Fuel Pressure Dropping

[Rub]

I have an '06 with 135k on it. Fuel pump was replaced a couple of years ago (stock). Fuel pressure on Isspro gauge was around 15 stock, and would drop several points when I had the Smarty Jr on and set to performance and got on it. I figured that to be normal. Couple of weeks ago I was going to make a trip from FL to IL towing my 8,000 lb trailer. Got the oil changed and fuel filter changed before I left. Smarty Jr was on tow. Maybe a few hours into the trip I noticed the fuel pressure was down around 5 while cruising on flat land at 72 mph. Normally would be up over 10 in this situation. Kept an eye on it and it slowly crept down even lower. On slight grades it would bottom out at 0 then would come back up a few points when I leveled off again. No noticeable power loss, however I was a lot easier on the pedal than usual. It eventually put out a code - can't remember the number but it was about low fuel pressure according to the Smarty Jr when I checked it. I cleared it and it never came back. I was a little lighter on the go pedal.



So now my pressure still reads around 5, and still dips down to about nothing if I get on it with the SJ set to performance. With no SJ it still is around 5 but doesn't dip as much when I get on it. Can someone tell me what's likely happening? The fuel pump was replaced a couple of years ago which is when it began showing 15 for pressure. It stayed in that range until this latest trip. Am I hurting anything? I hate to go to the dealer blind about this. Thanks in advance for any help.



Rub

Florida

 

[cerberusiam]

Before you start looking for parts check the fuel pressure with a manual gauge to validate it.

If you have the ISSPRO EV2 gauge with the electronic sender it could just be a bad sender. Mounting location is critical with the electronic senders as they do not like vibration.

I am surpirsed at the pressure. Normally 7-10 psi is what the in-tank pumps show at an idle and usually you can run 60-70 HP and still keep them around 5 psi under a full load. Just cruising it should stay at 7-9 psi.

 

[Rub]

Pretty sure it's a mechanical gauge, tapped into the bottom of the fuel filter housing.

 

[AH64ID]

I agree with cerberusiam, that 15 psi is a bit higher than you should be seeing from a stock pump. I would verify the accuracy of the gauge with another.

 

[Rub]

I'll see if I can do that. The 15 psi started immediately after I had to have the fuel pump replaced and was like that 2-3 years until the fuel filter was changed. Almost like something happened during the filter change...

 

[AH64ID]

2-3 years might be a big long on the filter change, but that still shouldn't have a bearing on the pressure reading.

If the sender is on the filter outlet is there a chance something got dropped into the pressure "T"?