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CamoCreeper 08-06-2012 06:57 AM

Need electrical/ fuel help..running out of parts to replace
Hello all! Posted in other forum but don't think it was the correct place so reporting here.. I just recently joined but have referenced there forums for several months now, so thank u for all the help so far! My current issue.. I have a 93 wrangler 4.0 5speed.. since I bought the jeep I have had to turn the ignition to just before it cranked, wait 30 seconds to a minute, hear the brrrr sound and look for the shift light on my dash to come on and she would start right up faithfully.. By reading the forums I heard it was most likely the ECM or possibly the pump.. I bought both and was waiting for a convenient time to work( never got there) went out the other day drove around and she stalled on me twice as i was clutching/ braking at stops.. Figured pump was about to go... Sure enough got home went in for 5 min and came out to leave again and turned key the shift light came on immediately with no brrrrr sound.. No pump,no fuel,no start, not even an attempt.. I since then have replaced fuel pump and sender, ECM, fuel relay, auto shut off relay, 30 amp fuel fuse, and traced wires. ( ground is well grounded)I have found that if I "jump" the fuel relay the pump kicks on regardless of wether the key is in or not.. But when I check for power at the fuse/ relay block ..i am reading i should have two of the four slots for the relay should have power..I have one constant like I should, but no other slot with power. I understand the other power/ hot should be hot for 2 seconds or so when first turning key and while cranking but can't get power at anytime even when cranking.. Any and all help is appreciated.. I live in butler " Home of the jeep" and the anual jeep heritage festival is just days away.. I have been working non stop on this for two days, burnt my last personal day trying to fix before the fest...

Que89YJ 08-06-2012 07:47 AM

Your problem is the ecu. The fix is either to replace it or do this:

jsawduste 08-06-2012 08:47 AM


Originally Posted by Que89YJ (Post 13977550)
Your problem is the ecu. The fix is either to replace it or do this:

This guy knows his stuff. ^^^^

But I want to understand a couple things. Especially since you already replaced the ECM.

You say shift light. Do you mean check engine light ? Does the CEL EVER come on ?

CamoCreeper 08-06-2012 08:20 PM

No the check engine light has never come on since I bought the jeep. The only light i have ever gotten is just the shift light.. Don't get me wrong the gauges all work, but as far as dumby lights the shift light is the only one that has ever came on. Would come on once pump was primed and obviously when I got to 2-3k on the tach..yeah I thought ECM too, that's why I replaced it right away when sender and pump being replaced didn't fix the problem..

jsawduste 08-06-2012 08:26 PM

The CEL lights up when the ECM goes to ground.

Could you swap bulbs with a known good one to see if the non-working CEL is a burnt out bulb ?

Do you have spark ? I am still thinking an ECM but want to be sure of a couple other facts first.

CamoCreeper 08-06-2012 08:36 PM

I have not attempted to swap bulbs or anything yet.. To be honest I just grew accustomed to it not being there. I will have to do that tomorrow evening so I can use that as a reference point to check things.. No I do not have spark. Found that out on my lunch break ( my garage space I rent is a block from my work ) Figured since jumping the relay gets the pump to run I would run the jeep a bit to charge the battery since I've been cranking motor to check for power at the relay block and what have you.. No spark..

jsawduste 08-06-2012 09:05 PM

To the ECM to check inputs/outputs
You should have 12V on pin 3 and 12V on pin 9 when the ignition switch is on.

Measure the ground to the ASD relay and FP relay to be sure it is ground(ing).

Probe the negative lead of your multi meter in pin 51 of the ECM and the positive lead to a known 12 volts. Ignition switch off you should have 0 volts. When you switch on the ignition you should have 12 volts but for only for a few seconds. This is the FP prime .Then it should drop to 0 volts after the prime.sequence.

Negative lead of your multi meter to pin 4 (which is a ground). Positive lead to pin 6. Turn the key on. You should see a 5 volt reading..This is the sensors 5 volt power reference signal..

If any of these measurements are off then the ECM is likely shot. OR you have a bad ECM ground but said you checked the ground.

Betting it is still the ECM. The ECM seems to be not even going into the FP prime function. Coupled with no spark further points to the ECM not working. Could still be a ground issue but you gonna have to do some probing for that.

CamoCreeper 08-06-2012 09:14 PM

Thank you. Very good info, just what I was looking for, a good lead to follow. And in words I can understand (Im more nuts and bolts than wires and fuses).. I will check those points tomorrow and see what I come up with.

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