i have an '82 300TD. I run it on WVO. Yesterday I changed my fuel filters and 15 minutes into driving stalled. Put it in park, turned the key, gave it some gas and it started right up and was fine. Today I drove an hour at highway speeds and it was fine. This evening I was idling in the driveway about to leave and it stalled. Looked under the hood and the pre-filter was totally empty. When I pump it I get bubbles but it never pulls any fuel into it.

The fuel gauge is reading a quarter tank and I had just put diesel in it this morning so I assume that is accurate. I'm wondering if when I changed my fuel filter yesterdday I the priming pump broke and now is leaking air? If that was the case there is no real way to bypass that for an hours drive to get home huh?

I suppose the fuel strainer in the tank could be clogged too but seems interesting that this all happened right after i changed a filter. Also, the fact that the pre-filter was totally empty (but not the secondary filter) after sitting for a day would indicate that there was an air leak and fuel drained back to the tank correct?

Any other thoughts on what I should look into?

THanks

I would set up an alternate fuel supply jug(no oil just good diesel) in the engine compartment, if the problem is in the tank or the lines that would allow you to drive some until you get it sorted out. I you hook up the alternate supply jug and the problem remains it would point to the fuel pump or the primer pump. If you've got an old style primer with the white plastic knob locking that down should prevent that from leaking fuel or air from it.

i have the newer style priming pump and sorry i guess i have one more question...if fuel drained all the way back to the tank and the primer pump was indeed still working would it have the power to prime the whole line? i'm parked on a slight incline if that matters.

You're parked nose up on the hill?

correct. nose up. not a huge hill but a few degrees of incline.

If so the fuel probably drains back because there is an air leak somewhere on the engine side of the primary filter. The only way for the fuel to "leak back" is if there is air leaking in the replace the fuel that flows away.

If there is an air leak that would explain why the primer is unable to draw the fuel back up through the lines also.

'engine side' meaning the secondary fuel filter, return lines or the priming pump?

If the fuel level in the tank is lower than where an air leak is it seems like gravity would pull the fuel in the line back towards the tank if it could.


If there's an air leak that could explain the stalling as well.

No I was talking about the clear or translucent small plastic filter.

If that is empty of fuel which I think you said, the air in their now came from somewhere, could be anywhere in the lines and connections back towards the tank OR forwards towards the engine i.e. short hose two clamps, fuel pump. to secondary can filter, and back towards the IP fuel inlet and return connections.

That's why if you rig up a jug with a two foot long hose from the jug to the primary filter inlet and another hose from the return flow outlet on the secondary filter housing. you are eliminating the tank and the lines under the car. I don't know how easy it would be to find a rusted through pin hole leak above the rear subframe at night but I'd be bummed if I couldn't get going any other easier way first.

ok. i'll see if i can get all the stuff together to rig up the jug plan. for some reason i have this gut feeling that the leak is from the priming pump...when i was priming after changing the fuel filter it never 'squeaked' like it normally does once everything is primed. at that point i think it was WVO in it and i wonder if it was too viscous and just broke it.

if i can't find lines and a jug easily tomorrow morning maybe i will try bypassing the primer by going from the primary filter directly to the secondary filter. then crack my injectors and try and prime it by just cranking it and see if that can get me home.

the jug sounds more reliable though..if i can find a place nearby to by some fuel line thats open on sunday.

If there is any question about air leaks after a filter change consider new flexible fuel line's, its surprising how a simple change of line's can solve a vexing problem.

Before you try anything make sure you try doing what you've already tried making sure you leave the fuel cap off the tank opening, that will eliminate any likelihood the tank vent is inoperative and causing a vacuum in the main fuel tank.

Any hardware store or Home Depot type place will have clear vinyl 5/16" ID hose for 75cents a foot, goo buy a couple tree liter bottles of cheap soda for jugs. spill the soda put a couple holes in the plastic bottle cap just about the size of the hose OD, fill a bottle with fuel and slide it down between the engine and the sidewall on the driver's side right near the IP, use a strong shoe lace around the bottle neck and something solid, make sure there isn't any belts or moving stuff near the bottle, you can grab a piece of corrugated cardboard to wrap around the bottle when your rolling so it doesn't swing crazy and puncture or something.

Disconnect the rubber hose from the primary filter have something to plug that so the fuel from the tank doesn't drain when the car moves. Get your 2-3 foot of 5/16" ID hose and attach one end to the primary filter inlet, use the clamp that was on the rubber hose if you need one, usually fresh new hose will stay on the filter barb. get another section of 5/16" ID hose run it from the return line hose bib at the filter housing banjo fitting and put the end of that hose along with the fuel source hose you first set up through the two holes in the bottle cap. You just need a small third hole or a loose fitting of the hole around a hose to let air into the jug as the fuel pumps out or you'll collapse the plastic jug.

if you get the jug set up, you'll know if it's the primer pump as soon as you start pumping because you'll be able to see whether the fuel moves from the jug into the primary filter. If it does great if not you have to check the short section of hose and the clamps between the primary filter outlet and the fuel pump inlet, if there is an air leak on that last section of original hose left in the loop you'll have a harder time getting primed.

If the lines and clamps are good and you still can't prime it's probably the pump and you're not going to get far without figuring something about that .

I you see fuel flowing into the primary and feel it being pumped by the primer, I'd loosen the hard lines at the injectors and crank 10 -20 seconds at a time until I see some fuel at the injectors then tighten up the 17 mm nuts when you do. If you're getting fuel to a couple injectors and you glow it a time or two it should cough and start then you can tighten any remaining nuts.

Fill up another jug or two of fuel and cap them, you can probably get at least 10 miles on a 3 liter jug, maybe even more. ether refill the jug or swap it for a full one. If you have a second cap with the two holes made up, when it's time to refuel lift the near empty bottle out of its place put a full capped jug of fuel in its place , take of the closed cap put your second extra cop with two holes onto the full fuel jug, now without even stopping the engine you can quickly pull the fuel feed hose out of the hole in the cap of the nearly empty jug and put it into one of the holes in the full jug cap, then pinch the return line by bending it back on itself , pull it out of the empty jug and put it into the empty second hole on the full jug. Make sure the ends of both hoses that you will put into the full jugs are cut at an angle so you have a pointed piece to make it easier getting it started when you push them down through the holes the uneven end prevent the hose from sucking up against the bottom of the jug and stopping fuel from entering the hose

Nothing will happen if you don't have the IP lift pump in the circuit, the injection pump itself needs to have a fuel feed about 10 or 12 psi at least

it was the small piece of fuel line between the preliminary filter and the priming pump. the hose clamp had worn a small hole in it.

sometimes it just takes a little daylight to see things correctly.

thanks for all your help batteredbenz