Hard starts, stalls. Surges too

[Stu Bailey]

Back at ya guys with another scenario. Engine cranks over, takes too long to start though. Once it does, it stalls out. Unless I give it plenty of throttle it will die. After a few times I can get her started and she will run but I get a surge of power intermittently, almost always at lower speeds and 2nd gear. Fuel pump? Air intrusion?
I did just replace all new return lines and those are working great, no leaks at all. I did that about 2 weeks ago though and it just started this whole no start and die on me thing yesterday with the surging. Is it possible that with new return lines it over powers the other old lines and fuel parts into malfunction, almost like they couldn't keep up with the new pressure? The truck is an 86 f250, 6.9, c6 with a shift kit and 153,000 miles on her. Almost everything is stock. Truck was babied by previous owner. I've only had to replace the return lines (which were crusty as ****) alternator, belts, neutral safety switch, batteries and filters. Fuel filter is less than 2 months old. Air too. Oh, replaced the voltage regulator other day also. Thanks again amigos

 

[Cubey]

It sounds bad air intrusion, but could also be a weak fuel pump? Any diesel smell from the engine after it stalls?

 

[Stu Bailey]

I'll have to give it a good whiff tomorrow morning when I crank it up. Any thoughts on the location of such bad air intrusion? Return lines should all be sealed up and good to go

 

[david85]

-Was this truck by any chance sitting for a long period of time?

Long time sitting could mean that even with a recent fuel filter, you could be dealing with crud getting knocked loose and clogging the new filter. This is not very likely, but still possible.

-How full is the fuel tank? Does this happen on both tanks?

Pickup tubes are known to fall off in the tank, causing the problems you are describing when the level runs below half.
Another possibility is that the tubes at the top of the sender have pinhole rust that could be allowing air in. Since the fuel is sucked to the engine by the lift pump, a leak at this location may not cause a noticeable fuel drip.

-Fuel lift pump?

Yes, that is a possibility. Have a look at the schrader valve of the fuel filter head. You should be able to get 5 psi at idle. I recently replaced my lift pump and it made a noticeable difference in performance, but mine wasn't having issues as bad as yours.

 

[Thewespaul]

Check and see if the water separator is hooked up, if it hasn’t been bypassed already that may be the source of your air intrusion

 

[Oledirtypearl86]

X2 on water separator you can stick a bolt in the drain hose and put a hose clamp on it If it's bleeding air

 

[Stu Bailey]

I drained the water separator about a month ago and it didn't look like too much water if any in there. That is one of the only things that wasn't stock on the truck. It's a racor filter by parker I believe. It's hooked up and has been since I bought the truck. The truck doesn't sit for longer than a weekend, she is my daily driver. It might be that fuel tank scenario, I recently switch over to the front tank and shortly after is when I got these problems. I'll have to switch back over and see what is going on with the rear tank. Thanks for the advice gents, I'll be back tm with an update I'm sure.

 

[Stu Bailey]

Running the truck from the good tank with the working sending unit to see if the problems are with the lines or sending unit associated with the bad tank...

 

[IDIBRONCO]

You could also try tapping on the FSV with the key on. If it's sticking, this may help. Of course it may not, but it's worth a try.

 

[Slicknik]

Question ? With bad tank , are you under 1/4 tank?

Also those "burts" you refer to are air intrusions in your fuel line, causes more air in the chamber which gives you sudden burst of acceleration.

And if the problem only.happens with the bad tank and not the good tank then your issue is before the tank selector.