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Difficulty starting a 2002 Ford Explorer

I’m having problem with my wife’s 2002 Ford Explorer (~80K miles). Last year in the late fall (Novemeber) and then again this year, we began having periodic problems starting the car. My general impression is that the problem only arises on colder (<30 degrees) days, but not every cold day, generally in the morning but occasionally in the evening. The engine will crank fairly strong, but not start. She doesn’t drive the car all that much, short drive to work (if at all), sometimes the car only gets driven once a week or less. Battery has been replaced twice, no help. Coil pack replaced last fall, helped at the time, but problem back this year. Ignition switch replaced, no help. Fuel line anti-free (Heet) added, hasn’t changed anything. I monitor the voltage on the battery and power coming off the alternator when running, and everything seems okay (12.2-12.5 V at rest, 13.5-14.0 running). One more thing, a consistent fix has been to jump the car. Sometimes it take 10-15 mintutes of connection, but the car has started up every time we’ve tried that. Any thoughts? Thanks.

I may well be wrong but after reading you saying it always starts after as boost leads me to suspect one off two things.

Weak battery (due to not being driven long enough to recharge) and/or faulty battery cables/connections (BOTH ends).

It wouldn’t hurt to have the fuel pressure checked. Have you heard the fuel pump priming the fuel system everytime you turn the key to the ON position?

Thanks.
I feel pretty confident that it’s not the battery being weak. I’ve had the car not start when my voltmeter still registered >12V. Not to mention the fact that I replaced the battery in mid-Nov, and had problems within a week. The cables and connections are something to look at. I saw in another discussion thread about corrosion on the body ground point being a problem that sounded similar to mine.

Haven’t tried listening for the fuel pump, and I’m not sure I’d know what to listen for. Can you describe what it might sound like? Also, would ambient temperature affect the pump starting and would jumping the car resolve it?

Sometimes you can hear a buzzing type noise for a couple of seconds after the key is turned to the ON position.

To really hear it (if it works) is to have a helper turn the key to ON while you open the gas cap and put your ear close to the fuel inlet pipe.

I don’t think the temp has any affect on a fuel pump. Aside from a fuel pump that has been starved for fuel and has run hot until it quits.

Yes make sure the (small) ground wire from the battery is grounded to a clean and tight connection. Also ensure the engine is grounded to the chassis.

Please clarify, when it does not start it does not crank?

It always cranks (fairly strong), just sometimes the engine doesn’t fire. That’s when I end up jumping the car off, which has gotten the car going everytime.

More information…This morning I went to start the car (to take it to a repair shop), cold morning (19 degrees), didn’t start. Listened for the buzz of the fuel pump priming the system (as per suggestion) and didn’t hear anything at first. I proceeded to jump the car. The car did not start right away, but after about ten minutes (intermittently trying to start the car), I tried listening for the fuel pump again and this time I heard the buzz then tried to start the car and it started. I drove the car to the repair shop. After running a few tests, driving the car they’ve concluded the fuel pump needs replacing ($717, not making me happy). They drove the car a bit, had it actually not start on them at one point, and they said they tested the fuel pressure and it read only 4 or 5 (I guess psi, don’t know the units on fuel pressure).
Does this make sense? I really need some confirmation. I still don’t really understand why jumping the car would be a consistent way of starting the car and temporarily bypassing a fuel pump going bad (or is it just coincidence?).

You jumped it using a running car right? Normal battery voltage is 12.6V, but the voltage from a running car would be 13.8V or more. Maybe that increase in voltage was enough to allow the weak fuel pump (probably bad bearings) to start running.

Yeah, I used a running car. Sounds like a plausible explanation. The mechanic had no explanation for the effect of jumping the car, except for coincidence. Thanks.