Empty secondary filter housing and stall - PeachParts Mercedes-Benz Forum

junker68 · #1 10-08-2013, 12:58 PM

Kind of at wits end here...

I had recently changed the fuel tank screen/filter and have about 5 gallons of fuel in the tank. Car starts right up and idles fine in the driveway.

As I drive up a long inclining hill, maybe a mile or 2, and an incline of about 30 degrees, to get additional diesel for the tank it begins to stall and then finally does.

When I open up the hood, the primary/clear filter is filled with clean fuel and the secondary filter housing is empty.

Any easy answer here, obviously there is a fuel delivery problem. Shouldn't 5 gallons be enough to get me over that incline/hill.

When I let the car idle in the driveway, no issues. It's idling as we speak, with no load on the car.

Any thoughts, thanks

junker68 · #2 10-08-2013, 01:33 PM

After messing with some of the connections and removing the fuel line from the primer pump to the secondary fuel housing, it appears when I push on the primer pump, fuel freely flows from the outlet of said pump to the fuel line to the secondary housing. So there is no obstruction.

With the car running and the secondary filter housing top "open" no fuel flows from the fuel line to the secondary filter housing, unless I pump it. When I pump it fuels dumps into the housing and the primary pump refills slowly.

Now does the primer pump control and pump fuel to the secondary housing or does the secondary fuel housing, "suck" that fuel into the housing?

And there is plenty of fuel in the tank.

Thanks in advance!

cooljjay · #3 10-08-2013, 03:12 PM

Are you using the new black push and pump primer or the original twist and pump white primer?

Any alternative fuel use?

Did you bleed the air from the system after you reinstalled the tank?

junker68 · #4 10-08-2013, 03:54 PM

Hi Cooljay,

I have a 1974 240d.

I have the black push button type of primer pump.

I had a wvo system, which I removed and ran fine after it's removal.

I emptied the fuel tank after numerous primary fuel filter changes with crud in it. Changed out the tank screen/filter.

I never removed the tank, just the screened filter in the tank and then refilled the tank with clean diesel fuel.

Just prior to changing the fuel tank screen/filter, I've ran into this problem, where the secondary filter housing is fuel starved, but as stated, the primer pump appears to freely send fuel through the primary filter into the primer pump and into the secondary fuel filter.

But when the car is running I see that the fuel is not entering the secondary fuel filter housing.

So the one question I had, does the primer pump control and pump fuel to the secondary filter housing or does the secondary fuel housing, "suck" that fuel into the housing?

Thanks for your help,

Dwayne

vstech · #5 10-08-2013, 03:56 PM

Quote:

Originally Posted by junker68

After messing with some of the connections and removing the fuel line from the primer pump to the secondary fuel housing, it appears when I push on the primer pump, fuel freely flows from the outlet of said pump to the fuel line to the secondary housing. So there is no obstruction.

With the car running and the secondary filter housing top "open" no fuel flows from the fuel line to the secondary filter housing, unless I pump it. When I pump it fuels dumps into the housing and the primary pump refills slowly.

Now does the primer pump control and pump fuel to the secondary housing or does the secondary fuel housing, "suck" that fuel into the housing?

And there is plenty of fuel in the tank.

Thanks in advance!

the primer pump only siphons fuel from the tank to get fuel flowing through the lift pump. from the lift pump it should pressurize the secondary filter can, then go out the return hose back to the tank... the IP sucks fuel from the filter outlet and pumps fuel through the injectors and the injector return lines back to the tank...

so, if you have an air leak on the top banjo bolt, and a stopped up fuel tank vent, you could empty the fuel filter...
I'd pull the center bolt, and replace the o-rings and then pump the filter full, and bleed the injectors, and see if it fixes the problem.

junker68 · #6 10-08-2013, 04:19 PM

Quote:

Originally Posted by vstech

the primer pump only siphons fuel from the tank to get fuel flowing through the lift pump. from the lift pump it should pressurize the secondary filter can, then go out the return hose back to the tank... the IP sucks fuel from the filter outlet and pumps fuel through the injectors and the injector return lines back to the tank...

so, if you have an air leak on the top banjo bolt, and a stopped up fuel tank vent, you could empty the fuel filter...
I'd pull the center bolt, and replace the o-rings and then pump the filter full, and bleed the injectors, and see if it fixes the problem.

Thanks VStech,

So based on what you are telling me, if I run the car with the top of the secondary filter off, I will not see fuel enter the secondary fuel housing? Because it is not a pressurized system.

Also, if I fill the secondary fuel housing with fuel and prime it, clearing air from the system and if all is working well this should pressurize the system and assuming all is working well (O-rings and clear fuel tank vent), we should be good to go.

One more, the fuel tank vent - where the heck is that and how do I determine if it's clogged.

I'm going to check the o-ring now.

Thanks,

Dwayne

junker68 · #7 10-08-2013, 05:20 PM

Well, the o-ring was ok.

I filled fuel in the secondary filter, primed the pump and started it on the first try.

Now it has been idling for about twenty minutes. When revving the engine I do not see fuel enter and flow through the primary/clear filter. It appears stagnant.

When I hit the primer pump that appears to be the only time I see fuel empty the primary filter then refill from the tank.

I assume if I open the secondary filter now it will be near empty.

vstech · #8 10-08-2013, 06:24 PM

You must have a leak between the filter and the IP

junker68 · #9 10-08-2013, 06:26 PM

Found the tank vent and it appears clear. Goes into the trunk into a plastic bowl and vents outside by the passenger side rear bumper.

junker68 · #10 10-08-2013, 06:34 PM

Quote:

Originally Posted by vstech

You must have a leak between the filter and the IP

Why do you say that?

I do not see a leak. I tightened all of the clamps.

You described the lift pump earlier. Could that be defective?

Once again, I believe the IP is feeding off of the fuel in the secondary fuel filter.

When I rev that engine, I do not see any fuel going into the primary/clear filter, no drips no flow.

Here is what I know, fuel is being fed to the primary pump when I prime it. So I would assume there is no restriction until the primary filter, correct?

Fuel is getting to the IP via the fuel in the secondary filter housing.

So would I be correct to assume there may be a problem with the lift pump and/or primer?

Thank again!

vstech · #11 10-08-2013, 06:41 PM

It could be the hose from the primary filter or anyplace up to the secondary

vstech · #12 10-08-2013, 06:43 PM

In order for the secondary to empty it needs air to get in

kerry · #13 10-08-2013, 07:25 PM

Lift pump could be defective. Remove the outlet hose, crank the engine and see how much the lift pump is moving.

junker68 · #14 10-08-2013, 07:40 PM

Vstech, Ok, when you put it that way it makes sense.

Thanks Kerry, I'll do that also.

Dwayne

cooljjay · #15 10-08-2013, 09:42 PM

Send us a picture of the injection pump area so we can see how your hoses are....

Any chance the return line and primary line from the tank got mixed up?

Since this is a w115 I believe the fuel tank lines are different.....have you confirmed the lines under the tank are hooked up correctly?

You said it was an on wvo but you removed the system....I want to think that a line some where is crossed...