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Old 03-04-2016
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99 Ranger Difficult Start

All,

I have a 99 Ranger with a 2.5l 4x2. I have this issue where it will crank over, cut out, then go back to cranking.

Sometimes when it fully cranks over, it fires once or twice then quits and I have to start it again. When it cuts out, its a hard stop.

When it is warm it starts fine.
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Old 03-04-2016
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The Ford Computer runs the fuel pump.
For safety reasons the fuel pump will only run for 2 seconds when key is turned on, it won't come on again until engine RPMs are above 400(engine is started).

The fuel system in a '99 should have 60-70psi of fuel pressure when engine is running, and stay above 50psi when engine is off, it will hold that pressure for a few months, not minutes, hours or days.....months

If you are losing fuel pressure when truck sits for a few hours, then the 2 seconds of run time for the fuel pump won't provide enough pressure to keep engine running.

To test for this loss of pressure try turning on the key, then count to 3 and turn it off.
repeat 3 times, key on, key off
Each time key is turned on you should get 10-15psi added to system, don't worry you can't "over pressurize" the system.
Now try to start engine.

If it starts up normally then you are probably losing pressure when truck sits, if you don't smell gasoline then the check valve in the fuel pump is most likely the problem, it is part of the fuel pump not a separate piece.


If engine doesn't start then problem could be IAC valve, it can be cleaned, or ECT sensor.
IAC(idle air control) Valve opens up all the way so engine can get enough air to start, then closes to set Cold Engine idle, high RPM, until engine warms up.
Computer runs the IAC Valve, it is a moving part so can get dirty and stick closed, causing starting and running issues.

ECT(engine coolant temp) sensor is used only by the computer, it tells the computer if engine is cold or warm, a cold engine needs more fuel and more air to run, that's what the Choke Plate did on a Carburetor engine.
Fuel injected engine can't use a Choke Plate, no Jets, so the computer must run a Choke Routine, more fuel more air, until engine warms up.
If ECT sensor is "telling" computer that the engine is already warm when it is really cold then engine would struggle to start and stay running until it was warmed up.
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Old 03-04-2016
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Thanks RonD.

I have replaced the fuel assembly unit already because the check valve was bad? I get the proper pressures i need as well.

Ive tested the IAC valve by unplugging it while idling (this was a test I heard) and if the RPMs drop and stall out, it is working correctly.

I have replaced the ECT (both) but that was 2 years ago and doesnt mean they havent gone again. It will start fine if I hold the pedal to the floor as well. I have a slow leak in the coolant so maybe this could be the issue? The coolant drains enough that the ECT cant read the actual temp so it thinks it is too cold?
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Old 03-04-2016
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Too cold shouldn't be a problem on cold start, loss of coolant wouldn't be cause of this "hard start" issue, but is a concern for overheating.

When you push down on the gas pedal during starting you are adding more air not more fuel, fuel injection is the opposite of a carb setup.

When engine is cold, key off, remove the IAC valve, it should be closed.
Turn on the key and valve should open all the way for starting, turn off the key and it will close, repeat this a few times to makes sure it is opening all the way each time.

Your test confirmed that you have no vacuum leaks, and that the IAC valve was closing.
But doesn't confirm it was opening all the way to let air in, pushing down on the gas pedal, letting more air in to start engine, shouldn't be required on any fuel injected engine.

This is not Ford or Ranger specific info, all fuel injected engines work the same way.
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