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AOMills
Member
- Joined
- Jan 14, 2014
- Messages
- 48
- Reaction score
- 3
- Points
- 8
- Location
- St. George, UT
- Vehicle Year
- 1990
- Make / Model
- Ford
- Engine Size
- 4.0L
- Transmission
- Manual
I've researched a few websites / threads on the problem but none of them give an solid answer. I've seen the same problems and symptoms, but no solutions.
Here's what's happening, when I try to start my 2.9 cold, on mornings when the temp is roughly 45 degrees or below, the truck won't start because the fuel pump does not receive power. The engine turns all day long, but doesn't start. I've pulled out my test light & mutilmeter to confirm it that it isn't getting any voltage. The fuel pump runs fine when everything's cold as well because I've hooked it straight to the battery and it's happy as can be.
After the temps rise during the morning, the trucks starts and drives fine. If the engine is warm and the temps drop, it starts and drives fine.
So, what is keeping the fuel pump from getting power?
- I've changed replaced the map sensor with a new unit
- Checked resistance across the coolant temperature sensor (the two wire one) and it changes when held over a heat source
- Checked resistance across the intake air temp sensor and it changes when held over a heat source
- Cleaned out the vacuum hose between in intake manifold and the map sensor
- Added HEET to the fuel supply on my last two fill ups
I don't really know what else is temperature sensitive under the hood. I do know there is another air sensor on the airbox itself but that reads something manually via vacuums and pressures. Does it talk to the ECM/ECU somehow?
Any help / ideas / leads will be appreciated.
Here's what's happening, when I try to start my 2.9 cold, on mornings when the temp is roughly 45 degrees or below, the truck won't start because the fuel pump does not receive power. The engine turns all day long, but doesn't start. I've pulled out my test light & mutilmeter to confirm it that it isn't getting any voltage. The fuel pump runs fine when everything's cold as well because I've hooked it straight to the battery and it's happy as can be.
After the temps rise during the morning, the trucks starts and drives fine. If the engine is warm and the temps drop, it starts and drives fine.
So, what is keeping the fuel pump from getting power?
- I've changed replaced the map sensor with a new unit
- Checked resistance across the coolant temperature sensor (the two wire one) and it changes when held over a heat source
- Checked resistance across the intake air temp sensor and it changes when held over a heat source
- Cleaned out the vacuum hose between in intake manifold and the map sensor
- Added HEET to the fuel supply on my last two fill ups
I don't really know what else is temperature sensitive under the hood. I do know there is another air sensor on the airbox itself but that reads something manually via vacuums and pressures. Does it talk to the ECM/ECU somehow?
Any help / ideas / leads will be appreciated.
