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spark fuel crank no start

doaxj

NAXJA Forum User
Location
dayton ohio
ok guys i really need help ive replaced the coil the cap and rotor all new plugs and wires and a new coumputer. i have spark i have fuel in the fuel bar it cranks fine but wont fire i also replaced the crank sensor. something got wet im sure of it either in the engine compartment or in the dash. are there any relays or fuses that i might not know about the would control fuel injectors? please help a guy out lol
 
have you tried running codes?
 
What year is your rig? I know on my 88 there is a starter relay by the coil that went bad and kept it from starting. That might be worth looking at if yours in that 86 to 93 range. Otherwise I would check your CPS again to make sure it didn't wiggle loose or something or maybe check the map sensor. Just some food for thought.

Good luck!!
 
Dont go by the FSM for plug wires if..

you are working on a V-6.

I just did plugs, wires, cap, and rotor. Wired according to the FSM, and it was wrong. No start. Suprisingly, my old Haynes manual had it right.

Starts fine now.:D

Tom
 
its a 1090 xj with a 4.0 in it the cranksensor is new and installed correctly their are 4 relays next to the coil i didnt think about does anyone know which one it the one that goes along with starting? also wheres the location of the map sensor? thanks guys
 
The relay with the black battery cable and 3 flat prongs on it is the one you are looking for (it is actually a ford style relay). The map sensor is on the firewall kind of above and to the left of the brake booster ( as you are facing the engine from the front of the jeep) with one screw in it.

HTH,
 
I very recently had the same problem on my wifes 90 XJ, tore my hair out trying to figure it out. It wound up being low fuel pressure, I pulled the fuel pump out to find the small piece of fuel hose that connects the pump to the hard line coming out of the sending unit had partially come off, still pushing some fuel thru the system, just not enough. You can also check to see if your getting voltage to the injectors by pulling one of the connections and testing it with a voltmeter or test light while somebody cranks it. Good Luck
 
ok here the entire story lol ran perfect last weekend went wheeling sunk in deep deep deep(did i mention deep?) mud pit. pulled it out took awhile but finally started. was running extremely rough. drove it home i figured i fouled some plugs and it was missing bad. got it out a few days later to clean it again started and ran rough. took the pressure washer to it inside and out. went to start it and it just cranked. then came the money pit started replacing everything. cap and rotor plugs wires ign coil and even the computer. so im ruling out fuel pump issues due to that i checked the valve on the tool bar and it spit gas half way to the moon so i know i have plenty of pressure i also got it to back fire yesterday so i dont think its a mechcanical issue i had to get something wet!!!!!!! but thanks for all the info keep it comming
 
Revived thread by PM

OK, so I didn't see much about wet - like inspecting the intake for water, new air filter etc (assume Mud has water in it...)

Have you checked all of the grounds (how aggressive was that pressure wash?) on the passenger's side of the block?

After cranking, can you smell/verify fuel in any/all of the cylinders?

Have you confirmed spark at the plugs (I know you said that you had spark, but where)?

Are you working with the OEM computer or your replacement? (is the replacement from the same year and drivetrain??)

I'm assuming that you washed the interior with a washer as well?? -- have you pulled and re-seated ALL of the fuses ?

What did you do for the ignition switch (besides power wash it?), any cleaning?

Is there a good sync signal from the dist? - backprobe pins "B" and "C" of the dist's connector (blue wire in 'B' should get +ve if your meter won't read negative DC volts) read the voltage present with the key in "on" not cranking -- should be like 5V... crank the engine - meter should fluctuate every revolution -- while you're there verify good ground on "A" (NOTE: Several revisions of the RenixII ECU will try to fire the engine without a valid Sync.. it'll pick a cylinder for the attempt - if it's wrong you'll get misfires or nothing...).

Backfire could'a damaged your MAP, but that'll show up after you're running....

The "real" pump pressure would be worth verifying even if it does shoot like a 15-yr old on prom night... (and be sure it's fuel! - a system that was rapidly cooled could easily draw in surrounding moisture...)
 
thanks well i got it started but now its missing and running pretty rich. i think maybe i sucked enough mud in to kill one of the cylinders. can you guys think of anything that would make the number 5 cylinder not fire? besides the obvious like bent valve bad rings etc? thanks
 
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