Bad lift pump?

[JBournes]

Ok here is the problem, i just put in my injectors and turned my starwheel a bit. But now sometimes the truck acts like it is starving for fuel. it looses rpms and runs really ruff. if i step on the accelerator it will run just fine until i let off again, and then after doing this a couple of times it will run just fine. Has anyone had this problem. Im thinkin maybe it is the lift pump and ist just not sending enough fuel at idle but when i step on the acc. it pumps enough, Any ideas. I just hope its not the injection pump, but if it is i guess it will be a great time to get the timing checked and advanced a bit, and i also remembered i had to get fuel at a place i dont usually get fuel so i am going to change my fuel filter and put half and half with additive to see if maybe i just got some bad fuel.

JEB

 

[BushWakr - RIP]

Jeb,



Are you sure you bled all the air out of the lines after putting in the injectors??

You may also want to check the fueling "pin" inside the AFC cover and make sure it is moving freely.



You'll need to connect a pressure gauge to see if your lift pump is bad though... . it should be providing about 7-9psi according to the "book"...



Bob

 

[jbolt]

Bob- wasn't there something posted awhile back about having the injector lines slightly misaligned with the top of the injector causing this kind of problem?



Jay

 

[BushWakr - RIP]

Jay, GOOD CATCH... . right on the money... . In fact it happend on my truck during the install of POD's.

I had a terrible stumble at idle, and any throttle at all pretty near killed the engine...

It turned out that ALL that was needed was to line up the fuel line exactly flush with the injector top, and while holding in place, tighten up the nut..... fixed, no more problem. . really bizarre considering we're talking a couple thous. in terms of "angle" difference...



Bob.

 

[JBournes]

OK

ALRIGHT here is the deal, it doesnt run ruff all the time just will start all of the sudden, doesnt matter if it hot or cold, and if i do step on the gas it smoothes right out, i bleed any air out of the system from the low pressure bleed, and that didnt change anything, but i did notice that when i put my injectors in that i had forgot to put the manual lift handle on my lift pump back in the up position and i have driven it about 500 miles since the replacement, so im thinking that the lift pump may have gone bad when it wasnt in the right position, what do you guys think, plus its probably the cheapest thing to replace to start chasing this thing down, any ideas???



JEB

 

[BushWakr - RIP]

JB,



The 'manual' does say that damage "could result" from leaving the lever down..... Is there any way you can run it for day or two with a pressure gauge in place before you toss some $$$ at it. . ??

You'd think that if the pump was bad, it would be rough all the time, not just intermittently though...



Guys !! any other ideas here... . ???



Our Lady of Acceleration moves in mysterious ways, to the confusion of mere mortal man..... Wooow ... . deep...



Bob.

 

[JBournes]

A LITTLE MORE

Ok just for fun i went and turned my fuel screw on the back of the pump in some more about half a turn, when i did this the engine was surging, it didnt drop in idle but it would surge, i looked in my manual and im thinkin more and more that it is the pump, what do you think bob, the only thing is that im still getting 20 mpg and it drives great besides the fact that it just starts dropping in idle and running really ruff every once and a while, its just agravating as all @%*$%#!$, well does anyone have any other ideas or try this?





JEB

 

[dpuckett]

Jeb,

When you say running rough, is it like it is cutting out, or more of a lope-miss? How much throttle to even it out? I had the lope miss thing in Mom's 92, and that is the thread that JLeonard and BushWakr referred to. It sounds to me like a lift pump, but... WHere did your injectors come from? Was it a reputable place such as PDR, that will balance and match them as a set? If they arent matched and balanced, with the higher flow, it could cause problems. With you leaving the lever down (25 hp penalty), it could have broken something inside the pump. not sure exactly what it is, but it prevents the pump from pumping. I guess one of the linkages. Know a guy who did that, and had to get a new pump.



Check your return lines for leaks or kinks. Check the hose feeding to the Lift pump for age related problems- cracks, dry rot, etc. What did you torque your injectors to? What washers did you use? THat could play a small part as well, and combined with the lift pump..... I wouldnt think adjusting the starwheel would have any effect- it only affects the rate of fuel delivery increase. I'm just taking shots in the dark- most of the problems associated with these faults will show a decrease in mpgs- and you are still getting the same, right? Or is it down to 20 from 22?

Good luck. anyone else?

Daniel