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Unread 07-07-2007, 02:59 PM   #1
taters
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jeep blows 30 amp fuse under hood when starting

does anybody know why my 1996 jeep cherokee blows the 30 amp fuse under the hood?it is in the box where all the relays are located.ive checked most wires cant find anything wrong took the starter off put it back on and it started 3-4 times then started popping the fuse again.thanks

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Unread 07-07-2007, 03:04 PM   #2
severous01
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which 30A fuse you talking about???

probably the sending unit....it's in the gas tank. look at the rubber grommet thingy on the tank with wires coming out the front of it. if that's loose or hard, you need a new sending unit. also, pull the pump out and look for crossed wires.
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Unread 07-07-2007, 03:11 PM   #3
taters
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the fuse aint marked it in the fuse panel under the hood behind the battery but when it blows it wont start it cranks over just fine but no start .
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Unread 07-07-2007, 03:23 PM   #4
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the fuse pops and it kills the fire to the engine
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Unread 07-08-2007, 11:28 AM   #5
severous01
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check wiring to the fuel pump...get back to me.

i hit a stick and grounded the pos wiring in the tank...had a nice little fire in there...surprised it didnt exlode...any way. it was the 30a fuse i was popping as well.

do some research and find out which fuse it is that's popping. it could be a main going to the ignition module. that was my problem and i needed a new sending unit. it's about 650 bucks but i found one in the yard for 75. came with pump.

do you get spark? do you get fuel? are you getting your CPS reading out of the sensor??? with out a rpm reading the engine will not start at all...

since you messed with the starter and it worked for a while, pull it off again and check the wires going to and from. maybe something is crossed...maybe something is shorted.
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[COLOR="Lime"]soon to be[/COLOR] 4.11 gear and and a ford 8.8 LSD rear and herc'd interior
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Unread 07-08-2007, 02:26 PM   #6
taters
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thanks for the info ill check it out and let you know, as for the fuse and what it controls,the best i can tell it runs the injectors and cpu but i un plugged all the injectors an tried it no luck fuse popped.by the way was your fuse the small 30 amp?it has the big fuses too,mine is the small one that keeps popping,ive been over every wire under the hood cant find anything wrong so it may be the pump thanks a bunch
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Unread 07-08-2007, 02:33 PM   #7
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My 93 has a diagram on the underside of the lid once you remove it you can narrow down what one it is.

It could be the ASD or fuel pump relay as mentioned. You probably have bad wiring somewhere. Figure out which it is and then get back with us.
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Unread 07-09-2007, 07:30 PM   #8
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it is the asd anybody know why? if i pull the asd relay it wont pop fuse,it wont start either.any suggestions? im leaning toward the crank sensor
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Unread 07-09-2007, 10:24 PM   #9
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i was going to guess it was the ASD, pretty much any short will pop that fuse, i had it pop when my o2 sensor wires shorted.

the asd fuse powers the asd relay, which powers the fuel pump relay, and the injectors. no asd fuse, no injectors.

if it were me i would first see if it does it with the key on, or just in the crank position, then start unplugging things, one at a time, see if it still pops (best bet is to buy a 30a circuit breaker w/ leads so you dont kill 4000 fuses). start at the fuel pump, and go though all the engine sensors.
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Unread 07-09-2007, 10:28 PM   #10
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Have you done any auxillary lighting/electronics? I had a bad ground on some stuff i installed on my XJ and it was blowing the same fuse. Fixed the ground and it was fine.
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Unread 07-10-2007, 04:42 PM   #11
taters
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ok itried all that i started in the back with the fuel pump worked my way up unplugging everything i could find,i got to the computer on drivers side fender unplugged all three plugs on it and it stopped popping the fuse with the asd relay plugged in.it does it in the on position on the switch.could it be the computer?i really appreciate every ones help on this.im driving my daughters 98 and she aint too happy about sharing her ride with dad!by the way i bought my jeep new in 96 up until now it was 200.000 trouble free miles.all electronics and lights are stock.
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Unread 07-10-2007, 06:48 PM   #12
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Here's a start about the ASD, I know a bit about it. anyways, my XJ is just like yours except I don't have the problem.

blowing 30 amp fuses...that's a lot. could be a internal short in the starter. the ASD is just a 30 amp relay, identical to the a/c relay next to it. the plastic box cover of the high power box under the hood tells you what's in each slot.

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crank no start.



beyond that, your fuel pump will energize for 2 seconds when you turn the key on. it is the ASD relay under the hood. 30 amp bosch relay. the a/c uses the same exact relay next to it. swap them no problem to check.

long story:

turn key on, ASD powers fuel pump for 2 seconds, then shuts off. you crank the motor, it looks for crankshaft turning signal on bellhousing CPS sensor, and also checks to see if the distributor CKP is moving, then it will sync the fuel injection and spark depending on where crank and distributor position is. if it does NOT see the crank moving, or crank moves but no distributor signal, then either no spark or no fuel. if no crank movement, then no fuel. the ASD will then kill the power to the fuel pump, leaving you go what the heck.

also:check battery volts. 12v off, 13-15 running. no less than 10v cranking, the computer and injectors need 9.5v, the coil needs 10v to fire.
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Unread 07-10-2007, 07:43 PM   #13
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ok ive done the switching the relays no luck. it not gettin any fire.i was gonna check the cps sensor .the manuel says to check contuniuty between b and c terminals on the cps sensor but mine aint marked ...according to the book they should be.starter makes sense to me cause like i said i took it off,checked it out ,put it back on and it started 3-4 times before it started popping fuse again this whole thing makes my brain wanna asd. thanks ill take starter back off and have it checked by a pro.i appreciate the input i aint givin up yet!
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Unread 07-10-2007, 09:35 PM   #14
severous01
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ohm out the injector lines. they sometimes get squished and crossed...and that will usually blow the fuse inside the pcm, however it could possibly bypass and blow the fuse that controls the entire circuit. you should ohm the terminals together for each socket, pos and neg for each injector.

it's easy, and all you need is a really small screwdriver to pull the metal clip away from the plastic connector and pull.
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[COLOR="Lime"]soon to be[/COLOR] 4.11 gear and and a ford 8.8 LSD rear and herc'd interior
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Unread 07-12-2007, 06:57 PM   #15
taters
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got it fixed! computer had a short in it,local computer geek checked it for me found the culprit,its running better than it has in a long time ! i wanna thank you all for your suggestions! hope i can help somebody one day!i own three jeeps 2 xj one grand cherokee,thanks again yall...by the way he fixed the computer with a six dollar part!!!!
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