I have a 6.9 L diesel engine quitting problem that has me a bit mystified. Several days ago in the morning I started the truck (it started fine), backed it up to load feed for the calves and as I loaded the feed the engine hesitated, slowed and quit. It wouldn't restart and sounded just like a diesel not getting fuel. The truck (former gasoline engine version) was equipped with a fuel pump in the tank which I left in place when I changed to the diesel (it has worked fine for a couple of months). I could hear in-tank pump running but when I removed the line from the tank to the fuel-water seperator there was no fuel being pumped up. From this I concluded that the in tank pump had failed. Thinking that I needed to replace the pump anyways I took the opportunity to replace the tank and install the heated fuel pickup for wintertime biodiesel use (did not plumb up the coolant lines yet). ( I haven't used BD for several weeks due to the cold). Given that the 6.9 comes with a mechanical pump and the heated fuel pickup bypasses the in-tank pump I replumbed without a electric pump. I couldn't get the engine to pump enough fuel to bleed the air, prime or run. So I installed an inline electric pump on the frame just where the line comes from the tank. This worked great. After bleedng the lines the engine started and ran great for the last four days.
Today after the arctic air mass moved in (5F overnight) the truck was a little hard to start I need one shot of ether and a jump even with a block heater. But once it started I loaded my feed and went down the road (1/2 mi) to feed the calves. It seem to run fine but when I let it slow to an idle in the pasture it quit. Same thing, no fuel to the bleed valve on the filter housing. I assumed that the new tank of low sulfur diesel had gelled especially since the inline fuel pump was clattering so I went to get 4 gals. keroscene and polar power. Just about the time I finished putting that in the tank my neighbor arrived so I had him crank the engine and I opened the bleed valve on the filter. Lots of air but soon nice clean clear fuel. Obviously gelling wasn't a problem (the truck did set in the sun for about a hour though). Finished bleeding the injector line and the truck started.
I immediately drove the truck out of the pasture and back home. Left it running while I went back to get my car. By the time I returned (about 5 min.) the truck had quit and wouldn't restart. I connected the battery charger and block heater and came in for lunch.
One other possible clue. When I bled the injector on the driver side second from the front a little fuel ran down the outside surface. I think I noticed air bubbles coming out where the excess fuel return line coming from the front injector connects to the second injector. There is one more curious thing. Several days ago before I changed the tank I put five gals of diesel into the tank from a can ( I wasn't sure I had enough to get to town to fill up). The fuel wouldn't flow easily into the filler hole. The tank acted like it was air locked (even though I took special pains to re-install the filler hose vent carefully). The same thing happen today. Thinking that the vent might be plugged I crawled under the truck and blew into the vent. It seemed clear. This tank filler design has always seem poor because when I try to add fuel at the station I need to run it slow. Don't think this is the answer because loosening the cap doesn't seem to help.

Is this problem indicative of a bad injector pump? Any suggests, anyone?

 

Have you changed the o-rings and return lines on the injectors. This is the most common area for air intrustion into the system.

 

I haven't replaced those items but will do so as soon as I can. It's pretty cold to work on it today.
Meanwhile I am trying something else. After I posted my initial request I concluded that a partially blocked fuel line might be causing some of the problem, this suggests moisture in the tank around the pickup or somewhere in the line. I remembered my neighbor telling me that his IH 966 had a problem with water freezing right at the fuel tank outlet and he would add a container of gasline antifreeze, (alcohol). Well I just tried it and after running the engine several minutes there still seemed to be good flow out the bleed valve.
Tomorrow morning I plan to start the truck and test it out on the road.

That's not to say that the lines and o-rings don't need replacing as well.
Thanks Kevin.

 

You may be suffering from your previous use of Biodiesel. The ASTM (6715)spec that covers biodiesel production has a significant flaw in it that I discovered this winter. I ended up freezing up my IP and after getting it replaced ended up plugging filters.


The problem with the Biodiesel I bought was that it would precipitate some margerine like solids in my tank after it froze and once it warmed up these solids do not readily re-dissolve and have been plugging up my fuel filters every since.


My guess would be you filter is coating over with the margerine like substance and occasionally plugging it. Sometimes it clear itself depending on how cold it is out, but if temperature drop the likelyhood of filter plugging goes up significantly.

Hooking up the glycol hoses to your new fuel pick-up might be enough to heat your fuel to the point were those deposits in your tank melt and re-absorb into the fuel and keep them from plugging up your filter. All it takes is a fine coating of this stuff over your filter media and not a drop of diesel will pass thru it even with 10 psig of pressure from your fuel lift pump. I ended up waking 3 miles at 20 F with my wife last weekend because I did not have a spare filter on me and I could not get a drop of fuel to pass thru the old filter.


Frustrating, I know.

Seb......

 

That's a good point but since I changed the tank last week I haven't run any BD and the problem reoccurred after I changed the filter this morning. That's not to say that there isn't some residual somewhere in the lines or the fuel water seperator but the sample dropped out from the fuel water seperator vent looked really clean.
I have experienced the problem you mentioned previously myself and that was the idea behind installing the heated fuel pickup.
Thanks for the thought though.

 

[QUOTE=rickgthf]That's a good point but since I changed the tank last week I haven't run any BD and the problem reoccurred after I changed the filter this morning. That's not to say that there isn't some residual somewhere in the lines or the fuel water seperator but the sample dropped out from the fuel water seperator vent looked really clean.
I have experienced the problem you mentioned previously myself and that was the idea behind installing the heated fuel pickup.
Thanks for the thought though.[/QUOTE


Ok you got clean tanks and a clean filter, so the problem must either be with your fuel lift pump or Injection Pump.

You can trouble shoot the fuel lift pump be putting on a pressure gauge to see if you loose fuel pressure. There is also a "Fuel filter" idiot light that should come on when either your fuel lift pump fails or your filter plugs up.

If the idiot light not on that you are looking at a potential problem on the Injection Pump or an air leak somewhere. An air leak would have to be rather bad to make the truck stall while it is running. You also would have lots of starting problems.

If it is not an air leak the problem would be with the IP itself most likely. There is not a huge amount you can fix on an injection pump. There is a fuel shut-off solenoid inside the top cover that could have gone bad. This solenoid relies on fuel flow to cool it and if your ever left your ignition key on for a long time the solenoid could have overheated and cracked and now intermittently shut your fuel off. I had a cracked solenoid on my 91' I bought last year. Be careful about working on the top cover, there is a procedure you must follow or if installed wrong your engine could run away on you when you start it.

Other than that the rest of the Injection Pump work is probably best left to a professional rebuild shop, At this stage your options are probably either a rebuilt replacement pump or a new pump. A re-manufactured pump will be cheaper, make sure you buy from a reputable re-build pump supplier.


Seb....