I installed Holley's Sniper EFI system on a 1987 420SEL. I got sick of my fuel relay and generally the ke-jetronic system. In the beginning I tuned the EHA to 0.6bar and left it unplugged and ran the car for awhile in 'carb mode' but it would always run its self out of fuel at high rpm.
Pin #4 of the overvoltage relay is deleted so no ecm or airbags. The transmission quickly locked the torque converter clutch at 45mph. I'll mod the air conditioning this weekend and bleed the brakes. The transmission pump is getting new seals soon.
So the throttlebody was replaced with a cast iron t3 2.5" Vband adaptor off ebay. The vband clamps to extended and welded 2.5 to 4.0 vband 'bell'. The top of the bell has a 3/8 mild steel 4150 carb plate from hellsgate and the efi is bolted on top. I installed a honda civic hybrid gas peddle from a previous project so I can run normal cable throttle linkage. The factory linkage seesaws starting at the transmission lever and its opposite side pulls the throttle. The efi runs at 58psi which is a breeze for the factory fuel pumps which are chinese 044 bosch clones off ebay. Factory bosch fuel filter. I plugged the oem injector holes with dimes and RTV. Most important is running a relay off the keyed switch for the positive side of the ignition coil. The relay keeps the voltage clean for the efi while cranking. EFI gets its tach signal from neg side coil. Efi has its own fuel relay spliced directly to the oem fuel wire #7. The overvoltage relay now only powers ABS. The egr thermo vac switch is removed and hole tapped 3/8npt for efi coolant sensor. Carb plate sits just above the temp sensor for the ecu/ignition system and a mrgasket 'lowrider' #4339 air cleaner leaves an inch of clearance under the hood. More to come soon