Re: Isolating the Computer, ESC, and Distrib Module

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John, Thanks for the inputs. I do think I've covered these steps. The Gray wire on the schematic is "Gray or Tan/Wht" (mine is Tan/Wht).
I did unplug the fuse - and had 0V on both pins. If the ORG wire were shorting to ground I would expect the ECMB fuse to be blown... no it's not that - but upstream of the fuse. Probably the ignition switch or wiring to the ignition switch. Seems more likely the switch because other functions do turn on from the switch (so there is power to it). Applying power to the orange wire???... Well, via a 2A/6A battery charger onto a 10A circuit it should be ok - even if there is a short somewhere. I concur that via jumper cables would be a bad idea - but it won't happen tonight. Elliott
John Alt wrote:

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Don't forget to bring your helmet :)
says...

FP-relay
hooked
few
the
or
for
them
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Nah - eye protection (glasses are good enough).
Battleax wrote:

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Oh you mean for LI Motorcycling (not hotting the wire) - yea I know NY has it's issues. I really liked NH, and Florida - where I didn't have to wear one, there was no income tax, car ins was optional. The Live Free or Die attitude beets everyone's heads up each other's business. Elliott
snipped-for-privacy@comcast.net wrote:

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NH rules. And they just abolished the need for a permit to carry concealed... yay.
~KJ~

dropped
hooked up

been
for a

voltage at

Haynes
connector
post
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NH, BAAAAAAAAAAYYYYYYYYYBBBBBYYYYYYYY YYYYYOOOOOOOUUUUUUUURRRRRR TTTTTHHHHHHHHHEEEEEEEEEE BBBBBBBBEEEEEEEEEESSSSSSSTTTTTTTT! Elliott
KJ wrote:

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"John Alt" wrote

Are you getting this information from an actual schematic? The reason I ask, is that many people are under the illusion that the oil switch is in series with the relay and can shut off the fuel pump if it fails, or if the engine doesn't develop oil pressure. In fact, as far as I can see by looking at an older schematic (and I know for certain on newer vehicles), the oil switch is nothing more then a parallel circuit that provides an alternative power source to the fuel pump in the event that the fuel pump relay goes belly up while the engine is running.
Ian
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Ian, Per my Haynes 82-93 schematic you are correct (in both diagrams, the 91/earlier, and 92/later). The 96 to 2001 book shows the same parallel circuits. Elliott
shiden_Kai wrote:

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snipped-for-privacy@hotmail.com says...

No, if you lose oil pressure, you lose the pump. Pulling the oil pressure switch connector will prove that. AFAIK, all TBI units were like that. I have no idea about the newer units, but I have no doubt you are right about them. I haven't had the good fortune to have to do any real serious troubleshooting of the wiring on anything newer than 94. I'd bet people getting left on the side of the road for a stupid oil pressure switch or a corroded connector woke up someone at GM.
Computer terminal b2 is fuel pump input. It does not drive the fuel pump, nor are there any other circuits to the pump except off the relay. They grey wire powers the pump in prime mode, while the orange goes to the oil switch, then connects to the grey wire to provide power during normal operation. The grey wire is in parallel, but it is hot only when the pump is priming. I had to look all this up when I converted a couple trucks to TBI. The factory manual I have has the diagram I am referring to on page 1a-57. This one is for the 89 Astro, which is the closest I have to his truck with the same 1227747 computer. I know for sure there are many, many errors in the Haynes diagrams. I can't find the post where I talked about it, but I'd given some specifics about an S-10 blazer I was working on a few months ago.
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John, That's interesting... I know there is paint on the blades of the oil pressure switch - so the connection isn't reliable. Still that shouldn't matter until after it's started. Will probably try hotting the ORG wire tomorrow if it's not raining (w/ a charger, not a jumper cable). Elliott
John Alt wrote:

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Pay attention, young grasshopper. The orange wire is the battery input for the computer. You don't have the battery regulating that line, since there is no voltage on it. Now you are going to put a poorly regulated, roughly 16V source with horrible ripple voltage onto your computer's power supply. These computers are tough, but there is no good in doing this.
If you must supply power to this wire, do so with a wire slightly smaller than the factory wire. Hopefully, if the smoke comes out, it will be through your smaller wire and not the factory harness.
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Wouldn't it be a lot easier and safer to disconnect the battery, unplug the ECM and connect a ohm meter between the orange wire and ground to see if it's shorted?
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snip

Finally someone brings some sanity to this thread :)
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Ooops, sorry.... didn't mean to. ;-)
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yea the ohm meeter test of the ornge wire is simple enough - will do. It's easier than stripping a spot on th wire. Elliott
Neil Nelson wrote:

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says...

Aww come on Neil, what would be the fun in that? Bob
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Well, after reading the ring and pinion thread, I'm not sure I can handle any more fun from Elliot.
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And he is an electrical engineer!
--
hank
2004 Chev Z71
  Click to see the full signature.
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In article <nonelson-
snipped-for-privacy@sbcglobal.net says...

He doesn't want to listen to reason. Besides, this is fun.
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OK good idea too. Thanks John, Elliott
John Alt wrote:

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