924Board.org

Gatornapper · Joined: 23 Oct 2021 Posts: 294 Location: VA

Once again, PBPWM. I've done my research and just want verification for my diagnosis.

Engine starts instantly hot or cold. But if cold, it won't continue running.
After 2 to 4 starts, it will run, but barely - keeps wanting to die. I keep nursing throttle a lot, and the longer I get it to run, the better it runs.

In a couple minutes, it's warm enough to run fine. Warm/hot starts are no problem - instant.

So, because it starts instantly always - the Cold Start Valve is obviously working fine. Correct?

But because engine will not continue to run until it just gets a little warmth, it sounds like the Auxiliary Air Regulator is not working. My opening the throttle repeatedly duplicates (somewhat) the function of the AAR, but not so smoothly.

I'd pull the AAR and test it, but is it not under the intake pressure tube and hard to get to?

TIA,

GN
_________________
'87 944 S, looks & runs like new - sold my sweet 931; '76 914 2.0 mostly restored; 2011 Porsche Cayman S in Meteor Grey, 3.4L, Softronics ECU tune 355+hp , PDK w/Sport Chrono. Got this thing for Porsche's.......

Fasteddie313 · Joined: 29 Sep 2013 Posts: 2596 Location: MI

More likely the WUR..

CIS pressures test time..
Cold control/warm control.. Bet that symptom is caused there...

Read up on adjusting your AFR screw with a swell meter too..

If you want to get it RIGHT and KNOW it’s right..
And not blow up your engine..
_________________
80 Turbo - Slightly Modified

Gatornapper · Joined: 23 Oct 2021 Posts: 294 Location: VA

Eddie -

Does Haynes call this the the WUV, or Control Pressure Regulator? They say it is out of the picture once the engine is warm and is either open or closed?

Mine does have 20 ohm resistance across the pins, so the heater element is working. And Haynes says this part rarely fails.

Guess I'm not understanding how it works - I know it controls pressure that controls the control pressure in the Fuel Dist.

And what is a swell meter?

I'm definitely ignorant on CIS....studying up on WUV now........

GN

Gatornapper · Joined: 23 Oct 2021 Posts: 294 Location: VA

Eddie - et al -

So is the WUV constantly regulating the pressure to the Fuel Dist.? or just during warm-up?

Haynes seems to say it is just during warm-up - and that the unit is rarely a problem or rarely fails.

From what I've read it does fail and may even need adjusting....which I am NOT going to try.

Thanks, and thanks for bearing with my ignorance.

GN
_________________
'87 944 S, looks & runs like new - sold my sweet 931; '76 914 2.0 mostly restored; 2011 Porsche Cayman S in Meteor Grey, 3.4L, Softronics ECU tune 355+hp , PDK w/Sport Chrono. Got this thing for Porsche's.......

Gatornapper · Joined: 23 Oct 2021 Posts: 294 Location: VA

Ok, after beginning to watch this video on rebuilding the WUV, it actually is pretty easy. I've rebuilt successfully a lot more complex devices than this.

https://www.youtube.com/watch?v=VVsnF2RlEqw
_________________
'87 944 S, looks & runs like new - sold my sweet 931; '76 914 2.0 mostly restored; 2011 Porsche Cayman S in Meteor Grey, 3.4L, Softronics ECU tune 355+hp , PDK w/Sport Chrono. Got this thing for Porsche's.......

924RACR · Posted: Sun Jan 02, 2022 1:55 am Post subject:

Yeah, Haynes doesn't know everything about these... but a tough cold start and OK warm-running as you've described is typical symptom of a WUR not working properly.

I've only had mine rebuilt, have not chased the DIY path... others can speak to the ease/success of that path...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Gatornapper · Joined: 23 Oct 2021 Posts: 294 Location: VA

Vaughan -

Where might I get mine rebuilt? or purchase a rebuilt one?

Thanks!

GN

Fifty50Plus · Posted: Sun Jan 02, 2022 1:12 pm Post subject:

Gator,
The warm up regulator (WUR) adjusts the fuel pressure down from a rich mixture condition as it heats up. It is initially heated by the electrical plug and then by intake manifold temperature (note where it's located - in a hellish location for removal/installation).
The rich condition along with a working cold start valve (several second operation) gets the cold engine running and over the next few minutes the WUR heats up and reduces fuel pressure to the upper chamber of the fuel distributor. It does this by dumping excess back to the fuel tank. The injectors then flow less fuel (lean out) from their initial needed rich mixture to a more usable operating pressure mixture.
Note that all of this is without touching the throttle.
If you have a CIS tester you should see an initial higher pressure that drops as the engine (WUR) heats up. If not, the WUR may not be heating up or is stuck in the warm state (i.e. BAD). If stuck "warm" the engine probably will start easily when it has recently been run. Otherwise, if the engine is cold, it will be difficult to get it running initially and require a lot of throttle applications to keep it going.
_________________
1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car

Gatornapper · Joined: 23 Oct 2021 Posts: 294 Location: VA

Auto Atlanta has the reman - WUV's for $207. $100 core charge.

Pretty reasonable to me.....

GN
_________________
'87 944 S, looks & runs like new - sold my sweet 931; '76 914 2.0 mostly restored; 2011 Porsche Cayman S in Meteor Grey, 3.4L, Softronics ECU tune 355+hp , PDK w/Sport Chrono. Got this thing for Porsche's.......

Gatornapper · Joined: 23 Oct 2021 Posts: 294 Location: VA

THANK YOU for the excellent and detailed explanation of how the WUR works. I had pretty much surmised that from all I've read, but you clarified it better than anything I read. And along with Vaughan confirm that the WUR is my problem.

I dread getting it out more than rebuilding it. I used to rebuild Holley & Rochester 4-bbl carbs in my sleep with one hand tied behind my back.....

The Cold Start Valve is working great as engine starts instantly cold every time.

Three starts and there is enough heat to keep running, tho very poorly. Once running, a minute or two and it runs fine. Once warm, engine always starts quickly.

Next question: If I keep running Seafoam or its equal in heavy dosages in the fuel, any chance that in time the WUR will get unstuck? I guess not likely as no fuel is flowing through it.......in the warm position.

No, don't have a CIS Tester, but looks like I probably should get one if I'm keeping this car - which is the plan. Not too expensive, if this one is ok:

https://www.amazon.com/Tool-Aid-33865-K-Jetronic-Injection/dp/B0002SR5NU

GN

Gatornapper · Joined: 23 Oct 2021 Posts: 294 Location: VA

Eddie -

Duh. Got it. By "swell meter" you meant a good AFR meter. Yes, that I do have.

Now to find the AFR screw........

GN

924RACR · Posted: Mon Jan 03, 2022 2:51 am Post subject:

He meant "dwell meter" - autocorrect strikes again, no doubt.

Pull the coil to make room to get at the WUR. Not ideal, but it helps. Also since they're allen head bolts, get a set of decent socket adapters and a short-handle 1/4" drive ratchet.
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Gatornapper · Joined: 23 Oct 2021 Posts: 294 Location: VA

Vaughan -

Thank you so much. Tips like this are priceless, and so appreciated.

Thinking how the WUR works and how it appears to be designed, I find it surprising (from a purely mechanical perspective) that the valve would stick in the closed position. Seems to me that long term storage would cause it to stick in the open (cold engine) position - unless stored in a desert or tropical area.

Unless the bi-metallic arm itself becomes broken. But does that happen?

Sorry, just the type of thinking my brain does.......

GN

Fifty50Plus · Posted: Tue Jan 04, 2022 1:23 am Post subject:

The to and from fuel lines to the WUR attach via 13 and 14 mm banjo bolts (I can't remember which is which right now). When you remove them don't drop the little copper washers. After removing the distributor for a bit more room you can attack the Allen bolts holding the WUR on the manifold. I cut a piece about 3 inches off an Allen wrench and use a 1/4 drive socket to remove the bolts.
Beneath one of the banjo bolts, there is a fine mesh screen in the WUR body. Check to see if that is clogged. If so, that was your problem. If not, it's time to dig deeper. This is where you make the decision to either send it out or take it apart.
I recently rebuilt mine with no discernible difference when back on the car. My problem was a clog back to the fuel tank thus no change in pressure. My WUR was not bad. The rebuild is straightforward, just looking for things that don't "look right". No magic.
_________________
1979 924 NA race car
1982 924 NA race car - Sold
1982 924 Turbo almost a PoS
1981 924 Turbo a real PoS, new engine
1982 924 Turbo nice body, blown engine
1972 911 E race car - going to Vintage
Various 944s to become IT-S race car

Gatornapper · Joined: 23 Oct 2021 Posts: 294 Location: VA

Chuck -

Wow. Please quit reading my mind! Exactly the detail I was going to search for on the web.

And would you believe my thinking was, "How do I keep from dropping the small copper washers that seal the fuel line fittings?"

Guessing the Allen bolts (2?) are 5mm? or are they 4? Need to know so I can get an Allen wrench to cut off.....

And I'm surprised a 1/4" drive socket can provide the torque to loosen them.....but as you and others have done it, it's clearly possible.

As my engine starts immediately and otherwise runs like a dream (for having sit for 17 years), I'm in agreement with everyone that it has to be the WUR keeping engine from running until it warms up a bit - but it doesn't take much.

I've successfully rebuilt many complex devices more complex than the WUR (from videos I've watched on WUR rebuilding) without rebuild kits, so I have no fear of rebuilding mine. Thanks for the tip on the screen.

Vaughan said pull the coil. You are saying pull the dizzy too? Didn't want to do that as I'd have to reset timing......

Oh - doing the rebuild myself. Auto Atlanta has to send it out and it takes 6 - 8 weeks.

Again, a thousand thanks for all the detailed info. Greatly appreciated.

GN.