new clutch, fuel mileage with the Comp, and a miss

[dripley]

 

The clutch

I got my SB 1947 OFE installed the last part on November. It was nice to now have a non slipping clutch again. I am impressed with the SB. In first it engages smoothly, it is a little grabby launching in 2nd but nothing to worry about. It holds like the Hulk and I am very happy with it. i made one run of about 475 miles with the 5th wheel in tow and the comp on 2X3 and it handled it just fine. This was on a good mix of flat and hill country. No long grades to speak of but a good many short 6% or so grades. The clutch held great no matter what I threw at it. When I got home maneuvering the 5th wheel into my driveway went smooth. I was pleasantly surprised how smooth it was in 1st and reverse. It is mostly flat but a 90* turn to back it in and takes a good bit clutch work to get it in.

Fuel mileage and the comp

I had to move the 5th wheel a few months before the clutch install. Since I new the old clutch was almost done I made the trip in 5th gear. The trip was 440 miles of mostly interstate like described above and I ran 65 mph as much as possible. I netted 10.1 mpg on the trip.That was with the comp installed but turned off which allowed me to build over 20 psi of boost without the ECM defueling the engine. When I made the return trip after the clutch install I still ran 65 mph but used 6th gear as much as possible. I have always towed in 6th as long as  it pulls good with about half throttle. I made the trip with the comp on 2X3 and netted 11.3 mpg. That is best I have ever gotten traveling at 65 mph. Driving around empty has been a lot fun to. The comp puts a lot of power to the ground and it was nice feeling like young man again. I am thoroughly impressed with it especially after driving with no chip for the past 2.5 or so years.

The miss

Now the rub. About 3 weeks ago I noticed i was picking up an intermittent miss under medium to heavy throttle. It is not like one cylinder cuts out it is intermittent and not constant. The truck idles fine with no miss and does not miss if I roll into the throttle and let the rpm build. it misses when I just stick my foot in it and every once in a while it does not miss at all. It also does not miss with the comp turned off no matter how hard I get on it. Not sure what to make of it, weak injector, fuel leak, weak cylinder, something with the comp maybe. The weather has been either too wet or cold to check much out.  Hope this turns out to be simple.

[IBMobile]

Sounds like lack of fuel on demand, Air leak? 

[Mopar1973Man]

I tend to agree it sounds like your picking up a bit of a air in the fuel.

[dripley]

Like as in between the tank and the lift pump, suction side of things? After all I do have those AD quick disconnects on the fuel lines.  I did have an instance of slow start the other day. Parked at work, nose up for a couple hours and had to hold the key for 2 or 3 seconds for it to start. Parked there again today and no issue. Not thinking that is related though. If the air is still tomorrow I might be able to look around a little. We have 30* for a high tomorrow and Sunday.

I am going to have to go to Idaho to find some warm weather. 

[IBMobile]

1 hour ago, dripley said:

After all I do have those AD quick disconnects on the fuel lines. 

I've heard of people having the same problem that you're having and had the quick disconnects.  I think they changed them out to the push lock fittings and that took care of the problem.

[Mopar1973Man]

Quick test to prove the problem. On the section side disconnect and wipe the male nipple clean and then grease the male nipple and reconnect. Do both ends tank and pump. Then start the truck again afterwards to reprime the line. Then park as you had it again see if thee problem occurs again.

IBMobile is right just replace all the crappy quick connects with Parker Push-Loc fittings.

[dripley]

The thing that is weird with the AD lines is half the ends are quick disconnect that you pinch and pull apart. The other ends you need a release tool. Always thought that was strange. 

Riddle me this why does it not do it with the comp off? I am assuming the demand placed on the suction side does not change since the lift pump should be a constant. Is it the demands of the added timing and fuel from the comp that makes the air a bigger factor and shows up as a miss?

 

 

 

[IBMobile]

13 hours ago, dripley said:

Is it the demands of the added timing and fuel from the comp that makes the air a bigger factor and shows up as a miss?

I think that's it.  The fuel demand of the VP is so great when under WOT and the comp box turned up  that a suction is created between the VP and the lift pump drawing in air.  It doesn't take much to create an air leak.  

[Mopar1973Man]

I still say to turn the grease trick it should make a temporary fix and problem should go away for a short time. Eric at Vulcan Performance has warned me of the suction line being known for rolling the o-ring back and getting air leaks. Thick axle grease should fill the void for a short time and make a change. If so then you know that it would be best to just change the fittings out and replace them with Parker Push-Loc fittings.

Edited February 14, 2016 by Mopar1973Man

[dripley]

I will give the grease a try if it will just warm up a bit  Cant stand having to work on the truck with thick gloves or frozed fingers. It did get into the high 20's today but the breeze sucked. Supposed to be colder tomorrow with more snow moving in. I am tired of winter. 

[TFaoro]

What are the exhaust temps when you stab the throttle? Like 300* then you stab it and it misses or what?

[dripley]

Depends on where I am at and what speed I am going. I am not seeing anything out of the ordinary but not paying a whole lot of attention. ???????

[TFaoro]

Just curious... mine will sputter like an SOB if I stab it and the EGTs are below 400 or so. Just not enough heat to combust all of the fuel. My result is usually white smoke as well.

[dripley]

If I stab it at low rpm it will miss right off. It does not sputter just a miss. I never watched the egt's. If I roll into it, it does not miss until about mid throttle. It never missed  lick when I towed the 5th wheel back from Alabama. I had it under heavy throttle quite often on that trip. This just started in the past month. 

[TFaoro]

Hmmmm that's weird

[CSM]

Just out of curiosity, how old is the vp?

[dripley]

150k and about 6 years old. 

[JAG1]

Dave do you have a tank sump or the 1/2'' drawstraw? I think you might be sucking more air if you have the tank screens and factory draw straw. I read of a guy with clogged tank screens. 

I never liked the factory draw straw with the little fuel filter cartridge on it. It has more screens inside.

Edited February 16, 2016 by JAG1

[dripley]

I have the intank fuel module which I believe is the same as the liberty tank module. The pick up and return are both in the module. The pickup is open on the end with no screen. There are no screens on the bottom of the module like the oe. I cant remember whether I had to drill any additional holes in the module for fuel. I just know I can pull the tank down to nothing. It was all part of a kit from Pureflow to remove the in tank pump for the AD install.

[dripley]

Well due to the cold, snowy, sleety, rainy and freezing rainy I did not get to try anything out on the truck. Funny thing is it has missed once in 2 days, no matter how hard I get on it.