1986 420sel Crank No-Start Problem - PeachParts Mercedes-Benz Forum

tbjcc001 · #1 04-30-2008, 11:26 PM

Hey Buddies:
1986 420sel 177k Crank - Nostart condition present!

Problem started with cutoff when at Stop! Restarts & drives fine, then cuts off at stop again!! Now cranks but won't start! Suspected FUEL PUMP RELAY! Jumped Fuel Pump & started okay! Idle fine!!

Replaced FP-Relay w/ good used, now cranks but, won't start & has heavier than normal fuel smell present!! Cranked until battery now completely discharged.

Suspect CPS / TDC Sensor but, NEED / WANT VALUED OPINION 1st!!!!
No SHOP Diag TOOLS available. Using DMM, Test-Light, Vacuum Gauge(s) & common sense (what little is left).

MAINTENANCE PREVIOUSLY PERFORMED:
Battery New
Plugs New
Wires New
Belts New
Oil & Filter Changed
Trans Filter & Fluid New
Rear Differential Fluid New
F & R Shocks New
Ins-Cluster Rheostat New
Oil Pan & Pickup-Strainer New
Cap & Rotor New
L & R Lower Ball Joints New
L & R Front Wheel Bearings New
ACC Mono Valve Insert New
Temp Sensor (Single-Pole) New
OVP & 10Amp Fuse (Replaced w/ good used)
Idle Control Unit Good (Replaced w/ good used)
Idle Control Valve Good
Fuel Pumps & O-Rings (both) New
Fuel Filter & O-Rings New
Coolant System Flushed & Replaced w/ Dexcool
Air Filter New
Fuel Pump Relay (Replaced with GOOD USED
Vacuum Leak(s) Corrected

Opinions & Suggestions please............
RSVP,
TerryJ

mbdoc · #2 05-01-2008, 08:03 AM

Measure the output of the crank sensor at the ignition module. Should create about 0.5V ac current while cranking.

david s poole · #3 05-01-2008, 09:53 AM

sounds like a classic case of dying crankshaft pickup[at the bellhousing on drivers side of centre].