Fuel Pump Mounting - Carter P4601HP

[Tomnistuff]

I am sure that several of you have become, like me, a non-masochistic purist, in that you have finally replaced your leaking-at-the-terminals Mercedes Bosch short fuel pump with a modern inexpensive alternative that you can replace about 12 times before you will have spent the cost of a new replacement Bosch short pump.  The one I am favoring is the one that is discussed in several threads by Joe Alexander, the Carter P4601HP (high pressure*) rotary vane pump.  Because I trust you implicitly, Joe, I have only one question, which is moot, since I've already ordered the Carter pump for my car.
Question:  Have you noticed any problems with pump priming resulting from the rotor being at the top and the terminals being at the bottom?  It looks like that mounting orientation (verified correct by a Carter fuel systems technician) will either result in a problem with the pump rotor being uphill from the "flower pot"TM, or the fuel pump terminals dragging on the pavement.

Tom Kizer
Levis, Quebec, Canada

* grain of salt goes here

[ja17]

Hi Tom,

I have used this pump a couple of times and had no problems. I mounted at the same level as the original. It is a little noisier than the original so use rubber mountings as original. I wonder if sound absorbing insulation on the metal shroud would cut down on the noise? I like the idea of staying original, but this seems like a good alternative or possibly a spare to carry along. 

[Tomnistuff]

I would have no qualms about fixing the original, in fact I thought I did.  Right after I "kitted" it, it was great but has been sitting for a few months and now leaks ai the wire terminals when running.  Having already read the wire terminal O-ring history, I was so happy it didn't leak.  So when it did, I surrendered.  As I have said in the past, "I'm a purist, but not a masochist.  I already had a 50 year old Ferrari catch fire on a back road at midnight, causing lots of rewiring and electrical system redesign.  The last thing I need is a gasoline fire on the road.
Thanks for your comments.  I'll install it terminals down.
Tom Kizer

[Tomnistuff]

I can't let this thread die without explaining what led to the new Carter fuel pump after having rebuilt and installed the original Bosch short fuel pump.

The reason bridges two thread categories, fuel system and non-original items.  I'm getting old enough to forget things, not just long ago things, but things like what I had for breakfast.  Without all the new modern bells and whistles like on my family Mercedes, I would leave the "manual" lights on in the Pagoda and run the battery down.  I decided to add a "lights-on" warning chime to save the battery and my pride.

Coming back home from PUB2015, I stopped at a Radio Shack and bought a 12V chime to install during my restoration.  Two weeks ago, I started installing it.  I tested it using the fuse panel, and having verified that it chimes when the lights are on and the key is switched off, and stops chiming when the lights are switched off, I decided to install it in the trunk.

I hooked the chime's red wire up to the left tail lamp bulb (+) wire (light switch activated) and started to wire the chime's black and blue twisted pair up to the fuel pump (+) terminal (ignition switch activated).  That's when I found the weeping leak at the terminal 0-Rings that apparently appeared while I was using the ignition switch to test the chime.  That led to the week-long effort to replace the pump with the Carter P4601HP modern centrifugal pump.

Anyway, knowing how you all like photos, I have attached a photo of the completed pump (without the chime wire which is now installed as well).  The pump is not as noisy as I thought it would be, probably because, in addition to the three little rubber isolation grommets between the pump and its mounting bracket, I drilled three holes in the Mercedes mounting bracket base plate, removed the three legs and installed the pump bracket to the original Mercedes mounting bracket base plate with the original rubber isolation stand-offs.  That mounts the pump a little lower but appears OK relative to the ground and still provides for two rubber isolation "systems" in series.  See the close-up photo of the pump mounts.

Everything works relatively quietly and I'm happy.  I still have to reinstall the pump cover.  I hope it will not be too much trouble to fit.  It never was the original cover so if I have to modify it, too bad.

Tom Kizer
Levis, Quebec, Canada

[ja17]

Good job Tom,   Seems I mounted mine with the wires up. But I like your installation a lot. Let us know how it works out.

[Tomnistuff]

Thanks Joe.  I sent the following question to the Carter Tech Help Line, and got the answer that is shown.

Is there a reason not to mount the pump with the inlet/outlet near the bottom and the +/- electrical terminals at the top?

Hello,
Yes there is.
This design pump uses the fuel flow through the motor to lubricate, and also cool it when in operation. Mounting, without the electrical terminals facing down, can cause them to not properly cool or lubricate inside.
Thank You,
         Bob Reynolds
         Call Center Technician
         Carter Fuel Systems

I don't have a lot of fuel in the tank so it may require some more for it to prime.  I'll let you know.

Tom Kizer

[Chris_ATL]

That's a clean set up... Are you considering adding a shroud to protect the pump?

[Tomnistuff]

Hi Chris_ATL,
Yes.  I mentioned the cover/shroud in the last sentence of REPLY #3, above.  My original shroud was not original.  It came with the car when I bought it in 1987.  It's from some sedan, but I forget which.  I'll do what's necessary to protect the pump since the shroud is not original anyway.
Tom K.

[Philippe VIARD]

Hello,
Over time, how does the Carter pump work in everyday life, in terms of priming after a prolonged immobilization knowing that the top of the pump is located higher than the bottom of the tank?

[Tomnistuff]

Hello, Philippe,

The pump is still working perfectly.  I have never had a problem starting the car with the aftermarket pump recommended by Joe Alexander.

I have an under-dash cold start injector switch to bypass my "no-longer-functioning" cold start system.  That allows me to add cold start fuel before or during cranking but I have never needed more than the one-second squirt that the original cold start system used for warm starts, because I keep my car in a heated garage and only drive it between May 1 and November 1 here in Quebec.

Additionally, I usually keep the fuel level above 1/4 full so the pump doesn't get starved, and also to reduce water condensation effects.  I worry more about water condensation in the fuel tank than pump starvation due to low fuel level. 

Tom Kizer

[Pinder]

Looks like a nice clean setup.   

When I rebuilt my original pump (I did it three times) , the first two times it would leak. to get it to seal properly I had to use sand paper of different grits (400, 600, 1000)  to flatten out the bottom plate. it was slightly warped. i used  granite counter top to take down the paper. I had also ordered nitro o rings for the electrical connection points.

[Paul99]

I used this pump on my other car (Ultima spyder) which has a 6.3ltr V8 engine so gives loads of fuel. Been running for 27 years all ok. Only problem is the noise.  Very loud compared to others. Did try the so called quiet kit but still fairly noisy.  I use a bosch on the pagoda, very quiet. 

[Pinder]

I have two of these pumps . Same make and order from Amazon. one was really quiet and the other was noisy.