96 Explorer won't start unless check engine light is on

[ExplorerMomTX]

Hi all. Hope you can help.

We have a 96 XLT. 2 months ago we had the fuel pump, filter, etc changed out because the car wouldn't start. Mechanic also said he had to change out the computer (chip? I think). Anyway, got the car back and a couple of days later it wouldn't start. My husband tried for about a half hour and finally it fired up.

We took it back to the mechanic and they had it for a week and couldn't get it to NOT start - so I picked it up and brought it home. The next day the darn thing wouldn't start again.

The mechanic suggested changing out the fuel filter again because the one they replaced was really grungy. My husband changed it out and the car ran great for 3-4 days. Then wouldn't start again.

In the last two days I have been trying to observe anything that would make it start not start. What I have noticed is that when I turn the key on if the Check Engine light comes on - the car will start right up. If the check engine light doesn't come on - nothing - it just cranks, but won't fire.

Called the mechanic and he said it might have had an alarm system (previous owner) and that there is something with the wiring. Of course he wants to charge us to rip it open and check that out. My husband is pretty handy at fixing our cars if he knows where to start and is refusing to take it back in again since we have already dropped almost $1000 and still have a really good looking paperweight inthe driveway.

Anyone with suggestions, experience in this - your help is hugely appreciated. I just want to get my car up and running. Thanks for taking the time to read through this......

 

[budwich]

The "check engine" light should come on with the key in "on". It should stay on until it starts and then go out. Why it doesn't come on is potentially your problem as the light is controlled / related to engine controls and "stuff" coming from the PCM (power train control module). So... if you turn your key to "on" and don't cause the vehicle to start, does the check engine light come on.... if so right away.... sometimes, always???? May be a simple fix.... check your PCM relay... it might be stuck / broken.

 

[marragtop]

When you turn the key to ON, do you hear the fuel pump run for a second or two? If not, then it's a fuel delivery problem. Check/replace the fuel pump relay. Could also be the inertia switch, but I've not heard of them creating an intermittent problem like you are having.

 

[ExplorerDMB]

Why did he replace the PCM? He had to of replaced the whole computer and not just a PROM because they are no long PROM Updateable (never were available for that year). Does it have an Alarm system from the factory? Keyless Entry, Key Pad/Fab, etc? If it does, your computer and the chip inside your key may not be talking sometimes. Those are sometimes tricky to diagnose.

-Drew

 

[ExplorerMomTX]

Engine light/fuel pump

Yes, when you turn the key to on and the check engine light comes on you can hear a little humming sound...... if the check engine light doesn't come on you hear nothing..... also, when you turn the key on if the light comes on it stays on but the car always starts when the check engine light comes on and never starts if the check engine light doesn't come on... also, it doesn't have an alarm system now and I am unsure if a previous owner had one in it. We see no indication of an alarm system or keyless entry, but that is not to say there wasn't one in the past.....

 

[exploded99]

Budwich is on the mark - your check engine light coming on indicates that the pcm (computer) is getting power. No check engine light means no power to the pcm or a bad pcm, or a wiring problem.

I would put in a new pcm relay - they are not expensive ( under $20 at the parts store) - and see if that fixes the problem. When you turn the ignition switch to on, the pcm relay gets powered up via a circuit from the ignition switch. It then closes and provides power to the pcm. Your check engine light then comes on, and the pcm turns the light off AFTER you start the car, and all the things that the pcm tests at startup have "passed" the tests.

And you deserve a little complement for slowing down, and really paying attention to what was happening when you tried to start the car.