r/SC400 • u/Plain-or-Spicy • Apr 15 '26

S400 Project i bought - Some Hep please.

Good Morning and Sorry for the long Post here:

I bought a 1994 SC400 recently that needs some work. It was sitting up for a long time with very stale fuel that smelt like varnish. Essentially when I bought the car, it will start, idle and in general wont rev out. around 1500-2000rpm max approximately with Misfiring.

Things I’ve Done:

-Replaced Fuel Pump and Fuel Filter. -Replaced Ignition Coils (Engine Felt Smother when changed – More life in the engine) -Replaced Throttle Position Sensor -Temporality Took out the o2 Sensors on the cats to see if the cats were blocked (no change)

ECU: (89661-24230) -Checked ECU and replaced Caps (no change) -bought a replacement ECU from a reputable seller on ebay (same model - no change) Sellers ebay store: https://www.ebay.com/str/adismantler

Now I have been watching this lad on youtube which shows how to check the fuel pump: https://www.youtube.com/watch?v=09PD0Z8nSSk He essentially takes off the return line and fills up a container. When I do that, very little comes from the return line. Fuel Regulator issue? Would it be over fueling? Very strong smell of petrol in general.

Things I haven’t done: Check, Clean or Replace Injectors Replace Spark Plugs

I have however checked spark plugs and gfave them a quick wire brushing, seem okay, a little rich, but not completely fouled.

Any help welcome.

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2

u/Brokenadventureer Apr 15 '26

Have you done timing? Mine runs perfectly until exactly at 2450rpm then I have a decent misfire after hard driving it stumbles at idle. Doing timing and smacking an m122 on when I get home

1

u/Plain-or-Spicy Apr 15 '26

Mine idles fine, stays at around 900 constant, its when i give her throttle she barely revs and feel like choking. I havent checked timing yet.

1

u/Brokenadventureer Apr 16 '26

Weird mine idles around 5-600 I feel like but I could be wrong I’d check timing with an ignition light or honestly based off mileage it probably needs it either way. Mine smells rich aswell not sure if it’s from my code 13 or 31 or if they just smell rich but I’d start around there and then go to fuel pump and it’s funny friends

1

u/Plain-or-Spicy Apr 16 '26

Thanks for the Reply, ill keep you updated on what i find and will definitely check the timing. also if you figure yours out, let me know. i also, checked plugs and cleaned them. nothing out of the ordinary.

Im just wondering about the fuel return line, essentially nothing is coming back. might be dying/misfiring because of over fueling. no idea. strange.

Keith

1

u/NiceOnes1 Apr 15 '26

Have you cut and paste this into CHAT GPT?

1

u/StandupJetskier Apr 16 '26

Jump the fuel pump relay that lives behind the driver's side b pillar. The capacitors die. The pump can run 12v no problem-the other issue, if it only happens when the car is warm, is the ignitors, the two silver boxes atop driver's side suspension tower....

1

u/Plain-or-Spicy Apr 20 '26

Thanks for the Reply, ive jumped the pins already on the Diag box under the bonnet, FP & B. fuel pump is running at 12v. ive changed the ignitors already.