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'99 3cyl transplant in tractor - need wiring info
Topic Started: Sep 9 2013, 09:47 AM (3,085 Views)
Mythstae
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Stand by again, editing links... still learning how to do this Flickr thing. I don't know why they're tiny...
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Mythstae
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Ok, I edited them, you can open them in separate windows, and they should be huge...
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Mythstae
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And, I really don't know if they will be the same, or not, there ARE differences between 96 and 99, but of course, I don't have a 98 book, so, I TRIED!
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kthelen
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Mythstae
Sep 12 2013, 11:58 AM
Ok, I edited them, you can open them in separate windows, and they should be huge...
Thanks! Those pages are much higher resolution than the ones I'd been squinting at when I made the list above :-)

But I think I found the problem myself: grounding issue.

When I grabbed the replacement ECM this morning, I intentionally left several inches of wire attached to its connectors. I used those pigtails to bench test both units - put B+ to the Key On and Memory wires, grounded the two grounds, and put a voltmeter on the Trigger wire. When doing it that way, everything seemed normal (0-1VDC).

So I went back to the engine, disconnected the engine harness completely, and did the same test again (same five wires, only through the harness instead of directly hooked to the ECM). The problem showed itself - and in grand style. Now I had full B+ coming out of the trigger wire!

At least I had something to go on now... problem most likely in the engine harness. Ohm-meter time! Key On, Memory, and Trigger wires were fine. But both grounds were open. Yikes.

Followed the wires through the harness. Discovered that the grounds from the ECM bolt to the intake manifold in one spot, and the grounds from the bulkhead connectors bolt to the intake manifold *in another spot* - no connection to each other within the harness. Short the two together, and suddenly the problem was solved.

So now I've cleaned up the two spots on the intake manifold (they were pretty dirty - likely the original problem) and am going to reattach everything. I strongly suspect that the poor grounds just happened to be creating the right amount of resistance to cause 5VDC to come out of the Trigger wire, which was what threw me.

Hopefully this problem is now solved, so I can move onto whatever the next one will be!
Edited by kthelen, Sep 12 2013, 12:09 PM.
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Mythstae
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I've gotta pass the wand to Glenn or Stiffchezze or somebody.
I have to go to bed soon (yay, night shift...)
If you don't have more diagrams by tomorrow, I'll try to find more information and post it then...
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Old Man


Go here and read posts #9 and #10
http://geometroforum.com/topic/4895211/1/#new
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Mythstae
Sep 12 2013, 12:08 PM
I've gotta pass the wand to Glenn or Stiffchezze or somebody.
I have to go to bed soon (yay, night shift...)
If you don't have more diagrams by tomorrow, I'll try to find more information and post it then...
3 PCM connectors, 47 wires and a hand full of sensors. No problem. You're on the right track.

If the components are working, and the wires are making the path through the connectors, it will eventually work when you get it all hooked up.





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kthelen
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This is turning into Opposite Day around here. First I couldn't get the igniter to STOP providing ground to the coil, now I can't get it TO provide ground. (That is to say, I have no spark.) Hitting the igniter's Pulse input with an extremely brief pulse of B+ does cause it to ground the coil, so I doubt it's faulty.

When cranking, I see small fractions of a volt (0.1-0.2VDC) on the Trigger wire. Not sure how much voltage I should be seeing.

I'm leaning in the direction of two possibilities:

1) The ECM isn't getting a proper signal from the CMP, and thus isn't applying voltage to the Pulse wire as it normally would
2) By subjecting both ECMs to the lack of ground condition earlier, I have fried them both

Anybody know how much voltage the ECM should be using to drive the igniter?
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Deleted User
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Is there an oil pan gasket installed? Oil pan gaskets increase the distance between the CMP and the teeth on the crankshaft gear to the point that signal generation becomes less reliable.

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kthelen
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Geo Glenn
Sep 12 2013, 01:03 PM
Is there an oil pan gasket installed? Oil pan gaskets increase the distance between the CMP and the teeth on the crankshaft gear to the point that signal generation becomes less reliable.

I haven't had the pan off. But it does look like the last person who did used RTV or some such in lieu of a gasket.
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Mythstae
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It has RTV from the factory. :thumb
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kthelen
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Grabbed a few known-good junkyard parts.

Distributer (and therefore CMP): no change
ECM: no change

When key is on, I see 0.5VDC on the trigger wire. When cranking, it's 0.6.

So I'm back to wondering... should that be enough to drive the igniter?
If so, I have a bad igniter. If not, I have other problems.



Found this thread, which seems to indicate that I should see around 2VAC at both the CMP and CKP while cranking. CMP is 0.2-0.3VAC, CKP is 0.5VAC. I'm starting to see a pattern here... but not sure what it means yet.

Also found this thread, wherein the OP was having a VERY similar situation. Sadly, that thread ended with him selling the car, so nothing there to guide me either. Aaaaaarrrrrrrrrgh.
Edited by kthelen, Sep 12 2013, 08:32 PM.
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kthelen
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From digging around the forum last night, it seems as though several people with voltmeters have contradicted the guy who says 2VAC should be coming out of the CMP and/or CKP. Don't have links handy now, but a handful of people who had spark were reporting 0.2VAC or thereabouts. So now I'm back to zero.

Wild-ass guess: I know HEI ignition modules have metal on the bottom, and that metal gets attached to a ground in order for the module to work. The Geo igniter also has metal on the bottom. Should I have grounded the base of it - could it be that simple?

Not near the motor now... will check when I am. (EDIT: Checked, no go)

Still want to know how much voltage appears on the pulse (orange) wire going to the igniter on a working, running car. Anybody know?
Edited by kthelen, Sep 13 2013, 09:43 AM.
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kthelen
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Still making no headway on this issue - so I decided to go another way. Went to the junkyard this morning and picked up a distributor from a '91 3cyl Metro, which I installed on my engine and was able to get working immediately. So I've got spark, but I suspect that if I couldn't get spark pulses out of the ECM, I probably won't be able to get proper injector pulses either (not to mention the fact that I've just switched to vacuum advance). So I've removed and set aside the existing ECM, harness, and other goodies.

I'm now debating whether to pull the (comparatively simple) '91 ECM, harness, and applicable sensors, and apply them to my engine - or whether to make an adaptor plate and install a carb. Neither is what I set out to do... but at this point, the grass is growing and my ideals for the project have to take a backseat to getting the mower back in service.

Will be heading to the junkyard again tomorrow to look the '91 over again, and decide if I want to pillage its electronics or not.
Edited by kthelen, Sep 14 2013, 04:43 PM.
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There are two kinds of '91's. Manual and automatic transmission. The manual transmission models have a Throttle Switch (TS) rather than the Throttle Position Sensor (TPS) that's on the automatic versions.

And, there are a lot of differences between any '91 and the engine you have installed.

To make a complete installation to '91 standards, so to speak, you'll need the intake manifold, the throttle body, the ECM and wiring harness.

Clean wire (burn off the insulation) is worth $2.40 per pound at your local, friendly metal recycling center.
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