2003 4.0 Ranger won't start when warm

[nesbit]

Hello TRS!

Well I've been pouring over forums and google looking for ideas. As the title suggests my 2003 ranger won't start when warm. It cranks fine.

This problem has slowly been getting worse over the years. At first it was just an occasional hiccup and it would start. Years later it became it needing to sit for a few minutes. Now it's up to hours. So it's not something that failed instantly. Once started it runs great.

So based on what I've read from other threads I've done:

- New Fuel Pump
- New Fuel Pump Relay
- New Fuel Filter
- New inertia switch
- New coolant sender
- New coolant sensor
- New thermostat

Doesn't seem to have helped

I'm going to put on a new crank position sensor. And am debating the ECM or coil pack. Truck has 45K miles. Is there something else that causes this that I overlooked? No CEL. Will try to pay attention to PATS light next time it does it long enough. Pulling my hair (and wallet) out.

Thanks!

 

[BlackBII]

When it won't start, is it not getting spark or fuel? Or both?

 

[RonD]

Well I would do a 50/50 test and find out if it is spark or fuel that is causing it

After you have a No Start, spray fuel, gasoline or ether(quick start), into the intake, and try to start it.
If it starts then lack of fuel is the issue
If it still doesn't start then no Spark
50/50

Lack of fuel could be a few things
Since you have replaced most of the fuel system, that would leave injector power, or possibly PATS shutting off injectors, and long shot of TPS(throttle position sensor) having a short and sending computer above 4.5 volts when throttle is closed, this turns off fuel injectors.

Use volt meter and test Red wire at any fuel injector, it should show battery voltage(12.5v) when key is on
PATS issue should show rapid flashing Theft Light

Fuel injection computers all have a "Clear Flooded Engine" routine:
key on
gas pedal pressed down to the floor, TPS sends computer 4.5+ volts
Computer sees 0 RPMs and TPS at 4.5volts so will enter "Clear Flooded Engine", which leaves spark on and shuts injectors off so engine can be cranked and get rid of extra fuel.
But I would expect this to effect starting cold or warm.

For spark, yes Crank Position(CKP) Sensor is the Big Kahuna of sensors, computer can't detect starter motor activation so the only way it "knows" you want to start the engine is when CKP sensor starts to send a pulse when crank turns.
So no CKP pulse = no spark, and no fuel injectors either
Engines can run with pretty much any other sensor not working, but not CKP
CKP sensor generates its own AC voltage, so you can test it with volt meter set to AC volts, it should show just under 1 volt AC while engine is cranking

 

[nesbit]

Thanks for the replies.

Where exactly should I spray the starting fluid? Where the intake attaches to the Air cleaner?

I've tried holding the throttle down while trying to start it and it didn't help. It idles fine when started. That should rule out the TPS at idle position.

Just put in the CKP. Course right now the weather is cold again here in PA.

I've made a mental note to watch both the CEL (should confirm ECM relay) and PATs (Theft light) when starting.

I've found ECM sellers on ebay that will program the vin and give preprogrammed blank keys. Was thinking about an ECM change but would an EMC slowly get worse over time as opposed to just failing?

Any wiring harness areas that are common problems?

Thanks Again

 

[RonD]

Yes, just take the big air tube off the intake, open throttle manually and spray fuel in, then try to start, you don't have to reinstall the tube to test start

Any wires close to exhaust

You can pull out the computer an open it up first, usually it will show darker places on circuit board if there is a failed area.
Computers rarely fail although they are often replaced, lol.

90% of sensors or electronic parts replaced by DIYers were working just fine
50% of those same parts are replace by Pro mechanics, and were working just fine, lol, but I think some of that is bill padding

If a sensor or electronic part, including the computer, has a problem there will be a specific code that says "this is out of range" or "I can't talk to this"
And most of the time it is just a loose connector or bad wire.

Electronics make engines so much more reliable these days and easier to work on since computer will tell you where to look if it is an electronic problem.
And if it isn't then back to basic mechanics, old school vacuum leaks, low fuel pressure and low compression

 

[nesbit]

I've read other posts where the computer fixed the problem that I am having. Also read one where there was a pin pushed back in the harness connector near the brake fluid and was not making good connection when warm. Might check that.

The dealer told me that they can't fix it unless it's doing it when I bring it in. Which I understand but it's sad the computer can't say "Hey I see your spinning the starter, and I see that it's not starting, let me see what sensors might be bad"

Would an ECM be burned out to the point of a black area, but be able to run fine once the truck is started?

Having fibromyalgia, I can't be out crawling around an engine for hours poking at wiring. So I'm just shotgunning parts. If you know any more I can shotgun let me know haha.

Thanks again.

 

[cbxer55]

My 98 3.0 was having intermittent crank no start problems. I had it towed to my dealer, they ran diagnostics. They found power and ground to the injectors were good, but insufficient flow from them. They cleaned them and put some stuff in my tank, it fixed the problem for a week. After it started doing it a second time, I started using fuel with ethanol in it, haven't had a problem since. Been three weeks and it starts every time, first turn of the key.

I'm afraid if I try and go without ethanol, the problem will return. So, from this point on it's ethanol all the way.

Evidently my injectors keep getting clogged up, and the ethanol prevents it from happening. I'm running a 5% ethanol mix, and it's not causing any problems with the check engine light at all. Tried running 10% once, and it did alright as well.

Here in Oklahoma, the stations mix their gas for mid grade (89). So 87 is 10%, 91 is 0%, and 89 is 5%.

 

[nesbit]

Hi CBXER55

In PA all fuels are 10% ethanol. Ethanol free is only available at sparse station. Guess it wouldn't hurt to drop in some injector cleaner as good measure though.

Thanks for responding!

 

[cbxer55]

We don't have that problem here. Most stations you have the choice of ethanol or not.

Anyhow, I've always used the non ethanol since I use premium in mine due to it pinging on anything less than 91. So now, I use the 93 I've always used and just add a half gallon of E85 to it when I fill it at the half way point.

For me anyhow, it has prevented the return of the no start condition.

As for injector cleaner, I use Berryman's B-12. It has a high content of methanol, MEK, acetone and toluene. It's always worked for me, where the other stuff such as Sea Foam and Lucas doesn't do a damn thing.

A new computer on mine in January did nothing. Also a bunch of new sensors such as the Crank and Cam sensor did nothing as well.

 

[cbxer55]

Hi CBXER55

In PA all fuels are 10% ethanol. Ethanol free is only available at sparse station. Guess it wouldn't hurt to drop in some injector cleaner as good measure though.

Thanks for responding!

Are you certain ALL fuels are ethanol? I know here in Oklahoma, most stations only have 87 with 10% ethanol. I know of no stations that have premium with ethanol. And thus, if you select 89 octane, you get 5% ethanol since the pumps mix the 91 and 87 50/50.

 

[nesbit]

Our common fuels have 10% ethanol. We are just starting to get the E85 flex fuels but they aren't common yet. Within 10 miles of me I can think of only 1 station that sells ethanol free. They have big signs about it. I get my mowers/generator gas there.

I bought a noid kit and spark tester. I'm going to try and determine if it's spark of fuel next time it acts up.

 

[moosemeadows]

when I was transplanting my 94 4.0 into my 87 Bronco ll I had a very similar problem. My would start fine and run until I stopped. When shut off it wouldn't re start until it cooled down for a spell. It was finally traced down to a bad ground. After that it's been good and reliable. Alot of good friends said to look for proper grounds and I'm now a firm believer. If in changing anything you may have touched or disturbed any wiring or grounds check the connections. Good luck and I do know how troubling that problem is.

 

[nesbit]

How would one go about finding the grounds on the truck? Just look for straps bolted to the chassis, remove and clean them?