1994 YJ 4.0 will not start. Was running fine with no issues when I parked it but two days later it wont start. It cranks over, has plenty of spark and is getting fuel. No trouble codes except the normal 12,33,and 55. ECU is only 4 months old. New TPS and CPS when I replaced the ECU. Battery and cables are also 4 months old and hold a good charge.
1. check engine light comes on when you turn the key and the fuel pump charges.
2. turn key to run and she just cranks. checked spark, fuel and have good spark and fuel pressure.
3. Changed plugs, and wires, none were fouled but #2 had a crack in the porcelain. still no start.
4. changed distributor cap and rotor. No change
5. changed power pack, No change
6. Fuel pressure is fine and even tried a little starting fluid.
Was looking for a little advise. Everyone knows you start over thinking this stuff and miss the small things. Thanks in advance for your help.
Could be a sensor that is giving a false reading that is within normal operating parameters but not where it needs to be for startup. Thereby not giving it the proper fuel spray. For example, if the Coolant Temp sensor was telling the ECU it was at 250 degrees then it would be too lean to start at if the actual temperature was 60 degrees. Get a scan tool that displays data and start looking. Does this vehicle show any attempts to start at all?
Doesn't try to start at all. Parked it on a Tuesday running fine. Hoped in it Thursday and it would only crank. Checked the basics. Getting fuel and spark. Then tried a little starting fluid. Still nothing. Fuel pressure at the rail was good all with in range. Good compression on all cylinders. First changed plugs, then wires, cap and rotor. No change. Replaced power pack/coil no change. Replaced crank position sensor, nothing... Yesterday changed coolant temp sensor no change.
Reset computer yesterday even though I had no codes except for 12 and 33. Cranked and checked again. Now throwing code 11 (no cam sensor signal/Hall effect). Today I'm going to put a new distributer in and see what happens.
Battery is 4 months old. Installed it with the new ecm. Swapped it out yesterday and didn't make any differance.
Is there any relays I can change?
If you're not getting a cam sensor signal it may not be firing the injectors. I would diagnose that first. If I'm not mistaken this engine has sequential fuel injection and needs the cam sensor for proper operation. I remember on some of the earlier GM stuff you could unplug the cam sensor and it would go into a default that would allow the engine to start which was how we quickly ruled out a cam sensor. I'm not sure if Jeep would do the same thing or not. My guess is probably not. That would be too easy.
distributor was installed by local mechanic thats been building jeeps and muscle cars for 30 years. Helped me out in the driveway and he couldn't figure it out so he took it to his shop. Free tow cant complain.
I did a valve cover gasket two days before the jeep died. After replacing the gasket I drove the jeep and it seemed fine.
Anyone have any knowledge about the two braided grounds off the engine? As for the braided grounds, I found the one off the firewall attached to the block wasn't even attached. It was just resting on the engine. The second ground off the fender that attaches near the dip stick was also not attached. it was just sitting on the fender.
Will or can this effect the computer or the starting? haven't seen much written up on these grounds and didn't have time to change them since its raining here in Boston.
They are engine electrical grounds. You really don't want to depend on your battery ground cable as being the only ground to the engine. Are they part of your starting issue? Maybe. Fix them to rule them out. Always fix the obvious stuff first.
Sorry for the delay but the Jeep is still not running. I swapped out the PCM with another jeep and still wouldn't start but mine worked fine in the loaner jeep. Tried new relays and fuses with no change.
My electrical box under the hood had allot of corrosion, still cleaning it all up.
Did get it running once and think we tracked it down to a short in one of the wires that goes to the injectors.
Between work and my two year old I have limited time to work on it but will post updates on what i come up with.
Hello, I have a 95 4.0 that has the same exact symptoms. I was stranded with my son last week and still wont start! What did your fix end up being? Thanks
If you have checked your basics...(power, fuel, air) the first sensor I would check would be the CPS. you can type it in here and ask how to check it and it will pop up with it. mine was going out intermittently.
Thanks Daniel! I had replaced the cps with Napa equipment without checking the old one. Still no luck, had spark at coil, not at plug so I replaced cap and rotor, still no luck. In the process of diagnosing the MAP and TPS now...
check you ignition switch as well.. i just has to redo the whole ignition system in mine.. the ignition switch would kick it over but they have 7 or so individual out puts.. the cost 16 bucks or so.. they also are common to fail..
Well I am stumped, checked timing, replaced ecm capacitors, replaced cap and rotor, replaced cps and cmp/pickup coil, other sensors seem to check out. I have fire at plugs, I have fuel at rail. Engine compression at 125psi. Tried to start engine on starting fluid..nothing. ECM not throwing any codes
zacattack-I have yet to check the ignition but would you know what the the individual outputs supply?
I thought pickup coil, usually when nothing else works its that. But, you got that... you have all three things you need.
And, if it ran when you parked it, its not timing. Timing doesn't just change itself all of a sudden.
Have you checked for water/moisture in the gas? Crank it for a few, pull spark plugs, look for water. Gas will spread into the metal so to speak, water will bead up.
You can also pull the fuel line, crank it over and push some fuel into a glass jar and hook the line back up. If you let it sit for a couple minutes, any water in the fuel system will turn into balls in the bottom of the jar as water is heavier than gas. If its the case, you want a can of drygas in there. Its a liquid, just named that because it eats up the water.
I'm stumped, you've done everything and you have all the things you need for it to run. Thats the only reason I think of maybe water in the gas. A little tiny droplet will cause it to foul.
Does it ever fire? will it even sputter or try at all to go on its own or is it completely no go when you crank it?
Alright guys, here to follow up. So after diagnosing the whole fuel system I found that it was getting to the cylinders. Figured I would go back to the ignition system, and even though the coil was showing spark, it wasn't sufficient enough to fire the cylinders so after a new Delphi coil from Amazon she is running better than ever. For anyone in the same boat the main symptoms were rich at idle,stumbled while driving a few times and then a run down river road east at big bend natl park on a 110 degree day, the hot coil finally took a dump. Thanks guys for the support