Bleeding Air From Fuel System

[spruce_capital]

I'm sure this may sound simple to most, but would someone mind telling me the proper way to remove the air from the fuel system after changing a fuel filter.
'87 Ford 6.9L engine.

Thank you for any responses.

 

[Mr_Roboto]

You fill the filter with clean fuel and then hold the throttle down to keep it running till the air clears out.

Assuming you have already tried to start the truck and let the IP get air locked, you will need to bleed air at the schraeder valve on the filter housing, and possibly at each injector line at the injectors.

 

[towcat]

press down on the schrader valve at the fuel filter mount as your'e cranking the motor.
btw. welcome to the site.

 

[forcefed]

like said above> Always helps to have an buddy to hold valve in as you crank. Do not crank more than 20 secs at a time or you will burn your starter up. If that doesn't work start cracking loose the injector lines at each injector. I never had to do this but I was told from this site to fill my filter with power service before installing and its worked great for me everytime. Good luck

 

[spruce_capital]

You fill the filter with clean fuel and then hold the throttle down to keep it running till the air clears out.

Assuming you have already tried to start the truck and let the IP get air locked, you will need to bleed air at the schraeder valve on the filter housing, and possibly at each injector line at the injectors.

Thanks to all three of you for your replies. May I run something by you. That being, the engine starts but not right away, by that I mean it needs to go around a few times before it fires.

I believe that you are right, in that, I didn't bleed it properly after changing the fuel filter, 'cause it used to start better before I changed the filter. 8 -(

I'm assuming IP = Injector Pump, correct?

From what I gather now, I will probably need to crack the injectors, one at a time to resolve my problem?

 

[MIDNIGHT RIDER]

Thanks to all three of you for your replies. May I run something by you. That being, the engine starts but not right away, by that I mean it needs to go around a few times before it fires.

I believe that you are right, in that, I didn't bleed it properly after changing the fuel filter, 'cause it used to start better before I changed the filter. 8 -(

I'm assuming IP = Injector Pump, correct?

From what I gather now, I will probably need to crack the injectors, one at a time to resolve my problem?

If I read right, you have already been starting/running the engine since the filter swap, right ??


These old engines always have self-bled themselves; in fact, the old 6.9s are about the easiest self-bleeders out there.


As soon as the engine fires and runs a few seconds, NO MORE AIR is in there to be bled out, UNLESS you have an air-intrusion, which in that case, if it sits for a couple days, the fuel will drain back on account of the air-leak, and then it will be hard to start all over again.


I have ran my old 6.9 completely dry of fuel, on a number of occassions when maybe I forgot to switch tanks; I never ever had to crack any lines or mess with the Schraeder; in fact, the Schraeder has never been messed with since 1985.

Ten to twenty seconds of cranking and away she goes.

 

[Diesel JD]

I believe that if you got it up and running without stalling you probably have gotten past the bulk of the air problems. You could have an air leak making ita bit harder to start otherwise something else in there is fouled up.
JD

 

[spruce_capital]

If I read right, you have already been starting/running the engine since the filter swap, right ??


These old engines always have self-bled themselves; in fact, the old 6.9s are about the easiest self-bleeders out there.


As soon as the engine fires and runs a few seconds, NO MORE AIR is in there to be bled out, UNLESS you have an air-intrusion, which in that case, if it sits for a couple days, the fuel will drain back on account of the air-leak, and then it will be hard to start all over again.


I have ran my old 6.9 completely dry of fuel, on a number of occassions when maybe I forgot to switch tanks; I never ever had to crack any lines or mess with the Schraeder; in fact, the Schraeder has never been messed with since 1985.

Ten to twenty seconds of cranking and away she goes.

Okay, the light is starting to get a little brighter and I think I'm getting on the same page as you. I think what may be my problem, is what you call an air-intrusion. It will normally start, but it just seems that it is going around a lot longer than what it used to, before it finally fires, after sitting for a while.

 

[Diesel JD]

Air leaks are an all too common occurence when you mess with this el cheapo fuel system. Make sure all your fittings are tight and none of the returns are weepy. Heck you may never find the culprit, it might just go away on its own or continue to aggravate you for awhile. I doubt that its anything serious or anything that will keep you from enjoying the truck.

 

[spruce_capital]

Air leaks are an all too common occurence when you mess with this el cheapo fuel system. Make sure all your fittings are tight and none of the returns are weepy. Heck you may never find the culprit, it might just go away on its own or continue to aggravate you for awhile. I doubt that its anything serious or anything that will keep you from enjoying the truck.

Thanks again for the info. It's still around -12C here, so I'll wait for a nice sunny day before I go poking around under the hood.

It has to start warming up sometime soon!

 

[spruce_capital]

Well since this post I've had my truck in to the fuel injection shop and had the return lines and O rings and such from the injectors replaced and also the lift pump. At that time I was told that my starter was drawing double what it should, so I changed it.

My dilema now is that it starts and runs for a minute and then dies (temp -26C). It will eventually start again after that but might take a couple times of cranking (don't want to crank too long) and then it will slowly start to fire and eventually runs normally. If I rev it up to about 1500 rpm once it starts, it will go through a spurt of dying but recover and after a couple minutes of that I can let it idle without fear of it dying. Once it is warmed up it runs quite well, but say after a day at work (-12C) it again will start and then surge for a while and before it dies completly I'll rev it up for a bit and then it's okay.

Would any of you kind souls have any ideas on this?

 

[icanfixall]

You are still having an air leak. What happens is just as soon as you shut down the running motor air starts to get drawn into the fuel system. Then when you try a restart you run ruff or its hard to start. Try checking the lines from the tank all the way up to the fuel filter. If you see any damp or wet spots thats where the aor leak is. The mechanical lift pump is famous for leaks. Mine was wet for a long time and hard to start. I changed it for the Holley Red electric pump. Now I have positive fuel pressure just as soon as I turn on the key. Is the motor oil thin and smell like diesel fuel? If it does you have a leaky pump diaphram on the pump. Change the pump soon. Other than this I'm out of ideas. Others will be along with other ideas. Its best to find the leak first instead of throwing parts at it hoping to fix it. Post back here for help anytime.

 

[LCAM-01XA]

Definitely sounds like an air intrusion at or before the fuel filter - your trucks lights off on the fuel that's inside the IP, but then the air hits it and it dies, you cranking it again purges the air and eventually it fires up again for good. Like Gary suggested, look for wet spots anywhere along the fuel lines, start from the fuel filter and work your way down to the lift pump then back to the tank selector valve, pay special attention to the steel line on the inside of the driver-side frame rail.

 

[spruce_capital]

Definitely sounds like an air intrusion at or before the fuel filter - your trucks lights off on the fuel that's inside the IP, but then the air hits it and it dies, you cranking it again purges the air and eventually it fires up again for good. Like Gary suggested, look for wet spots anywhere along the fuel lines, start from the fuel filter and work your way down to the lift pump then back to the tank selector valve, pay special attention to the steel line on the inside of the driver-side frame rail.

Thanks to yourself and icanfixall for your replies and info on this. I will have a look see when it warms up a bit more. Right now I've got it parked on a level spot and the temp has warmed up to -9C overnight and it is starting okay. Before this it was in the driveway, which is sloped, with the tanks to the rear. I don't know if this had anything to do with it or not?
Can you tell me if the fuel flow is from the tank selector to the factory water separator and then to the lift pump and then fuel filter?

Thanks

 

[EMD_DRIVER]

Can you tell me if the fuel flow is from the tank selector to the factory water separator and then to the lift pump and then fuel filter?

Thanks

That's exactly how the routing goes. My 87 also has the water separator, that is below the brake booster. These are notorious for air intrusion. If finances and outside temperature allow, you would be well-advised to get rid of it and install an aftermarket water separator.