i have 3.4,volts to coil,no spark


Asked by May 30, 2011 at 03:59 PM about the 1998 Jeep Grand Cherokee

Question type: Car Customization

98 grand cherokee,replced crank sen,cpi,ing module,even the auto headlite box under dash,put 3 extra grounds,still no spark,

6 Answers


You will need more than 3.4 volts to the coil. You should have 12v @ the positive side with the key on. If you attach a wire with a grounded spark plug to it and ground the signal side (-) you should get spark from a good coil.

3 of 3 people found this helpful.

thank you very much so'''i had baught a comp,scanner hooked it up and im getting a ererr message its saying it can't read my computer,im at a block wall,should i change the main ''cpi'' computer again?im lost..

1 of 1 people found this helpful.

Check your cigarette lighter/radio fuse(s) first. If the scanner doesn't pick up vehicle power from this circuit, it often will not do anything. Could still be a computer issue, but don't jump the gun.


i will check them ,i also just other day replaced the grey fuse center junction box with all new fuses,but the computer under hood bolted to firewall was used i think it could be bad,


Try this: http://www.topix.com/forum/mesa/TTC3KFC4OII4HPC1G.

2 of 2 people found this helpful.

Just had a 98 Grand Cherokee with no spark and no fuel pump. There was 3.6 volts coming to the ASD relay and fuel pump relay... There was a bad AC CLUTCH relay leaking voltage back through the CPU. Pulled it out and it fired right up. ... Got lucky, hope this helps you poor Jeep owners...

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