Ive got a rough idle symtom that has popped up in the past week. Problem is: Start truck(good), idles for .5-2 sec. ,then idle gets rough for 1-2 sec., then clears up and its fine from then on. Problem gets worse the longer it sits. Warm start its not realy noticable. I think 1-2 hours will show a little spudder. Up hill,flat , down hill. Dosent seem to matter. Most starts are on flat ground. No fuel on ground, no visable leaks, none around fuel heater(suspect).
This happened last winter and stopped a long time ago in the spring i guess. Never found the problem.

Trucks got larry's fuel lines. Fuel filter in spec with milage. New overflow(7/04). Fuel leak on top of tank, but dont think its suspect because the air in the fuel is close to the motor. (just after start-up).

Fuel heater is not wired from the factory.

Were should i start checking for problems? Thanks-Jake

 

The hardest leak to spot is where the bolt down tab is welded onto the steel lines on top of the bell housing. About all you can do is feel for it. Somewhat common place to leak after the tubing has been bent around wrestling with installing a new hose. If you find a leak just run hose all the way from the tank to the engine.

 

Update- Today, same exact driving i did yesterday, drive to work and drive home. Except today i had no spudder at all what so ever??? Yesterday it spuddered real good on both start-ups. Weird?

 

Is your starting problem most prominent under 1/2 tank of fuel? If so the pick=up tube sometimes gets a hole rubbed thru by a screw in the pick up assy or it just falls apart in the tank. If you have a leak on top of the tank, fix it first. If it is on the supply side it will let in a little air all the time, the lower the fuel the more air gets in due to more lift, then when it sets a while the air accumalates in the top of the filter and goes into the pump in a big slug causing a rough idle for a bit. Also the little bit of air going thru the inj pump continuously will cause excessive wear on the internals and pound out the injector seats over a period of time.

 

update- Started perfect this morning. Started this evening and almost cut-off 1.5sec after clean start-up. Was parked on a very very slight incline at work exactly like yesterday, but didnt happen yesterday. It just seems odd that its not realy consistant. I dunno. Trying to plan my attack. Does it still seem like my fuel lines are the problem? Thanks alot -Jake

 

Have you serviced the primary(lift) pump and fuel screen recently?

 

Im kinda having the same problem, I just replaced the fuel lines and it was fine for a cpl days then bam, hard starting and a very bad miss with lots of smoke. but if i put on 20 miles then it quits till next day start up Plus ive stated that my fuel lines are both 5/16 instead of 5/16 3/8 like on one of the other posts. thats why I just didnt go get the line kit that someone posted a link to.

 

I had the same problem , changered out all the fuel lines , the longer it sat the harded it was to start. I found out that the lift pump has check valves in it , and that was the problem the fuel was bleeding back to the tank , changed it out , every thing back to normal hope this helps
jman

 

I have not serviced the screen or lift pump. What does lift pump service involve?

Update- Very hard stumbling today after start-up. Even after shutting the truck off and restarting 5 min later, it stumbles lightly after start-up. Also, when cold, taking off from a stopsign and turning, half-way or just after the turn, it will stumble for 1-2 sec.

Note: About 4 months ago i noticed my tank was "moist" with fuel under the sending unit, coming from the top.

Thanks fellas- Jake

 

That "moist" area on your tank might be a good place to start looking. Find the leak and fix it first. Might save you a lot of time and money.

 

The lift pump isn't serviceable, only thing you can do is replace it.
Doesn't sound like your problem though, you have a leak.