short model fuel pump impeller

[PeterPortugal]

Bob,

Thanks for the update. I am sure many of us here appreciate your efforts with this development exercise and are happy to hear that progress is being made.

Also, that was a great article you submitted to Pagoda World !

Best Regards

Peter

[Benz Dr.]

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.

From what I've seen, all fuel injection, including modern systems, require some sort of cold start valve to promote an initial fuel mixture that will make the engine fire when cold or hot. I can only assume since this was all new technology 50 years ago, that MB did the best they could as the system was improved during this production run even though what they had was light years ahead of everyone else. Now new systems are using direct injection just like MB did in 1954 on the Gullwing. What's old is new again.   

[Shvegel]

I honestly think Bosch was limited by the fuel pumps of the day.  The very next system D-Jetronic (not a huge fan) was the first system to treat the entire fuel system as one pressurized system which held pressure with a single inlet check valve and a single outlet check valve with a rubber seat which is a huge step forward from 6 delivery valves relying on a perfect seal from their metal seats.  The thing I really like about Bosch as a company is that you can see a clear evolution between one system and the next.  If they have something that limits their system the next generation system clearly fixes it.  Good stuff.