Slow start under particular circumstances.

[mitchx3]

1998 Explorer, OHV, 185k miles. Runs well in all ways except for hot restarts.

Cold starts are great ( seemingly less than one engine rotation, instant).

Hot restarts ( example: drive 15min to a destination, do an activity for generally 30min+, return to care) are sometimes slow (3-5sec of cranking).
- crank speed (rpm) is very good
- once it starts it runs normally
- cycling key a couple times to run the fuel pump doesn't seem to change behavior
- if you leave it for a long time (hours but I haven't sought to get more specific) you get back to a cold start which is really fast
-- I'm not certain that it's temp related (but winter might offer more evidence)
- gas pedal state doesn't seem to impact outcome
- no CEL/codes

Ideas? Flaky (heat sensitive) electrical component(sensor, actuator, coil, etc)? Fuel/air temp state issue (heat in intake doing something)?
Not end of the world but kinda annoying.

 

[wollimann]

Sounds like the fuel pump has not enough pressure when warm.

 

[fosterzcj]

This is similar to a Honda Civic I used to have that would do the same thing. Fuel injectors need cleaning or a fuel relay needs replacing.

 

[410Fortune]

Doesn’t seem to be fuel related because cycling the key a couple of times does not help… but to be sure you should have a fuel pressure tester hooked up. 98 with two fuel lines should run at 36-42 psi. 98 with a single fuel line should run at 58-64 psi

Check fuel pressure first to rule it out, this is the most likely cause of a “long crank”

Cold fuel pump works awesome makes plenty of psi as it warms up it runs out of talent and fuel psi drops… she will still run, but the pressure is lacking in the rail during hot re start
Pressure gauge will find this quickly. Test when it’s hot (carefully!!!) and during the re start


Does your brake booster hold vacuum after being shut down for a bit? We are
Looking for large vacuum leak or lack of vacuum

Next would be to check your crank and cam sensor the camshaft synchronizer it used by the computer for starting to adjust timing. When it starts to go bad it can take the pcm a minute to determine the engine is turning

 

[Pete Deering]

Sound like the temperature sensor for the computer has failed.
Do you have code scanner? Read the engine temperature.
It start cold fine, because it in open loop, but once the engine is up too operating temperature, it does not. Because its still in open loop settings.

 

[mitchx3]

Finally got a >32F day. Replaced Coil, Plug Wires, Coolant Temp Sensor (the one directly above the thermostat).

Initial impression is that one of those solved this - will be certain in a few more days.

Coolant Temp Sensor (as Pete suggested) does seem more likely than coil but I didn't feel scientific enough to test between the various parts.