SR no start - has spark & fuel

[RBSilvia]

Hey fellas. I'm hoping someone can lead me in the right direction here as I'm running out of ideas.

I bought a redtop SR20 swap out of a running car, so I know the wiring is OK and there are no major issues (compression, sensors, etc). New fuel filter and spark plugs.

After doing the swap I had some problems getting it started. I added an extra ground to the engine block and it fired up out of nowhere. Even when I removed the extra ground it would stay running and always start. I drove it with no problems for like 400 miles. Then it just stopped starting again.

I've verified that all injectors are spraying (adequate fuel pressure, lines not reversed, etc). The spark plugs are also firing. I've reset the CAS a bunch of times (even trying 180* off to see what happens) with no luck.

It will sputter and run roughly for a few seconds if I spray some carb cleaner in the throttle body, which makes me think it's not getting enough fuel. But I've watched the injectors spray when I turn the CAS by hand. Is there any reason they would stop spraying when I'm trying to start it?

Any suggestions are welcome. Thanks!

[PyR0NiAk]

Got a friend with a known working CAS you can borrow?

[idahotuner]

what fuel pressure reg are you using. is it just cranking and cranking?

[RBSilvia]

I don't have a friend with a CAS, but I could probably buy one and try it...

It's got the stock FPR with a walbro pump. I don't think there are any problems with the FPR though. I've tried pinching the return line to effectively bypass the FPR and increase the pressure and that didn't help.

I tried a different ignitor last night, no change.

It seems like it has to be timing if there is spark and fuel, but I've reset it like 10 times. And it will run/sputter on carb cleaner. Would a weak spark ignite the carb cleaner, but not gas?

[PyR0NiAk]

stock fprs are known for failing once a high pressure pump is installed, but I still think this is a timing issue.

[RBSilvia]

when they fail it would cause low pressure in the rail though, right? By pinching the return line it should have started if the FPR was bad.

If the timing is off, why does it start with carb cleaner?

[RBSilvia]

So I think it's an injector power problem.

When I check voltage at the injectors, i get 12V. But it slowly drops to ~0V. Then if I turn the key on, or crank the engine, turn the cas, etc it jumps back up to 12V.

When I disconnect the engine harness from the grey plug (where injectors get power, from red wire) it holds a steady 12V.

So for some reason the voltage is dropping when I plug the engine harness in. I've inspected the red wire that powers the injectors (also the ECU backup power) and it looks ok. Are the injectors really supposed to have constant +12V? It seems like it should be switched power from the ign switch, but it's wired to ECU backup power from the factory. This red wire also goes to ECU pin 109 "Reverse electrical flow return circuit ". Does anyone know what that does? Could that be causing the voltage drop?

I might just try running a new power wire to the injectors using a relay and keyed source

[RBSilvia]

I should also add, the injectors all spray/click. But it's not very consistent. Every once in a while they will give a nice powerful spray, followed by a few quiet clicks where fuel just barely spits out.

I've swapped out different injectors from a running car so I don't think they're clogged or defective

[RBSilvia]

IT ended up being a loose connection of the red wire in the grey plug. The red wire is ECU Backup Power, as well as injector power. The loose connection wasn't supplying enough voltage to the injectors so they weren't spraying correctly. It's all good now, thanks guys!