Starting Issues

[Lukeinthewild]

Hey all, I'm new here. I'd say I'm a Saturday mechanic but that's a little generous so I'll say I'm learning and would like to understand more. I live out in the Bush (off the road system) of AK so resources are limited, though I can fly parts in within a few days.
The issue on 2001 Ford Ranger 4.0- won't start in the cold (multiple attempted fixes below)

I have had intermittent starting problems with the truck since last Fall. Sometimes it would start up first time, other times it would take multiple cranks. The problem got worse and the truck became much more unreliable. Looking back I'm not sure if the colder weather was the factor or something else. Maybe both.

I noticed my EGR sensor was fried (literally melted) and I replaced that. The starting irregularities persisted.
I didn't know the last time the fuel filter was changed so I replaced that. My problem was resolved immediately. Then it happened again as it got colder.
I checked the fuel pressure (off the rail, in the cold) and it read zero.
A friend helped me tow the truck into a heated airplane hanger and I checked the pressure again on the rail and now it read 62-63psi and the truck fired right up. I put some HEET in the tank to try to eliminate any moisture and drove the truck for quite a bit afterwards. No success. The truck wouldn't start after it was freezing out.
Thinking maybe I had water somewhere in the fuel system and that it was freezing, I decided to check the fuel tank (our fuel out here goes through multiple different bush containers and thought they could possibly have moisture in them by the time they get out here) and pulled the truck bed and the fuel pump to check the tank. I saw no evidence of water in the fuel tank but because it was original pump (150000 miles) I replaced the full sending unit. The truck started right up after replacing sending unit BUT again I was in a heated hanger.
When I parked it outside at my house and it froze- it wouldn't start again.
(Forgot to mention that I put in a new battery last year too as well as changing spark plugs.)
I tried looking into the problem again as it's been a little warmer (20's-30's) with no success.
A friend of mine came over to help me diagnose as I now had new problem as now it wouldn't crank like it did before. He thought starter. (We fully charged the battery after it sat for a while) He hit the starter with a hammer with no success but thought he could here the starter trying to engage but we couldn't get it going. We also noticed the 'full starter' fuse in the fuse box was clicking loudly when we tried to start it this time. We switched the fuses in the fuse box but it didn't make a difference. I have a new starter and new fuse ready to be installed when the temperature warms up so we can work on it again.
I've obviously spent a bunch of money throwing parts at this problem, to which I'd like to not keep doing, but am at a loss.
Any other thoughts would be appreciated. Thanks for reading my long post.

 

[RonD]

Welcome to the forum

All gasoline engines need to be Choked on cold start, the colder it is the more Choke needs to be applied
Can't use a Choke plate on a fuel injected engine, no Jets, so the computer must apply the Choke based on temp
So the ECT(engine coolant temp) sensor was added when engines were changed over to fuel injection
This is an added "sensor", no connection to the Dash temp gauge "sender" used for years
Sender is a 12volt unit
Sensor uses 5volt from computer

On the 2001 4.0l SOHC engine, ECT sensor will be on the thermostat housing, along with the temp sender, they are next to each other, both are 2 wire
Sender will have a red/white wire
Sensor a grey/red wire

IF..............the ECT sensor is not telling computer its -20degF, and only showing 50degF then you would get a no start and/or a very long cranking start, cranking does warm up the cylinders so would eventually start with minimum Choke

Not an expensive sensor to change just on speculation


Priming fuel system
For safety reasons, when you turn on the key the fuel pump primes the system but for ONLY 2 seconds
But you can turn the key off and then on again to get another 2 seconds, and then another, ect......
With engine running pressure should be 55-65psi
With key off it should hold above 30psi for MONTHS

Fuel pump doesn't come on full time until engine RPMs are above 400, cranking RPMs is 200

Each 2 second run time of fuel pump adds 10psi
If it was 0psi then you should cycle key on and off 3 times and then try to start engine, so 30-40psi

Outside of a broken fuel line the pressure in the system only has 3 outlets
The fuel injectors, which would cause running issues not just no or hard starts
Fuel pump, has a check valve/back flow preventer inside it
Fuel Pressure Regulator(FPR), on the fuel pump assembly in 2001, its connected to the 3rd hose on the filter

Since you replaced the whole assembly I would think you are no longer losing fuel pressure with key off


When you turn on the key the THEFT light on the dash should come on and then go OFF, that means the transponder key in the ignition switch PASSED the test, so "OK to start"
Flashing THEFT light means key did NOT pass test and no starter motor and no fuel injectors
You don't mention this so we will skip this

There is a Neutral Switch to prevent "starting in gear"
On a manual trans its the Clutch pedal switch
On an automatic its the DTR(digital transmission range) sensor on the transmission, drivers side, on shift arm

DTR must be in Park or Neutral position or key can't send 12v to starter relay
A loose column shifter in Rangers and any Ford trucks can cause DTR to not go all the way into Park position, transmission does, but not the sensor
Try starting in Neutral

Starting power pathway
Ignition switch in START(12v)------fuse 24 in cab------neutral switch------starter relay-----ground(from key passing test)

Starter relay is in engine fuse box
Check fuse 24 just because

Starter motor has 2 wires
Larger cable from battery positive
Smaller wire from starter relay in engine fuse box


My guess is that the starter failed because of the no or slow start use over time
The cause of the no or slow start, could be ECT sensor or lack of fuel pressure while cranking


Why gasoline engines need to be choked
A spark plug can't ignite liquid gasoline, yes the movie guys take liberties with that one, lol
A spark plug can only ignite gasoline FUMES/VAPOR
The vapor is what you can smell, and cold gasoline has very little or NO SMELL, so no vapor
So what a Choke plate did on a carb was to reduce air flow in, which created a higher vacuum below the plate which SUCKED IN more cold gasoline from the Jets
A Cylinder needs about 30% vapor for spark plug to ignite it
If cold fuel is 10% vapor then you need 3 times as much gasoline to get the 30%

With fuel injection the computer uses ECT sensor to calculate how much extra fuel is needed to get the 30%
This is called "choke mode" and computer will run high idle(1,100+ RPMs) along with rich fuel mix until ECT reports about 140-150degF, at that time regular idle level should be set, 700-750RPMs

In very cold temps Ether can be used to start engines, sold as "Quick Start", ether is a vapor at very low temps, so spark plugs CAN ignite it, once cylinders fire they get warm very quickly, so liquid gasoline will have more vapor as it enters a hot cylinder and is compressed

 

[Lukeinthewild]

Welcome to the forum

All gasoline engines need to be Choked on cold start, the colder it is the more Choke needs to be applied
Can't use a Choke plate on a fuel injected engine, no Jets, so the computer must apply the Choke based on temp
So the ECT(engine coolant temp) sensor was added when engines were changed over to fuel injection
This is an added "sensor", no connection to the Dash temp gauge "sender" used for years
Sender is a 12volt unit
Sensor uses 5volt from computer

On the 2001 4.0l SOHC engine, ECT sensor will be on the thermostat housing, along with the temp sender, they are next to each other, both are 2 wire
Sender will have a red/white wire
Sensor a grey/red wire

IF..............the ECT sensor is not telling computer its -20degF, and only showing 50degF then you would get a no start and/or a very long cranking start, cranking does warm up the cylinders so would eventually start with minimum Choke

Not an expensive sensor to change just on speculation


Priming fuel system
For safety reasons, when you turn on the key the fuel pump primes the system but for ONLY 2 seconds
But you can turn the key off and then on again to get another 2 seconds, and then another, ect......
With engine running pressure should be 55-65psi
With key off it should hold above 30psi for MONTHS

Fuel pump doesn't come on full time until engine RPMs are above 400, cranking RPMs is 200

Each 2 second run time of fuel pump adds 10psi
If it was 0psi then you should cycle key on and off 3 times and then try to start engine, so 30-40psi

Outside of a broken fuel line the pressure in the system only has 3 outlets
The fuel injectors, which would cause running issues not just no or hard starts
Fuel pump, has a check valve/back flow preventer inside it
Fuel Pressure Regulator(FPR), on the fuel pump assembly in 2001, its connected to the 3rd hose on the filter

Since you replaced the whole assembly I would think you are no longer losing fuel pressure with key off


When you turn on the key the THEFT light on the dash should come on and then go OFF, that means the transponder key in the ignition switch PASSED the test, so "OK to start"
Flashing THEFT light means key did NOT pass test and no starter motor and no fuel injectors
You don't mention this so we will skip this

There is a Neutral Switch to prevent "starting in gear"
On a manual trans its the Clutch pedal switch
On an automatic its the DTR(digital transmission range) sensor on the transmission, drivers side, on shift arm

DTR must be in Park or Neutral position or key can't send 12v to starter relay
A loose column shifter in Rangers and any Ford trucks can cause DTR to not go all the way into Park position, transmission does, but not the sensor
Try starting in Neutral

Starting power pathway
Ignition switch in START(12v)------fuse 24 in cab------neutral switch------starter relay-----ground(from key passing test)

Starter relay is in engine fuse box
Check fuse 24 just because

Starter motor has 2 wires
Larger cable from battery positive
Smaller wire from starter relay in engine fuse box


My guess is that the starter failed because of the no or slow start use over time
The cause of the no or slow start, could be ECT sensor or lack of fuel pressure while cranking


Why gasoline engines need to be choked
A spark plug can't ignite liquid gasoline, yes the movie guys take liberties with that one, lol
A spark plug can only ignite gasoline FUMES/VAPOR
The vapor is what you can smell, and cold gasoline has very little or NO SMELL, so no vapor
So what a Choke plate did on a carb was to reduce air flow in, which created a higher vacuum below the plate which SUCKED IN more cold gasoline from the Jets
A Cylinder needs about 30% vapor for spark plug to ignite it
If cold fuel is 10% vapor then you need 3 times as much gasoline to get the 30%

With fuel injection the computer uses ECT sensor to calculate how much extra fuel is needed to get the 30%
This is called "choke mode" and computer will run high idle(1,100+ RPMs) along with rich fuel mix until ECT reports about 140-150degF, at that time regular idle level should be set, 700-750RPMs

In very cold temps Ether can be used to start engines, sold as "Quick Start", ether is a vapor at very low temps, so spark plugs CAN ignite it, once cylinders fire they get warm very quickly, so liquid gasoline will have more vapor as it enters a hot cylinder and is compressed

Great. Thanks Ron. I'm going to replace the starter and look into the ECT sensor. Hoping these work!

 

[bills4065]

Lukeinthewild, I notice you said your EGR sensor was literally melted. You might want to check for a plugged exhaust also. Just a thought.

 

[Lukeinthewild]

Thanks Bill.
Update: I ended up replacing my starter and noticed that the starter was literally wobbling as one of the bolts had come loose. Not sure why this would've happened but I replaced the starter and it started right up afterwards. It's also above freezing now so I won't know if my cold temp problem will persist next time it freezes. I'm hoping this will solve the issue otherwise I'll come back here next winter. Thanks for the help.