All this to find a $5 part thats causing the problem most likely.

laybackman 07-12-2013 07:46 AM

Quote:

Originally Posted by Siva283 (Post 15668515)
Wow, If I read the right it looks like the fuel pump problem could also be causing the coil to lose power. Thats kinda strange. When my CPS went I still had power to the fuel pump. So here is what I am thinking. He needs to use 2 jumper wires and should jump the ASD relay and the fuel pump relay and then check for power to both the fuel pump and coil. Its early so my thinking may be wrong. While doing this he should just dissconnect the VSS. Once its running he can reconnect it. That way its taken out of the equation. He should also check all the above mention fuses. Also this may have been asked already but maybe he should do it again just to be safe. Are there any stored CEL codes. DOes the check engine light come on at key on and go off after 30ish seconds. This sounds like it may be the Brain surgery issue(2 bad capaciters in the ECM). If it is not the cap issue even if the sensors are bad it sounds like the fuel pump should still prime at key on but stay off after that. Also with the key on shouldnt there be 5 volts at the 02 sensor. It looks like if bad sensors the 02 should still get power but if it is a bad wire the 02 would not get power. Hopefully I am not making this more complicated than it needs to be. All this to find a $5 part thats causing the problem most likely.

The fuses are the first thing to check no matter what and I mean pull them and test them not just eyeball therm. Next the horn relay can get pulled and be used to test the ASD relay.
The crank, cam & VSS are on the same 8 volt circuit. If a dead short occurs in this circuit there will be no fuse popping, but none of these sensor can send a signal back to the ECM. The VSS is the usual culprit. It could be bad wiring anywhere in that circuit also or the other two sensor are junk, who knows.....:confused:

Some time back I was helping a fellow JF member locally (Rat). Oue89YJ was helping also (Thank the JF Gods) suggested unplugging the VSS sensor after we had swapped out or tested everything under RAT's hood. The damn thing fired right up! The only issue was Rat had no speedometer because his '95 YJ speedo was driven by the VSS sensor.
Bottom line is until the OP makes has a game plan to eliminate possibilities he will chase his tail until he flies up his own butt and disappears!

CEL check first, then fuses, then relays, then sensors and wiring.
And they have redundancy built into these systems. Or in plain English if Chrysler to keep the ECM small they melded up a bunch of similar sensors doing the same job! At Chrysler they must hire ex- Gov't bureaucrats as electrical engineers whose thinking is; The straightest distance between two point is a straight line...going the other way!:eek:


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