Rebuilt ECU's any thoughts?

[gheiser70]

Hi -

The 78 280z has been running well most of the time since my last go round with the salt bridge on the TPS and new injectors.

However I (and my son) have had intermittent stalling issues when on the road. Both times in the last month, we were able to "rap" on the ECU box with our knuckles and get the car to restart for the ride home. Once it happened after about 10 miles away from home, and once less than a mile. Both from cold starts. We have reflowed the pins from the 35 pin connector to the ECU board, but this seems to be a vibration issue. Some times I can change the way the car runs in the drive way by "rapping" the ECU.

Unless I can find something obvious, I'm considering a rebuilt ECU. Has anyone out there used one and how did it work. Cardone sells one through the general auto parts stores and MSA and z car source offer rebuilds as well for more money.

Any thoughts?

Thanks, Greg

[FastWoman]

My guess is that a "rebuilt" ECU is simply an old ECU taken from a (presumed) working vehicle, cleaned up, and possibly repainted. I can't begin to imagine that Cardone would know anything more than we do about the circuit boards, which contain proprietary, "black box" ICs. If they want your old ECU in exchange (e.g. have a core charge), I would probably not trust their "rebuilt" ECUs any more than I would trust their ability to repair a problem such as you are having. (I wouldn't.) I would trust their "rebuilt" ECUs far more if they don't want your core.

I think you would be just as well off to find a used ECU. I found one on ebay for $20 that ran the engine about the same as the one I was already using.

[siteunseen]

Sounds like it's loose somehow. What if you removed it and cleaned the ground, maybe use some deoxit cleaner and dielectric grease on the connector, then tightened everything back down real good?

http://atlanticz.ca/zclub/techtips/electricalconnections/index.html

[alternativez]

I'd pick up a used one with knowledge that it's working and correctly matched to your engine. Plug it in and see if the problem is fixed. Could be a poor wire in the connector?

[siteunseen]

I guess you reflowed the solder to try and fix the problem, :stupid:. I wasn't thinking, sorry.

[djwarner]

After 36 years, the solder joints in the ECU can crystalize. When this happens the joint can go from very low to high resistance. You may want to examine the PC board and connector solder joints. A good solder joint will have a shine. A cold solder joint will be a dull gray. Crystalized joints may look like a hodgepodge of the these two, part shiny, part dull.

Joints subject to vibration may also crystalize in a manner similar to work hardening. Whether you attempt a repair if you find one, will depend on your soldering skill set. Be sure to heat sink any leads to semiconductors.

Other things to look for are burned components and leaky capacitors.

Since we are on the subject of soldering, Edd China on Wheeler Dealers consistently shows improper soldering technique. He relies on the solder to make the mechanical connection between two wires. He simply lays the two bare wires along side each other and applies solder between them. Any mechanical vibration transmitted through one of his joints will work harden the solder and cause it to fail.

The correct way to solder spice two wires is to tin both ends and then twist them together to form of a double helix. At this point the twists in the wires provide a mechanical bond. Solder is then applied to ensure a low resistance electrical connection.