docmirror

So, you basically mimicked the idle air bypass(or idle aux) by using your foot to gently keep it running. You checked the resistance of the circuit and found it out of spec but did not resolve that. We know they have a tendency to stick as well.

j.kenzie@sbcglobal.net

Thanks, Dr. Bob. Is it far enough out of spec to cause this?
Oh heck. I just called 928 Int'l and ordered a good used one.
Dave

j.kenzie@sbcglobal.net

Hi again,
I had a thought. I have had a thermo-time switch bypass in place since 2006. It works like this:

Thermo-time switch bypass L-jet
A while back I was noticing a longer cranking time while I was starting my car. After some trouble shooting, I concluded that everything in my starting system was working fine. However, it was taking me sometimes 6-8 seconds for the engine to fire up.
Research revealed that the L-jet does not really use the cold-start injector to start the car in warm-cold start conditions or even cold-cold start in warm weather. This is controlled by the thermo-time switch located on the front of the water manifold. It is a temp-sensitive timer which switches the ground to the CS injector. The 12V to the CS injector arrives through the starter relay only when the ignition switch is in the START position.
I have concluded that in hot weather I don't have any starting enrichment at all, and probably most L-jets are about the same. I decided to disconnect the TT switch and ground the connector which the TT switch was refusing to ground in warm conditions.
Voila! Instant starts! I can't count "one-one-thousand" before it is started.
Now I understand that if the car doesn't fire up, the CS injector will continue to spray while the starter is turning, and this may flood the engine. So far the only time the car has cranked for any length of time was before, when the CS injector probably wasn't even firing.
I wil have to see how this works in different weather conditions, since I drive my car in winter. For warm climate cars this may be a useful improvement if you car is starting with difficulty.

Anyway, when I started having trouble this winter, I reconnected the TT switch. If my auxilliary air valve is stuck, I may be getting too much fuel through the cold start injector. With that in mind, I reverted to the TT bypass, and the car started and ran perfectly.
I already ordered a replacement AA valve, so maybe with a good AAV, I can use a functional TT switch with good results in the winter. Time will tell.
Dave

j.kenzie@sbcglobal.net

Thanks to docmirror.
I finally installed the used auxiliary air regulator. The car runs much smoother, warms up smoother and starts more easily in cold weather. I looked at my original part, and I found it did not open fully or close fully, compared to the replacement. We will see how it goes over the next few weeks, but so far it seems much better.
Thanks,
Dave

j.kenzie@sbcglobal.net

Hi again,
I thought I was OK, but today it is 0 degrees, and the car started with some difficulty. It stabilized at an idle of 1200 rpm, but every time I gave it throttle it would almost die. I let it warm up completely, but still it would not rev smoothly, and was therefore undriveable. As I said the AFM s a 4 year old rebuilt unit. TT sensor is new and ohms out OK. Temp 2 sensor ohms out OK. Thanks again for any ideas.
Dave

DKWalser

Is it possible the fuel pump has difficulty handling the low temperatures -- able to run fast enough to handle low RPMs, but not able to meet the demand for anything requiring more fuel? You say the car runs well in warmer weather and you've checked the systems that would adjust the fuel/air mixture for ambient temperature. That seems to indicate a fuel delivery problem. You've replaced the fuel filter. Next thing to check would seem to be the fuel pump.

No, I cannot think of a reason why the fuel pump wouldn't work well when its cold but work well when it's not.

dr bob

Dave--

Do you have a fuel pressure gauge you can hang on the rail for a short while as you have these episodes? That way we could confirm or eliminate fuel delivery in one pass, narrowing down the possible causes by half.

j.kenzie@sbcglobal.net

I did buy a fuel pressure gauge. Would I have to leave it in place to catch the failure mode? Is that safe?
BTW the temp went up to 17 degrees F. this afternoon and the car started fairly normally, and ran well.
Thanks,
Dave

dr bob

The gauges that were left on permanently suffered fromvibration-induced failures. Short-term installation for diagnostic purposes is exactly what those gauges are intended for. Jumper the fuel pump afterr you put it in to check for leaks as well as baseline pressure.

j.kenzie@sbcglobal.net

Sorry Dr. Bob. I wasn't very clear. I have a fuel pressure gauge with a set of adapters and a 6" length of flexible braided hose to attach the gauge. The car behaves pretty well most of the time, and I would have to leave the gauge set attached for quite some time to catch it failing and document the fuel pressure conditions.
Thanks,
Dave

19psi

Tomorrow is going to be another sub zero hell day. There's your chance.

j.kenzie@sbcglobal.net

Tempting. Ironically the ideal days to test the problem are pretty horrible for working on the car. We'll see though. It looks like I don't have an adapter for my fuel rail anyway.
Thanks,
Dave

j.kenzie@sbcglobal.net

Temp was 5 degrees this morning and 8 degrees tonight. Car started fine each time. It ran a little rough for 30-60 seconds, but then settled down and ran and pulled smoothly. I know that sounds good, but it feels a little uneasy to not know if it will start in cold conditions. I am looking into a fuel rail pressure gauge; Carl has one but lists it for 85 and after cars only.
Thanks,
Dave

Landseer

When is last time you cleaned up under distrib cap?

j.kenzie@sbcglobal.net

It's been a while. I changed the green wire last Summer, and I don't remember it looking bad, but I can take a look. The cap and rotor were definitley new in the last five years, changed by me.
Thanks, Chris, for any ideas,
Dave