short model fuel pump impeller

[offroadbob]

i successfully disassembled my fuel pump and found that my impeller is slightly damaged (some chipped vanes). i have looked through the posts pertaining to this style pump and can't find much info about it. i have a friend who runs a machine shop and he said it would be difficult to remake. the very thin vanes would probably snag or distort. i did see a impeller picture from the tall original style pump on this site and the vanes appeared to be much thicker. 1. are there replacement impellers for sale anywhere? 2. it appears that the impeller is made of stainless steel, and i'd like to find out what grade of stainless steel it is made from. 3. does anyone have a spec drawing of the impeller so it can be remade? 4. i ordered a reseal kit but the brushes were not included (didn't find the "rebuild kit" til after i ordered the "reseal kit") and as long as i have it all apart i thought i'd replace the brushes too, so does anyone just sell the brushes? i'm having a problem attaching pics to the post, do they have to be online with an address or can the be posted directly from my computer?

[Kevkeller]

I don’t know any place that supplies impellers.  However I was going to talk to a friend with a water jet that might be able to make them. I believe it is made of a hard aluminum not stainless steel. 

[BaronYoungman]

The impellers are no longer available have not been for at least 15 years. They are made of aluminum but they also have a chrome Center for the impeller to float on the fins are tapered which makes water jetting them very difficult I have had CAD drawings made and have been experimenting with them for the last 6 months I think I am close.
Bob

[ja17]

I suspect a CNC mill might be a little more feasible.  The cutter could be made to have the correct taper for the vanes. The center opening could be broached for the correct shape.

[offroadbob]

i was thinking it could laser cut to size. then then mill the angle on the vanes.

[offroadbob]

why would two different  metals be used? is it necessary? was the aluminum cast around the chrome center then milled? could it be duplicated by pressing a chrome center into a milled aluminum outer ring? sorry if these questions are too many, my ignorance is vast. but mostly trying to figure out a work around.

[BaronYoungman]

So it is an aluminum composite where they Chrome the center to harden it I assume that this is because the shaft is Steel and it would wear down the aluminum too fast and yes that is a original new replacement impeller and that is the correct number maybe you could search some Off the Grid parts places and they might still have one of these on the Shelf. As you can see from the second and 3rd pictures how the half moon Center rounded out after use which means then every time the motor starts it pushes the impeller over into the inside wall of the pump eventually jamming it.  I would offer to sell this replacement impeller but it is the one I am using as a template and control to make the reproduction ones.

[offroadbob]

thanks bob

[offroadbob]

here's what mine looks like. i would like your opinion on if you think it would still work.,

[BaronYoungman]

For idling or lower speed I think you will be ok, Long highway speed it is questionable.  What will happen is your flower pot (in fuel tank in back)  will receive less and less fuel back from the fuel injection unit because it is using it all, eventually, you will get fuel starvation especially on a turn or worse the pump will overheat due to no gas flow cooling the top of the can.  You might ask Joe A. he has more experience with what you can get away with and still function.  The pumps themselves are very robust and will take alot of abuse, but some of those teeth look to have lost about a third of their metal, they are just one small piece of rust or simply the weight of the gas on initial start up,  from snapping or worse bending and jamming the whole pump.  Would I use that in one of my pumps short answer NO.
P.S. you can tell exactly were the lowest point on the pump was while it was sitting, you can tell by the corrosion on the teeth.

[BaronYoungman]

I am very close on working models of the impeller, just needs to be perfect

[Pawel66]

What is the next step? 3D print, mould and die cast? Or you make it on a milling machine tool from a piece of metal?

[Benz Dr.]

Fuel pressure is directly related to fuel volume. No volume means no pressure. This fuel pump can produce 1 liter in 15 seconds and about 10 - 15 PSI which means it can empty the whole fuel tank in 20 minutes on a 280 SL. A full tank can go 360 miles or about 6 hours of driving. You should never run into a fuel starvation problem at road speed unless you don't have enough fuel volume. A working fuel pump should be able to circulate a full fuel tank about 18 times until empty. The IP uses only a very small amount of the fuel that passes through it which is how it was designed so that all that extra fuel acts like a fuel cooler.

There is no way that impeller would ever be able to create any volume or pressure. May it RIP.

 

[Shvegel]

At the risk of being ostracized The fuel sytem in our cars was under evolution during it's entire run.  Has anyone considered just "Evolving" beyond this rediculously expensive low volume and low pressure fuel pump?  Bosch figured out in the next generation that in order to Prevent vapor lock you needed to maintain a fuel pressure in the entire system above the vapor pressure of the fuel being used (15-18 psi for modern fuel.)  If we jump up a generation in pumps and put a regulator/ accumulator in the return I bet we could kill two birds with one stone.

[Benz Dr.]

You could increase the running pressure but it would mean having to change all of the rubber fuel lines to high pressure for safety purposes. I'm not sure if the IP would accept higher pressure without it somehow affecting how the pump operates. I will ask my pump guy the next time I talk to him.
The fuel pump is really just a charge pump in that it moves fuel up to the IP where the real work of getting the fuel ratios just right under all operating conditions is performed.  I was always under the impression that this system is low pressure high volume but maybe that's not right.

[Shvegel]

Dan,
High volume for the time.  Injection pump won't care as it is designed for at least 150psi through the chamber.  You have a valid point about the fuel lines I have actually run the setup I described for a couple years at 40psi and didn't change the lines.  I should have.  When I ran it I had zero issues with starting cold or hot.  I think what Bosch figured out on our cars is that what worked on a diesel isn't necessarily going to work on gasoline.  It was OK to just have the injection line pressurized with the engine off because the vapor pressure of Diesel fuel is much lower and the pressure in the line was much higher.  Going to gas the slightest leak in the injector or the delivery valve will cause the residual(engine off) pressure to drop below vapor pressure which allows the fuel in the lines to vaporise and push the liquid fuel down out of the lines (Vapor lock).  I used a pump and regulator / accumulator from an 80's Saab but given a clean slate what I would search for ideally would be a pump that could put out 30psi at the same volume as stock and a regulator / accumulator that would run at around 20psi.  even a separate accumulator (early Porsche?) would work it just wouldn't be as neat. 

[mbzse]

.../...I'm not sure if the IP would accept higher pressure without it somehow affecting how the pump operates.../...

According to sources in German M-B clubs etc, too high a pressure in the fuel line will come back to haunt you   0,8 bar is specified as ok, no more.
See Book of Tables or BBB.
The reasoning behind the spec is mentioned to be a risk for an increased fuel pressure to wash away lubrication and oil barrier in the Injection pump. With time, metal inside IP will wear! (expensive...)

As written before, when M-B state a specification (fuel pressure in this case) it has some basis in the design of the system (and hardware)!
To second guess the M-B design department is futile (well at least carries consequenses)

[Jonny B]

From Hans "To second guess the M-B design department is futile"

so is resistance.....

[mbzse]

You can only give in 
Wasn't it Marilyn Monroe who said "the best way to get rid of a temptation is to give in to it"

[Shvegel]

Oil barrier and lubrication in fuel injection pump is subject to 200psi(13 bar) at injector open and the low pressure fuel gallery is tested at 3 bar when the pump is assembled.  There are no seals that could be old or brittle either.    I just had my injection pump apart after running two years with 38psi(2.5bar) and there was zero sign of wear.  It went back together with the same elements.  From a vapor lock (fuel boil) standpoint this system was always a dog.  Bosch put Band Aids (Plasters) on it from day one.  The fuel enrichment solenoid, the start assist kit, the outlet fitting change and at the end of production the ball check valves.  This system was bad when gasoline was predominantly gasoline but with the mix of  things added to fuel these days it is even worse.   

You don't  need to run 38psi (2.5 bar) as I did but 20 psi would be plenty of pressure provided you could find a regulator / accumulator  that would work at 20 psi(1.5 bar).  That would give you a better fuel shot when cold and would be high enough to keep the fuel in the lines from boiling out.

I just did the reasearch.

This pump:
Pierburg 7.21287.53.0

This regulator:
Bosch 0 280 160 001

Mount both on a bracket in the original pump location so the pump cover covers it then route the return line into the fuel pump cover to the side port on the regulator.  The bottom port with the threads is the outlet back to the tank.  If you mount the regulator on it's side with the inlet facing down it will act as a small accumulator to allow some leakage from the check valve or injectors.  connect a gauge where the cold start line connects to the fuel hose assy and set the regulator to 1.5 bar.  Problem solved. If not I would creep up to 2 bar.

Pierburg make a good pump.  I just replaced the original one in my 2002 BMW with 150,000 miles on it. It was still running.

[Kevkeller]

Ok.  I have a friend with a 3D water jet that does angles.  He should be able to get the impellor cut easily. I would like to know what kind of aluminum we should use and also if we should make the center out of a different type of metal.

If someone has a CAD drawing that might help or maybe he can do it.

Kevin

[ja17]

Waterjets are amazing, but I will be surprised if they are precise enough for this part. I guess we will see.

[PeterPortugal]

Guys,
Any progress on the replacement impellers?
Regards
Peter

[Kevkeller]

I have been away from home quite a bit and haven’t seen my friend.  It’s still on the long list of things to do. I’ll try to move it up. I think Bob is making progress though.

[BaronYoungman]

I am in the long term testing of a prototype that I feel is of very good quality.  I intend to have a long term test of 200 hours on it which according to the sources I found is the equivalent of 10,000 miles.  My testing parameters are 5 hours on, then rest for 1 hour then 5 hours on and rest for 2 hours then 8 hours on then rest 3 hours and this works with my schedule so I expect to be able to look at wear results in approx 2 weeks I will start testing late this week.  Will let you know on results.  Sorry it is taking so long but had to get metals and forms just right and if you haven't figured it out by now, I am a bit obsessive.
Bob