Engine/Transmission (1998.5 - 2002) FASS, low pressure

[GCULP]

so last night while driving from Portland to Seattle I start watching the fuel pressure guage, it's hovering around 14. 5 psi and pulls down to 12. 5 on any hill. Usually I have 17 - 18 psi at idle, 16 psi while cruising and can barely pull it down to 15 on a hard pull. Here is some history. Changed fuel filter 2 weeks ago, added Edge EZ 1 month ago, fueled up just before getting on the freeway for the trip. The last two tanks have been down till the light came on. I am hoping there is some sediment in the pre-filter before the pump, otherwise I am a little worried about the pump. Pump is not hot to the touch, not overly noisy, fuel pressure is tapped between the filter and the VP44, any other ideas if it is not the pre-filter?

 

[GCULP]

update, after talking with the fellas at Source Automotive, they recommended checking with a test guage at the pump, and then replacing the antifreeze in the line from the isolator to the guage with silicone spray. I will let you know what I find.

 

[LowFly]

so last night while driving from Portland to Seattle I start watching the fuel pressure guage, it's hovering around 14. 5 psi and pulls down to 12. 5 on any hill. Usually I have 17 - 18 psi at idle, 16 psi while cruising and can barely pull it down to 15 on a hard pull. Here is some history. Changed fuel filter 2 weeks ago, added Edge EZ 1 month ago, fueled up just before getting on the freeway for the trip. The last two tanks have been down till the light came on. I am hoping there is some sediment in the pre-filter before the pump, otherwise I am a little worried about the pump. Pump is not hot to the touch, not overly noisy, fuel pressure is tapped between the filter and the VP44, any other ideas if it is not the pre-filter?

We talking HPFP or FASS here?



IF HPFP... (Pump only), its VERY important to use the correct strainer before the pump. NAPA 3270 is what we recomend. Its a 144um strainer that is almost no restriction and does a dandy job of prefiltering before our pump. NOW if you have a 10um filter... it will work for a while and then edventually start to cause low pressure and pressure drops. I would check to see if you have the correct filter/strainer inline.



ALSO Rip is right... . the number one reason i see pressure problems is due to isolators or gauges.



Let me know what you find... ... .

 

[GCULP]

thanks Diesel Dan, I am going to check the filter, I don't know exactly which one it is, but it is anodized blue with anodized red ends on it. I has 1/2" inlet and outlet on it, it is larger than. I bought it from Vulcan performance with the HPFP and big line kit. it has a 15 micron cleanable stainless mesh tube element in it.



Hi Flow In-Line Filter

 

[GCULP]

so it appears that cleaning the pre-filter has eliminated the problem, it didn't appear dirty, but a small piece of debris did fall out, I'm glad I went with a cleanable pre-filter and one large enough to handle the volume even with a blockage.

 

[LowFly]

so it appears that cleaning the pre-filter has eliminated the problem, it didn't appear dirty, but a small piece of debris did fall out, I'm glad I went with a cleanable pre-filter and one large enough to handle the volume even with a blockage.

Good to hear... ... glad it was a simple fix... ...

 

[stebbyron]

FASS Low pressure

I also have an apparent pressure loss. Source Automotive looked at it on Friday and they couldn't find anything wrong at that time. The day before the pump would run but no fuel came out of the pressure sending hole in the top of my filter for a bit. Checked the prefilter, clean, hooked it back up and the same symptoms with slow build up of pressure. The pressure slowly builds to around 10 pounds and then jumps to 15-16 and stays there. First thing in the morning when it is cool the pressure jumps to 15-16 when started. It is perplexing at best.

 

[LowFly]

I also have an apparent pressure loss. Source Automotive looked at it on Friday and they couldn't find anything wrong at that time. The day before the pump would run but no fuel came out of the pressure sending hole in the top of my filter for a bit. Checked the prefilter, clean, hooked it back up and the same symptoms with slow build up of pressure. The pressure slowly builds to around 10 pounds and then jumps to 15-16 and stays there. First thing in the morning when it is cool the pressure jumps to 15-16 when started. It is perplexing at best.

Fill in your sig if you don’t mind... that would help me help you.....



I would check the other things that were discussed in this thread and see if that helps.

 

[stebbyron]

I have an 01 Dodge 2500 that is stock except for the HPFP pump and the stock filter. Cleaned and checked the pre-filter correct filter, new filter in the stock housing and a billet filter cap and sensor from Geno's. Pressure is also checked at the Schrader valve. If the water bleed valve is opened when the pump is turned on the pressure jumps to full pressure immediately.

 

[LowFly]

I have an 01 Dodge 2500 that is stock except for the HPFP pump and the stock filter. Cleaned and checked the pre-filter correct filter, new filter in the stock housing and a billet filter cap and sensor from Geno's. Pressure is also checked at the Schrader valve. If the water bleed valve is opened when the pump is turned on the pressure jumps to full pressure immediately.

The thing about the water bleed is weird. That should reduce your pressure if anything.



We need to confirm gauge operation. First thing. Electric, i would check with a manual. IF you have an isolator of any kind, i would by pass it and check pressure.



I would pull out of a bucket of fuel as well and see if the issue still exists.