Weather Temp Swings Cause Engine Problems?

[Matt Schrum]

I tried researching this some online, but there are so many pages of "can't start your truck on a cold morning?" that the information I am looking for is drowned out. I'm hoping someone here might be able to help me narrow down my search.

I live in Colorado and my 2014 truck (65K miles; gas, not diesel) runs fine when the weather is cold. It runs fine when the weather is hot. It runs fine in between. The fun is that when leaving work after there has been a big upward temperature swing (say 30F for the morning commute and 70F for the commute home), I turn the key and my truck will turn over for a good 3-5 seconds before coming alive-- it isn't the battery (it turns over strong), the engine just sounds like it's not getting fuel for those few seconds. Every other instance it starts immediately. If it's been 0-10F all day or in the 100F's, it fires right up. A coworker had talked about maybe a partially clogged fuel filter, but I can power up the mountains without a problem-- so I don't think that's the case.

I had thought (and it's still my best guess) is that there is a check valve on the fuel pump and the line pressure is dropping/passing between the pump and the engine-- so it's having issues coming back to life... but I can't relate that weather temperature swings in my head. In addition, I can let the truck sit for a few days and it'll start on the first go when I hop back in.

Any thoughts? It's not a huge problem, but with spring weather in Colorado, it's happening a few times a week now and is fairly annoying (as well as somewhat concerning).

[Chase Mueller]

I live in Georgia, so I know what you mean. Yesterday was 58, today 71, tomorrow 85, and all starting out the mornings in the 30's. I don't believe that to be your problem. Sounds more to me like a fuel/air issue. I assume no codes?

[michael langman]

It sounds like the fuel pump is losing it's prime. On one of those days with the big temperature swings ,turn the ignition on but don't crank the engine for 5 seconde, then see if the truck starts right up.
It's good practice to turn the key on and prime the pump at all times before cranking the
he engine. It prolongs the life of the fuel pump.

[Chase Mueller]

It sounds like the fuel pump is losing it's prime. On one of those days with the big temperature swings ,turn the ignition on but don't crank the engine for 5 seconde, then see if the truck starts right up.
It's good practice to turn the key on and prime the pump at all times before cranking the
he engine. It prolongs the life of the fuel pump.

+1 on that. Turn the car on, don't start it though, should hear the fuel pump engage. After that, start it. Should fire right up. If it's under warranty take it to the dealer and have them check it out.

[Matt Schrum]

...On one of those days with the big temperature swings ,turn the ignition on but don't crank the engine for 5 seconds, then see if the truck starts right up...

Sounds good guys, I'll give it a shot as I usually do just hop right in and turn the key. It was warm this morning, but the weather pattern is pretty close to a roller coaster this time of year-- so I should be able to test it out a few times before the end of next week and see if the problem persists.

As for the warranty and codes-- negative on both. No codes and I blew past my warranty a while back. I haven't had any other significant issues with the truck-- and the only common factor I can find is the temperature swings. It's weird, but extremely consistent. Based on the weather, 99% of the time I can tell you if it'll start right up or crank before I even hop in my truck.

[Chase Mueller]

Best of luck and let us know if it helps!

[Kev Williams]

elec fuel pumps only run for about 1 second if the engine is off, so leaving the key on any longer than that's not going to help much...

What does happen with a 30° temp increase is a rise in the line pressure due to the gasoline expanding with the extra heat. Your fuel pressure regulator may be bleeding off the extra pressure, or the anti backflow valve may be leaking down. The regulator is designed to hold a certain line pressure, backflow valves aren't, which is to say if the regulator IS bleeding off the pressure, it should still maintain the normal pressure, and it appears that in use and without big temp swings it's doing just that... So my first guess would be the backflow valve, which means replace the fuel pump.

[JERRY BRINKMAN]

This is normally not a DIY project. I've been in the auto repair business for over 40 years. The first thing is to install a pressure gauge to monitor fuel pressure when problem occurs. If there is no fuel pressure the next step is to determine if power and grounds at fuel pump are good. If so then pump will need replacement. If missing either power or ground you will need to test the fuel pump driver control module inputs and outputs. So you see it gets complicated. With all that said, the most common failure is the fuel pump module in fuel tank. If your not willing to buy a fuel pressure gauge than take to your favorite shop for diagnosis. Replacement of the pump requires fuel tank removal or lifting bed off body for access. Good luck to you.

[George Bokros]

+1 on that. Turn the car on, don't start it though, should hear the fuel pump engage. After that, start it. Should fire right up. If it's under warranty take it to the dealer and have them check it out.

This is impossible to do on the new cars with push button start.

[Chase Mueller]

Not every new car has push-button start, including I think the OP's , but I would imagine you could still do it, provided you take your foot off the break first.

[Tom Stenzel]

Hi Matt,

It would probably help if you put what make of truck you have. Possibly someone with the same drivetrain will have run into this before.

I've two GM cars with this type of problems. One was my '97 Saturn. The fuel pumps were such a problem with these cars that the warranty was extended on the pump. It would leak down and cause long cranking times. I sold the car after 18 years and that same fuel pump was still in there leaking down. On that car I would turn the key to on, buckle the seat belt, then engage the starter. That did reduce the cranking time. I didn't have to replace the starter so that was some consolation.

My 2004 Venture has intermittent long cranking times. I haven't been able to pin it down to temp swings but hot restarts seem to do it when it darn well pleases. The fuel pump got intermittent and was replaced after 11 years. It didn't change the starting problem at all. The fuel pressure regulator failed (external leaking) and was replaced. No change with the starting problem. There's not much else left in the fuel system.

With that I recommend NOT throwing parts at it!

-Tom

[George Bokros]

Not every new car has push-button start, including I think the OP's , but I would imagine you could still do it, provided you take your foot off the break first.

If your foot is not on the break I believe it only turns on accessories and does not energize the ignition which would energize the fuel pump.

[Matt Schrum]

... It would probably help if you put what make of truck you have. Possibly someone with the same drivetrain will have run into this before...

Tom, it's a 2014 Ram 1500 with gasoline V6 and is not a push button start. So far I haven't had any real problems to complain about until I started noticing this issue. I'll keep you folks posted over the next week or two once I see if letting the key sit in the "Run" position for a few seconds before starting makes an impact.

[Jerome Stanek]

Back in the 70's I had a 260 Z that was hard to start when the weather changed like that. I found out that the fuel would pull back into the gas tank and it would need to crank for a while to get fuel back to the carbs. The fix for that was a electric fuel pump that had a check valve in it

[Chase Mueller]

Maybe so. At least OP doesn't have to worry about that.