1993 Ford F-150 Hard Start
Hey dave,
Interesting issue! Is the check engine light on? does it tend to "smell funny" out the tail pipe? Let us know!
Chris
Bingo!........ i think this issue is solved ....here's why
1. A disconnected coolant temp sensor will cause the ecm to "see" a default temp of something like 230 F
2. A " cold" engine needs a TON of fuel before it can warm up and go into closed loop. In fact this engine never goes into closed loop because of the disconned
coolant temp sensor. If the ecm is "seeing" a high temp then it will lean out the fuel sent to the injectors, causing a hard start when cold.
3. Though high idle may be caused by a bad coolant sensor, there may be another cause of this.
4. I recommend a new coolant temp sensor and if the high idle persists, then further diagnosis.
Let us know!
Chris
Suggested Repair
Replace the disconnected coolant temperature sensor so the ECM can read actual engine temperature and supply enough fuel for a cold start. If the high idle continues after the new sensor is installed, diagnose the idle problem further.
Conversation Summary
A 1993 Ford F-150 5.0L will not start unless a small amount of fuel is added at the throttle body, then runs normally until it is shut off. Spark and fuel pressure are reported as good, and the check engine light is on because the coolant temperature sensor was unplugged to stop a high idle. An expert explained that the disconnected sensor makes the ECM assume a very high temperature and lean the fuel mixture, preventing a proper cold start and closed-loop operation. The recommended repair is a new coolant temperature sensor, followed by further diagnosis if the high idle remains.
