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ECU not working!?

1K views 3 replies 2 participants last post by  S.M. Autoworks 
#1 ·
Ok, this all started about 6 months ago, my car was running great, then one day it started running terribly and was very hard to start. My engine was burning major oil, so I didn't look into it and figured I would fix it when I did the rebuild (I just tuned it to run well when warm). Now, I just got the engine all back together with the fresh head, etc. Runs better than ever when warm and tuned. However it still doesn't seem like the ECU is doing anything at all. It takes excessive cranking to get it to start when cold, and the engine runs very poorly until it gets warm, etc. I looked at the fuse on the OVP, it is good. How do I start testing this? I can't find anything useful in my manual, and ALLDATA has a different $500 tool for each probably irrelevent test.

Can I test to be sure the ECU gets power? What about signal to the CSV? Can I look to see if any thing is even getting power, like The EHA? The O2 sensor light is not on, but it had come on itermittently before this started happening. Since it takes so long to get it to catch when cold, I'm guessing that the CSV isn't doing anything, and that it would not be O2 sensor related?


Thanks in advance for any ideas, otherwise I'll have to sift through countless pages of ALLDATA to find something relevant. Oh, and BTW, I got my dash lights working, the alternator was unplugged (duh).

Car is a 1989 300E
 
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#2 · (Edited)
even if the fuse in the overvoltage relay is good, the relay itself can still be bad...

cold start injector is another good thing to test.... pull it out of its home (2 #5 allens I think) leave it plugged in, put the spray end in a dixie cup and crank it BONE COLD. See if you get a little spray in the cup....

just my two cents worth.....



you do mean SMALLDATA.... right? don't waste ur time :)
 
#3 ·
thanks for the advice, since it happened so suddenly and completely, I have a feeling it is something like a bad relay as you suggest. actually after some thorough digging I found exactly what I was looking for in ALLDATA, pinout voltage and ohm measurements for every pin, however I will def. be checking for +12v first ; )
 
#4 ·
cool! don't get me wrong, I use alldata all the time too, but I find that the info for 124's is scrambled. If you hunt hard enough, you usually will find what ur lookin for. I have to call the library for clarification alot, but it's way better info than Mitchell in my opinion.... GOOD LUCK
 
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