This is basically a problem with cold starting on a hot day with the sun beating down on the truck. Subject F150 is in signature below.

Here is what happens. When I park this truck on a hot summer day, like Thursday and Friday, which was in the mid 80s, and it sits all day from about 7:30 until around 4:15, with the hot sun beating on it. Then I try to start it and it won’t crank over right away and acts like it is not getting enough fuel. I immediately crank it a second time and it starts but roughly, though quickly smoothing out and then runs fine. It does this on either fuel tank and the last time I even key primed the fuel pump three times before cranking it, but it still stumbled and was hard to start.

Fuel filter was changed only 2500 miles ago. And today I left it at the shop from 8:30 am and then came back about 4 pm. It got up to about 88 F today. At 4 pm they put a fuel gauge on it and I cranked it. Well this time it started right up and no problem. Fuel pressure came right up too.

Now to make it even stranger, it has been doing this for two years, but never is a problem in cooler weather, no matter how much the sun beats down on the hood. And most of last summer I parked in a structure, so it was shaded from the sun. Even though we had 90+ days, it never had a problem starting when in the structure.

Again, this is the only running problem. It runs great at all times, just a problem starting a cold engine in really hot weather with the sun beating on the hood. I can drive the wee out of this truck on the hottest days and no problem. Shut down really hot and cranks right back up. Runs fine.

I’ll add that I can make it stumble if I switch fuel tanks while under load, but that has always been that way and should be normal. The other thing I’ll add is that this truck always (since I got it at 58000 miles) took a little more cranking than seemed normal to start, but never the roughness and feeling of lack of fuel that it gets under these hot day, sun on the hood days.

So, any ideas? What to do?

Can’t be any components like coil etc. because they get hotter when running than just sitting in the sun, right?

Should I get a fuel pressure gauge so I can monitor what happens?

Should I try lifting the hood for 5 minutes before starting it next hot day?

Anything else I can try?

 

You might have a fuel pressure regulator that doesn't hold pressure properly. When they go bad they can cause some really strange problems. I would say you are on the right track with hooking up a gauge so you can see what the pressure is doing at startup.

 

Well, since both tanks to it, it likely is not the fuel pumps, so that leaves the regulator. But how is it the regulator malfunctions on a cold engine with sun beating down on hood, but operates fine on a hot engine? Sure is a mystery. Guess I can throw a new regulator on it and see what happens.

How do I replace the regulator? Is this a do it at home job for a light weight wrencher? Typically I replace plugs, cap, rotor, shock absorbers, and change oil and tranny fluid, but avoid things like brake jobs, etc.

 

Run some gas line dryer 4 bottles in each tank, then a bottle in each, each oil change.
Let's just eliminate water in the gas from the equation. Now for the start problem, Get a can of keyboard duster and holding it upside down spray let's say start with the coil spray it a good 15 seconds and try starting, no start move to another component the spray times of different components will need to be changed a small metal part will take less time than a plastic part, due to conductivity of the material. You will want to use the minimum spray time you can. I use a paintball tank with a on and off valve and a hose with a little insulated handle to keep from freezing my hand. It is a lot cheaper in the long run to use co2, It has lots of other uses too you can fill tires, cool off the radiator, blast clean sparkplug holes etc. I just thought about something, if your computer is under the dash, you get in roll down your windows and try starting, well the windows are letting cool air in cooling the computer!! Try blasting it for a few seconds as soon as you get in and see if it will start on the first try. double check the connector if the heat is bending a contact(think christmas tree light flasher bulb) it is losing contact until it cools enough.

 

Great idea Blue Beast! Now I may have to wait 8 months to do the testing. Monday pushed 90F. Today was about 75F. Rest of week will be in 50s an maybe 60s.

If water was in the fuel and causing the problem, I would think it would be affecting it more than just that select situation.

OTOH, what does a pressure regulator cost. Looks easy to change except it is under the intake runners. I checked tonight and the bolts can be loosened. Just two bolts and the vacuum line, then a gasket and o-ring should do it, right? Can't hurt, may help. And if the regulator is bad, it could be affecting other things like the whiteish deposts all over my spark plugs with silvery deposits (Photos of plugs in this thread ), which the Haynes manual says indicates running too hot from, among other reasons, lean mixture. If the regulator is bad, it could be causing a slight lean condition, right? Best insurance may be to replace it. If problem not solved, next summer can hit with the CO2 spray.

 

The regualtor can be replaced pretty easily. It might not have anything to do with temperature, just the fact that the pressure bleeds off over time and doesn't come back right away. The regulator might also stick at different temperatures. Who knows? Regulators do wierd stuff when they go bad. I've seen GM 3.4 V6's set lean codes and rich codes at the same time because of a bad regulator.

 

Pep Boys has a fuel pressure regulator for $47. It's a Borg Warner. Says OEM quality. Should I go for it? Can't hurt, may help. At least will know it's not the FPR if it still does it and won't have to deal with leaky FPR diaphram ever on this truck.

 

If the water molecules are partially blocking the injector opening it would only let some of the fuel by, therby running lean. Water has a high surface tension so it can stick in small openings and the fuel won't be able to dislodge it. It is $7.00 for a few bottles and is worth a shot it can cause all sorts of weird symptoms depending how much is in there.

 

Okay Blue Beast. A very rational argument. I will do it, even though I always thought alcohol content of modern fuel was sufficient.

 

check fuel pressure when cold in the heat as someone cranks it. also take the vacuum line off, if there is fuel inisde then the diaphram has ruptured.

basically check the fuel pressure before ya start it when u think it'll give problems. should be 45-60 psi.

 

Guess I should buy a mechanic's fuel pressure gauge. They are about $40. Or maybe better to get a regular gauge and then I can always watch the pressure.

Just bought a can of CRC freeze off that is supposed to break loose rusted parts. I can try that on the regulator before I start it. Just don't know when we will get any more warm weather around here. High in 50s today. Nothing above 65F through next Wed.

BTW, does a regular (not the mechanic's gauge but one that mounts permanentaly) hook up to the Schrader valve?