I've Got Issues......

[Petri317]

fuel issues, that is. This morning, while driving to school, it ran great. I was cruising at 2700 RPMs (4:10's) on the freeway. I go to let off of the fuel pedal to exit an offramp and the thing starts surging and bucking. I put it in neutral and coast to the light. It maintained a rough idle (like one injector was not working properly.) Upon accelerating from the light, it was smooth, though a little less powerful(it seemed) between shifts, it kind of stumbles and "hangs" at an rpm or slightly increases rpm while returning to idle. And, while going down the road, if I let off the fuel, it starts bucking and erratically revving. When I get back on the fuel, it smooths out like normal. I've noticed, while revving it in neutral in the driveway, if I quickly rev it real high, it stumbles like it's going to quit, then returns to it's rough idle. I've checked all of the injectors (loosening the lines) and they all appear to be good. The IP is newly rebuilt, and the injectors and return lines are new. There is no leaking or puddling at the injectors or return lines, there is fuel at the filter shraeder valve (The filter/water sep is also new) I will be replacing the return lines next, but am baffled as to why this is happening.

I did finish up reinstalling my transmission yesterday and figure maybe I disturbed the return line from the back of the engine to fuel tank selector valve. But I've had that line leak in the past (replaced it) and not cause problems while running (only starting issues.) And also, it ran fine when I test drove it a good 10 minutes around town last night!This is so frustrating!!! Any suggestions guys?
Thanks in advance,
Peter A.

 

[pafixitman]

Do you use a fuel additive? My experience has been after a tank of not running it, she surges and bucks. Give it a healthy dose of your favorite flavor and see if that helps.

 

[Petri317]

Update: Now its starting to cut out at higher, constant RPM's as well.
Any suggestions, guys?

 

[Petri317]

Yes, it's got power service in there (more than it needs) it was last refueled about a week and a half ago.

 

[Dsl_Dog_Treat]

Kinda sounds like it may getting an air intrusion.
How's the lift pump?
Might check the oil level, hopefully fuel isn't goin into the crankcase.
I see ya refueled it it so the tank is over 1/4 full right.
That'll rule out a bad fuel pickup screen.

hmmmm.

 

[dsblack]

I an thinking about a leak between the fuel filter and the IP, and as the filter gets more clogged, the air leak gets bigger?

 

[Petri317]

Tank is 3/4 full and the lift pump is also new.
I'm going to put a new filter on and see what happens.

 

[deadeyeb]

I had a similar problem with mine at idle the tack pickup would read 0 then come back on after 2000 rpm ran alright but idles like crap . changed pickup and fixed problem, I think had more to do with auto tranny and lockup than anything.

 

[towcat]

I had a similar problem with mine at idle the tack pickup would read 0 then come back on after 2000 rpm ran alright but idles like crap . changed pickup and fixed problem, I think had more to do with auto tranny and lockup than anything.

yours is auto tranny related.
Peter-
time to put a clear line on the return and check for air bubbles.

 

[Diesel JD]

Sounds like air leaks...or perhaps your timing is way off. Additionally, there is some chance you got a bad out of the box rebuilt pump. Rotary pumps are tough critters to build correctly. Or it could just be a bad filter...hope you get it sorted out.

 

[dbarilow]

my first guess would be fuel filter. Since your having high RPM. Sounds like starvation.

 

[OkieGringo]

Check that return line back to the tanks. You might have pinched it closed when you put trans back in. Okiegringo

 

[Petri317]

Timing was just dynamically set. I'm going to troubleshoot it later today. (my day off!!)

 

[Petri317]

Update: Return line to tanks is good, I also replaced the filter to IP line as well as the fuel filter, and nothing fuel related on top of the engine is leaking. One observation; at high rpms, while holding open the shraeder valve, clear fuel flows. at idle/descending rpms, the fuel has a lot of air bubbles in it and is very foamy and semi-inconsistent in flow. I'm thinking possible the line from the tank to lift pump, or the hard line from lift pump to fuel filter bracket may be leaking. Any suggestions/thoughts/comments?

 

[tonkadoctor]

time to put a clear line on the return and check for air bubbles.

You can use the clear line on the inlet line just before the lift pump to check for air intrusion between the tank & pump, place it between the pump and filter to rule out a bad lift pump, place it just after the filter to see if the filter or housing is bad as well as place it in the return lines to see if the return line caps are sucking air and prolly a few other places too... Do it in that order as a process of elimination, doesn't cost much more than time and it will save you that if you ain't shooting in the dark.

Might even try sticking it here too if all else fails ........ Lord I'm sorry bout that there but cha gotta admit that was funny right there.

I would also get a reading of the fuel pressure too.

Good luck