924Board.org

[Rugbreyð]

Hey everyone,

I'm having issues with my Porsche 924’s warm‑up regulator (WUR). The fuel system pressure climbs to 5 bar but never drops to the expected 3.6 bar. I’ve already:

Rebuilt it using a repair kit

Checked the heating resistor—measures ~20 Ω, which seems correct

Despite all that, it won’t settle down. I suspect the wiring is messed up—maybe from work done by the previous owner. Any thoughts on where to focus my troubleshooting?
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i have no idea what i am doing, but i have a dreeaammm, and that is to see my shitty 924 work agian after 20 years of not working

[Raize]

Wiring wouldn’t cause that.

Basically the flow through your WUR is extremely restricted

Something is assembled wrong, maybe heater strip upside down is a common mistake.

[Rugbreyð]

i don’t think I did anything wrong during the assembly. I’ll double-check it, but I followed all the steps shown in this video:

https://www.youtube.com/watch?v=zW5qV208tCA

I didn’t use any fluid sealant between the metal disc, unlike what I did in the fuel distributor. Could that cause the malfunction?

[Raize]

It shouldn’t need any sealant.

Apart from a mechanical issue with your rebuild:

1. Not using the pressure tester correctly (valve is closed, or stem has snapped and you didn’t notice)
2. Pressure tester connected in wrong place (Should be connected to the fitting on top of the fuel dist)
3. WUR plumbed incorrectly (CSV swapped with WUR return is the only way this could happen I think)
4. Extreme blockage of the WUR in/out filter screens.
5. Previous owner has been hammering at the WUR fuel cell to try and lean it out and screwed up the depth setting. Check for witness marks.
6. Collapsed fuel hose somewhere.

[Rugbreyð]

I have connected the tester correctly, and no fuel hose is collapsed-

It could be extreme blockage of the WUR in/out filter screens, how could i check and also clean these filter screens.

And what do you mean by WUR plumbed incorrectly, and in number 5, what screw are you talking about, i dont think i have any screw.

[Raize]

The filter screens are just under the banjo bolts, it would be quite obvious if they’re full of debris, you could maybe dig it out with a toothpick or blow it out with compressed air.

You might have the fuel line for the CSV connected to the WUR return line which would mean that both sides of the WUR would just see system pressure. Easy to check - the return line of the WUR should trace back to the overall return line on the fuel distributor.

And by screwed up I just mean broken, no screws involved. The adjustment for the fuel cell literally is just tapping it in or out with a hammer.

[Riggard]

try blowing through the fuel return line.

Also, what you could try to do to rule out incorrect assembly/setup of the wur, is open the underside and remove the spring + pin. If control pressure drops after that, you need to fix the WUR.

[morghen]

I always struggled with WUR control pressures being either completely out of range or at least out of range for either cold or hot conditions.

Calibration is a very delicate process, you normally need a test bench with fuel flow attached to it, ability to warm up and cool the WUR, 12V and of course a pressure gauge.
And then you should be able to slowly adjust the WUR to fit the needs as best as it can.

If you dont want to do that, you can always order an EFI kit from me.
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Supercharger and EFI kits
https://www.the924.com

[Raize]

[Rugbreyð]

I’ve now taken the WUR apart again, and everything looks fine. The filters don’t appear to be clogged. I also tried starting the car with the bottom section and spring removed from the warm-up regulator, but nothing happened. it stil is at 5 bar fuel pressure.

However, I didn’t have power connected to the WUR during that test, does it need power for anything to happen in that scenario?

Also, when you guys mention “calibrating” the WUR, what exactly do you mean by that?

[Rugbreyð]

And here are some photos i took of my warm upp regulator

Images inside the WUR





Images of the filters

[gml]

I'm dealing with my WUR right now. I had system pressure = control pressure (4.6 bar) even with the bottom half removed (no spring), and even though I rebuilt my WUR. My inlet filter screen looked as clean as yours, but I still blasted throttle body cleaner from the inside out. After a few rounds of that I'm reading control pressure is 0.6 bar without the WUR bottom half (no spring)

The inlet screen consists of 5 mesh layers that get increasingly more fine. I suspect the most fine layers are clogged up with old fuel varnish that needs to be patiently dissolved.
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George

1982 924 NA 5-speed

[924RACR]

Thanks for the pics, that helps the discussion a lot too.'

The recalibration or adjustment is done by moving the base of the bimetallic strip - where it's secured on a stud with a nut. That sits on a plug that's inserted in the upper body of the WUR, and by moving the plug in and out the pressure can be adjusted.

But as this is done by tapping or pressing - it's a real pain to do outside of a test bench... so linked in the other thread from gml there's the instructions on how to fit it with a screw to make it a bit easier to adjust.
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Riggard]

The fact that removing the strip does not change the pressure, means that either the WUR, or something else in that path is clogged.
Fuel goes from a very small hole in the distributor to the WUR and then is fed back to the tank via the return line.

When I had this symptom (System pressure = control pressure) the return line was clogged. I blew it through and that helped. But it could also be the WUR itself as mentioned above.

With calibrating the WUR, we mean setting both the cold and warm pressure. The warm pressure has to be set first, by pushing in or out the black fuel cell. The cold pressure can be adjusted by adjusting the pin, which is often done by tapping a bolt in it with a nut. I would say this has to be done whenever the WUR is opened/rebuilt. Though I've rarely seen people do it properly.

[924RACR]