Air Intrusion ..... Stumped!

[chillman88]

I have a 6.9 but haven't run into a water separator yet.
Thanks for the clarification on the coffee can.

Yeah I wasn't completely sure. I do know 87 was a transition year I just don't know what all changed for sure. Do you have a water drain on the bottom of your fuel filter? If you do you likely won't have a separator on the firewall unless the filter was swapped.

 

[Brian VT]

Nope. Fuel filter looks the same as an oil filter.
But now I at least know where the water separator would be, if I have one. On the driver's fender.
Can I get a fuel filter for mine that has a water drain? My boat's fuel filter claims to also be a water separator but it has no drain.
Sorry to the OP for getting off track. But it might not be? ;-)

I have heard mentioned here that over-tightening the fuel filter can cause the sealing gasket to deform and allow air intrusion? A simple and cheap source to consider.

 

[Jesus Freak]

I have a 6.9 but haven't run into a water separator yet.
Thanks for the clarification on the coffee can.

I think most of them have been removed. It's not on the fender it's on the firewall beside the brake booster.

 

[Brian VT]

Gotcha. Thanks again.

 

[Austin86250]

That's a vacuum canister/reservoir.

The water separator was only on the 6.9 trucks I believe. On the 7.3 it's integrated into the fuel filter.

Yes the 6.9 specifically 83-86 the 87 6.9 had the 7.3 style fuel water sep

 

[SkylabTech86IDI]

That's a vacuum canister/reservoir.

The water separator was only on the 6.9 trucks I believe. On the 7.3 it's integrated into the fuel filter.

I have one of those coffee cans on my truck that’s rusted a large hole. I admit I haven’t traced the vacuum lines to see where they go.

What the heck does this vacuum canister do, anyways? I thought diesels didn’t produce vacuum (due to a lack of throttle plate)

 

[chillman88]

I have one of those coffee cans on my truck that’s rusted a large hole. I admit I haven’t traced the vacuum lines to see where they go.

What the heck does this vacuum canister do, anyways? I thought diesels didn’t produce vacuum (due to a lack of throttle plate)

They don't. That's what the vacuum pump under the alternator is for. Provides vacuum for the brake booster, HVAC controls, cruise control, and in your case the modulator valve for the C6 automatic transmission.

That vacuum reservoir is most likely for the cruise control, but I'm not certain. Hoses are too small to make much difference in the braking system.

 

[Jesus Freak]

I have one of those coffee cans on my truck that’s rusted a large hole. I admit I haven’t traced the vacuum lines to see where they go.

What the heck does this vacuum canister do, anyways? I thought diesels didn’t produce vacuum (due to a lack of throttle plate)

The vacuum canister helps hold an extra volume of vacuum produced by your vacuum pump (the thingy that the little belt off your alternator goes to) so your brake booster can help you stop.

 

[ROCK HARVEY]

Did you replace all the olives in the steel lines? Mine were so hard and crumbly I couldn’t believe they used to be rubber.

 

[captain720]

Yes the 6.9 specifically 83-86 the 87 6.9 had the 7.3 style fuel water sep

The 1987 6.9 that I own has the firewall mounted water seperator.

 

[franklin2]

I'll bleed off the air out the fuel head schrader valve and after I keep cranking It'll finely start.

Once I get it started and come back a couple of hours later it'll start right up.

Now, when I let sit over night it will not start even after bleeding the head off again.

So now in the mean time I've got the batteries charging. I'll go out later this evening to try again.

If you want to experiment, after you get the truck going and are ready to park it overnight, you can pinch off the return that that runs down the back of the engine. Then see if it still has air in it the next morning.

If it still has air, the next move would be to pinch off the rubber line that goes to the fuel pump. See what that does. Just see if you can figure out what path the fuel is taking when it leaves. And for sure you still have a air leak somewhere. The fuel can't leave without the air coming in and taking it's place.

I have said before this fuel system is just like taking the straw in your drink, putting your thumb over the top of the straw and then drawing the straw full of drink out of the glass. As long as you keep your thumb over the straw, the drink is going to stay in it. That is the way these fuel systems work. As long as the fuel system on top of the engine is sealed, the fuel will just hang there in the lines in the top of the engine.

 

[Jesus Freak]

If you want to experiment, after you get the truck going and are ready to park it overnight, you can pinch off the return that that runs down the back of the engine. Then see if it still has air in it the next morning.

If it still has air, the next move would be to pinch off the rubber line that goes to the fuel pump. See what that does. Just see if you can figure out what path the fuel is taking when it leaves. And for sure you still have a air leak somewhere. The fuel can't leave without the air coming in and taking it's place.

I have said before this fuel system is just like taking the straw in your drink, putting your thumb over the top of the straw and then drawing the straw full of drink out of the glass. As long as you keep your thumb over the straw, the drink is going to stay in it. That is the way these fuel systems work. As long as the fuel system on top of the engine is sealed, the fuel will just hang there in the lines in the top of the engine.

My concern with this experiment is that after you pinch the ancient rubber line it might not unpinch. So even if you decide it wasn't the issue, you have a NEW issue.

 

[jax1463]

Update. I changed out my fuel filter and cleaned my inline fuel filter.
Got it running better, but still a little hard to start in the morning. I think it is definitely drain back from the fuel pump.
I'm thinking about going to an electric fuel pump. Thanks for all of your guys input!