What are some possible causes for having to crank the engine for 5 to 6 seconds before it fires up on a cold start? This happens whether the outside temperature is 100 or 0 degrees. Once it starts, it runs fine and will restart immediately even if the engine has not warmed up enough to go into closed loop operation(1990 F150 351W).

The air induction system is clean and tight from the throttle body to the upper/lower intake manifold gasket. Throttle air bypass valve and egr valve are clean and functional.

I have tried(with no effect):
Waiting for the fuel pump to pump up to pressure on key on
Turning key off
Starting in the normal manner

Air valve at mouth of throttle body is in factory set position.

Once the engine starts, it warms up normally and runs great in all operating modes.

Any ideas?

 

have you pulled the cannon plug and checked the base timing with a timing light. just because its fuel injected doesent mean the computer will do it all it still needs correct tining to start. how many miles are on it it may need timing chain i had a similar problem but mine would crank and idle rough then straighten out after several cranks.

 

Taking time to get fuel back to the injectors?

 

Thanks for the replies.

I'm think the fuel injectors have fuel available because, if I crank the engine for one second, a second crank will start the engine immediately.

Does anyone know how the computer controls the fuel injectors during a cold start? Is there a difference in the commands to the injectors during a second start?

 

Have you tried pulling codes from the computer? There may be a code in the computer that will point you in the right direction. http://fordfuelinjection.com click on "Getting Codes" on the left side of the screen. The computer should control the injectors the same way under the same operating conditions, i.e. same input from ECT, ACT, MAP and TPS.

 

Check the fuel pressure regulator by checking the fuel pressure at the fuel rail. Sometimes the stock regulators are low on pressure to pass smog #@$#%, especially in California. Fuel pressure should be 40 to 45 psi. A clogged fuel filter or fuel injectors could also be the cause. My '89 F-250 351W had a similar problem plus was down on power because Ford de-tuned it to pass CARB regs in California. I installed a "Accell Adjustable Fuel Regulator" (located at the back of the engine by the fire wall) and adjusted the fuel pressure and it really woke up my motor. Good Luck!