1995 E420 - Slow starting (extended cranking)

[dchesrown]

I am on my 2nd w124 last one lasted 220,000 k. I now have a 1995 E420 with 80k miles, it is my daily driver and runs and drives like new all but the slow start. It has new plugs, rotors, plug wires, fuel and air filters plus new fuel pump check valves. I get a long crank time to start the car. If I hold the gas down it fires up but revs more than I like and I can also smell gas after doing this. If I just crank on it it cranks and eventually starts but takes at least 10-15 seconds. It seems like the fuel is draining from the lines and it has to make it back to the injectors. This is why I replaced the check valves.
Where should I go next? Fuel pumps? Is there a fuel pressure regulator on the 420? Any input appreciated.
Thanks
David

 

[jhodg5ck]

Re: 1995 e420 slow start

is this warm or cold hard start? Did you check fuel pressures @ rest? Pressure regulators @ the fuel rail fail with some regularity.

improper signal from an engine temp sensor can weird things out as well.

jono

 

[gsxr]

Re: 1995 e420 slow start

If the fuel pressure regulator is original... I'd try that first, it's located at the driver side of the fuel rail where the hoses connect. Pull the vacuum hose and see if there is any sign of fuel, there should be none. Ideally you can connect a fuel pressure gauge to the rail and see if you are getting correct pressure during the extended cranking.

If the car runs normally once started, it isn't likely the pumps are bad, but if they are original you'll need to replace them sooner or later (Bosch only!).

BTW - any error codes? Particularly any codes from the EZL about the crank position sensor?

 

[dchesrown]

Re: 1995 e420 slow start

is this warm or cold hard start? Did you check fuel pressures @ rest? Pressure regulators @ the fuel rail fail with some regularity.

improper signal from an engine temp sensor can weird things out as well.

jono

Both warm and cold start. I had the pressure tested it bled down after sitting. I think I will try the pressure regulator next.
Thanks

 

[gsxr]

Re: 1995 e420 slow start

Both warm and cold start. I had the pressure tested it bled down after sitting. I think I will try the pressure regulator next.
Thanks

Pressure spec is to remain above 2.5 bar (36 psi) for 30 minutes after shutdown. What was the time & pressure when you tested?

When the key is turned to start the car, the pumps run for 1-2 seconds, and the pressure should jump from zero to ~50psi during this time, and remain around 50psi during cranking.

 

[dchesrown]

Re: 1995 e420 slow start

Pressure spec is to remain above 2.5 bar (36 psi) for 30 minutes after shutdown. What was the time & pressure when you tested?

When the key is turned to start the car, the pumps run for 1-2 seconds, and the pressure should jump from zero to ~50psi during this time, and remain around 50psi during cranking.

Pressure dropped to 16-18lbs. after sitting. Car runs and drives perfect other than long crank time and the smell of fuel right after.

 

[dchesrown]

Wanted to provide an update. Replaced the fuel pressure regulator and the car is fixed. Starts right up.

http://www.benzworld.org/forums/w140-s-class/1568146-photo-diy-fuel-pressure-regulator-r.html