Series 60 Problem

I take it you have a Freightliner, look into the fuel tank and see if there is compression in the return fuel. if it is getting a lot of it it will effect the power output. It could be as simple as a loose injector. Not that it makes a difference you have to pull them all and change the copper washer and the "O" rings.
If it is compression you should have dark residue in the filters. If it is sucking air you will not have the dark residue.
You have a Davco filter, if the leak is before the filter you should be able to see the air coming into the housing. The "O" ring on the fill cap is not leaking is it?

 

the bubbles mean you have a leak in the system. a leak on the suction side may not drip fuel but it sucks in air. if the truck is.old and has the braided fuel lines you may start with replacing them. they swell internally and start deteriorating. they look just fine on theoutside. check all your fittings

 

My 83 seems to be running out of fuel on accel. Seems to run good most of the time through the first few gears, but the longer you stay in the throttle it starts to loose power, no change with new filters. with a scanner on a long hill, boost running 15 psi and loosiing speed with an empty dump. ddec ii flashed at 425. Misses at times and power never seems good. Max psi we got was 20, no smoke at any time. going for a fuel pressure check in the next few days. Sure feels like it's loosing fuel pressure.

 

I've got one of those primary fuel filters with a plexiglass bowl on the bottom. Took it apart recently and found only O-rings sealing the heating element and water level sensor. Reassembled them with red hi-temp silicone, no more air bubbles in the return line.

Maybe your Davco filter needs a good inspection- and resealed O-rings? Maybe the drain valve leaking?

Collapsing fuel lines can cause a fuel starvation problem, or clogged fuel tank vents.

 

There is a fuel pressure regulating valve in the back of the cylinder head that can be faulty this will cause fuel starvation problems in a Detroit

 

Thanks for the heads up. I hope to check the pressure today. Mine is a 93 model not an 83 which would not make any sence. I know there is a orrifice in the return some say to drill out, which I have not done. Opening it up should not help pressure so I didn't touch it. Is the regulator valve in the head or in the line? I don't recall seeing one, but that doesn't mean anything cause I have slept since I had the head off!

 

There is not a preasure regulator the preasure is regulated at the fuel transfer pump. The flow is regulated by the restrictor fitting in the back of the head. There is a check valve to try and stop drain back from the head.

 

Thanks for the replys, I didn't mean to high jack this thread. My friend with the fuel preasure gauge has been busy so no preasure check yet. I am still leaning toward the transfer pump, but guessing only relieves you of cash. Will let y'all know what I find.