some days good-some not so good

[hdm48]

OK, here's one for you. Why is it that some days my truck will make 28# boost and some days 25#? Some times in the same day he boost will vary. I know the temp didn't change very much and the barometric pressure didn't go up/down much either.

I don't know, maybe the earths magnetic field changed or the planets and stars shifted.

The so-called local experts say it's normal with the VE pumps. There has got to be more to this.



Anyone???



thanks --dave--

 

[R.E. Miller]

hdm48, I hear you!

We have three of these trucks, and they all seem the same. The injection pumps seem to perform differently everyday, maybe not every day, but some good some not too good. Small differences for sure, and I do not see boost differences, but it is acceleration that goes from great to sluggish :-{}. Oh well



Russell

 

[KEENO]

Funny That You Boys Have Mentioned this... .



My truck also exhibits many of these same tendancies! I had the injector pump rebuilt & enhanced by JRE 2 years ago and now I'm starting to get 'variable' performance & useable powerband width.



At fist I thought it might just be the operation & advance of the KSB and cooler weather. I also thought my timing might have slipped from it's 1. 35mm setting. I now believe it's back in the pump after checking a few things (air filter/fuel filter/valve adjustment).



How about it Power Wagon (or others)... . any insight on this concern?



KEENO

 

[ERMiles]

Me, too !

I've enjoyed this feature since I've had the truck (40K mi. ) I always figured it was like me - good days and bad days. I do notice big differences on wet days like this morning when there was a fine rain coming down. I think it's like having a mist injector - more power and smoother running. There don't seem to be any temperature correlations. Sometimes it runs smoother when it's not fully warmed up. I'm going to have the timing checked. But, bottom line, I look at it as a part of the truck's personality!

 

[NeedMoPower]

I also have to chime in on this one. I never said anything because I figured it was just me and I didnt want to look like a fool. It seems like my truck runs better whens it fair weather... . 65-85 degrees. I'm often left wondering why it runs better at certain times and certain temperatures. Maybe it's the humidity?

Cody

 

[KEENO]

With mine... . I can drive it and it's awesome! Killer power & black smoke and then shut it off for a few minutes and it becomes a "Kitty Kat" when started again! Same day & weather.



What gives? The differences in smoke output lead me to believe it's the internal workings of the VE Pump. Sure don't want to have to buy another one of those!



KEENO

 

[JFitzgerald]

Me too!

Haven't tied it to weather or anything. Some days it seems strong, others not so strong.

 

[ERMiles]

This is a mystery !!!

I wonder if there are any 1st genners that don't have this quirk?

I, too, have noticed times when I'll be idling for a few minutes and she'll go like a bandit or I'll shut her down and restart after a few minutes and notice a difference. I even notice it in idle - sometimes it's smooth and quiet and sometimes it's rough. Could it be something sticking in the pump? I haven't gotten into it except to adjust the idle and fuel screws.

 

[KEENO]

When my last pump failed it was because the horizontal pin that rides on the eccentric "Fuel Rate Delivery Pin" (under the AFC diaphragm) had become stuck. I wonder if this pin needs lubrication as maintenance on occasion or it causes inconsistant performance???



What kind of grease does Cummins recommend? I asked this question before but no definite answer was given.



Just my sporadic thoughts... .



KEENO

 

[bflood]

I gotta say ditto. I've seen variations from one day to another from 24 to 27# boost. I thought it was stronger on crisp mornings and rainy days but thats very unscientific. Anyway, it was enough for me to notice and be curious.



I don't have any answers but I'm glad you brought it up hdm48. Maybe someone knows?

 

[ERMiles]

Russell;

Could you go into what you did to free the sticking Fuel Delivery pin?

What's involved in taking that area of the pump apart? What you say about fuel use is ringing a bell with me - my mileage has been running around 14-15 mpg. and I have the "good day - bad day" behavior.

 

[R.E. Miller]

Smiles,

I do not know how to free the pin, but apparently it can be done. I know that I read that info here, just somewhere I can't remember.



My mileage is weird. When I first got my truck, I got on average unloaded 17-20 MPG and towing brought me down to 14-15 MPG. And at the time, with the pump the way it was and the original 21cm^2 housing, I had a good amount of smoke when I got into it. Now with the 12 housing, AFC spring tension up, and no smoke other then a puff right before spool-up, I can only get 14-15 MPG towing or not. And this mileage then went south before I modified the turbo, so I don't know what's up?



Russell

 

[KEENO]

Now, wondering if some of this intermitent performace might be related to faulty a Fuel Cutoff Solenoid.



See this posting Fuel Cutoff Solenoid



KEENO

 

[MMiller]

Yes on the humidity, the more humid the less performance, the hotter the amdient temp the less performace. Go to the local drag strip and on cool, dry nights the cars are faster then on hot humid afternoons, just ask the racers. Ever drive your truck all afternoon then when the sun goes down and the humidity drops the truck runs better? This is really noticible farming when the tractor is pulling the same load across the field all day then come evening it seems to come alive!