Hi Everyone,

Looking for some guidance. 2003 early model F350 with low miles. On a recent trip with the camper I started getting some fuel pressure readings that concerned me. I've installed the blue spring mod a few years ago. Since then it runs a steady 60-65 psi under normal weather conditions. Maybe a couple pounds lower in very hot weather and maybe up around 67 when it's very cold (winter morning). No problems starting, running, or towing. About 1000 miles ago while towing down and back to Virginia I noticed the fuel pressure very slowly dropping as the tank level went down. At first it would drop a couple of PSI during hill climbing then bounce back, but slowly the average seemed to creep down. Below 3/8 of tank level, I was down in the 55 range with wider swings. Stopping the truck and refilling the tank brings it back to 60+. On the last day, it was swinging down almost 10 PSI and flirting with 50 during the hill climbs.

At first I thought it was the difference between hot fuel and cold fuel, since I was driving all day and sure gets hot under the chassis of these truck. Then I noticed it happened sooner after each fill-up. So, then I wondered if it was the filters clogging up. The filters were brand new about 3000 miles ago (Racor OEM fuel filters). So, I opened up the secondary filter housing and found nothing but clean diesel and no dirt on that filter. Then, I drained the HFCM and got out a few bits of rust and clean diesel, no water. I guess I should pull out that filter also but I saw no indication the fuel was dirty.

Has this happened to anyone else and if so, what was your experience? Could this be debris clogging the pickup in the tank, a fuel pump on it's way out, or something else I don't know about? The truck does sit in the driveway a lot, it's my weekend ride. I try to keep the tank filled to minimize condensation space, but I've never removed it or inspected it inside.

Any advice you have I would welcome.

Thanks

 

If everything else is good to go (FICM, BAtts, IPR, ICP etc) then you may have a problem with your pump providing good fuel pressure dynamically. Statically KOEO pressure might be good but going down the road your pump may have a problem under load. Since the pump is gravity fed and it has to draw it from the tank that may account for the less psi produced when the tank is lower. Fuller tank the pump works less. Food for thought.
However if the lowest you get is 50 PSI that should still be good unless you are having other problems related to the fuel pressure.

 

That's good to know, thanks. Yes, all the other items seem to be OK at the moment.