If I say, drive my truck for a few miles so it warms up, and stop it to add fuel, then try to restart, it does not want to start. I have to pump the gas petal, and after a few seconds it reluctantly starts. I then put it into gear, and it immediately stalls. This is repeated a couple of times, but after pumping the gas petal repeatedly, it gets going and drives normally until I try to hot start it again. The check engine light is on, and it starts normally cold, and does not stall. I replaced the fuel pressure regulator of the front side of the intake manifold, and after an OBD 2 sensor said "low coolant temp", replaced the temp sensor. Neither change did any good. Thoughts?

 

Welcome to the forum

2000 Rangers don't have fuel pressure regulators(FPR)?
In 1998 Ford changed all Rangers to Returnless fuel systems so no FPR could be used at engine end of the fuel system

Next time you have a no start unplug the MAF sensor and see if it starts, if so Clean MAF sensor

4.0l OHV has TWO temps "sensors", one is a SENDER for the dash board Temp gauge, the other is a SENSOR for the computer, code number?, would only be for ECT sensor.

Temp Sender is not monitored by computer

So did you change the right one?

Fuel injected engines don't have a "gas" pedal, they have an "air" pedal, so when you "pump the gas pedal" you are not adding more fuel like on a carb engine, you are adding more air.

If adding more air helps then you could have a leaking injector, flooding out a warmed up engine, cold engines LIKE more fuel, warm engines do not.

There is a Computer Routine in all fuel injection computers
"Clear Flooded Engine" mode
To put computer in to this mode
Turn on the key
Press "gas" pedal to the floor and hold it down all the way, Throttle position sensor(TPS) sends computer 4.6volts and with 0 RPMs showing computer starts Clear flooded engine mode
Now turn the key to START

Engine should NOT start up, it should not fire at all
Spark is on but Fuel injectors are OFF, thats what this mode does, turns off all fuel going into the intake to Clear Flooded Engine

If engine fires then you DO have fuel leaking in to intake causing flooding

As soon as you release "gas" pedal, fuel injectors will start working, even while cranking
Or if engine RPMs reach 400 Clear Flooded Engine mode will end.

I would do this test while engine is cold, when you know it should start.
This way you know what to expect, a no start, when you do the test on warm engine.
And no you can't get stuck in Clear Flooded engine mode.

I use it every morning when starting my 4.0l OHV that has almost 400k on it, I want to get oil pumped up through the bearings and valve train before engine starts.
So I hold down the "gas" pedal for 5 seconds or so of cranking then release it so engine starts wet instead of dry

 

Thanks for your prompt reply. More info, this engine has had a fuel odor on the dipstick in the past. The item I referred to as a "fuel pressure regulator" is on the front right side of the intake manifold with a vacuum line and a fuel line leading to it. It looks like a small canister. I think I replaced the temp "sending" unit, on the front top of the intake manifold, I was unaware of another one. The leaking fuel injector sounds like it could be the problem, how would I determine which one? I'm going to pull the plug on the MAF, and put some dielectric grease on the terminals, and plug it back in. I bought some MAF cleaner in the past, and cleaned it...

 

What you describe is an FPR, so maybe this is not the original engine in this 2000 Ranger?

You can use the Clear Flooded Engine routine to ID a leaking injector
First do the test to see if that is what is happening

Then with engine cold
Disable spark by pulling off the 4 wire connector on Coil Pack
Cycle key ON and OFF 3 times, that will build up pressure in fuel system
Do Clear Flooded engine and crank it a few times, count to 5 each time

Now pull out spark plugs and see which one is WET with fuel, thats the one that is leaking

 

I have owned this truck since 2001, (I believe 2nd owner), it had 18K when I bought it. I did replace the cylinder heads at about 100K (internal unrepairable crack) and it has ran flawlessly ever since till this problem. (Brand new castings from Australia). I don't believe the engine was replaced. I just went out and unplugged the MAF and squirted some dielectric grease in the 3 contacts, and plugged it back in. It's going to take me a little while to try the test you suggested, but I like it. It looks like I'm going to have to remove the top half of the intake manifold to get to the injectors. No problem, I've done that before to replace leaking rocker arm cover gaskets. Do you think some fuel injection cleaner might resolve the leaking injector?

 

This engine seems to be the last year of the 4.0 OHV engine, maybe the FPR existed until then? In 2001, the OHC engine did have some changes...

 

Anything is possible, but from the shop manuals for 2.5l, 3.0l, and 4.0l from 1998 and up all were switched to Returnless system, only 1 fuel line from gas tank, no return line(what FPR was connected to) and all had 65psi fuel pressure listed.

1997 and earlier FPR system ran 35psi.

2.5l SOHC and 4.0l OHV both were dropped in 2001 and as far as I know both got returnless in '98
1998 was start of 3rd generation Rangers, which was why they did that change then and a few others.

But if you have two fuel lines and an FPR then you do have the 35psi system and a unicorn, lol.

There was no extra power or any performance benefits from returnless, just cheaper to use 1 fuel line and no FPR

 

Well, I did the test to see which plug got wet and removed all the plugs on the drivers side and to my dismay and disgust, the plugs look really bad. I ordered new plugs and they should be here on March first, or slightly later. This could be part of my problem! Should be a little better weather by then anyway...

 

What did the plug tips look like, they can tell you what is happening inside the cylinder.

Google: spark plug tips images

4.0l OHV engines eat spark plugs, Motorcraft or Autolite are the only brands that seem to last

And "heads up" about Fords Waste spark system
Only use regular copper or DOUBLE Platinum, do not use single platinum or single anything, waste of money

Ford sparks two spark plugs at the same time, so 1 spark is "wasted", hence the name Waste Spark System
This also means 1 spark plug will spark from center to tip(normal) and the other one will spark from tip to center(reverse)

So single platinum will wear out the same as regular copper on 3 of the 6 spark plugs, so waste of money
There can be some confusion on 4.0l OHV and SOHC spark plug numbers
Reason is that Ford often used two different spark plugs in the same engine at the factory, single platinum tip and single platinum center for the normal and reverse spark, lol.
When you are buying literally THOUSANDS of spark plugs difference in price between single and double adds up, so why not save the money.
Thats why there are often 2 number listed for same engine same year
When just buying 6 spark plugs then regular or Double

And make sure you gap them at least 0.054 go to 0.058 if you do alot of idling