2000 explorer ohv 4.0 trouble starting

[88SDIME]

My wife's 2000 explorer with the ohv 4.0 has trouble starting when cold outside. No problem in summer. The engine turns over but never catches. Eventually, after 5-10 min, it will catch. Sometimes we have to trun the key all the way off, not just acc, to make it start. Had battery checked, and was on the "low" end for cold cranking amps, but the engine dosen't lag like a dead battery would. Last winter we replaced a gasket on the upper part of the engine thinking that it wasn't flexible enough when cold outside and was getting the air/fuel mixture wrong. No check engine light. I think that covers everything.

[shorod]

Did replacing the intake manifold gasket last year seem to fix the issue then? Are you currently experiencing difficulty starting regardless of if the engine is warmed up or not? When is the last time the engine was tuned up (spark plugs, plug wires, fuel filter, etc.)? Have you checked fuel pressure and spark intensity?

-Rod

Originally Posted by 88SDIME

My wife's 2000 explorer with the ohv 4.0 has trouble starting when cold outside. No problem in summer. The engine turns over but never catches. Eventually, after 5-10 min, it will catch. Sometimes we have to trun the key all the way off, not just acc, to make it start. Had battery checked, and was on the "low" end for cold cranking amps, but the engine dosen't lag like a dead battery would. Last winter we replaced a gasket on the upper part of the engine thinking that it wasn't flexible enough when cold outside and was getting the air/fuel mixture wrong. No check engine light. I think that covers everything.

[88SDIME]

Originally Posted by shorod

Did replacing the intake manifold gasket last year seem to fix the issue then? Are you currently experiencing difficulty starting regardless of if the engine is warmed up or not? When is the last time the engine was tuned up (spark plugs, plug wires, fuel filter, etc.)? Have you checked fuel pressure and spark intensity?

-Rod

Replacing the gasket seemed to work, but I don't remember it being cold after replacing. After it is started in morning, starts fine rest of day. Tune-up done less than a year ago. How do you check fuel pressure and spark intensity?

[shorod]

Fuel pressure is tested using a fuel pressure gauge on the fuel rail. Your local parts store may have a Load-a-Tool program with a fuel pressure tester in it.

To test the spark intensity, you can use a spark tester and confirm that you get a nice bright blue spark, or you can get a clamp on plug wire probe for use with an oscilloscope, connect to a scope, then get a pretty good idea of the voltage from the coil to confirm that you have a strong enough spark. Generally the inexpensive spark tester is plenty good enough.

-Rod

[88SDIME]

I guess I'll have to get back into this thread. Same issue; will not start when cold. Could this be a fuel pump issue or air intake issue?

[shorod]

Well, yes. It could be a fuel pump issue, it could be an air intake issue, it could be an Engine Coolant Temperature issue, it could be an intermittent connection issue (open circuit when contracts due to cold). You're going to need to determine what you don't have in the correct amounts - fuel, spark, or air. Confirming proper fuel pressure and good spark are the simplest to check for, so I'd start with those.

-Rod

[88SDIME]

Can you test fuel pressure without the truck starting?

[shorod]

Yes, your Explorer has an electric fuel pump. When you first turn the key to the Run position the fuel pump should run for a second or so to prime the fuel rail for starting. This is referred to as the Key On, Engine Off, or KOEO, fuel pressure.

-Rod