Stroking the E30

[digger]

When hot, the car will crank but not start. Most times there is a brief sputter on the first try, then nothing but cranking. I then have to wait until the temp gauge is down to about halfway between straight up and cold before it will refire--about 10 minutes. The phenomenon is new since the build. When the car is running the injectors click away merrily.

Today I swapped out the injector harness. No change.

have you checked spark when engine is cold to see if it is the same as hot as you mentioned it looked weak. also have you checked all of them? what wires are you using? an incorrect timed spark would cause issues but cant think of a mechnism that would cause that hot other than a short and harness was swapped

what ecu are you running? have you checked that there isnt something funny with the cranking vs temperature map assuming you have access to that? fudge the fuel up or down and see what happens

i had hot start issues once but it would always start just crank for 10s, not a no start for 10min, ended up being something about the injectors although they tested fine on bench.

if you pull the plugs is there defintly fuel being injected? its probably hard to pull rail while engine is hot in time to test and fire risk is real

what injectors and where did you buy? lots of knock offs around

[PEZ2]

Well this is disappointing thought the CPS was going to be the answer. I have the exact same problem with my 2.9L. Was going to swap out the CPS but, considering WAKman your results, may hold into since it tests 550 hot or cold. What I know is in my case it indefinitely is a fueling issue, cause it always starts on "starting fluid" hot or cold.

[82eye]

have you swapped out / checked the coil ?

know you have spark, but i recall a similar problem leading to a coil earlier. it also had spark but was weak. car would start cold, get progressively worse as it warmed, and would have a hot no start problem.

[WAKman]

The coil is within spec, and a replacement didn’t solve the problem.

At this point, I can only surmise it’s the ECU. The ECU is a Megasquirt, and I have at present zero experience with them, so I’m going to wave the white flag for now and take the car to Patrick at Midnight Motorsports, who wired in the ECU.

[Panici]

The ECU is a Megasquirt, and I have at present zero experience with them, so I’m going to wave the white flag for now and take the car to Patrick at Midnight Motorsports, who wired in the ECU.

Standalone ECU is very likely the issue. There are multiple enrichment tables based on air and coolant temperatures, both of which could be causing your hot-start issue.