Time for the clear line test?

Discussion in '6.9L IH & 7.3L IDI Diesels' started by OldIron82, Jul 9, 2018.

  1. OldIron82

    OldIron82 Full Access Member

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    Hello all. 3 years later, still starting the 89 7.3 with ether. If you don't put your foot on the throttle, it will stall. Glow plug system works good, new controller ( disabled ) and new Beru ZD9. New stage 1 R&D injectors with new o-rings, new return lines caps and olives, new designed fuel filter with the water drain part of the filter itself, fuel heater deleted tapped and plugged. Now I'm getting very close to installing the 6.9 I've been trying to rebuild for 3 years. I will NOT use ether on that. My thinking is if I can't get Old Faithless 7.3 to start by itself the problem is probably going to continue on the 6.9 if it's fuel related. The injection pump is a junkyard variety of God only knows what condition and is timed by ear. I'm thinking I still got a air leak somewhere. I hope whoever designed this fuel delivery/return system did not work in the aviation field because I think it is one of the most catastrophic multi failure point menagerie I've ever dealt with. Just my opinion.

    It's time to get down and dirty with old faithless here and I think the clear line test is my only option to finally find where I keep getting air in the system. Any thoughts and direction would be immensely appreciated and I'll follow any advice with military precision. I've had enough of this nonsense. No matter how annoying and aggravating it may be I need this never ending problem fixed. Just a note, I will not be getting a new injection pump for this slug. I still need to buy a Rd90 or Bull moose and get a pyro for the 6.9 so absolutely no major purchases will be spent on the n/a 7.3. I'm hoping to get it properly timed asap but that's all. Sorry for the crappy attitude but I'm still heated from this slug letting me sit at my buddy's after a overnight kayak/camping trip. I left my can of ether at my shop. Hooked the plugs back up, held it flat, didn't even try to start and I wasn't killing the batteries or starter ( that would be the 2nd starter fried )

    Thanks
     
  2. nostrokes

    nostrokes Full Access Member

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    I would be suspicious of the junk yard IP. Old pump with new injectors usually is not a good combo. The old pump may not be able to pop the injectors until it gets spinning fast enough.

    Definitely do the clear line test and try ruling out air in the lines or fuel bleed back. May also have a bad lift pump, does you're oil smell like fuel?
     
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  3. OldIron82

    OldIron82 Full Access Member

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    Negative. Oil does not smell like fuel. Lift pump one year old. I will begin the clear line test asap. Thank you for the reply.

    ****NEW THOUGHT****

    This is a 89 F350 cab and chassis truck ( dump ). The rear plastic fuel tank is ready to fall out on the road due to the previous owner using it for his tree service business pulling a wood chipper. The metal shrouds that encased it were packed full of wood chips that never dried out and rotted everything to the point I was afraid to put any fuel in it until I get around to fixing and bombproofing it. The tank has been empty for at least two years...There's no way air could be getting sucked into the fuel system through that tank is there? The fuel selector switch should completely prevent that no??? Oh boy, now I gone and done it. Gonna be hard to get to sleep now with this in my head.

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  4. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    Sometimes the FSV can get "stuck". Maybe it could not completely close off the lines from one tank or another. You could try bypassing it if you want to check this. Also, if your pump is worn, there may be something inside it that allows a little bit of fuel to drain off. It could also be seeping externally allowing air to get inside when the engine's not running.
     
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  5. Agnem

    Agnem Using the Force! Staff Member Supporting Member

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    One important question. When you crank it, does it start, then die, or does it not just start? If it is the former, you have an air leak and clear line makes sense. If it is the later, you probably would be chasing your tail. How does it act when hot and shut down then restarted?
     
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  6. OldIron82

    OldIron82 Full Access Member

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    Cold, it starts then dies IF you dont put your foot heavily into it. I absolutely loathe revving a cold engine even in the heart of summer so it's a delicate balance of keeping her lit but not screaming. Usually half throttle "pumps" until it smoothes out. If you don't throttle it, it will light and immediately stumble out. After she's warm she'll run flawless all day long and restart no matter how hot the weather gets. Last Monday here in NEPA it was almost 100° with heat index in the 110's. Started no problem when hot. Let her sit over night, forget it. You'll crank until you burn the starter or the batteries weaken ( using glow plugs ). Give it a baby breath of crack she'll light but once again, only pumping it to keep her running. Interesting tid-bit I found out; If I park the truck at my mom and dad's house with a 500 foot long driveway on one hell of a steep hill, I can light the glow plugs and roll it down the hill and let the clutch out and she'll light. I simply cannot get a successful start with just the glow plugs and starter.

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  7. Agnem

    Agnem Using the Force! Staff Member Supporting Member

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    Does sound then like air intrusion. Confirm by checking the fuel filter before you try starting it for the first time next day. If you unscrew the filter, and no fuel spills out, you have a return line leak.
     
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  8. OldIron82

    OldIron82 Full Access Member

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    Will do! Truck has sat for 3 days so it should be a good test if air is leaking in.

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