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WUR and strange control pressure

 

I had my WUR rebuilt several years by 928 Classics. ?Recently, it has been giving me fits starting when cold.

Pressure testing showed the cold control pressure was over 30 psi. ?When rebuilt, the screw/locknut mod was done. ?No amount of adjustment would bring the cold pressure down.
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Yanked it and disassembled it. ?Everything looks fine inside. ?Tested the warm up strip. ?It works.
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If I connect it back to the fuel lines on the car with the bottom 2 halves off (ie no spring pressure), the cold control pressure is fine at 14psi.?

If I depress the cup where the pin sits, the pressure smoothly rises, as it should.

But when I put the bottom back on, the two springs compress and raise the cold control pressure back up to mid-40s.
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I have done this several times. ?The pin sits in the cup in the circular disc assembly properly. ?The spring cup and the springs are assembled properly.
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Any ideas what could be going on?
 

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Cold start ¨C Engine starts hard or fails to start:

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  1. Cold-start valve or thermo-time switch faulty
  2. Fuel pump not running
  3. Air-flow sensor plate rest position incorrect
  4. Fuel pressure incorrect
  5. Coolant temperature sensor or wiring faulty (KE injection only)

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A few things to check.

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Michael

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From: [email protected] <[email protected]> On Behalf Of Peter S s/v Dawa II
Sent: Wednesday, October 30, 2024 4:42 PM
To: [email protected]
Subject: [PacNW928] WUR and strange control pressure

?

I had my WUR rebuilt several years by 928 Classics. ?Recently, it has been giving me fits starting when cold.


Pressure testing showed the cold control pressure was over 30 psi. ?When rebuilt, the screw/locknut mod was done. ?No amount of adjustment would bring the cold pressure down.

?

Yanked it and disassembled it. ?Everything looks fine inside. ?Tested the warm up strip. ?It works.

?

If I connect it back to the fuel lines on the car with the bottom 2 halves off (ie no spring pressure), the cold control pressure is fine at 14psi.?

If I depress the cup where the pin sits, the pressure smoothly rises, as it should.


But when I put the bottom back on, the two springs compress and raise the cold control pressure back up to mid-40s.

?

I have done this several times. ?The pin sits in the cup in the circular disc assembly properly. ?The spring cup and the springs are assembled properly.

?

Any ideas what could be going on?
 

Here's a good discussion on Rennlist.
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Have you check the vacuum to the unit?
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Let us know when you figure it out. I haven't dove into the CIS/WUR that much since I got lucky with my 79 and all is running great for the moment.
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CSV is fine. ?Power to the ?thermo element in the WUR. ?System pressure is fine, as is the leakdown time. Plate height is adjusted properly
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The hard starting is completely due to the high control pressure, caused by spring tension in the WIR.
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If I remove the springs, cold start pressure is dead on, and the car starts beautifully. ?But then belches black smoke when the engine warms up

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