Vapor lock with Diesel

[cur.bill]

I am in So Fl and am wondering if it possible to create vaporlock on my 7.3. I am running a heat exchanger in line for veggie oil use. I am having a problem with stalling after running with diesel as I do not have vo in my tanks. The truck stalls and when I pull the filter off it is only half full. I have replaced two smalls lines that might be leaking air and have tightened all clamps. I have new return lines on the engine and have replaced the hoses if there is any sign of detoriation. The filter light comes on and within 3 or 5 minutes I find myself on the side of the road. I put atf in the filter and am able to drive for acoupla minutes before it starves again. I have a electric pump pushing fuel to the mechanical pump. The filters are new. Any suggestions would be helpful

 

[smoking89IDI]

Is the mechanical pump filling the crankcase with fuel?

 

[h2odrx]

If you have a elec pump, bypass the mech one to start with. is the elec pump keyed or what?

 

[GREASE FIRE]

I am in So Fl and am wondering if it possible to create vaporlock on my 7.3. I am running a heat exchanger in line for veggie oil use. I am having a problem with stalling after running with diesel as I do not have vo in my tanks. The truck stalls and when I pull the filter off it is only half full. I have replaced two smalls lines that might be leaking air and have tightened all clamps. I have new return lines on the engine and have replaced the hoses if there is any sign of detoriation. The filter light comes on and within 3 or 5 minutes I find myself on the side of the road. I put atf in the filter and am able to drive for acoupla minutes before it starves again. I have a electric pump pushing fuel to the mechanical pump. The filters are new. Any suggestions would be helpful

first of all, as i understand it the only advantage of an electrical pump is that you don't have to worry about the mechanical pump leaking fuel into the crankcase (but since they are so cheap you could eliminate this risk by replacing it once in a while).
But since you have the electrical pump it should be very easy to turn it on and let it run without starting the engine, then push open the bleeder valve on the fuel filter (mine has a tire valve, i assume that is what they all have) and wait until fuel comes out in a steady stream.
does this happen? if not then you are not getting fuel from the tank - perhaps there would be a problem with the fuel pickup like on my truck right now, which will run out of fuel when the tank says 1/4 full.
If you do get fuel coming out you may want to crack a few injector lines and crank until fuel comes out to make it easier to start - bleeding the injector lines could save your batteries and for that matter your starter.
i don't know why the filter light would come on unless you got water in there or perhaps it has a sensor that tells you when it is clogged? But if it is not even full of fuel that probably is not the problem here.
Let us know what you find.

Paul

 

[Exekiel69]

I am in So Fl and am wondering if it possible to create vaporlock on my 7.3. I am running a heat exchanger in line for veggie oil use. I am having a problem with stalling after running with diesel as I do not have vo in my tanks. The truck stalls and when I pull the filter off it is only half full. I have replaced two smalls lines that might be leaking air and have tightened all clamps. I have new return lines on the engine and have replaced the hoses if there is any sign of detoriation. The filter light comes on and within 3 or 5 minutes I find myself on the side of the road. I put atf in the filter and am able to drive for acoupla minutes before it starves again. I have a electric pump pushing fuel to the mechanical pump. The filters are new. Any suggestions would be helpful

You said You run veggy, is it wvo or bioD? do You still have metal lines sections in the fuel system? If yes, You have to replace all the lines with rubber hose and connect the electric pump directly to the filter (use #2) and see if that fixes it. wvo will clog the fuel lines over time if they are metal (copper, steel) and Your symptom look like this is the case. That includes the heat exchanger.

 

[GREASE FIRE]

come to think of it i tried a system like that once while troubleshooting some problems - i had the facet 12v fuel pump pushing the the fuel to the stock lift pump (on my 6.2 van but same pump) and it was fine at idle but as soon as i got on the highway the vacuum of the mechanical pump pulled the plunger on the 12v pump so it stuck and would not pump anymore and not enough fuel would flow through it and i lost power and was just about to stall out on the highway when i switched to the veggie tank and that saved the day as usual - so that could also be your problem.
you could try getting two T's and a check valve and plumbing the 12v pump in parallel to the check valve, that way the stock pump could pull fuel through the check valve and you could just use the 12v pump for priming the system, and have it controlled by a toggle switch. That's what i do.

paul

 

[cur.bill]

Thank you for the response. The truck only has 3,000 miles on a total rebuild. That is not enough time to plug up the steel lines. All hoses are new. The return lines are new. She starts right up in the morning and runs for up to 1 1/2 hours without any problem. The filter was new. I have changed these filters each time this problem took place. We did find 2 small holes in 2 3/8 inch rubber hose. I am using gates right now. I have two electric pumps hooked up to the system so that if the walbro craps out I can switch over to the backup. I put a new (2 hours) ford pollak valve on. The heat exchenger is similar to Frybid one. It is basically an air conditioner coil from a ice machine. I only have diesel in the tank as I just had the tank steamed out and new pickup hoses put on. The stalling only takes place after the truck runs for awhile. It has had some trips up to 4 hours with out any problems. It has only started this problem since I installed the heat exchanger on it. Thers is no water in the system from the heat exchanger.

 

[hahn_rossman]

Are you only running one tank through the heat exchanger? It's not really a great idea to heat diesel up to 180F. The lubricity drops a lot and can cause problems with your IP and injectors.

Do you have the fuel starvation issue with both tanks? People have reported air leaks with the stock 6 port valve. If the problem is only with one tank...well the pick up is the obvious choice or some of the plumbing.

Air leaks are enough to cause a grown man to weep. The best solution is to use a sight glass in line with your fuel system. Start as close to the tank as possible. There should be no bubbles. The stock fuel system can eliminate some entrained air, but it runs better with none.

Good luck.

 

[RLDSL]

is your fuel tank vent plugged? That will cause exactly what is happening to you in a heartbeat .

Some mud got up in a curved steel tank vent line and dried on one of my diesel cars a while back and I have to leave the fuel cap a bit loose to keep that from happening right now till I have a chance to replace the line.
If I forget to leave the cap loose, on a short trip, next time I go to start the thing, it won't start, or on a long trip, it'll stall going down the road.

 

[cur.bill]

The shop pulled my electric fuel pump out of line and now I am just using the mech pump. The shop said the electric pump was overheating from the fuel and creating a air blockage. Now only one tank is usuable.when the truck went in I had use of the front tank now only the back tank. The 6 way is brand new from Ford at a tune of 250.00. Talk about crying. My boss says just run one tank for now. At least my mercedes diesel works.

 

[hahn_rossman]

Are you sure the 6 way valve is dead? Are you using it with the stock wiring? What have you changed to start running WVO?
We have some brand new pollak 6 way valves at Frybrid from way back when they seemed like a good idea. I'd be happy to send it to you for a song. We also have some of the 3 way pollak valves as well.
Currently we don't use any of them, as the hydraforce valves are a lot better. They also cost more...funny how that works.
I'd recomend using on tank for WVO and one for diesel. Ditch the factory six way valve and use 2 three way valves for switching feed and return. The feed should be located as close to your lift pump as possible.
Good luck.