83 6.9 idi hesitation and stalling - Ford Powerstroke Diesel Forum
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Old 03-03-2012, 11:16 AM
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83 6.9 idi hesitation and stalling

I'm new to diesel and to these boards, let me start by appologising if there is a more appropriate forum to have posted in.

I recently aqquried a 83 6.9, the truck is really an 83 f250 standard cab with a duelly long bed and duelly rear end. This truck was origionally towing a speed boat and the rear is geared for towing. It's got a 4 speed manuel and two tanks.

I'm new to diesel and to these boards, let me start by apologizing if there is a more appropriate forum to have posted in.

I recently acquired a 83 6.9, the truck is really an 83 f250 standard cab with a dully long bed and dully rear end. This truck was originally towing a speed boat and the rear is geared for towing. It's got a 4 speed manual and two tanks.

Now this truck sat for 6 years but ran great when it was taken off the road (I've driven the truck years ago while it was still driven regularly). As i went to put it back on the road i manged to throw two fresh batteries in and get it started.

Long story short the truck starts and runs but it doesn't run right, sometimes it shuts off on its own, other times it will idle all day but will stall if I blip the throttle. If I gently ease into the throttle and gently let off the throttle the truck wont die but throttle response is extremely laggy.

I started by throwing treatment in the front tank and a few gallons of fresh diesel, I also removed the duel tank selector valve and am only running off the front tank , I thought I could have been drawing air from a faulty valve and never seemed to switch to the rear tank anyhow. I removed it to make the truck easier to diagnose.

The truck still acts the same regardless of my efforts. When I bleed the air from the schrader valve on the fuel filter housing the truck sometimes runs better and sometimes stalls but I don't think I should have to repeatedly bleed the system. While the truck was running halfway decent I pulled the relief (or purge) on the water separator and discovered that it was bone dry.. I removed both the 'in' and the 'out' lines and started the truck and found nothing came out from the line marked 'in'. I also discovered that the line marked 'out' had suction.. none of this seems right to me and I'm hoping someone can shed some light on the situation.

I don't know if I have a clog or if something is wrong with the transfer pump. Where exactly do the separator lines come from? Is it before the fuel pump, is it before the the fuel filter housing? Is it on the return side of the system? If the separator is dry how does the truck still (kind of) run?

Sorry if my questions seem a bit novice I am an experienced mechanic but still new to diesel, I tried doing a google search to see if someone has a diagram of all the fuel lines and where they end up but I've had no luck.

Something tells me I'm not getting enough fuel to the injector pump or I still have a problem somewhere that is introducing air to my system.

A thank you in advance for any help
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Old 03-03-2012, 02:46 PM
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So I found this and if this is in deed how fuel makes it from the tank to the Injectors and back I have no idea how I even get my truck started

there is no evidence that the separator has seen diesel any time since Ive started playing with this truck.. how on earth am I getting the amount of fuel I am ??

the line running out of the separator has a vacuum to it so I assume I'm drawing all my air from the separator (since theres only air and not fuel) but I don't know why there's no fuel whatsoever.. could this point fingers toward a faulty lift pump?
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Old 03-03-2012, 03:02 PM
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The first thing I would do if it really has been sitting for 6 years is to get rid of all the old fuel and put in fresh stuff. Then I would change the fuel filter. I'm thinking that is whats causing most of your problem. Its possible that your getting air in somewhere, so I would get some clear hose and put it between the pump and the filter and see if their is any bubbles in the fuel. A common problem with these IDI's are the return lines, and when they leak the an cause start up issues and other running problems.
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Old 03-03-2012, 04:24 PM
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Return lines from the injectors or the return to the tank? What's the best way to find the leaks? should I spray the lines with soapy water while it's running and look for air bubbles?
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Old 03-03-2012, 04:26 PM
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The return lines from the injectors that go to the tank. Usually when they leak they will leak fuel when running.
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Old 03-03-2012, 05:22 PM
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Gotcha, any idea why I have no fuel getting to my water seperator? It kind of has me concerned.
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Old 03-03-2012, 05:56 PM
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That's why I'm thinking your filter is clogged. Its probably just clogged up with rust and trash. Its the water separator on the bottom of the filter right?
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Old 03-03-2012, 06:23 PM
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No sir, I'm referring to the the water separator on the firewall right in front of the driver seat. It has a ring on the top and two fuel lines comming from underneath the truck somewhere. Then there's a tube running straight down to the ground where it's supposed to piss when you pull the ring to Purge it. And it's not getting fuel at all and I think its supposed to see fuel before the filter housing if that schematic is right
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Old 03-03-2012, 06:40 PM
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Maybe try taking off the IN line and putting some air pressure in the tank and see if you can get anything to come out.
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Old 04-22-2012, 09:40 PM
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So I did blow out the lines and drain both tanks, put fresh fuel in the front tank (since I'm only running off the front right now), replaced all 4 belts, and changed the fuel filter.. The truck runs exactly how it ran 6 years ago. I warmed her up drove her and changed the oil hot. So far 150 flawless miles, I am so happy that's all it took to get this truck road worthy. Tomorrow I'll betaking her to the inspection station the right to napa to get a water separator. The only thing I notice is diesel smell and mist coming from the valley. It looks like a slight leak but I cant for the life of me find where its coming from, I cant see anything wet but the valley pan and the base of the IP.

Is my best bet to add some sort of dye to the fuel or is there a way to pressure test the injector side of the fuel system for leaks with air form the shredder valve on the filter housing?

Thanks for steering me in the right direction and educating me on my six nine!
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