Hot start issues

[19psi]

Been doing some searching and this appears to be a common problem...possibly similar to what Maleficio posted about a few days ago.

Cold start typically fires up within 2 seconds. Burns rich, almost as bad as my old carbureted Vette. Clears up within 5 minutes, definitely don't want the garage door closed during start up. Idles smooth and performs good during this time, just not something I'd expect from EFI.

Hot start is difficult from 15 minutes to several hours on a warm engine. Cranking can take up to 10 seconds before starting. Runs perfect once started.

Cold Start Valve....Cold Start Injector Is this two names for the same item?

I see some pictures show it attached to the front of the spider. Instead I have a fitting with a braided hose going to a rectangular device attached to the cross brace and the injector is at the rear of the engine.
What is this item attached to the cross brace?

Not a good picture but you can sort of see it:



Going further...am I right in assuming an accumulator is only used in the early US models?

Lastly I want to see if it's leaking down. I see the port shown in the shop manual but there is no flange to place a back up wrench. Is the manifold pretty sturdy or will it bend easily?

[Maleficio]

There is a troubleshooting checklist in the WSM. Right now, I cannot recall the likely culprits for hot start issues. Obviously, rule out the cold start circuit. Something is not responding after it's good and hot.

My first thought is fuel pump relay. Can you hear it humming during cranking?

WSM calls out a few units for hot start issues. Wish I could remember them.

[Maleficio]

Aahh.

My new mantra now, after my horrendous no start last winter, is verify/clean/replace ALL grounds before doing any troubleshooting. Remember that metal expands after being heated. My issue was a loose ground for L-Jet. In your case, your bad ground may become good after it's cooled off, and rested back into place. Good luck.

[Maleficio]

I think the device on the cross brace controls the supplemental air valve. Or something similar.

[19psi]

I didn't go too far into the manual on the cross brace item. More or less just curious as to what it is since it attaches where the cold start valve does on other models.

Fuel pump is definitely running during cold and hot starts. Right now I warmed it up and disconnected the cold start time switch. Will go out in a bit and see what happens.

Hate to say it but I'm suspecting leaking fuel injector(s). The last emission test had 45K miles in 2005 and I bought it last month with 45K miles. They were supposedly cleaned but hard to say how. I suspect just chemical. Idles smooth as glass with perfect response so hard to say at this point.

[Maleficio]

If running well, it's not your injectors. And thermo time switch may prevent a hot start, though it won't command the cold start injector to open. In fact, I think the WSM calls it out. Yesterday I proved that disconnecting it will prevent a start, hot or cold. Supposedly you can jump a couple of pins on the connector, not sure. That switch has a lot in it, and is costly. Yours may be bad. Kind of makes sense.

[Maleficio]

The ECU looks for it, whether it needs it or not.

[Maleficio]

Very much like the Signal Data Computer in F/A-18's. It looks for grounds to verify signal continuity. The loss of ground indicates a failure. This switch is designed the same way. After prescribed time, bimetalic strip retracts from ground stalling cold start valve operation, and signalling the ECU to monitor oxygen sensor signal.

[Maleficio]

It's uncanny how many similarities I see between the 928 and the semi-modern fighter jet. In fact, learning how the 928 works helped understand better how the F/A-18 works, and vice-versa. Symbiotic.

[19psi]

I let it sit about 30 minutes and just went out and started it. About 3 seconds and she fired right up nicely.
I'm thinking it's out of range allowing the csv to engage when the engine isn't cold enough to need it.
Since the circuit is now completely open it's either thinking the temperature is above 104ºF or it's in an open loop mode (not seeing at least 160 ohms) and substituting a fixed value...at least I hope the ECU is intelligent enough to do that as I have an '82 motorcycle that does.
If it doesn't it probably won't start when stone cold tomorrow.

I'm not sure why your car won't start with it disconnected? I pulled the brown plug to the left of the regulator...is that the one you disconnected? I would think the ECU should substitute a fixed value for any disconnected sensor to avoid leaving you stranded.

[Maleficio]

Originally Posted by 19psi

I let it sit about 30 minutes and just went out and started it. About 3 seconds and she fired right up nicely.
I'm thinking it's out of range allowing the csv to engage when the engine isn't cold enough to need it.
Since the circuit is now completely open it's either thinking the temperature is above 104ºF or it's in an open loop mode (not seeing at least 160 ohms) and substituting a fixed value...at least I hope the ECU is intelligent enough to do that as I have an '82 motorcycle that does.
If it doesn't it probably won't start when stone cold tomorrow.

I'm not sure why your car won't start with it disconnected? I pulled the brown plug to the left of the regulator...is that the one you disconnected? I would think the ECU should substitute a fixed value for any disconnected sensor to avoid leaving you stranded.

I agree. I disconnected the thermo time switch, no start, not even a stumble.

Try it sometime. If I'm right, good way to disable your car if you need to.

[Maleficio]

Three seconds of cranking? Wow, I blip my starter for micro-seconds, no start, blip it again, starts. Three seconds is a long time, and reminds me of my Volvo with a defective rubber flange that seals the pump to the tank. Recall. With a new pump and fresh flange, starts up in no time now.

Extended cranking is an indicator, in my opinion.