Checking Fuel pressure

[FlipTrac_511]

Is there a a way for me to check fuel pressure while cranking and also while running? I'm getting rough starts one out of every twelve cranks. I've already cleaned the MAF sensor, IAC valve, and changed fuel filter. Dealership recently replaced the IAC valve altogether. Trac runs great otherwise.

 

[Kevin Palmer]

There is, you need to hook a gauge up to the "Shrader Valve". Most garages will have this tool as well as Autozone I believe, (They rent them for free. They hold the deposit and return the deposit upon return).

 

[Shelby Crane]

I can read my fuel pressure with my scanner on my 07.



Maybe someone has one you can borrow.

 

[Richard L]

If you have a fuel pressure problem the engine may start fine but will have difficulty accelerating due to a lack of fuel. If you have difficulty starting, but runs down the road fine, it's not a fuel pressure problem.



When the outside temperature cools and the engine is cold, the computer turns on the injectors a bit longer to enrich the mixture like a choke on a carburator. I suspect that you may have one or more injectors that are dirty or not flowing a good spray pattern. That's what's causing your rough idle. You probably need to have you injectors cleaned. You can buy the cleaners in a pressurized can that screws into your fuel rail. Then you should add a can of a good quality injector cleaner into your gas tank every couple of oil changes to keep the injectors clean.



You might also want to look at the brand of gas you are buying. Cheaper brands often do not contain enough detergent additives to keep the injectors clean. Brand name gasoline like Exxon, Shell, Mobil, Chevron are some the brands that contain enough detergents that you will not encounter too many dirty injector problems.



One last thought...an injector can be dirty or malfunctioning where is drips a little. If the vehicle sits all night, it can dump a lot of raw fuel into that cylinder. When you start the engine it may run rough unitl it burns up all that excessive fuel, and then the drip may be too small to upset the engine while driving at highway speeds. You will probabl see a small drop in fuel mileage if it's a serious leak.



...Rich

 

[FlipTrac_511]

Thanks for all that info Richard. I apologize for the innacurrate choice of words. Please allow me elaborate on my "rough starts". What I mean is the engine won't turn over unless I keep cranking for about two seconds. After that it starts it runs fine. Seems to happen randomly. Also, sometimes it starts right up but idles immediately around 600rpms.



I've been putting nothing but 76 (Conoco) and have recently been putting Chevron (I read somewhere that it was good to alternate brands). On my last tank I also put in cleaner I forget which one). My mileage has dropped but I'm certain it's due to less highway driving. It may also be my new tires.

 

[Richard L]

FlipTrac,

Early model Sport Trac's had problems with a leaking fuel pump. The pump is located int the gas tank and they would leak on the pressurized side so that siting overnight would lower the fuel pressure and make the engine hard to start. Once they started, they ran fine.



Your 2004 model sounds like it is getting early symptoms of a leaking fuel pump.



If your ST is hard to start after sitting overnight but starts fine if it his only sat for a couple of hours, then I would suspect the fuel pump leak.



One way to test it is before you try to start the engine in the morning is to turn the ignition on and let the pump run for about 5-10 seconds to build up pressure before you attempt to crank the engine. If the engine now fires immediately, my bet would be a linternally eaking fuel pump.



...Rich

 

[FlipTrac_511]

Thanks Richard. The hard starts aren't just occuring after the Trac has been sitting overnight. I remember one instance I drove home from work (8-mile, fifteen minute drive) and had the Trac parked for an hour or so at home then I decided to go to Pep Boys. I shopped for not even 20 minutes and when I got out to start the Trac, you guessed it...it hesitated to turn over. I had to crank for about 3 seconds. Up until that point I had no issue with starting the Trac that day. This was in the summer time in SoCal FYI.



I don't understand how the injectors could've gotten so dirty already at less than 34K miles (and much less when I first notice the issue). I mostly use Unocal 76, and sometimes Chevron and Mobil at very presentable stations.