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BurialWings
Joined: 12 Nov 2020
Posts: 12
Location: Albuquerque New Mexico
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 Posted: Fri Apr 16, 2021 11:03 am Post subject: No spark 87 924s |
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| So I am having a no spark issue. Coil tests good, dme relay tests good, dme relay jump made no change. Brand new ref sensor properly gapped, tach is bouncing. Down to thinking it could possibly be the SCR pulse trigger in the DME, though upon inspection it looks great. Any ideas or tests I could try out would be greatly appreciated. |
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11733
Location: PacNW
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| Posted: Fri Apr 16, 2021 11:23 am Post subject: |
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How did you verify it isn't sparking? When did the car last run?
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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BurialWings
Joined: 12 Nov 2020
Posts: 12
Location: Albuquerque New Mexico
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| Posted: Fri Apr 16, 2021 11:31 am Post subject: |
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| Rasta Monsta wrote: | | How did you verify it isn't sparking? When did the car last run? |
Tested spark with test light, spark plugs, and a screw driver from the main line. It's been sitting awhile. I bought it non running with smashed pistons and valves and did a rebuild, so I have never had it run but was obviously running to cause catastrophe for the previous owner. |
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11733
Location: PacNW
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| Posted: Fri Apr 16, 2021 12:11 pm Post subject: |
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Sounds like you verified the coil isn't firing.
Fastest test involves a known good DME. If you're committed to the car, the Focus9 solid state DME is a great investment.
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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safe
Joined: 18 Mar 2017
Posts: 703
Location: Sweden
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| Posted: Fri Apr 16, 2021 8:23 pm Post subject: |
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Jump the DME relay for a start, pin 30 to 87 and 87b.
If that doesn't work I would check/replace the crank sensors.
Edit: Also check that the relay socket connectors have a good connection , sometimes they can be a little loose so the connection is poor.
Not sure if the 924s has any of the old cheramic fuses, those can be prone to corosion and moving them a little might sometime solve issues. Same with modern blade fuses, just not so much.
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/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe |
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BurialWings
Joined: 12 Nov 2020
Posts: 12
Location: Albuquerque New Mexico
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| Posted: Fri Apr 16, 2021 10:39 pm Post subject: |
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| safe wrote: | Jump the DME relay for a start, pin 30 to 87 and 87b.
If that doesn't work I would check/replace the crank sensors.
Edit: Also check that the relay socket connectors have a good connection , sometimes they can be a little loose so the connection is poor.
Not sure if the 924s has any of the old cheramic fuses, those can be prone to corosion and moving them a little might sometime solve issues. Same with modern blade fuses, just not so much. |
Crank sensors are new and gapped. I jumped the relay and tested it with a multimeter, it reads as functional on the multimeter, but jumping it made no change.
I'm going to pull the fuse boxes later today and check on connections, it is the old style ceramic ones.
Ordered a new dme relay just to check but will be a few days, though that doesn't seem to be the issue as jumping it didn't do anything. |
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11733
Location: PacNW
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| Posted: Sat Apr 17, 2021 12:33 am Post subject: |
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When I suggested testing with a known good DME above, in case it wasn't clear, I was referring to the computer itself.
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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Paul
Joined: 02 Nov 2002
Posts: 9491
Location: Southeast Wisconsin
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| Posted: Tue Apr 20, 2021 6:57 am Post subject: |
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Make sure the rotor is not loose on the distributor shaft.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy. |
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BurialWings
Joined: 12 Nov 2020
Posts: 12
Location: Albuquerque New Mexico
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| Posted: Tue Apr 20, 2021 7:17 am Post subject: |
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| So fiddling around today, when a new dme relay came in, it seems that plugging it in forces the socket of 87b out the back rather than connecting to the relay. So trying to get it to hold position without much wiggle room for my fingers on the wire. Hopefully it solves the issue. |
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11733
Location: PacNW
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| Posted: Tue Apr 20, 2021 7:19 am Post subject: |
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I'd lower the relay panel and fix that wire. Disconnect negative sure of battery first.
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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