2008 F115TXR fuel regulator problem?

cleaned vst filter,changed filters,new injectors...bogs down and quits running...disconect the vacum to regulator and runs much better..fuel pressure 42psi with vacum disconnected and 36psi when connected...what's the deal?...put vacum pump to fuel regulator and pressure drops to 40psi...need some advise

Did you install the new injectors first and run the engine then clean the vst? If yes, Chances are the injectors are clogged with all the dirt you knocked loose, you need to remove the fuel rail and clean the injector filters or replace them and clean the rail.

The regulator is not cheap and I have replaced a few of them this year for the same symptoms you are describing.

Try cleaning the injectors and the fuel system first before changing the regulator.

I have experienced plugged up filters and a bad fuel regulator on my two f115s. And I had a high pressure pump go bad on my f150. On the f115s the engines always idled fine but would bog down at higher rpms under load. When the high pressure pump went the f150 was completely dead.

When you say it bogs down and quits running, is this just at higher rpms under load?.....or does it quit running at idle in neutral too? Once filters and injectors get plugged up, it's important to know why. In my case it was bad corroded tanks that kept causing the problem. Although the engines would run good for a while after changing filters, eventually things plugged up again. I ended up replacing two tanks all lines and then new filters and the problem was solved.

When I replaced the fuel pump on the f150, I tested the fuel regulator with compressed air and when I dialed the air pressure up to 41 psi the regulator started hissing. When the regulator was replaced on the f115 I hadn't gotten into fixing the motors myself yet so I don't know what was wrong with it. But in my opinion a drop to 36 psi shouldn't make the motors bog down and die. In my opinion reading the fuel pressure when it is bogging down will define what's wrong. If the pressure drops off as things drop off it could be the regulator but more likely plugged filters. If the pressure remains constant while things change it could be plugged up injectors.

the owner changed injectors then I got the engine to find out what was wrong, I cleaned the vst and replaced the filters (the main racor to engine,the small one on engine and the one between pump and vst, the injectors could be clogged but I dont think so because the engine will run smooth and throttle up to high rpm when I disconnect the vacum hose to the fuel regulator but I don"t know why it responds that way, I ran the engine at idle for a couple of minutes and touched the ISC valve and it was hot, I see that there is a small filter going to the ISC and I wounder if it is clogged...with the vacum line attached to the fuel regulator if I just start to throttle up the engine dies right away but if I disconnect the vacum hose from the fuel regulator and throttle up it reacts just fine...whats the deal? could it be a bad ISC or clogged filter to the ISC or both? While we are talking diagnostics where can I buy a yamaha yds diagnostic 1.33 software and harness kit? thanks for the help....I checked the fuel pressure when the motor bogs down and the pressure stays at around 40psi

If you have good fuel pressure when it bogs down it rules out VST pump/filter problems in my opinion. And if the fuel pressure remains strong with or without the vacuum line attached to the fuel regulator I would think its affect on the motors performance would be more related to air flow, or whatever else a leaking vacuum line would impact. And when you start getting into the ISC, the electrical system, or diagnostics.............I haven't had to go there yet as I didn't have problems beyond what I described above. I'll bet Chris/dockside above may be able to help you out there.

Good luck and report back with what ends up being the solution.

The engine has a IAC( Idle air control) not an ISC(Idle Speed Control).
According to your post the regulator is working fine.
Have the injectors serviced and it will run fine. As I stated above, if you change the Injectors ran the engine and then changed the VST filter afterwards the injectors are fouled again.
FULEINJECTORMAN DOT COM. He does a good job. $16.00 each vs.$240.00 to replace. Fast turn around time.

Chris,
Thanks for the information, I studied alittle more and got schooled on the difference between the two IAC/ISC... i will change/clean the injectors and follow up when i reinstall them.This is a great forum.Boolie

Chris,
I had the injectors cleaned installed them and the engine runs great, thanks for the help..if you are ever out in Hawaii I owe you a fishing trip...Boolie

Glad to hear it. Good Luck.