1995 E300 W124-Om606 pressure in fuel tank - Page 6 - PeachParts Mercedes-Benz Forum

Diseasel300 · #76 02-03-2017, 09:32 PM

Your clear lines should be full of fuel at all times, even with the engine off.

If you have an air leak big enough, the pump will never prime. Given the amount of air you were sucking in the video you posted, I'm truly shocked it was even running.

To help you further, we need pictures, or a vehicle-specific fuel line diagram. I'm familiar with the 603 engine, and Funola is nearly an oracle on the 617, but knowledge is lacking on the 606. You need to start tracing fuel lines back (this means using your hands and eyes) and making sure you don't have leaks. If there's an O-ring in a joint, change it. If there's a rubber hose, replace it. If there's a hose clamp, install a new one. All the way back to the tank.

The lift pump isn't going to prime and your problems aren't going away until you find and FIX the leak in your suction line.

I'm really surprised and a bit disappointed none of the 606 guys are replying to this thread!

packerfan · #77 02-03-2017, 09:41 PM

Quote:

Originally Posted by funola

The pre filter should be the suction side. Since you have air in both lines, air could be coming from the prefilter, or a loose pre filter hose clamp, and everything from there back to the tank. Try tightening the clamps on the prefilter first. Does that eliminate the air bubbles? If not, the next thing to do is unclog the tank vent. It is most certainly clogged from all you have described. Take the vent off and blow compressed air into the line with fuel cap open. You should hear fuel gurgling in the tank. If you don't hear gurgling, you need to clear the line till it's clear and hear gurgling. Then run the engine w/o the tank vent installed and see if the bubbles go away. If not, you have to keep looking for source of air. Do not replace the lift pump yet.

I did replace the lift pump in a panic. Now I am second guessing myself if I may have reversed the lines on the lift pump. I have the line from port on the lift pump nearest the engine going to the fuel filter. can you tell me if that is correct?

Diseasel300 · #78 02-03-2017, 09:51 PM

Can you confirm if this is your fuel line diagram for your car:

If so, the fuel gets sucked from the tank, through the fuel heat exchanger, through Pipe 1 to the top side of the prefilter.

From there it goes out the bottom of the prefilter through hose 2 to the TOP REAR port of the shutoff solenoid, then out the BOTTOM FRONT port on the shutoff solenoid to the OUTER PORT (driver's side) on the lift pump.

Lift pump discharge is the port closest to the engine, goes through 4 back into the port on the driver's side of the canister fuel filter. Then goes through 5 into the TOP FRONT port on the shutoff solenoid. Overflow is through 6, then out through the banjo fitting furthest to the passenger side on the canister filter back to the tank.

Way more complicated setup than the 617 and 603. It appears that nearly every joint has an O-ring too. If they haven't been already, they need to be replaced!

packerfan · #79 02-03-2017, 11:10 PM

Quote:

Originally Posted by Diseasel300

Can you confirm if this is your fuel line diagram for your car:

If so, the fuel gets sucked from the tank, through the fuel heat exchanger, through Pipe 1 to the top side of the prefilter.

From there it goes out the bottom of the prefilter through hose 2 to the TOP REAR port of the shutoff solenoid, then out the BOTTOM FRONT port on the shutoff solenoid to the OUTER PORT (driver's side) on the lift pump.

Lift pump discharge is the port closest to the engine, goes through 4 back into the port on the driver's side of the canister fuel filter. Then goes through 5 into the TOP FRONT port on the shutoff solenoid. Overflow is through 6, then out through the banjo fitting furthest to the passenger side on the canister filter back to the tank.

Way more complicated setup than the 617 and 603. It appears that nearly every joint has an O-ring too. If they haven't been already, they need to be replaced!

I will take a close look at it tomorrow but from what I can see is line 3 does not look correct. on my car it goes from lift pump to lower side of pre-filter.

packerfan · #80 02-03-2017, 11:48 PM

Quote:

Originally Posted by Diseasel300

Your clear lines should be full of fuel at all times, even with the engine off.

If you have an air leak big enough, the pump will never prime. Given the amount of air you were sucking in the video you posted, I'm truly shocked it was even running.

To help you further, we need pictures, or a vehicle-specific fuel line diagram. I'm familiar with the 603 engine, and Funola is nearly an oracle on the 617, but knowledge is lacking on the 606. You need to start tracing fuel lines back (this means using your hands and eyes) and making sure you don't have leaks. If there's an O-ring in a joint, change it. If there's a rubber hose, replace it. If there's a hose clamp, install a new one. All the way back to the tank.

The lift pump isn't going to prime and your problems aren't going away until you find and FIX the leak in your suction line.

I'm really surprised and a bit disappointed none of the 606 guys are replying to this thread!

Thank you for hanging in there with me and helping me with this mess. would you happen to know the I.D. of the black rubber hoses that go from the hard pipes on the fender well to the injection pump so that I can replace those lines as well?

packerfan · #81 02-04-2017, 07:00 PM

Quote:

Originally Posted by Diseasel300

Your clear lines should be full of fuel at all times, even with the engine off.

If you have an air leak big enough, the pump will never prime. Given the amount of air you were sucking in the video you posted, I'm truly shocked it was even running.

To help you further, we need pictures, or a vehicle-specific fuel line diagram. I'm familiar with the 603 engine, and Funola is nearly an oracle on the 617, but knowledge is lacking on the 606. You need to start tracing fuel lines back (this means using your hands and eyes) and making sure you don't have leaks. If there's an O-ring in a joint, change it. If there's a rubber hose, replace it. If there's a hose clamp, install a new one. All the way back to the tank.

The lift pump isn't going to prime and your problems aren't going away until you find and FIX the leak in your suction line.

I'm really surprised and a bit disappointed none of the 606 guys are replying to this thread!

The part circled in red is the culprit. The red arrow is pointing to the black plastic nipple that the rubber hose coming from the tank connects to. the nipple was cracked at the base. what is that part called so I can get one ordered?

funola · #82 02-04-2017, 07:49 PM

Per Diseasel300 "the fuel gets sucked from the tank, through the fuel heat exchanger, through Pipe 1 to the top side of the prefilter" that's the fuel heat exchanger.

spock505 · #83 02-05-2017, 11:08 AM

That's a lot of air for sure, couple of things to consider when tracking down air leaks which may help.

As the fuel leaves the pump (pipe 4) you should see diesel leaking rather than air being pulled in, this is down to the pump being in 'push' mode as opposed to 'pull', obvious when pointed out but perhaps not so at a casual glance.

Another part that sometimes gets overlooked is the fuel return valve, this keeps a certain pressure within the fuel delivery system regulating supply back to the tank.

This should be similar to the one fitted although they do have subtle changes.

edit, this was mine off my OM605

Diseasel300 · #84 02-05-2017, 11:39 AM

A leak at the relief valve will not cause the pressure in the tank or the air he is getting in the lift side of the pump. If the relief valve leaks, you'll have fuel dripping out externally. If it is worn out internally, it can bleed pressure off to a certain point, but will not cause the pressure in the tank or the air in the suction lines.

OP has identified the leaky culprit as the fuel heat exchanger from the looks of things. Now he needs to either replace it, or bypass it (if possible on the 606).

My 603's fuel heater thermostat had the famous O-ring leak allowing large amounts of air in the system. Replaced the O-ring only to find that the thermostatic element was stuck wide open and continuously heated the fuel, so the point that after a 30 mins or so drive with about a 1/3 tank of fuel, the lines to the lift pump were uncomfortably warm. The side effect was excessive pressure in my fuel tank. Bypassing that thermostat and fuel heater on my car ended my problems. I don't live in a cold climate, so it was unneeded for my application anyway. At some point I'll replace the thermostatic element, but it's pretty low on the priority list.

spock505 · #85 02-05-2017, 02:59 PM

I must admit to losing track of what was happening here, couldn't quite see the reason for switching out the lift pump before other remedial measures were ruled out.

In all honesty, I cannot see the benefit doing anything without clearing the tank vent first, this will almost certainly override anything else that is done up front.

packerfan · #86 02-07-2017, 01:25 PM

Quote:

Originally Posted by Diseasel300

That's a massive air leak. I hadn't had a chance to view the video until today, and frankly I'm shocked the engine runs on that.

Here's a fuel line diagram for your car:

The intake line to the lift pump is the lower line coming out of the prefilter 70/1 and going to the Y1/1 shutoff solenoid. If that's a clear line, see if it has air in it.

I'd be willing to bet the air is coming from the heat exchanger 60 or a rotten line or O-ring somewhere.

I am curious as to how the thermostat in the heat exchanger works?
I would think it would restrict fuel flow when engine is cold.

Diseasel300 · #87 02-07-2017, 02:38 PM

The fuel heater thermostat determines how much fuel will flow through the heat exchanger. When the fuel is cold (winter weather) it flows the fuel through the heat exchanger to warm the fuel up to help combustion/vaporization. As the fuel increases in temperature, the thermostat closes to bypass the heat exchanger, sending the fuel directly to the fuel filter and pump.

packerfan · #88 02-07-2017, 07:01 PM

Quote:

Originally Posted by Diseasel300

The fuel heater thermostat determines how much fuel will flow through the heat exchanger. When the fuel is cold (winter weather) it flows the fuel through the heat exchanger to warm the fuel up to help combustion/vaporization. As the fuel increases in temperature, the thermostat closes to bypass the heat exchanger, sending the fuel directly to the fuel filter and pump.

Brilliant,
Diseasel300, is there anything that you don't know about Mercedes diesels?
You and the other guys here have been so helpful. I am actually starting to enjoy doing maintenance on this old car, it has almost 400,000 miles on it and has been so reliable to me. It does not leak or burn a drop of oil between oil changes.

Diseasel300 · #89 02-07-2017, 08:22 PM

I could fill a book with the things I *DON'T* know about diesels! Working on things helps keep me centered and I enjoy working on my car and learning more about it. I'm helpful on your issue because you're doing a similar routine to what I did with mine when I first got it. The 606 is an evolution of the 603, so the basic mechanics aren't too different. If you had a CDI though....me and electronic engines do not mix!

packerfan · #90 02-07-2017, 10:07 PM

Quote:

Originally Posted by Diseasel300

I could fill a book with the things I *DON'T* know about diesels! Working on things helps keep me centered and I enjoy working on my car and learning more about it. I'm helpful on your issue because you're doing a similar routine to what I did with mine when I first got it. The 606 is an evolution of the 603, so the basic mechanics aren't too different. If you had a CDI though....me and electronic engines do not mix!

I'm sort of happy to here what you said about not being too interested in electronic CDI engines. I was thinking of looking for a newer Mercedes CDI diesel because my E300 is not going to last forever but I am very leary of getting into something that I would be totally lost in as far as working on it myself should problems arise.
If I were to upgrade from the 1995 E300 to something else, what would you recommend as far as year and model, I would deffinetly want a turbo this time around?