Will excessive cranking cause premature leaning by the WUR?

[DMC1890]

Thanks Ron and Dave M.

I concur that initially unplugging the WUR will help with the startup after hibernation, and in fact have observed it. But, if I take a gamble and don't do that, does anyone know of a way to get the control pressure down temporarily after the WUR has heated up prematurely - perhaps with the vacuum inputs to the WUR?

[David T]

The least invasive thing to do is just wait a few minutes. It should cool off rapidly. The WUR senses temperature 2 ways. One is from the internal heating element and the other is from the valve cover. If the motor hasn't started the valve cover will be cold and cool the WUR quick. The vacuum portion of the WUR is only for sending a pulse of fuel like an accelerator pump in a carburetor would do and only once the motor warms up.

[DMC1890]

I suppose you're right. What I was thinking was to do step 3.c, on page D:02:01 (apply vacuum directly to WUR lower chamber) to force the lower control pressure for starting. But by the time I go find my vacuum pump and hook it up, the WUR heating element may have cooled off. BTW, doesn't the vacuum enrichment normally work only on a cold engine?

Robert

[Ron]

I suppose you're right. What I was thinking was to do step 3.c, on page D:02:01 (apply vacuum directly to WUR lower chamber) to force the lower control pressure for starting. But by the time I go find my vacuum pump and hook it up, the WUR heating element may have cooled off. BTW, doesn't the vacuum enrichment normally work only on a cold engine?

Robert

I think you meant 3.b?

You might try, disconnecting and plugging the vacuum line that does not have the delay valve. Since it usually starts (but then dies), it might create enough vacuum in the lower chamber before it dies to deflect the diaphragm down making it richer. (The delay valve holds for ~10 seconds.) No idea how much it would change the A/F ratio...might flood the heck out of it, especially after it stared idling a while...Plugging the port too might help if it's too rich.

Thoughts:
I agree it should cool off rapidly as David T said, IFF it does not start/run. Mainly because I don't think short cranking times does much, considering the OEM purpose/design. 104°F is not very hot, and that is the top end of its effectiveness. All that and the pressure you reported indicates the WUR/CPR is on the high side but ok (at least at that radiant temp), which makes me think the problem is elsewhere, even if related to the WUR/CPR....
FWIW, I would double check all of the things I'm sure you already looked at (timing, vacuum routing/leaks, TTS & CSV operation, ..., set CO last). Then confirm that the primary pressure is correct and not throwing off the ratio with the control pressure, and then record the radiant temps-control pressures as it warms up.
If it turns out that the control pressures are off, you can adjust the WUR/CPR.

(Sorry for the repetitions ;-)

[DMC1890]

Thanks to all you guys.

At this point, it is a moot issue for me. With the current weather here in Houston, I'll probably drive the D every 2-3 days. And in that mode, it starts and runs perfectly!

But I think I've learned a good bit now about the WUR as well as the RPM relay, which will come in handy in the future.

[David T]

If the motor does not start right up (even cold) or idle badly when cold, maybe it is time for a tune-up? Worn spark plugs, bad wires, dirty fuel injectors, vacuum leaks can all contribute to hard starting and excessive cranking. Even with a perfectly operating WUR, the A/F ratio is not optimum and the motor will not run all that great til it warms up. These systems are to get the motor started quickly and run as smooth as possible till it can warm up and get into closed loop.