There is no fuel in the vac line to the fpr. Could it be an injector problem. I guess I will start pulling plugs an see if any are fuel soaked. All you guys are great for all the help so far. Thanks

 

This statement is what needs to be addressed an injector problem won't cause your fuel pressure to bounce. But the FPR or pump can.

If you run a fuel pressure gauge and a vacuum gauge at the same time and go for a drive there movements should match each other. Fuel pressure should rise equal to a drop in vacuum, if vaccum goes from 20 to 5 during high throttle that's 15 fuel pressure should have an equal change say from 30 to 45, if not you still have a fuel pressure problem.

 

I am going to replace the FPR had see what happens, Thanks

 

Consider an adjustable one, you may find it usefull down the line to tune or diagnose.

 

You can have a bad fpr and not see fuel in the vacuum line, I know I did...

 

If I change the FPR even though I know that it is one of the problems, Even if it has 35lbs and 42lbs w/ the vac. line off but it will not hold pressure once the key has been turned to the run position it pressurizes and then drops right to 0psi. Will this make the truck run any different. It still feels likr the truck has alot of power low but it feels like some thing is hilding it back. Could it be O2 sensors, and it uses a lot of fuel.

 

The pressure droping off very quickly is an indicationon a leak. Most likely leaky injectors or possably an actual leak. Do you smell fuel if not it's probably not leaking. Then it is time to replace the injectors.

Have the injectors ever been replaced or professionally cleaned? How long sence the O2's have been replaced? Both of these are maintinance items on a high mileage motor and should be adressed anyway. The O2 is unlikely your problem at full throttle the computor largely ignores the O2. However badly leaking injectors could be very much your whole problem, replace them it's cost effective and not that hard to do.

 

I thought that if the pressure bleeds down as soon as you pressurize the system it would be a FPR problem but if it drop as soon as you turn the key off it would be an injector problem, because there is no power closing the injectors. And this just started. The truck has 131,000 and everything is stock, as fare as injectors and O2, and FPR. As long as your easy in the throttle the truck seems to run great.

 

The injectors are closed in there resting/off state. It is true that the pressure droping off right away could be the FPR also, the FPR should be closed completely when the engine is off, and the fuel system should not allow reverse flow.

Is the fuel pressure still bouncing? It sounds like you haven't replaced the FPR yet?

If you are wondering about wether or not to replace the FPR or injectors and it has been a while sence the injectors have been serviced, at least take them out and have them flowed. If you've never seen this, there are injector service shops that flow test the injectors. They mount them so they fill a clear graduated cylinder and then pressurize and run them, Doing this they can measure the flow rate of each injector and see the spray pattern to make sure they are good and then see what they do when off and pressurized to see if they leak, a good shop will have it set up so you can watch.

These injector service places will also sonic clean injectors they flow them with a cleaner while sonicely vibrating them to clean them, then replace all the external parts, if replacement is to expensive and not needed, but generaly these days the replacements are not that expensive and a better option.

 

Ya, what happened was it gauge started bouncing and would hold some pressure when the key was turned off, and slowly started to drop, and the next day I noticed that it cranked a little longer before it started. And after later I checked the gauge again and found that is was not holding any pressure ether way KOEO or key on in run position.

 

It's hard to say what is going on with your fuel system there are so many unique symptoms. The fuel pressure should not hold for a long time with the KOEO the fuel pump will only run for a few seconds them wait until the engine is cranked to go again, and the system is never closed enough for the pressure to stay up for more then say 10 minutes until it reaches 15psi in an ideal/new engine. If the presure is droping off completely within 30 seconds of the pump stoping then you got a problem, I would think that fast could only be the FPR but I guess some really bad injectors could leak that bad.

 

OK replaced FPR and it still the same way no different. I started to unplug drivers side injectors one at a time with the truck running and they changed the way the truck idles. Any other help or other ways of checking the injectors w/ out pulling plugs.

 

OK this is what I found out, All injectors are fine,
FPR is fine , It turnrd out to be the one way check valve in the fuel pump unit which I come to findout is called the (FDM). Which then you must replace the FDM. Ha everyone that help me out thanks and have some good hoidays. Mike