1988 yj 2.5 tbi no spark, its driving me crazy!

[jurob]

first off, hello to everyone!

i've posted this on a few other boards with no luck, hopefully it will be different here (crossing fingers)

i bought this from a friend not running. ran fine then one day about six months ago after sitting a few hours at his mothers house it wouldn't start and has never started since.

i've determined there is no spark.

1st thing i did was change the cps, for some reason someone cut the plug off so i had to do the same with the new cps. still no spark.

i've since replaced the coil, plugs, wire, cap, rotor and both the fuel and spark relay next to the battery (asd relay). no spark.

i then decided that maybe the cps wiring is bad so i hard wired the cps directly to the ecu prongs # 28 and 11 (off the top of my head). no spark still.

my voltmeter died so i couldn't check to see if i had power to 11 and 28 while grounding on the #1, but will check in a few when my neighbor gets home. i tried with a test light and didn't get light from the ecu at all.

any ideas on what to do next would be greatly appreciated.

rob

 

[old_man]

three common things that cause this situation are:

Corroded / loose Connector C101, above the brake booster. It was such a PIA that they wrote a tech note saying to just cut out the connector and wire everthing staight.

Corroded / loose connectors on ECU, under the dash

Corroded or Brake fluid damaged firewall connector / fuse box.

Ignition module / coil assembly. Your coil / ignition module is the same as on the 4.0L Renix if I remember right. Check the chapter forum and you may find somebody local you can team up with to get this fixed.

They are listed from most likely to least. The ECU could be causing the problem, but it is much less likely. I still have a spare ECU if you need one to trouble shoot with.

 

[jurob]

tk you sir!

i messed with it some more today, chiltons diagnostic all checks out good. but of course i cant start it.

messing around today i was checking coil voltage while the wifey was trying to start it. motor caught for about 3-4 seconds and ran smooth. was never able to repeat the start.

from the way things are looking it appears that my ecu is working fine. i may go to the store and buy an ignition module and see what happens.

tks again

 

[RichP]

You bumped something then, start checking grounds. I had an 89YJ 4.2L with the carter carb, real PIA, had starter problems with that and it turned out to be the Neutral safety switch on the auto tranny, ended up grounding it out permanently...but I would for sure pull EVERY ground, clean it and where it connects to.

 

[Matthew Currie]

I agree with Rich, try to check every connection, every wire. It's worth going out and getting another cheap digital meter for the ohms. If you were working around the coil, check also the pigtail coming out of the distributor. It's possible that there's a fault there.

 

[jurob]

tks guys, i had the ignition module tested, it was bad. replaced it and it started right up with a high idle (2400)

no obvious vacuum leaks and new tps.

when i disconnect the vacuum to map it lower to 1500, when i disconnect power it dies.

i'll test that and look for vac leaks and hopefully find the problem.

any other ideas?