Engine/Transmission (1998.5 - 2002) fuel pressure

[Tractorat]

I just went out to start my truck and the low fp led light came on and stayed on. I clicked the key for codes, and there weren't any. Then I started it again, and this time the led did not come on. Drove it around the block a few times and shut the engine off. Started it again and the led lit up again. Again, with key clicks, no codes. But when I started the truck again, the led did not light up.

I changed the fuel filter on the FASS about 600 miles ago. I used a baldwin bf7633.

Any ideas what would cause that ?

Thanks

 

[Tractorat]

Update. Let it sit for a while then tried it again. This time I let it idle for a few minutes with the led on. Truck started running rough.

 

[JR]

I'd say it's one of two things, either a plugged fuel filter or the pump is on its way out. Cartridge filters are easier to diagnose as you can pull and inspect them for foreign debris. The only option with a spin on filter is to replace it and see if it alleviates the problem. If it turns out it's not a filter issue you could drain it and store it in a zip lock baggy for your next service. *

What happens if you bump the starter to engage the fuel pump? Does it build enough pressure to shut the idiot light off? *Any unusual noises coming from the lift pump, IE bad bearings? This is where a true gauge becomes valuable. You can see specifically what pressure it is putting out.*

Another possibility is the way the FASS is regulated. Some have a return line back to the tank with a check ball and spring to control pressure. *Some just have a screw you turn in or out to adjust pressure. Both can malfunction and cause pressure issues.*

 

[Tractorat]

Thx. BTW, its only been a couple of hundred miles, not 600 since I changed the filter. I wonder if it might be a good idea to just unscrew the filter, bump it a couple of times, and try again ?

 

[Tractorat]

Well, I unscrewed the fuel filter and bumped the key a few times to run the pump. Then screwed it back in while it was still spilling fuel. Seems to have solved the problem. I would have thought that if that was the issue, it would have presented itself by the time I had a couple of hundred miles on it.

 

[Tractorat]

Problem is back. Tomorrow is Memorial Day so I guess Ill have to wait until Tuesday to try a different filter or take it somewhere.

 

[JR]

Is the pump noisier than normal? They will sound distinctive if they are cavitating. Bad bearings is another possibility which you should also be able to hear.*

I'd also look at the way the the lift pump is regulated. They will Cause a low pressure condition. If you have the type of pump with a spring and ball in the return line to the fuel tank the ball may be jammed in the spring. As an easy test you can GENTLY pinch off the return line while the pump is running to see if the pressure goes up. *Just make sure you use something that doesn't damage the line, like a small c clamp or vice grips. Anything with a smooth jaw.

 

[Tractorat]

I loosened, bled, and retightened the filter again this afternoon. Checked it a few times and still holding. When I first replaced the filter a couple of weeks ago, I only had some 0w20 oil to run around the gasket. I used the same oil yesterday when I retightened the filter and had a bad result. Dont know if it makes any difference, but today I went and got some 30w oil for the gasket. I think Im going to get a real FASS filter tomorrow since I dont have any trust in this baldwin now (whether its the filter or not). Has anyone had luck with the baldwin, good or bad ?

 

[BigPapa]

They're all we use on our 800+ bus fleet for oil, fuel, and air. Never had a filter related problem beyond the occasional bad filter that leaks.

 

[Bob4x4]

I have seen intermittant failures with the FASS system,contact the vendor you bought it from and they can give you some good diag tips

 

[Tractorat]

Thanks, thats my plan. I would called them today, but its Memorial Day and they are closed.

 

[SnoKing]

And if you like your current VP-44 get a fuel pressure gauge! Idoit lights are for .........! Snoking

 

[SnoKing]

Dup post! Snoking

 

[Tractorat]

Still trying to figure this out. I found out that the new fws3003 fuel filter should not have the inner gasket installed as that can restrict fuel, so that has been removed. Worked for a short while. However I still have the problem. When I replaced the fuel filter, I also replaced the water separator can. I did reinstall a new inner gasket for that can. Can anyone tell me if that can restrict fuel flow ? After I reinstalled the water separator (w/o inner gasket), I still had no fp. However, I cracked open the fuel filter and bled it and now it starts right up with no low FP light coming on. But I dont know for how long. BTW, fuel pressure was checked yesterday at 16 for both idle and wot.

Thanks