Anyone know the symptoms of cold start injector being stuck open?

[Maleficio]

Upon startup now, I get plumes of exhaust vapor for several minutes. This is new. Replaced the fuel injectors a couple of months ago, made a huge difference in driveability.

It doesn't smell like coolant, nor oil, just badly mixed fuel/air.

I kind of wonder if my cold start injector is stuck open, or is not being commanded closed soon enough. But even if it's closing when it should, seems the car shouldn't blow that much exhaust. It didn't do this last winter.

I guess I can remove the injector, aim it into a bottle, fire it up cold, if it will fire up, and see if the vapors subside.

When I let off the gas, and cruise in gear, I can hear constant popping in the exhaust, as if unmetered fuel is being dumped into the intake. Very similar to a fuel control solenoid on a carb not closing fuel flow when it should, causing constant popping out of the exhaust. (Experience with old Mitsu SUV).

I wonder if the cold start injector is just all screwed up? Staying full open way too long, and not closing fully after warmup.

Thankx in advance.

[Pete R]

It would make it run rich. It could also be the temp sensor that controls it. I quick check would be to just unplug it when the symtoms occur and see it that solves it. If it does it's the temp sensor.

[Maleficio]

Originally Posted by Pete R

It would make it run rich. It could also be the temp sensor that controls it. I quick check would be to just unplug it when the symtoms occur and see it that solves it. If it does it's the temp sensor.

I was thinking the same thing, but it's the abundance of exhaust vapor that makes me wonder. The temp sensor commands it open and closed, but that command shouldn't affect how the injector operates when open.

[Pete R]

It's a simple valve either open or closed. Unless it's clogged or messed up so it shoots a stream rather than an airated spray it's okay. The only other thing that can effect it is fuel pressure.

[Maleficio]

Originally Posted by Pete R

It's a simple valve either open or closed. Unless it's clogged or messed up so it shoots a stream rather than an airated spray it's okay. The only other thing that can effect it is fuel pressure.

Exactly, and I'm wondering if it's only shooting a solid stream of fuel.

[Mrmerlin]

test the temp sensor,
add some Techron to a half tank of fuel,
do short drives to let it work

[Maleficio]

Went out and disconnected the thermo time switch, cranked the cold engine, would not light off, not even a stumble. Seems like the ECU will not pulse the injectors without seeing a good connection. Reconnected, engine lit off instantly, minimal amount of exhaust vapor, no more than a new car, no huge plumes billowing out for five minutes, but it's much warmer out today. Disconnected thermo switch, no change to engine operation or exhaust vapors, suspect cold start is working as advertised, at least on a warmer day. Will try again when ambient temp drops to around 35F.

Disconnecting the thermo time switch seems to be a good and easy way to fully disable a cold engine. Easy way to pressurize oil before lighting off if sitting for an extended period of time. Or maybe even to prevent someone from stealing the car.

[waynestrutt]

The thermo time switch opens the csv. To close it you can ground the wire to the csv.