As you all know, I Semi Retired and started driving. Older Pete with a 3406E, been slowly losing fuel pressure according to the owner for a few months(Since last service, minimal miles put on it) and I have been paying pretty close attention as it has steadily dropped a pound or two a week on the dash indicator from 65 when I first set foot in it to a low of 52 last week, owner stated it used to keep the gauge pretty well buried with boost on the turbo has also reflected the change down. Yesterday it(whatever is dying) decided to start throwing up hard, would swing in a pull from 52-55 down to low forties and pulsate harsh, then decided to go back to normal fifty-ish, was running reasonable so made my loads then headed to the yard where in transit it dropped and stayed at mid forties, never achieved the 50 mark all the way back. First thought was trash in a filter, maybe water as fuel around here has gone to **** and the owner just picks a cheap location to fill. Got back to the yard and swapped fuel filters, DID fill the replacement, started the engine where it ran an instant got the typical bubbles in the system hack and died. Tried the primer, still fuel firm, showed just less than 30#(dash gauge if I can trust it) after pumping on it a bit and now will crank, no start. Bugged Junkyard last night, he sent me some guidelines from the service manual, went back in the dark, vented the dash ga line, pressure went to zero, cranked engine stayed zero, pumped primer as hard as I wanted and ga read just at thirty and solid again. NOT looking good, I don't get paid mechanics wages and the owner won't pay me that much(has no idea if I am any good or a money pit-his words) so the owner is calling out a mechanic he knows to come look. My bet is stuck a relief in the fuel pump or the return check.
I have had the lift pump go bad on a 3406E although it didn't lose fuel pressure, it was pulling air in somehow and causing it to run rough at certain times.
Whats the fuel look like in the first filter? Any trash? Steel fuel tank on this truck?
'97 Pete 379 and no, aluminum. Fuel from both strainer(Pri) and filter(Sec) was clean minimal water in strainer, little to nothing in FF, just clean fuel. One note, fuel lines appear to be OEM(11 years), still have the PACCAR P/N ID strip tags on them(illegible). May have the one from strainer to pump disintegrating internally. In which case may not be a good day if those and the pump need be changed.
Check the fuel pressure at the top of the main filter housing and remove primer pump and check to see if the check valve has crap in it or partially rolled not seated. Truck Shop
Wish I could, new boss has called the guy he usually calls, outa my hands now. Knows the work from the other guy, does not wish to be prudish but likes him as a wrench. That and I won't mechanic for what I drive for $$.
My opinion is collapsed fuel line[rubber] & what truck shop says.. Be sure & let us know..
Most likely, I will await the outcome as a bystander this time. Will pass on what comes up.
Hopefullyguy does a proper diagnoses and finds the actual problem and not just load up a parts cannon and shoots.
I know you're not doing the job but one thought I just had was to connect a short hose right to the lift pump and stick it a a can of fuel and see if that changes anything. I like to by-pass as much as possible to narrow down where a problem might be.
That was one of my suggestions last night lol. I gave him all my E model tips but boss man overruled us all! Haha.
I am with Truck Shop. Gauge on the filter housing, drive and watch it. Install a clear line and check for air. Then the problem is before or after that point. We all all watching with you.
I have had a lot of transfer pumps slowly die out like that on the 3406E and C15.
Got word from the guy doing the work as owner left my number while he went out of town, two fuel lines from tank to strainer and strainer to pump all is good again Fuel PSI in pull 75+/- pounds and stable. He noted the line from strainer to pump had either an old skive or bubble was lifting internally, he had done as noted run a line to a pail, engine essentially started right up. Could or would pull fuel with the hand pump but as soon as any hard demand would slam shut. Lines were as thought OE, he was amazed that they went this long. Strainer needed seal replaced as he dug the ring out and was brittle, suspects the service shop is not changing that often enough.
So do Junkyard and I get to split the prize for the best troubleshooting suggestion?
My vote is for a Missouri pot holder.. & I do mean a "hot pot" holder.. Lol I don't know WHY I keep suggesting those things..?? Probably because they're cheap & just about everyone uses one.. I know I do.. dam-near every day..
Why yes you fellers do! Truck Shop
So do Junkyard and I get to split the prize for the best troubleshooting suggestion? So where do I send the Fur Lined **** Pot you won to!!!
Send it up to NY he needs it worse than I do!!
How cheap are you and your boss? Ill' help pay postage to send all three of them a fur lined one.