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Daniel Wilson
Daniel Wilson,
Category: Medium and Heavy Trucks
Satisfied Customers: 5558
Experience:  Owner at DJ Wilson
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Have an 07 Freightliner VIN#1FUJALCK57LY17905,,, it decided

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have an 07 Freightliner VIN#1FUJALCK57LY17905,,, it decided one morning not to start, primed system with a 382 fuel processor filter with the clear bowl on top, a little snort of either and it runs but you can see bubbles in bowl as it empties then picksup air and shuts off,, replaced the fuel lines from tanks alll the way to pump (no difference) bypassed filter (no difference) both tanks full of fuel, pick up tubes located 1/4 way up tanks with down turns so no way of sucking air there, replaced return to tank check valve... still nothing.... I pressurize the tanks with air to prime system ,it shows no leaks anywhere
Good evening
Yes we had a truck like this last week and the was a leak on the return side, pressure test that side of the system and see, if ok isolate the leak and test at 40 psi and see if a injector oring is failing, let me know how you do, one last thing some engines have a shut off at the secondary filter make sure it is all the way open.. Ty
Customer: replied 1 month ago.
now the system after the check valve should not matter,,,correct?
Monday I will attempt to check system but I have one question first.... the return line comes out of the head and then goes to a "T", one end is the check valve and the other goes into some type of module,,,, can you tell me what this is for, and should I also isolate that for leaks as well
Good morning
That module is the fuel doser block, never seen that cause a starting issue, it has a device in there that stops fuel going through it (fuel cut off valve), so I would leave it.
Good evening, I see the question is still open Do you have any other questions?
Customer: replied 1 month ago.
we are testing the system now
Customer: replied 1 month ago.
alright, we charged air coming from the fuel water seperator and capped off fuel return check valve, installed a gauge on filter passed the fuel cut off valve with 40 psi... it held for ten minutes,,, put everything back together, left gauge in place,, primed system and cranked motor, can get it to pick up with a little either.. fuel pressure went to 35 psi and truck started to run but then pressure dropped and it seemed to stop sucking fuel,, then picked up again and sucked all the fuel in the water seperator out but would not run...
not sure if this thing can get air locked, do I just need to prime it longer or is it possible my fuel pump is bad
Good morning
If everything checks out, then I would replace, nothing showing on the return side?
Customer: replied 1 month ago.
I did not check past the return check valve, I can't see any leaks and don't think that part of the system would make a difference
Funny I know
But we had a leak at the return fitting at the head, that caused the hard start, curious, did you put a site glass on the inlet side of the fuel pump and see any bubbles?
Customer: replied 1 month ago.
That return check valve is past the is the last thing in line before the hose returning to tank, I believe it also acts as a pressure regulator.... And yes we did replace it..
The fuel water seperator has that clear plastic bowl on top... Yes you can see it bubbling as it sucks the fuel down... We checked that for leaks and even bypassed it.... We did replace all the lines from the tanks and bypassed the T block on top of transmission...both tanks are completely full to eliminate pick up tubes sucking air...
If you can put, the suction and return into a bucket, may have to make up lines to do so..another option before doing fuel pump, just to be sure
Customer: replied 1 month ago.
We put the suction in a bucket...still nothing, replaced pump, truck would run with good pressure until it sucked filter down... Put hose back in bucket truck runs fine, hook it to tanks bypassing filter and it runs for 30 seconds and cuts off, isolated left tank, same thing... isolate right tank and it runs fine at 1000 rpm or better but if drops below that it will eventually choke itself out again... Like I said earlier, we already replaced fuel lines from tank to motor, bypassed the T block on top of transmission...
I could understand why one tank is bad,, but 2!!!???


this is a tough one,wish is was there to see it for myself

i will opt out and see if there are other experts that can help you

Hi my name is***** will be glad to help. So there is absolutely no trouble running this out of a bucket. If that is the case double check the new lines for restrictions in case one has some debris or a rubber flap restricting the hose from the fabrication process. If okay, check the tank vent and your return/supply to be sure none have restrictions or leaks. Try running the fuel lines into the fuel fill of the tanks and see if it will pick up that way confirming the fuel lines are good and there is a problem in the tank pickup tube or a restricted fitting or venting issue. Let me know

Customer: replied 1 month ago.
this is crazy.... when you look in tank there is a crossover line between return an suction tube,,, when we dropped the retun line in a bucket and block off tube, the truck runs fine but the return fuel is fuel of air!!!! it is coming right out the return check valve full of foam.... I'm thinking injector orings or cups,,, but I'm hoping you can tell me some good news

Thanks for the update. If no air on the suction side viewing with a clear hose or sight glass but air on the return it points to injectors, o rings and cups. Is the return fuel turning black with soot? If so it is a sign compression is being forced past the injector and then getting into the return. Id pull the injectors and take a look at the o rings and cup condition. It may be just failed o rings. But is could be a failed injector as well. Have your local injection shop test them. Let me know

Customer: replied 1 month ago.
I don't really have any way to run a sight glass, but if this foamy air was going into the head, it seems to me the motor wouldn't run or at least run poorly

Any clear hose adapted inline will serve as a sight glass from your local hardware store.

Customer: replied 1 month ago.
ok... it may take a day to get this together

That is fine. We can follow up as needed.

Customer: replied 29 days ago.
finally got the clear hose set up.. ran it from the filter to the head,, no bubbles going in,, white frothy foam coming out of return check valve.... before i start pulling injectors, you don't think there is any way fuel doser valve is doing this?

That is a possibility. Try to block that off and recheck for bubbles to confirm.

Customer: replied 29 days ago.
ok... let you know

Pleasure to help. Please remember to return and rate my answers once you are satisfied with the information I provided as tht is how the site credits my time helping on the site. We can still always follow up as needed here.

Daniel Wilson,
Satisfied Customers: 5558
Experience: Owner at DJ Wilson
Daniel Wilson and 3 other Medium and Heavy Trucks Specialists are ready to help you
Customer: replied 29 days ago.
gotcha! thanks

pleasure to help