My '95 F150 4.9L is very hard to start in hot weather if it has sat very long (say 30-45 minutes or more) in the hot sun. On the same type of hot sunny day, if I park in a garage, it starts easy. Also starts easy in the winter. (This has been going on for several years.) The other day I thought to try something new after it sat in the hot sun, so before I tried starting it I lifted the hood for a few minutes. Remarkably, it was easier to start. What could it be? It seems that too much heat under the hood is causing the problem, but how? Some part must be defective. But what?
Hard Starting in Hot Sunny Weather
- Thread starter TallPaul
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Originally Posted By: TallPaul
My '95 F150 4.9L is very hard to start in hot weather if it has sat very long (say 30-45 minutes or more) in the hot sun. On the same type of hot sunny day, if I park in a garage, it starts easy. Also starts easy in the winter. (This has been going on for several years.) The other day I thought to try something new after it sat in the hot sun, so before I tried starting it I lifted the hood for a few minutes. Remarkably, it was easier to start. What could it be? It seems that too much heat under the hood is causing the problem, but how? Some part must be defective. But what?
These hot start issues can drive you nuts! I get a surge on a hot restart, had it for years, had some of the best mechanics look at it and till this day I have not resolved it. If you haven't checked the Air temp sensor, and Coolant temperature sensor, do so, and while you're at it any sensor that monitors temperature. Check for vacuum leaks, IAC, TPS, O2 Sensor, you name it. That was my condensed version of what I've done. In some cases the computer might think its cold when its hot, or hot when it's cold. If you find the problem give me a shout!
My '95 F150 4.9L is very hard to start in hot weather if it has sat very long (say 30-45 minutes or more) in the hot sun. On the same type of hot sunny day, if I park in a garage, it starts easy. Also starts easy in the winter. (This has been going on for several years.) The other day I thought to try something new after it sat in the hot sun, so before I tried starting it I lifted the hood for a few minutes. Remarkably, it was easier to start. What could it be? It seems that too much heat under the hood is causing the problem, but how? Some part must be defective. But what?
These hot start issues can drive you nuts! I get a surge on a hot restart, had it for years, had some of the best mechanics look at it and till this day I have not resolved it. If you haven't checked the Air temp sensor, and Coolant temperature sensor, do so, and while you're at it any sensor that monitors temperature. Check for vacuum leaks, IAC, TPS, O2 Sensor, you name it. That was my condensed version of what I've done. In some cases the computer might think its cold when its hot, or hot when it's cold. If you find the problem give me a shout!
Long cranking time, or an actual no start? (Pet peeve with service writers for making ROs with the complaint of "hard starting" as I didn't have my psychic abilities yet.)
Excessive crank time warm- most likely fuel pump, far second place a bad coil. Both easy to check.
No crank when warm- most likely bad starter, second place (and a close second) bad connection to the starter solenoid. The small wire on some of those was just a male-female connector that always caused problems (corrosion/loose etc). The wire retained with the eyelet/stud was much better, but can come loose (rare). On a '95 I6, that might still have had the fender mounted solenoid, in which case do a voltage drop test across it while powering the S terminal. Even better, a clamp on ammeter to check current draw. Any starter draw over~225 amps is suspect.
EDIT: I remember that demarpaint. ACTs are not uncommon points of failure on a 4.9.
Excessive crank time warm- most likely fuel pump, far second place a bad coil. Both easy to check.
No crank when warm- most likely bad starter, second place (and a close second) bad connection to the starter solenoid. The small wire on some of those was just a male-female connector that always caused problems (corrosion/loose etc). The wire retained with the eyelet/stud was much better, but can come loose (rare). On a '95 I6, that might still have had the fender mounted solenoid, in which case do a voltage drop test across it while powering the S terminal. Even better, a clamp on ammeter to check current draw. Any starter draw over~225 amps is suspect.
EDIT: I remember that demarpaint. ACTs are not uncommon points of failure on a 4.9.
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It starts, long cranking time, sputtering and missing at first. On the worst (really hot) days it even runs crayppy at first (half mile or so), and throwing it into neutral and revving it good a couple times seems to help.
I had a problem with the Aerostar before where it would run like carp, not hold an idle, and sometimes die and not restart. I had all the electronic stuff replaced, distributor, coil, ignition module, etc. and it improved significantly. Still occasionally idles poorly but not like it used to be. Sounds like that may be what the F150 will need before I am done. (My '84 F150 had a lifelong problem that never really went away, it was like the engine was jinxed.)
But here is an idea: The F150 is dark blue. What if I painted the hood white or silver, something to reflect the heat away instead of soaking it up. Might work.
I had a problem with the Aerostar before where it would run like carp, not hold an idle, and sometimes die and not restart. I had all the electronic stuff replaced, distributor, coil, ignition module, etc. and it improved significantly. Still occasionally idles poorly but not like it used to be. Sounds like that may be what the F150 will need before I am done. (My '84 F150 had a lifelong problem that never really went away, it was like the engine was jinxed.)
But here is an idea: The F150 is dark blue. What if I painted the hood white or silver, something to reflect the heat away instead of soaking it up. Might work.
Originally Posted By: punisher
EDIT: I remember that demarpaint. ACTs are not uncommon points of failure on a 4.9.
LOL I changed that too. Honestly I'm beginning to think in my case it is a bug with the early 4.9L engines that were fuel injected. I'm going to try advancing the timing slightly with mine, I also have an annoying intermittent stumble when taking off along with an occasional surge. I have a 5 speed MT, and it is not driver related. I think in my case all problems are caused by 1 part, fix that and fix them all, so far no cigar. LOL
BTW you were a tremendous help, thanks again! I just think this is one of those things that won't ever be 100% for me.
EDIT: I remember that demarpaint. ACTs are not uncommon points of failure on a 4.9.
LOL I changed that too. Honestly I'm beginning to think in my case it is a bug with the early 4.9L engines that were fuel injected. I'm going to try advancing the timing slightly with mine, I also have an annoying intermittent stumble when taking off along with an occasional surge. I have a 5 speed MT, and it is not driver related. I think in my case all problems are caused by 1 part, fix that and fix them all, so far no cigar. LOL
BTW you were a tremendous help, thanks again! I just think this is one of those things that won't ever be 100% for me.
I'm surprised no one mentioned gas vapor lock. This would be the 1st thing I would consider.
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Originally Posted By: friendly_jacek
I'm surprised no one mentioned gas vapor lock. This would be the 1st thing I would consider.
Yup, I'm thinking the same thing.
OP: Next time, cycle the key about five times. You should be able to hear the pump prime and stop. I believe it runs for 5 seconds. So turn the key on for 5 seconds. Off. On for 5 seconds. Off. Do that 3-5 times, then try to start it. If it fires right up, it sounds like the fuel is boiling in the rail.
I'm surprised no one mentioned gas vapor lock. This would be the 1st thing I would consider.
Yup, I'm thinking the same thing.
OP: Next time, cycle the key about five times. You should be able to hear the pump prime and stop. I believe it runs for 5 seconds. So turn the key on for 5 seconds. Off. On for 5 seconds. Off. Do that 3-5 times, then try to start it. If it fires right up, it sounds like the fuel is boiling in the rail.
Originally Posted By: friendly_jacek
I'm surprised no one mentioned gas vapor lock. This would be the 1st thing I would consider.
Well, I kind of did. A bad fuel pump ck valve will get you a dry fuel rail sometimes. Good way to test is to cycle the key 4-5 times to make sure the rail is full, then crank it.
EDIT: Beaten to the punch.
I'm surprised no one mentioned gas vapor lock. This would be the 1st thing I would consider.
Well, I kind of did. A bad fuel pump ck valve will get you a dry fuel rail sometimes. Good way to test is to cycle the key 4-5 times to make sure the rail is full, then crank it.
EDIT: Beaten to the punch.
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Originally Posted By: OVERK1LL
Originally Posted By: friendly_jacek
I'm surprised no one mentioned gas vapor lock. This would be the 1st thing I would consider.
Yup, I'm thinking the same thing.
OP: Next time, cycle the key about five times. You should be able to hear the pump prime and stop. I believe it runs for 5 seconds. So turn the key on for 5 seconds. Off. On for 5 seconds. Off. Do that 3-5 times, then try to start it. If it fires right up, it sounds like the fuel is boiling in the rail.
That thought crossed my mind too. I thought vapor lock was a problem with carbs and not so much with EFI. If it is the case, how would you resolve it with EFI? Re-routing the rail would be difficult I would think. Still something worth looking into.
Originally Posted By: friendly_jacek
I'm surprised no one mentioned gas vapor lock. This would be the 1st thing I would consider.
Yup, I'm thinking the same thing.
OP: Next time, cycle the key about five times. You should be able to hear the pump prime and stop. I believe it runs for 5 seconds. So turn the key on for 5 seconds. Off. On for 5 seconds. Off. Do that 3-5 times, then try to start it. If it fires right up, it sounds like the fuel is boiling in the rail.
That thought crossed my mind too. I thought vapor lock was a problem with carbs and not so much with EFI. If it is the case, how would you resolve it with EFI? Re-routing the rail would be difficult I would think. Still something worth looking into.
High mileage or older systems can drive you nuts.
I've had older F.I. vehicles that seem to lose fuel pressure if they sat for any length of time.(overnight). Turn the key on, wait 5 seconds and then try to start. Fuel rail leaks down over time.
May be that way with high heat as well.
Weak fuel pump, leaky check valves, or pressure relief valve.
Try the 5 second prime test.
This may not work with the new one-way F.I. systems.
I've had older F.I. vehicles that seem to lose fuel pressure if they sat for any length of time.(overnight). Turn the key on, wait 5 seconds and then try to start. Fuel rail leaks down over time.
May be that way with high heat as well.
Weak fuel pump, leaky check valves, or pressure relief valve.
Try the 5 second prime test.
This may not work with the new one-way F.I. systems.
The key priming did not seem to work as well as leaving the hood open for a few minutes. Will have to try it some more to be sure.
What is an ACT (mentioned above)?
What is an ACT (mentioned above)?
ask your fuel supplier, what there reid vapor pressure is. also read up on reid vapor pressure.
I have a buddy with one of those straight six early computer controlled FI F150s.
Problems! Practically unsolvable!
You may want to disconnect the weird breather tube from the metered inlet. it makes no sense.
You can hang in the breeze, but a filter on it would be a good idea.
Of course, plug the hole in the intake piping!
Problems! Practically unsolvable!
You may want to disconnect the weird breather tube from the metered inlet. it makes no sense.
You can hang in the breeze, but a filter on it would be a good idea.
Of course, plug the hole in the intake piping!
Originally Posted By: mechtech2
I have a buddy with one of those straight six early computer controlled FI F150s.
Problems! Practically unsolvable!
You may want to disconnect the weird breather tube from the metered inlet. it makes no sense.
You can hang in the breeze, but a filter on it would be a good idea.
Of course, plug the hole in the intake piping!
Where is the weird breather tube located? I only know of the PCV tube back to the air box.
I have a buddy with one of those straight six early computer controlled FI F150s.
Problems! Practically unsolvable!
You may want to disconnect the weird breather tube from the metered inlet. it makes no sense.
You can hang in the breeze, but a filter on it would be a good idea.
Of course, plug the hole in the intake piping!
Where is the weird breather tube located? I only know of the PCV tube back to the air box.
Originally Posted By: TallPaul
The key priming did not seem to work as well as leaving the hood open for a few minutes. Will have to try it some more to be sure.
What is an ACT (mentioned above)?
Air charge temperature sensor. If memory serves it is in the #1 intake tube. Didn't work on a lot of 4.9s, so memory is sketchy, although one 4.9 that punched 2 rods out of the block and still drove into the shop sticks in my memory. I know ACTs did gum up and give erronious temps causing lean/rough running conditions sometimes.
High RVP fuel can cause long cranks and even stalling on hot days. Here in TX sometimes you would get a hot spell in late April/early May while the refineries are shipping their winter blend/high RVP trash to the load rack, and anything with a borderline fuel pump was in trouble. High RVP/winter fuel is cheaper to mix as refiners can dump all of their high RVP fractions they have been storing in the mix and make a buck on it, while still meeting specs. In Austin the first hot day in the mid 90s saw a service drive filled with cars on the hook, and a lot of happy performance techs.
EDIT: for really bad spelling.
The key priming did not seem to work as well as leaving the hood open for a few minutes. Will have to try it some more to be sure.
What is an ACT (mentioned above)?
Air charge temperature sensor. If memory serves it is in the #1 intake tube. Didn't work on a lot of 4.9s, so memory is sketchy, although one 4.9 that punched 2 rods out of the block and still drove into the shop sticks in my memory. I know ACTs did gum up and give erronious temps causing lean/rough running conditions sometimes.
High RVP fuel can cause long cranks and even stalling on hot days. Here in TX sometimes you would get a hot spell in late April/early May while the refineries are shipping their winter blend/high RVP trash to the load rack, and anything with a borderline fuel pump was in trouble. High RVP/winter fuel is cheaper to mix as refiners can dump all of their high RVP fractions they have been storing in the mix and make a buck on it, while still meeting specs. In Austin the first hot day in the mid 90s saw a service drive filled with cars on the hook, and a lot of happy performance techs.
EDIT: for really bad spelling.
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