My truck runs fine, then occasionally while driving starts losing power, white smoke comes out the tailpipe, and the engine runs really rough and will die if I give it a lot of throttle.

I can restart it immediately and it acts like nothing is wrong. Power is back to normal, no white smoke.

This is very reproduceable. It happened three or four times this afternoon while I was driving home from work (25 miles).

At first I thought I had a fuel filter issue, but I guess that doesn't make sense. If I had a clogged filter, the truck wouldn't restart right away.

Any ideas what's going on here?

 

maybe sucking up some crud in the fuel tank? then when you turn her off the suction breaks and the crud floats away...until it catches again.

 

Ok, so I'm thinking I have crud (asphaltene?) at the bottom of my tank. I remember the PO saying something about the engine doing this once in a while, so I think it's just a problem he didn't manage to solve.

I'm trying to think what I can do about it. Taking the bed off isn't really an option, because I have a 100-gallon aux tank in it (and that's 2/3 full of fuel). Dropping the main tank is a better option, but it's also nearly full of fuel. I could pump it into something, but I'm thinking probably the fuel I have in it is ruined because of the sludge. It's probably likely there's sludge in the aux tank too.

So ... nuts. Looks like I not only have to clean out both tanks but I have to get rid of a bunch of what I thought was good fuel, too.

 

We have been going through our truck, and replacing plenty of fuel bits & pieces...

Prior to starting in on replacing the parts to get that fuel gauge working properly, and the fuel tanks to empty completely, we were running okay. We replaced the parts in the rear tank. A few days later the truck felt like it was running on 7 cylinders (per my amateur assessment - and having more experience with gasoline powered vehicles).

It then died on the freeway... restarted five minutes later, then died two more times - before having it towed home. A local mechanic came over, claimed a fuse had burned and that was it... it wasn't.

The mechanic then helped me replace the front Sending Unit & Pickup...the mechanic convinced me we needed a new Selector Valve (ended up buying two, since the the first did not fit). Note that the Selector Valve was never tested to determine if it was functioning properly (which is all of my fault for not demanding such).

After doing all of this we fired up the truck - only to have it feel like it was still running on 7 cylinders! We then purchased a new Fuel Filter along with the aftermarket Water Separator (located on the Driver's Side Fender).

No change in the performance... Being simple-minded I figured it just needed to get on the freeway and burn up some fuel... wrong! It didn't make it five miles before it died again. We then decided we could do nothing more and our helpful local mechanic was costing us more than it was worth.

Had it towed over to Diesel Tune (in Downey, CA). They have a good reputation - and appear to understand 6.9's better than any local Ford dealer. Honestly, we were fearing the worst; possible Injector Pump failure. We had to wait three days to get it in the shop, only to be informed that the truck had zero problems - other than sucking far too much air into the system.

The effect was that the engine was sucking far more air than fuel... which meant it could only operate for a few minutes/miles before starvation. The cause was that aftermarket Water Separator... the actual cast housing mount/fixture (and not the filter) was defective.

Diesel Tune replaced the Water Separator, charged me some serious coin, and it runs like it should. They also informed me that it needed a new Motor Mount (Isolator)... so that was the source of that annoying vibration.

I am new to these diesels, and could have ended up replacing far more bits and pieces than you could shake a stick at. I finally smartened up, admitted defeat, and let the experts have their way.

Bottom line; if it feels like it's running rough... running on less than eight cylinders... stalling out a few miles after firing right up... it could very well have a problem with air being sucked into the fuel delivery system.

Good luck


*** As well, we started having White Smoke coming out the tailpipe when this issue cropped up (which it has never had before, nor since it was repaired)!!!

*** Save for the broken Pickup pieces in the bottom of the tanks our tanks had zero crud/gunk/rust... absolutely amazingly clean... then again, this truck has been in Southern California all of its life.

*** It is very difficult to retrieve the excess fuel in either tank - with the > long < filler necks in place... we thought we had emptied ours, and found the front tank was - at least half-full... you can still drain them once they are lowered from their perch, once you remove the Sending Unit(s).

*** Locate a large barrel for your diesel fuel, and use a transfer pump... I seriously doubt you will find too much debris in that fuel.

 

I will look into air intrusion. I hadn't really considered that. Thanks man!

 

Sounds like a failing lift pump imo. How much fuel is shooting out of the schrader valve when you hit it? I dont remember the exact measurement but it should be a pretty healthy squirt.

 

Hello Everyone, There are usually only two reasons for white smoke...I am not saying there is only two ways...just the very most common...

1. Timing.....2. Air Intrusion....

The way you are describing your truck symptoms...(runs fine)...I would say air is getting in from somewhere and that's where I would concentrate my diagnostics....

BeerCan500

 

That is something I've been thinking too. I have no idea how old my lift pump is, and I worry about it leaking into the crankcase. Time for an e-pump.

 

Ok, so let me sum up what I've done so far to fix the issue:

I got a new fuel filter, filled it with Diesel Kleen, and put it on the truck. Didn't solve the problem; same symptoms as before.

--

I disconnected the main fuel tank (this truck only has one) and ran new rubber lines from my 100-gallon aux tank to the hard lines (supply and return), thinking there was a clog in my main fuel tank causing this issue.

That didn't solve it. Same symptoms as before, drawing fuel from a different fuel tank.

--

I replaced the lift pump and the rubber line between the lift pump and the hard line. Again, same symptoms as before.

--

When I first start the truck, it starts quickly and idles smoothly. When I start driving, it gives me good power for a few minutes. Then suddenly the engine starts to lose power -- I have to put the pedal nearly to the floor to maintain speed -- and white smoke starts pouring from the exhaust pipe. If I put the pedal to the floor, I can limp the truck along for a while, but eventually it starts bucking, surging forward and falling back. If I pull over at that point and take the truck out of gear, the engine almost dies as it returns to idle, then starts idling rough (and also much quieter (less diesel knock) than usual). Once the engine has lost power, the power does not return.

However -- if, once the engine is running rough, I turn off the key and then restart the engine, it's back to normal. The process repeats; I get normal power and no smoke for a few minutes, then the engine loses power and starts smoking again.

I can repeat this as many times as I like.


Now ... knowing that I've replaced the fuel lines between the hard lines and the tank, the fuel filter, the lift pump, and the rubber line between the lift pump and the fuel supply hard line, what do you recommend I try next?

Does this seem like air intrusion to you? If so, where is it likely coming from? What I don't understand is: if it's air intrusion, why does turning off the engine correct the problem (for a few minutes, anyway)?

Could air intrusion from the return side be causing this?

It's been suggested that this could be a timing issue, as well. If so, why does it come and go? Why does the engine run fine for a few minutes, then run like crap, then back to normal after I restart it?

 

i would say that you clearly don't have air intrusion on the return side. we all know the symptoms of that, and they ain't yours. on the supply side, i've had intrusion, and it produces a whole lot of power for not much pedal. at least thats the case for minor air intrusion. i would think that more major leaks would cause you problems, but also leave a puddle on the ground after you turn off.

i'm wondering if maybe the issue is in/on your IP. lets say the FSS is going half-bad, and once it warms up for a couple miles it gets stuck at half-on, causing starvation...i don't know if they fail that way, but i'm trying to think what we have that would be affected by switching the key off and back on...

 

to check for air intrusion before the filter let it sit for awhile and remove filter
if filter is full most likely the airleak is after the filter
if the filter is not all the way full then most likely you have a air leak from the filter back to the tanks

it almost seems like you may have a air leak on the hard lines going from filter to IP?

I also wonder if there is a short in the wiring to the Fuel Shutoff Solenoid (FSS) inside the IP would it give less than 12 volts at times causing it to close some or all??

the main clue is that it happens soon after startup but repeats itself after almost every startup but doesn't cause a no-start...and white smoke which clearly indicates a air leak no?

What about a failing Throttle Position Sensor (TPS)? mmm

Unless you have done so already, at some point you will have to drop tanks and replace the pick up tubes as they have either eroded or will erode soon...

double check your lines

was it doing this before or after you replaced the lines?

did you change anything before this started or when/how did it start?

 

Ok ... so let me tell you about what I did over the past couple of days.

I tied off the 100-gallon aux tank (and the main tank has already been tied off).

I got a 1-gallon can and filled it about 3/4 with pump diesel and 1/4 with Diesel Kleen.

Ran a 5/16 line from the 1-gallon can to the tee on the return lines (directly behind and under the air filter) and ran a 3/8 line from the can to the lift pump input port.

The truck ran great. No problems, the symptoms completely went away.

Switched it back to the 100-gallon aux tank and the problems returned. Truck runs like crap.

At this point I'm ready to conclude it's a problem with my fuel (50/50 centrifuged WMO and pump diesel).

So I drained the main tank and put in about five gallons of pump diesel, and hooked the main tank back to the engine. Engine runs with no problems ...

The symptoms are the same no matter what setup I use. The only thing that seems to make the problems go away is to run the truck on clean diesel.

So, I don't know. I haven't had this truck long enough to run multiple batches of homemade fuel through it, so I don't know whether this batch had something go wrong or if this truck just doesn't like anything other than pump diesel.

Regardless, I'm moving and can't take my fuel equipment with me, so it's kind of a moot point. Thanks for the help guys.

 

Well im glad to hear you got it figured out, I dont know too much about running different fuels, im sure there is good information on here about all that if you look.

Good luck on the move.

 

i have no problems on a 10% WMO mix, but 50% is more than i'm willing to put in mine.

i have to wonder if we have any members near you who might want your equipment you can't take with you - NM is a bit far for me, but we may have someone interested.

 

I advertised it all over the place -- $750 for the lot (and it was a lot of stuff, including a complete appleseed biodiesel reactor and a centrifuge setup) and got zero bites. For equipment that cost me north of $2500 ... bad economy, I guess.

All the equipment's gone to my former business partner down south, but if you find someone who wants to take it off his hands and will make it worth his while, let me know and I'll put you in touch.