Mechanical fuel pump question

[Scutch]

My car died today while I was in another town. (Not too convenient.) I was low on gas and I thought I could go a little farther. It stalled, but I had the symptoms of running out of gas. So I went and got 1.5 gallons and put it in and nothing happened. I have since put in another 1.5 gallons.

I checked to see that gas was only sputtering out of the fuel pump. So I am pretty sure I need a new one. It looks like where the foot pivots is the problem. The fulcrum there is loose and seems to be slipping out of where it attaches to the body of the pump. This is my second one in a couple years.

I have the kind that sit vertically and have a foot that gets kicked by that shaft that goes in and out off the side of the engine. They seem to sell them at autozone and the like.

Autohauz Az 1150900150 and Fastlane W0133-1607159 parts have the kind that sit horizontal. I assume these horizontal ones will fit fine, I just have to take those other two, (I think) allen bolts off the casing on the engine? Then the horizontal mount will fit, yes?

It looks like a lot of oil will leak if I take those two bolts off.

Am i right that these will work fine on my 68 230s? Judging from the look I am a little concerned that the metal bar that comes out of the engine is too long to fit with what I am seeing in the pictures of the horizontal ones.

The ******** one is $34. Does that mean it will also be crap? What is recommended? What mount will I get if i order from Mercedes?

I haven't called on parts yet cause I was troubleshooting till closing time. Was just hoping to get some feedback for tomorrow's scramble to get my car out of the other town.

Thanks
Eddie

[MunichTaxi]

Check the oil level; make sure gas isn't filling the crankcase.

Is gas flowing to the fuel pump? Might have to jack up the car, so gravity creates a flow.

Perhaps the filter screen, where the gas exits the gas tank, is plugged. Of course, you'd have to empty the tank, to inspect the screen.

I got burned with an aftermarket pump; have since converted to the Carter Rotary vane, 5 psi.

[Scutch]

I bought the 1150900150 Pierburg fuel pump and it will not fit. If all the mounting metal around the power steering pump wasn't there it would fit fine.

I looked to see if I could take all the steering pump stuff off, install the fuel pump and put the power steering stuff back on. But that won't work. There is just no room.

Has anyone else had this problem? All these horizontally mounted pumps look the same size. What am I doing wrong here?

I bought an electric pump.

I have called around for fuel pumps and I am hearing from Mercedes that they are no longer available.

Eddie

[Scutch]

I realize now why I am having a problem getting the fuel pump to fit on the car. See below.

Has anyone else dealt with this? I called the Classic center and they have the original right angle mounting pump for around $350. I would prefer to use a mechanical pump, but that is too much money.

The side-mounting Pierburgs are $100.

In 2007 I took off the AIR system stuff, but left the pump and pulley setup. Now it is in the way.

Any alternatives?

Thanks

Eddie



Originally Posted by Mark DiSilvestro View Post
What you've described is not EGR (Exhaust Gas Recirculation) but an AIR (Air Injection Reaction) antipollution system, used on some US-market 6-cylinder Mercedes from 1968 to 1970. If all of your AIR system is still there, you should have a belt-driven airpump mounted below the power steering pump, connected by a hose to a check-valve on the end of that tube, to force air into the exhaust ports. The vacuum line to the carb should be connected to a backfire-suppressor valve installed somewhere between the pump and check-valve. If your original AIR components are damaged or missing (and probably unavailible), and you're in an area that isn't emmissions-testing '68 cars, your best bet may be to remove that tube and plug the holes in the head, as most likely you actually have exhaust leaking from that crack. Alternately it may be possible to braze or weld the crack.

Happy Motoring, Mark

[Mike D]

Listen to Munich Taxi. Best way to go. The solenoid style aftermarket fuel pumps work fine as a "pusher" but they just don't have the suction required for top end rpms if you mount them on the fender well. Remove the mechanical pump, plate the opening and supply power to the pump by way of the ballast resistor supplying the coil. You can use a voltage relay and use the ballast feed as a trigger or use the ballast feed as supply. I've done both with no problems.

[Scutch]

Mike,
Let me make sure I know what you are saying. Solenoid style pumps are electrical, I guess if you are mounting them on the fender well.

You are then talking about still using a electric fuel pump, but another one, I guess that will suck enough.

Thanks for the wiring tips, I was looking for something simpler than going all the way under the dash to the ignition fuse. If you are talking about the "trigger" then are you talking about the solenoid type electric pump?

I got a $45 4-7psi electric pump from Checker auto. Will that work? Or is that the aftermarket kind that won't. I figure everything that is not the right angle pump is aftermarket.

When You and Munich Taxi say aftermarket pump I am not sure if you mean electric or mechanical.

What do you mean by trigger? I have two wires. I should be connecting one to something that switches with the ignition and the other to ground.

Are you saying I can connect the red to ballast next to the coil and the other to ground?

My apologies. I made this much harder than I am sure it is.

Eddie

[Mike D]

Solenoid pumps are usually cylindrical. The supply line is on one end and the outlet is on the other. A straight through design. A vane style has a large canister which houses the actual pump motor. It looks like a filter element canister.

By "trigger" I am talking about wiring a standard voltage relay which requires a 12V feed line, a ground and a trigger wire (12 volt feed which simply switches the relay "on). The advantage of using the relay is the 12V supply is not tied to the ignition circuit. You avoid the current draw of the motor on the ignition circuit. I've had no problem running my pumps from the supply side of the ballast resistor but it is an option.

By aftermarket we do mean electrical. We say "aftermarket" so someone doesn't think they can pick up a fuel pump from a pick and pull and wire it in. The Mercedes electric fuel pump delivers too much fuel pressure for a carburetor.

The red wire needs to connect to the supply side of the resistor not on the side which leads to the coil.

[Scutch]

Mike,

I appreciate your patience. I think I've almost got it. I have a solenoid pump, per your description.
You are suggesting two options. One has the red wire connecting to the supply side of the ballast resistor. Black to ground. This setup will send juice to the pump as soon as the key is turned to the ON position and my gen/alternator light is red, and will shut off not when the car shuts off, but only when my key turns off, yes?

Option two has an extra switch in the circuit that I assume you would control under the dash or something. This system still runs off the supply side of the ballast resistor, but only if the switch (standard voltage relay) is activated manually by the driver. Yes?

The other part you mention though was that the solenoid pumps may have a problem at high RPMs "if you mount them on the fender well." Is there a better place to mount them? Mine is going right in front of the battery just below the coil. That seemed like the place best suited to draw the fuel from where it comes out of the metal line just under the battery.

Are you saying that I should dump the pump I have, that it may not be strong enough and I should use a Carter rotary Vane type instead. Or does proximity of the pump make a difference?

Thanks again

Eddie

[Mike D]

The ballast supply is live when the engine is in the "run" position and on your car it is probably when the "gen" light is on. It shuts off when your car engine is shut off. If the engine stalls and dies the pump continues running, the same as your coil as it is still getting power.

The voltage relay option is simply a standard voltage relay (square box with 4 or 5 terminals on the bottom) available at any parts store and used on almost every car since the mid 70's. One terminal is supplied power from anywhere, even straight from the battery, one terminal is ground, one is "switched" power and one is the trigger. The "trigger" is usually the ignition circuit. The relay is activated and power flows from the supply through the relay to the unit needing power. No current draw on the "trigger", the relay simply uses the trigger to complete the circuit. Turn the key off, the relay opens and no power to to the unit. It sounds more complicated than it is.

Try the solenoid. It may work fine for you. If you can return it for credit against the vane style then that is what I suggest you install.

[Scutch]

Thanks again Mike!

I am gonna try the simple wiring option on the ballast resistor.

Eddie