924Board.org

ggrecian · Joined: 20 Oct 2013 Posts: 29 Location: Pa

1987 porsche 924s crank no start.have spark.tach bounches when cranking.have fuel pressure to the rail.fuel injector do not show pulse with noid light.with multimeter both plugs have voltage on fuel injector electrical connector.PLEASE HELP!!!should i get voltage on both injector plugs?how to fix or diagnose no injector pulse?
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porschelover

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

This might help

http://www.clarks-garage.com/shop-manual/ts-01.htm

Its just an early 944, so there's lots of documentation available on how to diagnose the 944 EFI system.

Typically injectors are instructed to fire by the computer based on the computer receiving proper signals from various sensors on the engine. If those signals are not received or not in the proper specification and it will not fire the injectors for safety reasons.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

ggrecian · Joined: 20 Oct 2013 Posts: 29 Location: Pa

Thanks much!clarks garage definately has a Wealth of information.which sensor would u start with..tach hops so does that mean the speed and reference sensors are good?alsoi accidently swapped the speed and reference sensor plugs.could that have damaged computer?
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porschelover

ggrecian · Joined: 20 Oct 2013 Posts: 29 Location: Pa

Tach hops when cranking..so does that mean that the reference and speed sensors are good?
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porschelover

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

No idea. Neither of my cars use them, so I'm out of my depth.

From what I understand, the sensors are interchangeable? If so, I doubt that it could cause ECU damage, but I've been wrong before (and will again! heh)

Might check over on the Pelican Parts forum where there is more traffic and potentially more answers.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Did you measure pressure on the rail, or just basing it on the fact that fuel is in there? I might try a known good DME if you have one available.

Oh, and swapping those sensors should not hurt the DME.
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

ggrecian · Joined: 20 Oct 2013 Posts: 29 Location: Pa

yes have 37 psi when cranking.any other ideas
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porschelover

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Interesting Motronic thread:

http://forums.pelicanparts.com/porsche-911-technical-forum/659459-motronic-injector-signal-testing-2.html

Pay attention to the bit about bad grounds.

Also, if you don't know the history of speed and ref sensors, I would replace them for piece of mind. Cheap replacement is Facet 12141710668. Also check condition of the engine harness plugs for crank sensors.
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3