Possible air leak in fuel system?

[DmaxProf]

Today the temp was about 104 degrees. My wife left the engine running with the A/C on for about 15 minutes while she went into a store. After she finished shopping, when she tried to pull out into traffic, she said it seemed like the truck had no power and did not respond to the throttle. She managed to baby it home and shut it off. After she reported her experience to me, I went out and discovered that I could pump the fuel filter fairly easily. After pumping it until it was difficult to push down, I started it up and it drove normally.

My question is: Should I be able to pump the fuel filter easily or should it be difficult as it is after bleeding the air when changing the filter? This afternoon the fuel filter continued to be fairly easy to pump. However, the truck cranked and ran fine. Do I have an air leak in the system or is everything working normally?

[DmaxMaverick]

Your experience with the primer pump sounds normal. After the engine has ran, it will be easy to pump. The fuel system is suction up to the fuel pump.

You could have an air leak, but enough air to cause a problem will usually shut it down completely. The high pressure pump is not self priming, but once it's running and stays running, it will digest a lot of air before you have problems. The high pressure side is self bleeding. Too much air will either stop the engine or set a DTC and the SES lamp. A bad fuel filler cap, on the other hand, could cause a problem. Did you get a SES lamp? If not, it could be a number of things you'll probably not figure out. If you park it hot, and it starts again once cold, you don't have a significant air leak.

High temps will exagerate turbo lag, and could give the impression of no power if you don't wait for it, or get the RPMs up enough to spool the turbo. 104° is up there, and I notice a significant performance hit in that heat. Unfortunately, I see it quite often. It can change turbo spooling from 1300 RPMs when cool to 2000 RPMs when over 100°, and it gets worse with long idling.

[DmaxProf]

DmaxMaverick, thanks for the helpful and informative reply. I did not get a SES light and today the truck seems to be running just fine. So, I guess there was not a problem with the fuel system--at least not an air leak. I had never tried bleeding air from the fuel filter except when changing the fuel filter, so the fact that it had so little resistance was surprising to me.

[precision37]

A low fuel level in the tank, dirty fuel cooler and high temps with extended idle time could cause performance issues due to high fuel temps.