84' 380SE stalls - PeachParts Mercedes-Benz Forum

Spam16v · #1 08-25-2008, 05:52 PM

been searching, reading and searching some more.

working at a european car shop, not much of a merc guy, more of an Audi/vw rat.

info, 1984 380SE sedan. intermittently stalls, will NOT restart without waiting a while. ordered overload and fuel pump relays. performed a crap-load of service work too. IE: belts, hoses, tranny hoses @ radiator, new radiator ect ect..... fuel filter previously replaced by someone else along with fuel pump and fuel presure regulator behind distributor head.

replaced BOTH overload AND fuel pump relays, dead on the rack. starts until key is released from start position and pumps shut off. jumper pins 7&8 and it purrs like a kitten. diagram reads "solid state" inside fuel pump relay, pulled old one apart and insides are cooked in a few spots, swapped back to old one, still dead. what does this relay need for signal to make it work? IE: what signal is not strong enough or is breaking up that i need to rectify the situation?

thanks!
-Zac

mbdoc · #2 08-26-2008, 08:15 AM

The fuel pump relay needs a square wave signal at the TD pin for the fuel pump relay to operate the fuel pump.

That signal comes from the ignition module (EZL).
You can somewhat measure that signal with a volt meter.

Try checking that signal with the fuel pump relay removed & then compare that signal when the car WON'T stay running & the fuel pump jumped again.

Spam16v · #3 08-26-2008, 09:05 AM

fantastic, i wasn't sure if i was looking for an on or off or a variable voltage signal depending on rpm b/c i see the FPR acts as the fuel cut off for the rev limiter function.

and me in a shop without a scope... aprox. duty cycle @ idle, of about what voltage? so i can check it with a multi-meter.

pin one of DLC connector under hood goes to same terminal as pin 10 @ FPR. multi-meter results, RPM:650, Duty cycle%:37.2, 8.5mS on time and about 47.3-43.7Hz. and a rough voltage reading is from about 7-9 volts

and now the silly thing isn't broken anymore.... wish i had this info to chcek when it was acting up. starts up and runs great now, warm up was a tad rough but it runs without using a jumper. if i have a new FPR and my signal looks in spec what would be my next rabbit hole to go chase down? would worn secondary ignition components degrade that signal? IE: cap and rotor? they're pretty whipped upon visual inspection.

thank you so much.
-Zac

mbdoc · #4 08-26-2008, 09:50 AM

Secondary ignition has no effect on that ONLY the EZL.

Spam16v · #5 08-26-2008, 10:24 AM

Worldpac has two styles available, are they interchangeable? connectors look similar but design is completely different.
thanks again!!
-Zac

mbdoc · #6 08-26-2008, 11:02 AM

Either will work.....$$$$ would be the difference

Spam16v · #7 08-26-2008, 11:17 AM

Quote:

Originally Posted by M.B.DOC

Either will work.....$$$$ would be the difference

i was using price logic, the smaller one that looks different is cheaper so it's typically not going to work with my luck....

thanks again, i see your email posted, once i get it to break and find there is no signal and replacing the EZL works you get an E-thank you-Card!
-Zac

Spam16v · #8 08-27-2008, 02:08 PM

here are all the offending parts, OVP, FPR and EZL. all of which have some sort of heat damage, burns or melted plastic inside them. last straw was yesterday doubting the condition of the EZL and not being able to get it to die again. grabbed a screwdriver and started the vehicle and tapped the EZL with the handle and it would cut out for a split second whenever it would get shocked. junk.... Overload relay: $51, Fuel pump relay: $94, Ignition module, $93, Radiator $170, Expansion tank: $26, whole set of Conti-tech belts, all new Zebra hose clamps, fresh coolant, brake fluid and a Mobil 1 oil change and my uncles "Silver Fox" is ready to ride again.

thanks everyone!!

and a picture of my toolbox with a cool car in front of it.