No spark,no fuel pump

squirrley · 10-19-2010, 08:17 PM

Ok get your thinking caps on cause iam out of ideas. First, its 95 yj with 4.0.
Second, started jeep to go to store one night in the rain and the wife reminded me that the fuse for the park lights was blown. I shut off the jeep so i could unlock the tool box to get the fuses and when i finished replacing it i went to start it and i had nothing. the next day i got out my trusty rubber mallot to club on the fuel tank to see if the pump would run while the wife turned on the key. I heard not a sound. check the schreder valve on the fuel rail and no pressure. Now i got the fuel pump out and tested it by putting direct power to using the fuel pump relay. the pump works but not on start up. after doing some checking and a whole lot of reading i found that i have no spark. Checked power wires to the coil and i have nothing,yes the key was on. Now under the dash is the ignition switch that supplies power to ECM and relays etc. when you turn on the key. I unplugged this and hooked up a new one. Dont worry if you have to get out your haynes or chiltons for this one i wont tell. I just need some help on figuring this one out.

sbsg2005 · 10-19-2010, 11:23 PM

when you turn the key on does the check engine light come on

squirrley · 10-21-2010, 04:44 PM

no

Mark05059 · 10-21-2010, 05:15 PM

its either burned out or that is your problem. There is a thread here on how to check to be sure that the computer is the problem.

yjman92 · 10-22-2010, 08:47 AM

this has nothing to do with the no spark issue, but i found out the power line to my fuel pump was rotted out.

Aahzmandius · 10-22-2010, 09:36 AM

Check the engine light to see if its good, if it is, and still no light, check the pickups of the back of the gauges. Especially if your shift indicator doesn't work, shares a pickup with your Check Engine Light. Had to replace my gauges becase the pickups were corroded. Still no luck, use this:
http://www.jeepforum.com/forum/f12/9...lained-490788/
Was invaluable for me, my problem was a loose terminal.
And while you have the meter out check the power to the fuel pump.

This shows how to fix the ECM, never done it myself, but my geek friends say its the way to do it.
http://www.jeepforum.com/forum/f12/c...rs-ecu-492597/

Good luck squirrley, keep your stick on the ice, we're all in this together.

squirrley · 10-22-2010, 10:14 AM

I have a freind that has a 95 yj with a 2.5. if i take his PCM out and put it into my 95 yj with the 4.0 would it make everything work(fuel pump, spark) although it would probally not run the engine right? This would just ot see it the pcm is bad.

Roadyy · 10-22-2010, 10:33 AM

It should work and even crank it if it is the problem. The 4.0 ECM is setup for 2 more cylinders is the only difference. It just doesn't have the extra 2 wires connected to the harness from the ECM.

Edit : just realized I read your statement backwards,,dislexia is working over time.

Roadyy · 10-22-2010, 10:36 AM

It will give you the CEL using his to retrieve codes in other areas and it atleast tell you if this is the problem on yours..

MurtleDaTurtle · 05-23-2012, 01:16 AM

ecu had the same prob 120 bucks auto comp exchange will bet my house on it lol.

pete1991YJ · 05-23-2012, 04:40 AM

If you have no CEL light then you should check to see if you have 12v on pins 3 and 9 at the ECU connector. This will tell you if the ECU is actually good or not, instead of just throwing stuff at it.

If you do have juice there, then the CEL is connected between pin 32 and ground. You could use that info with a test light to retrieve the codes.

So, first check that the ECU is getting juice in the first place. It might not be getting juice even tho you replaced the ign switch.
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