• DCRC 2024

96 wrangler 4.0 starting problem

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NuCKinG FuTS

Member
i have a engine out of a 96 wrangler thats been swapped into a 90 wrangler. im having a problem with the engine not starting. its getteing fuel to the fuel rail and the engine is cranking. it has had a new cap and rotor put in and new plugs and wires. i just cant seem to get it to fire up. i have one idea that it may be the crankshaft position sensor on the 904 transmission is not hooked up at all but im not sure if that would be what was causeing it not to fire. any help on this would be greatly appreciated
 
I Lean

I Lean

Mbryson's hairdresser
Vendor
Location
Utah
NuCKinG FuTS said:
i have a engine out of a 96 wrangler thats been swapped into a 90 wrangler. im having a problem with the engine not starting. its getteing fuel to the fuel rail and the engine is cranking. it has had a new cap and rotor put in and new plugs and wires. i just cant seem to get it to fire up. i have one idea that it may be the crankshaft position sensor on the 904 transmission is not hooked up at all but im not sure if that would be what was causeing it not to fire. any help on this would be greatly appreciated
Click to expand...

Even if it is hooked up, the CPS is a common problem on 4.0's. Check that first--make sure it's hooked up. If it already is, then consider replacing it.
 
T

tfritz

Registered User
Have you checked your coil? I assume your not getting any spark at all right? Was it a running donor? If not it could be a timing chain problem. Don't know if the ECU and wiring harness being a different year could make a difference.
 
N

NuCKinG FuTS

Member
well ive pulled to fuel rail to see if i was getting any spray from the injectors at all and they werent spraying at all. the motor had been sittin for a while. could it possibly be clogged injectors?
 
T

tfritz

Registered User
First the injecters will not "fire" if the CPS is not working. I'm sure how to test the cps. You may be able to test the injecters by hot wiring them. The injecters have a two wire connecter the dark green wire with a orange strip is the positive side the other is the ground. Be careful to point it away from you when you do this. You don't need the ignition on during the test just switch it on to pressurize the fuel rail then turn it off. Don't leave the power connected for more than a second. You should see a spray of fuel. If not then it could be the injecters but I wouldn't think they would all go bad at the same time. This is the wiring codes from a 94-95 YJ. You said you have fuel pressure right? Did you test this with a test gauge or did you just push the shrader valve in on the fuel rail? This may be a stupid question but do you hear the fuel pump come on when you turn the key on?
 
T

tfritz

Registered User
First the injecters will not "fire" if the CPS is not working. I'm not sure how to test the cps. You may be able to test the injecters by hot wiring them. The injecters have a two wire connecter the dark green wire with a orange strip is the positive side the other is the ground. Be careful to point it away from you when you do this. You don't need the ignition on during the test just switch it on to pressurize the fuel rail then turn it off. Don't leave the power connected for more than a second. You should see a spray of fuel. If not then it could be the injecters but I wouldn't think they would all go bad at the same time. This is the wiring codes from a 94-95 YJ. You said you have fuel pressure right? Did you test this with a test gauge or did you just push the shrader valve in on the fuel rail? This may be a stupid question but do you hear the fuel pump come on when you turn the key on?
 
N

NuCKinG FuTS

Member
haha yeah well i tried the green w/ orange tracer jump and i could only get a few of those injectors to work so im thinking i may need some new injectors. but at 59 bucks a pop i dont think i want to dump any more money into gettin the dang thing running.
 
mbryson

mbryson

.......a few dollars more
Supporting Member
Location
Bountiful, land of rocks
Take it to TDC, install the distributor with the rotor pointing to the #1 cylinder (whatever the firing order is--I really can't remember) and fire it up. If that doesn't work, take it to TDC again, install the distributor again and try it again. Repeat as necessary. 4.0L are SENSITIVE little buggers--it ain't a small block Chev. Everything is timed quiter precisely. If you're off, it won't fire.

Sounds like a CPS to me. The CPS is CRITICAL. Get a dealer part. Don't even try anything else, it's NOT worth the headache (been there, done that, have the t-shirt, 4 shops opinions and lots of $$$ down the drain).


{oh, and there's no such thing as a '96 Wrangler--you've got your '95 YJ or your '97 TJ.....'96 didn't exist-that's like asking for a thermostat for a VW beetle}
 
mbryson

mbryson

.......a few dollars more
Supporting Member
Location
Bountiful, land of rocks
tfritz said:
First the injecters will not "fire" if the CPS is not working. ...............
Click to expand...



I'm not sure exactly how accurate this is, but it seemed correct with my '91 4.0L. I'd make sure the CPS is working and then go from there.
 
N

NuCKinG FuTS

Member
ya ive already checked and replaced the crankshaft postioning sensor (new) im not sure if the injector problem is just all electrical or what but. the whole deal is i had the 4.2 carburated brick of an engine in there and i was swapping in the newer 4.0 for obvious reasons haha. but the engine is a 95 and the coputers a 95 also the engine harness that goes with it. one thing i think may be a n issue is that the wiring harness also has all the conections for the antilock brake system on it. well i dont have abs on my jeep and so those wires are not connected to anything. could that be a possibility?
 
Hickey

Hickey

Burn-barrel enthusiast
Supporting Member
Location
Grantsville, Utah
The relays are the larger black plugs on the left side I think. Pull one out, they have about 5 spades on them. Try switching them around, say using the AC relay for the ASD relay.
 
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