If you have an F150 and notice that it won’t start after being idle, you could be perplexed about the reason for the issue and how to resolve it.
Your Ford F150 hard starting is the typical issue that occurs when the engine runs hot. There could be several parts that get affected when the engine gets overheated.
If your Ford f150 is hard to start when hot, then the reason could be a bad battery and its connections, faulty fuel pump relay, bad starter motor, relay, and its solenoid, dirty throttle body or IAC or MAF sensors, leaky cooling system, bad inertia switch, malfunctioning fuel system parts or vapor lock.
Getting your vehicle on the road again requires that you deal with the problem without delay. If you’re having trouble starting your F150 after running for a while, then stay tuned!
Ford F150 Hard To Start When Hot? 9 Causes And Solutions to Fix It!
When the engine gets too hot after idling for a long time, it can cause an electrical short in the fuel pump, fuel injectors, ignition coil, or distributor cap. If this happens, you’ll see no spark with your plugs and difficulty cranking the engine over.
A lot of times, when the temperature of your car’s engine starts to get too high and the engine is overheating, it will cause your car not to start.
The following can be one of the few things when your Ford F150 is not starting when hot.
Bad Battery
Is the battery replacement overdue? Have you replaced the battery a long time back? Then it is time to check the battery health before checking other parts.
The battery when it is failing or when the engine gets hot and increases the battery surrounding temperature, it is will not supply adequate voltage to the engine parts required for its effective operation and leads to Ford F150 hard to start problem when hot. Unless the engine cools off, your F150 won’t start.
Fix
The first thing you should do when Ford F150 hard to start when hot is to check the battery and ensure it’s fully charged. If it’s not, then you’ll have to recharge or replace it.
You’ll also need to ensure that your alternator is working properly, so test it out by running a voltmeter on its terminals. If the voltmeter reads less than 12 volts, your alternator is going bad and may need replacement.
You have to check the battery problem and to check this, use an ohm meter on one lead wire from your battery’s positive terminal until it reads ‘0’ Ohms for about 10 seconds.
If it does not read ‘0’ Ohms, then you know that there is not enough voltage being supplied by your battery, and it will need to be replaced.
The battery may be floppy enough to cause the PCM to not function after the truck gets hot. Heat also affects the battery performance and causes vehicle starting problems.
The battery may show full voltage when there is no load, but it could be weak during cranking. The battery needs to be load tested to confirm its effectiveness. If it shows less voltage in load condition, then it is time to replace the battery with new one.
It is worthwhile to check the battery cables for any damage, heat can affect these cables and can cause them to stick together and prevent the battery from fully charging.
Faulty fuel pump relay
The fuel pump relays are typically located inside a TIPM box (Total integrated power module) along with other relays & fuses.
When the engine gets hot, it is possible that some of the relays and switches malfunction and work unpredictably.
One of the reasons for your Ford F150 hard to start can be a malfunctioning fuel pump relay due to exposure to the engine’s high temperature.
The fuel pump relay gets its signal from ECU and decides whether power shall be supplied to the fuel pump.
Fix
The fuel pump relay can cause the engine not to start when it gets too hot. When it gets hot it doesn’t work like it should until it cools down.
To fix this, you will need to replace the fuel pump relay with a new one. If you know how to replace this switch, avoid taking your vehicle to an expert for repairs!
Bad starter motor
The starter gear is supposed to engage only during the vehicle start, but if the starter motor is failing, it won’t retract back from the flywheel, hence the gears would remain in continuous contact with the flywheel and cause wear and tear.
A lot of heat would be generated in that process and the starter motor would start working intermittently.
Also, the heat from the engine can toast the already failing starter motor until the engine cools off because of these reasons your Ford F150 will be hard to start when hot.
Fix
It is recommended to either install some sort of heat shield around your starter motor or replace the starter motor with a new robust one to do away with the hard starting problem.
Bad starter solenoid or relay
When the F150 is hard to start when hot and if the starter isn’t even cranking, then there could be an electrical problem related to the starter motor.
Have you checked if there is any corrosion build-up on the post of the starter solenoid?
The starter relay could take too much current due to the corroded posts causing the relay switches to build heat and thereby could abruptly break the switch contacts.
Once the contact is broken, the starter motor will not work as intended and you would face the issue of the Ford F150 hard starting issue when the vehicle is running hot.
Typically, these relays and switches are sensitive to the high surrounding temperature. That’s why the car could start when the engine is cold or you have parked the vehicle for quite a time.
Fix
Ensure that the starter solenoid posts are free of corrosion to ensure that the starter solenoid receives an uninterrupted power supply to energize and engage the starter motor with the flywheel.
If there is a clicking sound from the starter relay but there is no power supply to the starter solenoid then you also need to check the wiring harness for continuity and voltage after cleaning the corroded posts. If there is no electrical problem, then the issue would be in starter solenoid which needs to be inspected and replaced based on troubleshooting analysis.
You may try switching the starter relay with any other relay of equal ampere rating in the TIPM box and see if the F150 starts.
That would tell you if you have a bad starter relay. If you are unable to locate the starter relay, you may refer owner’s manual.
Similarly, you can diagnose the PCM relay as well to confirm that the ignition system is functioning correctly and is not affected by engine heat.
You may also need to check the grounding of the starter motor. If it is not grounded properly, then the starter motor would run unpredictably and would lead to hard starting problems.
Ensure that all of the grounds are appropriately connected and corrosion free. A bad ground can cause the starter to run slowly as well, especially if the ground wiring harness is not large enough to carry the starting current.
Leaky cooling system or clogged radiator
Is the cooling system intact without any leaks? Typically, a leak in the cooling system or a clogged radiator usually makes the engine overheat as there won’t be adequate coolant to take up the engine heat.
The engine overheating leads to several other problems related to electrical connections and fuel delivery.
This happens more often in older vehicles than new ones, so if yours is old, this could be happening more often than you realize!
Fix
A lot of issue arises out of engine overheating especially the hard starting problem.
You need to check the coolant level and replenish it with adequate quantity to keep the recommended coolant levels.
If coolant is not readily available you may add water as a temporary solution till you take your car to any nearby auto store.
Also, check whether the CTS (coolant temperature sensor) is functioning fine and sending correct data to the ECU.
A bad CTS could lead to improper cooling of the coolant due to inappropriate radiator fan operation which in turn results in all problems related to engine overheating.
It is essential to inspect the cooling system and replace faulty parts to come out of F150 hard starting issue when it gets hot.
Malfunctioning fuel system
If you are done with the troubleshooting of the above parts and none of them is working to find out the root cause of the Ford F150 hard starting problem, then there could be a problem with one of the fuel system components in your engine like fuel injector, fuel pump, etc.
This can likely cause an engine to misfire, thus preventing it from starting when it gets too hot.
Have you checked the fuel pressure at the Schrader valve in the fuel supply line? If the pressure is less then there could be a hard starting problem when the engine running hot.
It could be a leaky fuel injector or a leaking pressure regulator check valve at the fuel pump return line.
Plug a pressure gauge into the Schrader valve and check the fuel pressure.
If the readings are in the range of 30 to 45 psi at the ignition key on condition and 28 to 50 PSI while the engine runs hot, then the fuel system parts can be ruled out.
On the other hand, if the pressure is low in ignition ON condition, then the fuel pump or its pressure regulator check valve could be the culprit.
But if the pressure is ok in ignition ON condition but not ok in running condition, then there could be a bad injector or vacuum leak in the pressure regulator fitted at the engine end.
Vapor lock
When you have the issue of Ford F150 being hard to start when hot, then the reason could be a failing fuel pump.
When the engine gets hot, the fuel in the supply line gets vaporized and if the fuel pump is going bad, then there could be a possible vapor lock issue in the fuel delivery system which would prevent fuel supply to the engine.
This issue is more predominant in old vehicles where the fuel is being supplied at lesser pressure.
Fix
You would need to either replace the weak fuel pump and see whether your F150 hard starting problem goes off when the engine gets hot or try putting a heat shield over the heat source where the fuel supply hose is running closer to drive away the heat radiated towards the fuel hose which typically leads to vapor lock.
Dirty throttle body, IAC, or MAF sensors
Often if the F150 servicing is overdue and the hard starting problem is experienced then there may be a large carbon deposit on the throttle body or sensors like IAC (idle air control valve) or MAF (Mass airflow sensor).
A simple cleaning of the engine air or fuel intake system parts would get rid of starting problems which get aggravated when the engine is running hot.
Also check whether the crankshaft position sensor is not faulty which can contribute to Ford F150 being hard to start when hot, since it sends the signal to the PCM for fuel pump operation when priming and running.
Bad inertia switch
Apart from the fuel pump relay, the battery power is connected to the fuel pump through the inertia switch.
The inertia switch is supposed to cut off the power supply to the fuel pump in an accident case to avoid a fire hazard situation to prevent fuel supply.
Fix
Sometimes a bad inertia switch or a damaged connector can induce high resistance in the power supply circuit thereby causing the voltage to be low and would lead to a hard start issue in your ford F150 especially when the engine is running hot.
It is recommended to inspect the inertia switch and its wiring harness and replace it with a new one.
Conclusion
Often vehicles face the issue of hard starting when the engine runs hot. The problem could be as simple as an electrical connection issue or a failing battery or may be complex like a faulty starter motor, relays, sensors, cooling, or fuel system components.
It could also be due to something that you’ve done to your vehicle recently that may have damaged the wiring or caused other components to fail.
The root cause for the hard starting problem stems from engine overheating conditions which ends up damaging the under hood surrounding parts that are sensitive to high temperatures.
Once the ambient working temperatures cool down to normal values the parts function as desired and you would be wondering why your car is hard to start when hot.
Happy Motoring!
References
https://www.f150forum.com/f118/truck-hard-start-after-getting-hot-sitting-2-3-hours-488840/
https://www.fordf150.net/forums/viewtopic.php?t=129291
https://www.f150online.com/forums/v8-engines/271047-hard-start-when-warm-5-4l.html
https://repairpal.com/engine-restarts-very-rough-when-warm-133
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