air intrusion or what??!!

[jocephus30]

Just today the old girl started giving me a hard time. About 45-60 shes starting to surge short bursts of crazy acceleration then calms down. But the wierd thing is after then its almost like thes not getting fuel she right after the surge then shes still running and starts to coast even putting my foot to the floor she still looses speed for almost 5 seconds or so then she will start to run right until she surges again. If it is air intrusion its not near as bad as when my return line cap was out and she wouldnt even start right, she will start fine idle fine no surging or wierd running until I am at 45-60 for any lenght of time then she will start the surging then dying. So my question is is this just air intrusion and if so besides the return lines where are other likely places I am getting air and will I see wet fuel at that spot? If it sounds like something different please let me know use this truck for work and cant afford to have her down. One more thing is I usually drive her nice and easy never ******* throttle but a couple days ago at work while cutting down some trees she almost got stuck in field and really had to lay into her for about 100 yards to get her out of mud if that may have anything to do with it let me know. Incase my specs are not in sig line its 1986 6.9 crew cab dually 4x4 auto. Thanks in advance for any help.

 

[gandalf]

How old is the injection pump on your engine? The surging sounds about like the classic signs of a worn out IP.

If the IP has over about 100,000 to 150,000 miles, it might well need replacing.

If you have a high mileage IP, ask here for instructions on how to clean it to MAYBE give it just a bit more life while you find a new one. Be careful on buying a new IP. Before you lay your hard earned cash down, be sure to read The Hall of Shame thread at the top of this portion of the forum. There are some IP dealers you want to avoid like the plague.

 

[IDIoit]

or what.
youre running out of fuel.
so its either the lift pump is done.
you have a clogged fuel line
or youre simply out of fuel.
could be a broken pick up.

 

[jocephus30]

I was worried about injection pump not sure on mileage she had motor replaced turbo rebuilt and transfercase rebuilt about 20,000 miles ago but one thing missing off the invoice was a new injection pump she has about 285,000 total miles are on her now and no idea at all when IP was last replaced. On the running out of fuel running off rear 19 ga tank has about 12 gallons of fuel in it. But if lift pump could be causing this then obviously that would be a whole let better then pump. one more fact maybe sitting so long could have caused problems the 16000 miles on those replaced parts before i bought it but that was from 2001 when new motor and such and 2013 sat for long time and just recently sat for year and half but here lately I have a job I have to use her for and but more miles on her in last couple weeks then have the 6 months prior. Could her sitting for so long have anything to do with this problem.

 

[icanfixall]

Most fuel tanks will not suck out the last 1/4 tank because the suction shower head breaks off. so the gauge tells you there is 1/4 tank left but you run out of fuel. Rerpair is a simple add 4 inches of 3/8 hose to the suction line in the tanks.

 

[jocephus30]

ok I was planning on redoing the rear tank anyways hope that does the trick

 

[Kevin 007]

Sounds like heavy air intrusion to me. And that was my main symptom with my last two intrusion issues.