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Changed the #7 injector and both fuel filters 2008 6.4. WE…

Customer Question
Changed the #7 injector...

Changed the #7 injector and both fuel filters 2008 6.4

Mechanic's Assistant: Is the fuel filter an external one, or is it inside the tank?

WE have followed every possible idea for bleeding the fuel system and just keep having air issues.

Mechanic's Assistant: What is the model of your '08 Ford?

Inside the frame rail and on top

Mechanic's Assistant: Are you fixing your vehicle yourself? What have you tried so far?

We even replace the o-rings on the water separator

Submitted: 4 months ago.Category: Ford
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Customer reply replied 4 months ago
F350
Customer reply replied 4 months ago
We can connect a hose to a custom made banjo bolt with bleeder screw (opposite corner from the schrader port) purge till we get no bubbles, crank for about 5 sec and it will start and idle.... but as soon as we crank..... massive bubbles start under the pulsing of the fuel pump in time with the engine cranking.... while idle the hose is calm.... but still massive bubbles..... if we pinch the hose... truck dies.... if we rev.... the truck dies...The Truck was just purchased with an apparent rod knock which we gambled was an injector.... we drove it on a test drive and drove it home... no issues.... a week later drove it into the garage and started the work.... once is fired after the work the knocking was gone... there was a cheap aftermarket injector installed in #7. This is all I can think of to share right now.
Answered in 44 minutes by:
3/10/2018
Ford Mechanic: Scott W., Ford Technician replied 4 months ago
Scott W.
Scott W., Ford Technician
Category: Ford
Satisfied Customers: 3,604
Experience: 28 yrs. experience as Ford ASE Master Technician. Accolades include being a 2005 Ford PTS Regional Finalist and 2006 ASE Ford National Technician.
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H​ello my name is ***** ***** you have verified air bubbles in the fuel after bleeding, I suspect you have combustion gas entering the fuel system, it could be the copper washer on the injector, the injector, the fuel injector is loose, or injector orings. You can either pull out all injectors and inspect or replace all 8, or you can access the return fuel lines on the front of the heads, install a latex balloons on the return line ports and disable fuel pump, then using a remote starter see if one side of the balloon blows up, if it does, you can then remove one glow plug at a time on that side that is blowing up until you find the cylinder that is the problem, then remove that injector for inspection or replacement.

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Ford Mechanic: Scott W., Ford Technician replied 4 months ago

H​ere is a diagram of the return lines.

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Ford Mechanic: Scott W., Ford Technician replied 4 months ago

You could also install a balloon at #5 with fuel system disabled, and see if it blows up, if it does, you could just start removing glow plugs one at a time until you find the cylinder that doesn't blow up the balloon then inspect or replace that injector.

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Ford Mechanic: Scott W., Ford Technician replied 4 months ago

I​f you have any more questions just ask, all I ask is when you are finished, please take the time to rate my service as this is how I am paid for my time, thanks Scott

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Customer reply replied 4 months ago
How could it be combustion gas when they appear immediately upon the first crank of the starter.... Seriously instantly.... It doesn't start for 5 to 8 seconds after that.
Ford Mechanic: Scott W., Ford Technician replied 4 months ago

You stated massive air bubbles pulsing in time with engine cranking, sounds like combustion gas to me. Have you checked the return lines for bubbles?

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Ford Mechanic: Scott W., Ford Technician replied 4 months ago

C​ombustion gas is what Ford calls it, although the engine hasn't started, so basically it is compressed air, Ford still calls it combustion gas.

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Customer reply replied 4 months ago
I'm understanding.... Cylinder air compressed .... getting into fuel lines through leak in an injector.... Isn't that fuel system pressure like thousands of psi vs hundreds of psi in cylinder compression? I don't see how that's possible....
Ford Mechanic: Scott W., Ford Technician replied 4 months ago

Combustion gas enters past the copper crush washer, the combustion gas enter the return line fuel, then it pushes its way back toward the fuel cooler then to pump. It will get combustion gas and pass from one point to the other and it doesn't take much to stall out. When a injector fires, there is no way combustion will enter the tip, however when there is no pressure it can. 6.0's were real bad, 6.4's not so much, but you definitely have combustion gas if it is pulsing, you just need to find out which cylinder or at least which head.

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Ford Mechanic: Scott W., Ford Technician replied 4 months ago

H​ere is Fords test for combustion gas.

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Customer reply replied 4 months ago
Ok so before I treat this thing apart again... Do you have any literature or formal resource for this combustion gas theory? I've spent the last two hours trying to find a back up source for this issue...I can't
Ford Mechanic: Scott W., Ford Technician replied 4 months ago

I​ gave you all the info I have above, I wish I had a video I could show but I don't, I can only go off what you tell me and from past experience, since you stated it is pulsing air bubbles, it has to be coming from somewhere, and the pulsing is in line with compression. I would at least get down to #5 connection in picture above of the return line and install a balloon and make sure that is where it is coming from, this checks both heads. Then once verified you can start removing glow plugs until the pulsing stops and then go after that cylinder.

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Ford Mechanic: Enes, Volvo Technician replied 4 months ago
Enes
Enes, Volvo Technician
Category: Ford
Satisfied Customers: 5,695
Experience: 18 YEARS WITH VOLVO AS THE MASTER VOLVO MECHANIC&ASE
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the Combustion gas enters past the copper crush washer, combustion gas than enters the return line fuel, then it pushes its way back toward the fuel cooler then to pump the article above you can use sorry some questions cant be answers good thru online but you got idea what to do at last

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