starting problems and staying running 4 cyl renix, ecu?

its a 1988 4 cyl renix .
it will start sometimes and act fine.
other times it wont start. when it doesnt start , if i hit the brakes the fuel gauge will go all the way to the full and past that, and the rear defroster light comes on, and this relay in the dash, big and silver, directly to the right of the steering wheel with the dash pulled off, makes a noise like that relay/fuse/solenoid is turning on too. basically sometimes it will start and run fine, and sometimes it does that wierd stuff and will turn over and wont start.
also , when i unplug the ecu, it does the same as the above. my guess is that the ecu is probably shot, i cleaned all grounds, checked a ton of wires. there is nothing i do other than wiggle the hell out of the wiring going into the ecu to get it to start.
my guess, ecu is shot, maybe a board in there is cracked or something???

also, even though i followed most wires around and everything looked fine, there is oil everywhere in the engine compartment due to a previously leaky valve cover. its on everything. even on the wires going down into the ecu

blondejoncherokee said:

its a 1988 4 cyl renix .
"if i hit the brakes the fuel gauge will go all the way to the full and past that, and the rear defroster light comes on, and this relay in the dash, big and silver, directly to the right of the steering wheel with the dash pulled off, makes a noise like that relay/fuse/solenoid is turning on too." Theres a Short somewhere. When the brake switch is activated its sending power to the Fuel gauge....
"when i unplug the ecu, it does the same as the above. my guess is that the ecu is probably shot....there is nothing i do other than wiggle the hell out of the wiring going into the ecu to get it to start."
Defiantly sounds like a short between wires. If youre unplugging the ecu, you are removing a variable from the equation, thus it not the problem.

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Also, I'm sure you'll agree, I think the oil isn't helping the situation.

I thought RENIX was the 4.0 six cylinder, produced 87-90. What year 4 cylinders were under the RENIX designation?

Renix was a designation of a fuel injection system jointly built by RENault and BendIX. I'm fairly certain that's the system on the 4 cylinder throttle body system used until they went Chrysler multi-point in later years. 1987 to 1990 4.0s had Renix fuel injection and so now the term Renix seems to be used to identify them.

yah it is a renix, it says so on the ecu. anyway, ill se if ic an get a ecu for cheap and try it out...
yah renix was 87-90

You've got bad grounds somewhere. That's why some things are being activated by turning other things on. The items you're turning on have bad grounds and are getting their grounds through the others. Replacing the ECU without first addressing the ground issues is a total waste of time IMO since your ECU works by grounding stuff.

cruiser54 said:

You've got bad grounds somewhere. That's why some things are being activated by turning other things on. The items you're turning on have bad grounds and are getting their grounds through the others. Replacing the ECU without first addressing the ground issues is a total waste of time IMO since your ECU works by grounding stuff.

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i would agree on this. Hold the brakes and see what kind of voltage youre getting under the dash at the grounds. Renew all the grounds as well.

i already checked many grounds and cleaned them. i started with all the main grounds , batt to engine,engine to firewall, and then hit everything else i could find.

Well then, get a FSM and look up on the wiring diagrams where the grounds are cuz that's your problem.

sweet! good to know. ill look into it! at least im not wasting cash on the new ecu!