84 f250 6.9 starting problems
 

I have an 84 f250 with the 6.9 that i am using for a pulling truck. My grandpa got it cheap at an auction and it was a purdue campus truck so we know none of its history. When he first got it he couldnt get it to run unless he bypassed the water seperator but once it was bypassed it ran good. Then it sat for about 1 yr and then we've had problems since. I beleive it is getting air in the lines somewhere but not sure because i can't get it started unless i bleed some air off of the schrader valve on the fuel filter. But once it starts it runs pretty good except about every 5 min it will cut out almost like a backfire but still idle good, it does that consistently at idle. Sometimes if you rev it up or hold the rpms up and then let off whenn it drops back to idle it will hesitate and be rough for a second then smooth out. Also when its running i will press the schrader valve bleeding the rest of the air off and almost immediatley after that i will try it again and there is air right back in the fuel filter. As long as the truck doesnt sit for a while it will still fire right back up , but if it sits i have to do that all over again. I know starting fluid isnt good but every now and then when i give it a little shot to start it'll fire right up and other times it doesnt help. Any suggestions will be much appreciated because i am no expert on diesels and this is the first i have ever worked on! Please let me know if you need more information as im sure im forgetting something to maybe help you guys out.THANKS!

Glow plug work + fuel line and lift pump inspection :) At the worst IP is bad.

Sounds like you have a pretty big air intrusion somewhere. Have you replaced the return lines on the injectors? They're the rubber lines that run between the injectors with the plastic caps. Also, the factory water separator is known for letting air into the system. Lots of people bypass it or replace it with an aftermarket unit.


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check the fuel lines from the tank to the fuel pump, if you are getting air into filter right after start up, the fuel pump has to be sucking in air, if it was after the pump, it would be pushing fuel out of the lines. also possible the fuel pump is going bad, a new one would be good security on an old truck liket that. I used to have an 86 with a 6.9L and i put an electric pump on it, make it really easy to bleed. just turn the key on and open the schrader valve and it would push the air out until it was just fuel. saved a lot of time, battery and headache.:tu:

I have replaced the return lines along with the o-rings and plastic fittings. The mechanical fuel pump on the block has also just been replaced. The electric fuel pump sounds good because i have to hook the charger up everytime i work on it. Any suggestions on fuel pumps to get and what all would that include, just using the electric pump and bypassing the mechanical one? So if there is air anywhere in the line whether its before or after the filter, that will allow the fuel to drain back to the tank?

I bought an 85 6.9 that the PO had installed an electric fuel pump. I think it was a Holley pump but don't know what model.


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What kind of GPH pump would i need or what psi

I'm not sure. I'll ask my friend who is a mechanic if he would have any idea and let you know what he tells me.


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My friend said Carter makes one that looks just like a cummins pump. He didn't know the part # on it and was really busy at work today so didn't have time to look it up. He also said that these engines flow so little fuel that you don't need to worry about GPH or psi ratings. I'd say just get go to summit racing, jegs, or somewhere similar and pick an electric pump and you'll probably be fine.


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ok thanks for all the help, im working on it today and plan on replacing the fuel lines, hoping to take care of the air problem, we'll find out.