Am looking at picking up a 1991 Mitsubishi RVR S AWD 5spd (same as Expo/Summit) which has the DOHC 6 bolt 4G63 engine but the later 2G style AFM.
The engine will start (but idle a bit rough, though comes right when there are more revs), but the MPI relay will click itself off just seconds after the engine starts, causing the fuel pump to die and the engine subsequently stalls. I've taken the cover off the relay and if you hold down the tab against the contacts the engine stays running. It is only one of the two relays inside the main relay box that seems to click off right away. The current owner has swapped out the AFM and the idle stepper motor thinking they were the culprit, before focusing towards the clicking noise he could hear when the engine stalled. I did notice when I got someone to hold down the relay contacts and giving the engine a bit of a rev the check engine lamp came on, but I didn't have an LED on me I could use to check the fault codes stored.
The ECU is part number MD166265 which I believe is specific to the 91-92 6-bolt 2L DOHC RVRs, and I tried to use the MD311121 ECU from my '93 RVR Sports Gear which has the 7-bolt 4G63 but the ECU plugs were totally different. The '91 RVR S appears to have the same plug layout as the E33A/E39A 6G Galants but I am unsure how a 6G Galant DOHC ECU would work in it as the RVR uses the later 2G style AFM. I didn't get a chance to open up the existing ECU to check for leaky caps.
I'm just wondering what would cause the relay to click off just seconds after the engine is started - I'm guessing it is somehow ECU related but in my experience with the dud ECUs the problem is usually just no running full stop. I guess I will have to clear the ECU fault codes too to see what's up.
Any advice, thoughts and comments are welcome.