83 300sd. Since I live in hawaii and have converted it to run wvo using a single tank system. The system comes out of the primer pump and goes through a fphe, then a boost pump, a 30 micron stanadyne fm-100, 5 mic fm-100, and finally injector line heaters. Also I have cut off the in tank strainer. I have a good oil source and filter it after settling to 10 microns.

I have been having issues with air getting in the lines I think. At first the problem was I couldn't prime the fuel system, after much reading I found my vent was clogged and since then just disconnected it where it comes out of the tank and no more whoosh when opening the fuel cap. That seemed to solve my problem but then a few weeks later the car starts to hesitate again and there is air in the system. I went over every connection and tightened the hose clamps, bled system, then two weeks later same thing. Then I thought maybe there was a blockage in the tank so I drained the tank and the oil was clean, no blockage whatsoever. When re-installing I noticed the little rubber line from the tank to metal lines kinked just a little bit due to the sharp angle. So I replaced both the return and feed line. Then yesterday coming up a hill it hesitates again. I pull over and bleed the system and it runs fine. Then today coming up the hill again and same thing. I'm starting to get really frusterated, especially because the problem is so inconsistent. What should I do next?I should also mention I changed the fuel line to 3/8" just after the primer pump via an adapter. After the last filter it goes directly into the stock fuel line fitting into the injector pump, it seemed to fit pretty snug and the hose clamp is very tight, anyone know what the stock line size is?

I was thinking about replacing the hose clamps on the lines I just replaced to start. Should I just replace all the fuel line back to stock size? Is the 5 micron filter maybe too small and causing too much backpressure? I appreciate any advice or help, I'm about to break down and take it to a mechanic. Aloha

Do you still have your stock spin on filter? If so, The bolt that holds the filter tight has 2 o-rings on it, change those 2 o-rings with new metric, these can and do get hard and flat and will suck air.
Good Luck

I have removed the stock filter setup. I used a T to connect the three lines that were on top of the filter housing before. Any other ideas?

Update: So today I did a few things. First I bypassed my 5 micron stanadayne filter and took it for a test drive. It ran fine, had no hesitation. I was thinking maybe the 5 micron filter is just too fine and causes too much backpressure which causes air to seep in through one of the connections?

Since I only have a 30 micron pre filter I replaced the stanadyne 5 micron filter with a 10 micron whole house water filter, I have the same setup in my 300d and it works fine. I also put in a section of clear line from the filter to the injector pump. When pumping the primer pump I could hear a high pitched squeeking noise coming from somewhere near the injector lines. Only happens when there is a air bubble going into the injector pump. I sprayed everything with soapy water and pumped away and didn't see bubbles anywhere? But I can feel the return line vibrating with the squeek. After about a billion pumps there seemed to be no more air bubbles at least in the clear line section. I took it for a test drive again and it hesitated just like before, it happens when going up hill around 60 mph and full throttle 25k rpm. I pulled over and sure enough I can see an air bubble in the clear section fuel line.

Is my squeeking noise almost certainly an air leak? Any ideas on how to find it since the soapy water didn't seem to work? I'm really starting to get tired of working on it but I know if I take it to a mechanic he will only rape me and likely not fix the problem. Any ideas? Thanks

You know you have an air leak, I don't now how far the hill is that you are having trouble getting up,
But if it were me, I would take some hose and bypass the filter and go straight into the pump as a short test, Go up the hill and see what happens.
Good luck!

I did bypass the filter and the car seemed to run fine. Then when I installed a new 10 micron filter it started hesitating again. My thinking is that the filter adds more restriction causing the air leak to suck in air faster. I guess I just have to find the mysterious air leak. I was going to replace the crush washers on the fuel line fittings that go into the injector pump, anyone know if I could get these at ace hardware, or parts store? Since I live on an island it makes getting parts difficult sometimes, I pay huge shipping sometimes for a tiny part.

Even with the air it doesnt seem like it will flow well enough.

__________________
http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

I took off the two fuel line fittings that go into the injector pump. The fitting on the front of the injector pump has 2 gaskets that are silver in color. The fitting on the back side of the pump has two copper crush washers. Can I use copper on the silver looking one? I Checked at ace and they don't have any, napa doesn't either. I might be able to get it at this other parts store in town, anyone know the exact size or specs of the crush washers???

The silver crush washers are aluminum and can be replaced with copper ones. Unless they are really smashed and deformed copper washers can be heated red hot and dunked in water and reused after scrubbing the black tarnish off of them.
The banjo connection washers that go into the upper half of the IP are under pressure and will not suck in air as fuel will come out of them they leak. If you reuse the aluminum washers on the pressure side of the fuel system and they do not leak fuel out you are OK and they do not need to be replaced.

__________________
84 300D, 82 Volvo 244Gl Diesel

I forgot to mention the hand primer as a possible source of an air leak.
Also I replaced my stock (Nominal Micron Rating) 10 Micron secondary fuel filter with a 2 Micron fuel filter (using regular diesel fuel though) and I have normal performance.

__________________
84 300D, 82 Volvo 244Gl Diesel

I have replaced the primer pump with a brand new one so it's probably not it. I replaced the crush washers that looked bad and put everything back together. Took it for a test drive and it didn't seem to hesitate where it did before. Then today I took it for another drive and it did hesitate full throttle steep hill going fast. It didn't seem to hesitate as bad as before though. So I've called a mechanic and will likely drop it off on monday, even though I vowed to never go to another mechanic He was reccomended by a friend and he knows about wvo. The only other thing I can think of would be to essentially replace all the fuel line and possibly even the 30 mic stanadyne prefilter, but that doesn't seem right what do you all think?

I would want to have at least the 10 Micron secondary filter protection and the 20 micron small plastic filter protection that it came from the factory with.
If your car came with a tachometer when the car would hesitate did the Tach. show RPMs drop; or was there a hesitation and the RPMs went up slightly. I do not know much about the transmission problems but it seems to me that if something in the transmission was slipping it would also seem to hesitate.
I had a similar experience on a motorcycle that had a dry plate clutch (they type of clutch a car with a manual transmission has). The rear main seal was leaking and had saturated the clutch firction disc/plate with oil. I could ride along at 45 mph and be OK but if I was hit by a heavy gust of wind the clutch would slip and I would slow down (and the RPMs would go up). Same thing in on a hill or if I raised the speed above 45 MPH. The bike would slow down (engine RPMs would go up) and I guess when it got hot it would grab on and operate normally. Of course eventually it got so bad I realized what might be happening and took a look at the clutch finding it soaked with oil.
Automatic transmissions can also slip; but in the case of a diesel if the RPMs start to go up the IP governor might bring the RPMs back down. Just a wild guess.

__________________
84 300D, 82 Volvo 244Gl Diesel

I due have a tach that I just fixed actually. The rpms seem to stay about the same or go down slightly when it hesistates. It kind of faint sometimes, doesn't feel like the trany slipping at all, feels kinda like a plugged fuel filter. I do have the stock prefilter on there. Maybe I will just re-do everything I did and pay really close attention to every fitting when re-installing without the stanadyne filter. Any other ideas? Thanks

I think that you have a good idea to go back to the stock setup and see if the problem goes away. After that is done maybe try putting the suction side hose with the plastic filter still on into a container with regular diesel fuel (enough for you drive far enough for you to safely test the car) and that will eliminate any possible problems between there and the fuel tank.

__________________
84 300D, 82 Volvo 244Gl Diesel

Thanks for the help, I'm pretty sure I fixed it finally. I went through and replaced all the fuel line again. When replacing I found my 3/8 fuel line was a bit big for one of the stock fittings going into the injector pump. I hadn't noticed before. I replaced it with a 5/16'' fuel line and it fit much better. Now I don't have any more air issues, no hesitation, knock on wood. Glad I didn't take it to a mechanic. I think my a lot of my frustration was coming from working on it in the sun, I pulled into the car port and it made a world of difference. Aloha