Losing Ground?

[Zachary Lawson]

My ECU seems to lose ground or connection when I drive for long periods of time. It pretty much stops working, and overloads the injectors. The only way to fix this problem is to push really hard on the connector on the ECU. I've taken it out and clean it a few times. Another problem I have that might be related too it is the tick hand, and the light above the heat controls. These work about 10 percent of the time. If I park on a slope, they work 99 percent of the time when I get in my car. Within 5 or 10 minutes later, they both stop working. When the tick hand is working, the car seems to run better. I'm losing ground on my wiring harness? Are these related?

Edited March 17, 2013 by Zachary Lawson

[FastWoman]

Another possible reason for your problem could be a cold solder joint somewhere inside the ECU, hence the issue being solved when you press really hard on the connector. You might open up the ECU and inspect the solder joints very carefully under a magnifying glass. You would likely be looking for a cold (fractured or separated) solder joint in the area of the electrical connector. Another approach would be to break out a soldering iron and to re-flow the multitude of solder connections (re-melt the solder at each connection).

[bartsscooterservice]

Or get another ecu?

Are the pins in the connector that go in the ECU all good?

[Zachary Lawson]

That's what I thought, so I went ahead and bought another ECU from ebay. It seem to improve, but done the same thing.

[darom]

In this case I would get the Fuel Injection Book and do all the tests the book mentions dealing with all kind of problems done at the _ECU harness connector side_. Hopefully, your multimeter will give you a clue which circuit is loose or disconnected. This will take you an hour.

For example, while running the temp sensor tests, your multimeter shows 15kOhm reading when the book shows 0.5kOhm. You now go directly to your temp sensor engine connectors and repeat the test. It shows the correct reading. Now you identified the electrical wire pair which causes this abnormal reading.

Regards!

[FastWoman]

Well, your resolving the issue through connector shoving is a major clue. Wherever you're shoving, you have a bad connection or a short. If I were you, I'd open up the connector shell to examine the wire connections inside. And then unwrap that segment of the wiring harness to look for shorts or other weirdnesses. Obviously also look for bad grounds. However, I think the ECU is grounded through the case (maybe I'm wrong??), and you've already done an R&R of the ECU.

[Captain Obvious]

I think the ECU is grounded through the case (maybe I'm wrong??)

That is not the case. (Get it? Not the case?) Nevermind.

They are NOT grounded through the case*. In fact, they were very careful with their grounding scheme, and while the case is in fact grounded (by virtue of being bolted to the body), there is no electrical connection between the case and anything inside. All of the grounding of the ECU electronics inside is done through the EFI harness wire connections.

*I've not messed with years prior to 77, but I assume they're all the same in that regard.

[Zachary Lawson]

In this case I would get the Fuel Injection Book and do all the tests the book mentions dealing with all kind of problems done at the _ECU harness connector side_. Hopefully, your multimeter will give you a clue which circuit is loose or disconnected. This will take you an hour.

For example, while running the temp sensor tests, your multimeter shows 15kOhm reading when the book shows 0.5kOhm. You now go directly to your temp sensor engine connectors and repeat the test. It shows the correct reading. Now you identified the electrical wire pair which causes this abnormal reading.

Regards!

Yeah I'll check into that.

[Zed Head]

When the tick hand is working, the car seems to run better. I'm losing ground on my wiring harness? Are these related?

What the heck is the tick hand?

[Zachary Lawson]

What the heck is the tick hand?

I meant RPM Hand.

[Zed Head]

Well, that's interesting because the tachometer and the ECU both get their signal from the negative post of the coil. So, in addition to whatever is going on with your connector, you should check connections at the coil and ballast resistor. You might have a loose connection there.

It could also be that your ignition module is going bad. That will cause your tachometer needle to jump around too.

Edited March 19, 2013 by Zed Head

[Willoughby Z]

What the heck is the tick hand?

"the Americans and the British are identical in all respects except, of course, their language".