Procedure for diagnose intermittent hard-to-start?

[mr49]

Hello all,

Once a while, my 2001 explorer sport would turn over but not start. If I turn the key a few more times, eventually it will start.

This symptom seems has been discussed numerous times. The potential cause ranges from air intake sensor, relay, to fuel pump. But I wonder if there's a better diagnosis and isolation procedure to pinpoint the issue, other than replacing each of above mentioned parts, and waiting to see if it still happens.

jia

 

[shadowless127]

I would do a compression test, and fuel pressure test.

 

[shadowless127]

Also check the connections to your inertia switch and fuel pump; make sure they are clean, and fully connected.

 

[imp]

Reiterating: I had a similar hard-start condition which was finally traced to clogging of the fuel pump inlet passage. The problem existed as an intermittent one, making pinpointing difficult. Sometimes the clog allowed sufficient fuel flow to permit normal start/run, no problem symptoms noticeable.

The clogging originated from half-dissolved, mushed-up debris from a separater the pump supplier had installed in the "foot" strainer mesh, apparently to prevenmt it's collapsing, as it became partially clogged over time.

Fuel pressure checks at the Schrader valve showed sometimes inadequate pressure, never zero pressure. That's when I dropped the damn fuel tank for a look. imp

 

[mr49]

Reiterating: I had a similar hard-start condition which was finally traced to clogging of the fuel pump inlet passage. The problem existed as an intermittent one, making pinpointing difficult. Sometimes the clog allowed sufficient fuel flow to permit normal start/run, no problem symptoms noticeable.

The clogging originated from half-dissolved, mushed-up debris from a separater the pump supplier had installed in the "foot" strainer mesh, apparently to prevenmt it's collapsing, as it became partially clogged over time.

Fuel pressure checks at the Schrader valve showed sometimes inadequate pressure, never zero pressure. That's when I dropped the damn fuel tank for a look. imp

Thanks, imp. This sounds very much like my car's symptom. I finally got a hold of a pressure gauge, and checked the fuel press. When key is on, but engine isn't running. I have less 5psi pressure. However, when the engine starts running, I have normal 65psi.

Since, to my knowledge, the fuel filter has never been replaced in the life time of this car, I will try that first. If that doesn't help, I will look into what you suggested.