Fuel pump dead?

[dseretakis]

My brother's 1970 280SL will not start. The car was running when it was parked 14 months ago. The car cranks but won't start. The fuel pump doesn't make any noise. The fuel pump fuse in the fuse box is ok. Where do we go from here? Any ideas?

[ctaylor738]

You can give the pump a couple of gentle whacks with the key on and see if that wakes it up.  If no luck, test for voltage at the pump's + and - terminals.  If you have voltage with the key on, time for a new pump.  If no voltage, check the wiring.

[dirtrack49]

Most likely you have a stuck impeller from sitting with stale gas inside the pump.

Take a look at the Technical Manual under the topic Fuel Pump, How to fix a gelled up pump.

Pretty easy to do even on the long pump that I have on my 66 230SL.

[dseretakis]

Thanks for the replies. I will try these tests and see what happens. If impeller is stuck will pump not make any noise?

[ja17]

If the impeller is stuck, the pump cannot turn and there will be no noise. Twist that fuel pump fuse back and fourth, the ends corrode. This might renew the connection. As Chuck mentioned, check to make sure you have power to the pump.

[ctaylor738]

The gentle whack will hopefully free up the impeller.  Also, if it's stuck, you can put your hand on the pump and feel a "chunk" when the ignition is turned on.  This is quick indicator that you are getting voltage to a dead pump.

Cheers,

CT

[Mike K]

I had the same issue last year with the fuel pump. The impeller was stuck as a result of dirt from the old fuel tank. I ended up replacing both the tank and fuel pump.

While you're trying to get the pump going, it's a good idea to keep checking the fuse in the fuse box.  
Mine kept blowing the fuse each time I tried to get it going, as the pump was heating up with the impeller not turning.

Good luck.

Mike

[tel76]

Do not discard a pump that has slight grooves in the base plate, it is salvageable.

[dseretakis]

So I checked and there is power at the pump. I also banged the pump around while the ignition was in the on position but the pump would still not work or make any sound. I also did not feel a thump while holding the pump with the ignition turned on and off. I guess I will drain the fuel tank, remove the pump and try to take it apart.

[enochbell]

Save some time and don't drain the tank.  You can shut of the fuel lines with clamps specially designed for the purpose or, and I hesitate to admit this trick for exposing myself to a yellow card from some of the real mechanics on the forum, you can use a couple of sockets inserted over the jaws of a vice grip and use that contraption to pinch off the flow.  Once you have the pump disconnected from the lines just plug them with a suitable stopper and release the pressure on the clamps...it is probably not good to clamp them like this for any extended period as it may weaken the walls of the line.

g

[georgem]

Hey enochbell,

I`m a back yard mechanic, not a "reaL" and but I have not heard of the sockets and vice grips technique before - its now in my little black book of tricks on how to do things - great idea.

[scoot]

rebuild kits are available but I don't know where at present.

[ja17]

Be careful of old dried out fuel lines. Sometimes they start leaking after they are clamped. If so they need replaced anyway.

[dirtrack49]

I think you can do the same with the short fuel pump as I did with my earlier long pump. In order to get the pancake screws off of the bottom of the pump and get to the vane (impeller), take the pump off of the car and sit it in some PB Blaster. I just took a lid from an old pickle jar and filled it up enough to cover the screws. I let mine soak in this solution for a week. After soaking, take a screwdriver that fits the screws perfectly, tap the screwdriver with a hammer on each screw to help break any welding of the metals. Now push down on each pancake screw with as much force as possible, and turn. Hopefully, all of the screws will come out without a problem. I was lucky, after 48 years mine came out without breaking any screw heads off. If you do break some off, you will find other solutions on this forum to take care of that.

Like Joe said, make sure your fuel lines are not brittle. Most of these cars need to have all of their lines replaced after all of these years.

Good luck.

[mnahon]

Here's a rebuild kit:

http://www.ebay.com/itm/MERCEDES-W108-W111-W113-SHORT-STYLE-FUEL-PUMP-REBUILT-KIT-PAGODA-/221644511010?pt=Vintage_Car_Truck_Parts_Accessories&hash=item339b0ad722&vxp=mtr

(no connection to seller)

[dseretakis]

I decided to give the pump a few more vigorous whacks before taking it apart. It now works!! Thanks to all for the advice