Help please, '88 5KCSTQ needs at least 3 hrs rest!

[Louis A. Mulieri]

My 1988 5KCSTQ cranks a loooooong time if I try to start it after a 1 hr 
cooldown from normal driving temperature. Sooner than 1 hr and it starts 
in a few seconds but from 1-2+ hrs after normal running it cranks up to 1 
min before firing a few cyls and then stumbles along for another 15-20 
seconds before coming to life. 3-hrs or overnight rest and it starts 
instantly so it seems unlikely to be leaky injectors.

I had long cranking even after overnight rest this summer whenever the 
outside temperature was above 78F.

There are no fault codes registered. Energizing the fuel pump with a 
jumper wire (pump sounds good) for 30 sec before and during turning the 
key to start does not eliminate the long crank time during the 1-2+ hr 
slow-start period.

I replaced the fuel filter underhood and checked fuel delivery rate as 
well (750 cc/30 sec as per Bentley).

I suspect the temperature sender that signals the cold start valve 
controller may be erroneously indicating "warmed-up engine" when it's 
cooled down for 1-2 hrs when it should be indicating "cold engine".

>From Bentley I concluded the likely temp sender was the double-spade 
terminal one pointing toward back of engine out of the top goosneck and that it 
should be a resistance unit rather than a thermal switch. Ohmmeter check 
revealed open circuit between terminals as well as from each terminal to 
ground. Jumping the terminals with a fixed, 1 kohm resistor did not 
eliminate long cranking.

Ordered a new one (22 mm brass hex housing with red dot on nylon 
base of terminals and 9 mm threaded end into block, stamped: 07-93 and 
110-97, 130 C max). The new one also reads open circuit regardless of 
ice-water or flame exposure. I'm confused as to whether the new sender is 
bad or that I'm not looking at the right one on my engine.

There are two other temp-like units screwed into the water jacket in this 
area. A small one with a single spade terminal screwed directly into the 
head ahead of the top goosneck and a large, 4 or 5 terminal socket one 
pointing downward from underneath the top gooseneck.

Can anyone help me to identify which sender is the one used by the 
computer to control when to pulse the cold start valve and what it's 
temp-resistance readings should be and/or what other causes there could 
be?

Thanks for ideas,
Lou