PeachParts Mercedes-Benz Forum - View Single Post - Fuel Injection diagnostic 103 engine. Need advice.

dpetryk · #9 11-01-2001, 10:19 AM

I have seen the situation where the fuel leaks out of the control piston in the fuel distributor. There is no seal on the piston other than very close tolerances and after many miles the piston can leak - which is not really a problem since the fuel simply evaporates and gets inhaled by the running engine. It might explain the leakdown pressure problem.

However - I dont think the leakdown problem is causing your long cranking times. When the fuel pump is started, fuel pressure is almost immediately at maximum. It does not take more than 1 second to reach maximum even if the accumulator is not pressurized.

Can you verify that the fuel pumps are indeed running when the problem happens? I had a similar problem and it turned out to be the fuel pump relay. There were micro-cracks in the solder joints on the board. It could have caused low voltage at the fuel pumps. Anyway, I resoldered the board and everything is fine.

You can build a poor mans fuel pressure tester by getting an old fuel line with the appropriate fitting and welding a pressure guage fitting to the other end. Install a 0-100psi guage and you have it. There are two places on the fuel distributor that can be monitored for pressure. Buy a fuel line from the local MB place and modify it.

Proceedures for testing leakdown rate are on the CD.