First, I’ve been reading threads on here for years, but this is my first post (long time listener, first time caller). This is definitely an awesome site!
I’ve got an 88 LB9 5 speed w 53000 original miles.
I had the car for 5 years and it’s ran great until recently. It’s difficult to start cold or hot. It’ll also randomly misfire at full throttle. I’ve replaced the MAF, FPR, IAC, did a smoke vacuum leak test with no leak indicators (except out of my oil dipstick which I thought was a bit strange?), readjusted my TPS and checked its voltages, replaced MAF solenoids and fuel pump solenoid, and replaced the oil pressure sensor next to the oil filter. Still no luck with the starting issue. This all sounds quite common up to this point for LB9 hard starts.
However, hopefully this next bit of info will help one of y’all lead me to the problem: when I shut it down normally with the key, it’s difficult to restart - but when I stall it (ie put it in reverse and don’t add throttle like an idiot, it’ll fire back up immediately hot or cold). So normal shutdown = hard restart, stall it = immediate restart.
Thanks.

 

That LB9 is a tuned port? Has the 9th injector for starting? I'd check that injector out. You can get a pulse tester for injectors pretty reasonable and watch fuel pressure while testing that injector.

 

Thanks Tom3 for the advice. I pulled the 9th injector and cleaned it and I replaced the coolant temp sensor that’s right next to it. Still takes about 10 seconds of cranking to start, cold or warmed up.
However, when I pop the clutch to stall it (to shut it down without the key), it’ll fire right back up (even after sitting all night).
Is there something that triggers a ‘release’ of fuel pressure when the key is turned to the off position?

 

I'd put a fuel pressure gauge on and watch it while cranking.
Isn't there a fail safe for the fuel pump relay?.. once the engine sees oil pressure, it supplies voltage for fuel pump...or something like that.