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Location: Dawsonville, GA
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Thanks. Replaced those when I damaged them fixing the clutch. Also you can see that I'm getting a good signal from the scope shot. I will recheck the crank position sensor to make sure it is providing a good signal to be sure.

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Old 10-19-2016, 05:21 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #41 (permalink)
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"Control unit" in the test-plan is DME. Tests & specs apply to pre-85.5 cars too.

Wiring connector on the speed/ref sensors are standardized. But the wiring to the DME did change with how the shielding is grounded I think.

On the ref-sensor, make sure the signal starts with a positive slope. I've seen hanrness repairs with the wires reverse going into the connector.

BTW, test all these signals & the DME connector.
Old 10-20-2016, 06:28 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #42 (permalink)
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Could have had the scope ground/signal swapped

I found this picture on my phone from when I first started looking at the speed sensor and reference sensor waveforms on the oscilliscope.

As you can see, it starts with a negative slope where it should be a positive slope to start. This could be because I had the scope probe and ground swapped. I will re-check.

I'm not sure how this could be the problem. By that I don't mean starting with a negative slope rather than a positive slope. The car was running, then wouldn't. None of the these sensors had their wiring modified, other than to plug and unplug them at the connectors so that I could get a stronger speed sensor input.

I have a few minutes now before going to get my son at the soccer field so I will go check.
Old 10-20-2016, 02:11 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #43 (permalink)
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Reference sensor is good

Ok, snuck out to the barn and took these measurements. Here is how the scope was connected:



And here is the waveform:


As you can see, it is within specifications.

I will try the removing O2 sensor next, but for now, off to the soccer field.
Old 10-20-2016, 02:52 PM
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Barn? I wish I had barn to work on the car in! I can't even open both doors at the same time!
Old 10-20-2016, 11:39 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #45 (permalink)
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Originally Posted by DannoXYZ View Post
Barn? I wish I had barn to work on the car in! I can't even open both doors at the same time!
It is rough, sometimes I have to turn on the heat or AC when the temperature outside gets ugly.
Old 10-21-2016, 06:31 AM
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Pulled the fuel filter and it was pretty bad. New one will be here next week.
What drew me to this is that stepping on the gas causes the car to die faster than not stepping on it. However, spraying carb cleaner rarely made a difference in run time after releasing the key.
After I swap out the filter, I'll be looking for someone with a pre 1985.5 that I can try my DME in.

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Old 10-22-2016, 09:22 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #47 (permalink)
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Ok, swapped out a really rusty filter and put in a new one so I could do a fuel pressure test. I turned the key and saw... No pressure?
I put power to the pump, at the pump, and ... No pressure?
I noticed the fuel line to the filter bulging and then it started to leak. What the heck?
Something is blocking the flow of fuel. I guess I'll start by first fixing the fuel line from the filter to the pump then make sure it is getting through the new filter.
Any ideas on where up stream from there I could have a block that would stop fuel from getting to the rail?

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Old 10-28-2016, 06:06 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #48 (permalink)
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Was using pressure gauge wrong :(

Ok,

AFTER bleeding the pressure gauge for a little, I was able to get fluid to it and check pressures:

39 psi with just the fuel pump running
31 psi with the car trying to fire

so the fuel pressure is fine.

I did manage to get the dirt out that was blocking the fuel flow by spraying carb cleaner into the fuel gauge bleed line then hooking my air hose up and blasting it backwards and out prior to where the fuel filter plugs in.

So... I can only now conclude that I blew up my DME when I didn't have the ground wire connected.

Anyone have a spare pre 1985.5 DME?
Old 10-29-2016, 05:42 PM
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So what I've noticed is that as long as I am turning the key, I can see that I'm getting spark, the fuel pressure is good, and the signals from the reference and speed sensors are strong. I also tested the AFM, and it is in spec. Shortly after I stop turning the key, firing stops, then I hear the fuel pump stop.
It does seem like the DME is working, but what else is there? Could I have some how re-enabled the alarm system?
Thoughts?

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Last edited by DeadPorsche944; 10-31-2016 at 11:01 AM.. Reason: Spelling
Old 10-31-2016, 11:00 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #50 (permalink)
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Ignition switch? Is it still powering the DME relay in the ON position after you release it from START? Try wiggling the key and see if the power cuts out.

Also, did you test the AFM signal at the DME connector itself? Will need to probe the back of the connector so you can get a live signal while the engine's running.

Last edited by DannoXYZ; 11-01-2016 at 07:40 AM..
Old 11-01-2016, 07:19 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #51 (permalink)
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I had a new ignition switch so I swapped it in two weeks ago. I'll check to make sure the power to yhe DME is not glitching away when the key is released, but I'm doubtful. It behaves the same when I have the DME & fuel pump jumpered on.
I've looked at the AFM signal at the DME connector, and it tracks nicely to spec as I manually move the flap. I have not looked at it while trying to start the engine.
The bummer is that everything was working fine until I snagged the wiring that was jury rigged to have switches power the DME & fuel pump. I didn't realize that the DME wasn't getting power, and thus no spark until after I increased the output signals from the crank and reference sensors. In doing this, I forgot to connect the ground wire that might have ultimately fried the computer. I only tried to turn it over once, but that could have been enough.
Prior to accidentally disconnecting to the DME & fuel pump, the car ran great. This is leading me to the conclusion that the DME was fracked up when I neglected to connect that ground. :-(.
That being said, I recently took my Subaru to the shop for a knock sensor and fluid changes. They finished, took it for a yest drive, and a head gasket blew on their way back. Crap can happen that is unrelated to the work being done, but probably not that often.

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Old 11-01-2016, 09:21 AM
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I had good luck with the ECU Doctor in. They test and rebuild units.

Specialized ECU Repair, Replacement, & Testing - Restore or Exchange your Electronic Control Unit (ECU)

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Old 11-01-2016, 02:34 PM
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Sounds like a bad DME to me, if you have a spare or can get access locally to one, you can potentially rule out the DME without throwing a ton of $$$ at it.
Old 11-02-2016, 09:29 AM
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Originally Posted by fiily View Post
Sounds like a bad DME to me, if you have a spare or can get access locally to one, you can potentially rule out the DME without throwing a ton of $$$ at it.
That's what I'm hoping to do.

It's just so strange that the car is doing all the right things until I let go of the key. I have a nice newish interior to put in, but until it is running, I'm holding back.

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Old 11-02-2016, 09:33 AM
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Now that improved solid state ECU are available, I would no longer rebuild factory ones.
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Old 11-02-2016, 12:55 PM
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Originally Posted by Rasta Monsta View Post
Now that improved solid state ECU are available, I would no longer rebuild factory ones.
Where & $?

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Old 11-02-2016, 12:56 PM
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http://www.ftech9.com/new-products/

DME and solid state DME relays too, very cheap prices for new tech and what you get.

Here ya go

Last edited by fiily; 11-04-2016 at 05:16 PM..
Old 11-04-2016, 05:13 PM
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Damn.. That ain't a bad deal. Under $400 for a solid state DME. Duly noted... and bookmarked.
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Old 11-04-2016, 06:25 PM
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Most definitely. It looks like you have to have an 1985.5 or greater. I'm an 83...

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Old 11-05-2016, 05:43 AM
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