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Yeah, Zig, at least I call it the car's brain (such as it is) and I think others here have too.
Here's an update on what I have done more in this vein:
On noting that whatever I read on here wasn't hot enough (by 100 degrees) and on the suggestion that I should try reflowing the solder at the power transistor legs, I got back to work.
On all three 900 NA ECUs I have, I tried, one, resoldering the leads to all the power transistors on the board, four and a five-legged similar cousin that all share the heat sink, and two free standing ones. No change in behavior on any of the three brains.
Then re-baked them all, in turn, at 385 degreees F. for 10-plua minutes, cooled gently, and re-tried and again no change in behavior.
The board that works but has proved cold-failure prone was still failing to start on cold mornings until warmed up, after the resoldering. I haven't tested its cold-morning behavior since baking it. It started yesterday on into the late evening, temp at 14 F., and re-started this morning, temps again in the teens. I'll have to wait till tomorrow a.m. to recheck it when it's really cold. It's now about zero out and will go probably below zero.
I think it was on here that I read that the failure of the fuel pump signal on '89s has been traced to one of the free-standing transistors, a Phillips ON957. I did some Googling and think I found that some of those are available, though I didn't seriously try to buy any. Also checked cross-references and there are some suggested similar substitutes.
On the '90 ECU I'm using that lacks the fuel pump trigger signal, the ON957 position on the board is filled with a different transistor, brand name a stylized ST and the numbers, on successive lines, 80, 437, then 9 924.
Wherever I read about the above transistor also mentioned that sometimes the injector triggering pulse also fails on these boards, my real problem with the '90 ECU. But the poster didn't know which transistor was responsible.
Near the ON957s on both the '89 (-564) and '90 (-580) ECUs there is another transistor, Phillips ON958. If I suspected strongly enough that this one was the one sending a pulse to fire the injectors I'd maybe try to get a few of each and try substituting new ones to see what happens.
For now, I'll try living with the problem. On extra cold mornings I'll blast the ECU with a heater or unplug it and bring it in to warm up.
And I'll dedicate myself to getting my '96 9000 head gasket job under way.
posted by 71.173.7...
, Mon, 16 Feb 2015 09:41:23
, Wed, 11 Feb 2015 10:19:03
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