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1998 F150 won't start when it's hot....vapor lock?

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Old 06-15-2011, 04:22 PM
jehuie jehuie is offline
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1998 F150 won't start when it's hot....vapor lock?

This was happening last year and now that it's hot again it's driving me crazy once again. On hot days the truck will start and run a little bit rough for 10 or 15 seconds and then it's fine. But if I drive it a few miles and then stop, it won't start again no matter what I do. But if I let it cool down for an hour or so it will fire up again.

It only happens on hot days. And it's not consistent but it strands me somewhere at least a couple times a week now. I don't think fuel injection engines suffer from vapor lock do they? And it doesn't have an Ignition Control Module right? So what else could it be?

I've taken it to the shop twice and they haven't been able to help. Anyone? Please?!
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Old 06-15-2011, 07:36 PM
jehuie jehuie is offline
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Oh and I forgot to mention...I have replaced the thermostat and the fuel filter so those are out as potential causes.
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Old 06-15-2011, 08:02 PM
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blue2golf blue2golf is offline
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I'm having the exact same trouble with my '99 F150XL. I replaced the fuel pump relay, the fuel filter, tried opening the fuel cap to expel excess pressure and had it scanned by a local mechanic....no luck and my only code was the EGR causing the check engine light to come on.

However, I did ask the mechanic to check my fuel pressure. It was too low...fuel pump is going out. That might be the root cause. My mechanic could not be for sure that it would 100% fix the problem, but it probably would and that I need a new fuel pump anyway.

I'm buying a whole new sending unit tomorrow night and will install it this weekend. I'll update everybody on if this solution was effective or not.
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Old 06-15-2011, 11:28 PM
Bluegrass 7 Bluegrass 7 is offline
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Bluegrass 7 has a very good reputation on FTE.Bluegrass 7 has a very good reputation on FTE.Bluegrass 7 has a very good reputation on FTE.
Possible that one of these sensors has a plugup issue or sensor issue.
The Crank Position , the Cam position Sensor.
In the fuel circuit the pump relay and crash sensor.
EEC relay.
Loss of fuel pressure.
Check for codes and see if the PCM has been rebooted from power failure at any time.
When the problem is present you need to do the testing to find anything or it's just guessing.
Seem it's a heat soak issue as the engine bay gets hotter after shut down for at least 5 minutes due to the lack of fan cooling.
.
On my truck, I have a fan cooled aux transmission cooler with auto operation. In hot weather if the fan is not running it come on after I shut the motor off and runs for about 6-7 minutes before it shuts down.
The control sensor is sampling the trans inlet line at the radiator but still samples the engine bay as well so I get both functions from it set as about 185 to come on blowing air into the engine bay through the cooler and radiator.
Good luck
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Old 06-19-2011, 09:38 AM
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Quote:
Originally Posted by blue2golf View Post
I'm having the exact same trouble with my '99 F150XL. I replaced the fuel pump relay, the fuel filter, tried opening the fuel cap to expel excess pressure and had it scanned by a local mechanic....no luck and my only code was the EGR causing the check engine light to come on.

However, I did ask the mechanic to check my fuel pressure. It was too low...fuel pump is going out. That might be the root cause. My mechanic could not be for sure that it would 100% fix the problem, but it probably would and that I need a new fuel pump anyway.

I'm buying a whole new sending unit tomorrow night and will install it this weekend. I'll update everybody on if this solution was effective or not.

Replaced the fuel pump yesterday. It hasn't been hot enough yet to see if this solves my problem. We've got some days forecasted in the 90s coming up. It shouldn't be too long of a wait.
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1996, 1999, 2002, 2003, 2004, bronco, f150, ford, hot, ii, lock, ranger, start, v6, vapor, wont

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