Injector Pulsing while Car sits w Engine off?
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Injector Pulsing while Car sits w Engine off? Hey everyone,
I have a issue I have been dealing with for a long while. I believe my injectors are pulsing while the car sits off. I believe this because I changed the oil today at 1pm and confirmed oil was at the full mark. I started the car after the oil change and let it idle for 10 min. Shut the car off, oil still at full mark and fuel pressure holding 50 psi at 1pm.
check the oil again tonight at 11pm, car oil is 1/4" above full mark. Oil smells like gas, fuel pressure gauge at 0psi. Fuel injectors were professionally cleaned and DO NOT leak off the car as per pro test results. No dtc codes, engine starts, runs and pulls hard like normal.
car is a 98 Trans Am, Ls1, full exhaust. Lid, dyno tune, compression test results good, engine drove great for 5 yrs and then out of nowhere the oil started smelling like gas. I've been scratching my head at this problem for a few seasons now.
Any thoughts? Is there a way for me to manually switch off injectors or something. Anything else this could be? My charcoal canister was bone dry, I thought it might be that but no.
Any thoughts would be appreciated 🙏
I have a issue I have been dealing with for a long while. I believe my injectors are pulsing while the car sits off. I believe this because I changed the oil today at 1pm and confirmed oil was at the full mark. I started the car after the oil change and let it idle for 10 min. Shut the car off, oil still at full mark and fuel pressure holding 50 psi at 1pm.
check the oil again tonight at 11pm, car oil is 1/4" above full mark. Oil smells like gas, fuel pressure gauge at 0psi. Fuel injectors were professionally cleaned and DO NOT leak off the car as per pro test results. No dtc codes, engine starts, runs and pulls hard like normal.
car is a 98 Trans Am, Ls1, full exhaust. Lid, dyno tune, compression test results good, engine drove great for 5 yrs and then out of nowhere the oil started smelling like gas. I've been scratching my head at this problem for a few seasons now.
Any thoughts? Is there a way for me to manually switch off injectors or something. Anything else this could be? My charcoal canister was bone dry, I thought it might be that but no.
Any thoughts would be appreciated 🙏
Test your theory by disconnecting the battery immediately after shutdown. That eliminates some one in a million phantom pulse issue. If you still gas up your oil, you know it is just a regular injector leak.
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I'm going to do that, thanks for the advice Gametech. I will post my findings in a few days.
If that's what it's doing, it should run like absolute garbage when you start it and smoke like crazy. I would also expect at some point you would have hydro locked it.
You could also unplug the injectors.
You could also unplug the injectors.
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It's normal for the oil level to rise a bit while the engine sits. I've never measured it but 1/4" sounds reasonable to me. While the engine is running it's sending oil to the heads and wrist pins and such. After it stops, most of that oil drains back to the pan.
It's alsonormal not-unusual for the fuel system to depressurize. Sometimes from leaking past the regulator - that's very common with aftermarket regulators like the Aeromotive in my Subaru. Or by leaking backward through the fuel pump (some day I will add a check valve to my Corvette to fix this).
It's also
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It's normal for the oil level to rise a bit while the engine sits. I've never measured it but 1/4" sounds reasonable to me. While the engine is running it's sending oil to the heads and wrist pins and such. After it stops, most of that oil drains back to the pan.
It's alsonormal not-unusual for the fuel system to depressurize.
It's also
Extremely unlikely the injectors are pulsing without the engine keyed on. To check that possibility or leaking injectors:
- Unbolt the fuel rail assembly (with injectors still clipped) and lift it off the manifold.
- Take a large old cookie sheet (or 2 medium ones) and line with shop towels.
- Set the sheet(s) underneath the injector tips on both banks.
- Key the ignition to run (but not crank). Wait about 5 seconds, then turn the key to off.
- Record your fuel pressure.
- After a half hour, record the fuel pressure again.
- You should still have some pressure in the fuel rail (although it will likely have dropped a bit), and shop towels should be dry. If any leak you should see wetting on the towels.
- If that checks out, retest; but this time after recording the fuel pressure disconnect the injector wire harness where it meets the engine wire harness. After the same duration, you should see similar loss as the first test.
Last edited by 68Formula; May 30, 2024 at 08:05 PM.
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^this (especially over that long of a period).
Extremely unlikely the injectors are pulsing without the engine keyed on. To check that possibility or leaking injectors:
Extremely unlikely the injectors are pulsing without the engine keyed on. To check that possibility or leaking injectors:
- Unbolt the fuel rail assembly (with injectors still clipped) and lift it off the manifold.
- Take a large old cookie sheet (or 2 medium ones) and line with shop towels.
- Set the sheet(s) underneath the injector tips on both banks.
- Key the ignition to run (but not crank). Wait about 5 seconds, then turn the key to off.
- Record your fuel pressure.
- After a half hour, record the fuel pressure again.
- You should still have some pressure in the fuel rail (although it will likely have dropped a bit), and shop towels should be dry. If any leak you should see wetting on the towels.
- If that checks out, retest; but this time after recording the fuel pressure disconnect the injector wire harness where it meets the engine wire harness. After the same duration, you should see similar loss as the first test.
-So I have last summer checked for leaks from the injectors with them out of the intake but still attached and no leaks. Wired up and not wired, no leaks.
-The pro cleaner said no leaks from his tests
-sounds like it's extremely unlikely for injectors to pulse and if it did, the car would run like ****. My shut off with batt off test isn't raising the oil level so far.
Here are spark plugs. Do they look rich? Exhaust smells rich.
So I will conclude injectors are not the problem.
-fuel pressure is good
-any pointers on how to check the maf? Car was tuned 10yrs ago by a well known pro. I haven't modded anything since besides gears.
-do you guys think the tuner can detect a sensor is out of which by looking at his data logger now and comparing it to the tune on file?
I appreciate all the help fellas
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I think I'd start by looking at AFR and fuel trims to see if that stuff is reasonable. If an injector is spraying too much fuel, the PCM will try to balance that by making the fuel trim negative.
But without logs from before you noticed the smell, a slightly negative fuel trim wouldn't really tell you anything - that's actually pretty normal. If it's pulling 25% or whatever the maximum is, that would indicate a problem. But if it's just a few percent negative, that's probably nothing.
But without logs from before you noticed the smell, a slightly negative fuel trim wouldn't really tell you anything - that's actually pretty normal. If it's pulling 25% or whatever the maximum is, that would indicate a problem. But if it's just a few percent negative, that's probably nothing.
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Hey guys, so checked a few things tonight.
I Teed in a 1/8" vacuum gauge to one of my vacuum lines. Car was steady 19 in vacuum. Then I removed the gauge and to introduce a vacuum leak and checked the short term and long term fuel trims on my Blue driver live data log. Things didnt change much with the vacuum leak, short term increased 1% and went to 3-4%, long term stayed at 0% and voltages on o2 sensors where both going up and down like normal.
Maybe the tiny line wasn't a big enough leak? I can remove the 3/8" line and see if anything changes.
I Teed in a 1/8" vacuum gauge to one of my vacuum lines. Car was steady 19 in vacuum. Then I removed the gauge and to introduce a vacuum leak and checked the short term and long term fuel trims on my Blue driver live data log. Things didnt change much with the vacuum leak, short term increased 1% and went to 3-4%, long term stayed at 0% and voltages on o2 sensors where both going up and down like normal.
Maybe the tiny line wasn't a big enough leak? I can remove the 3/8" line and see if anything changes.
Last edited by WS6wanted; Jun 6, 2024 at 08:05 PM.
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Hey guys,
I have a question on what to look for when data logging on my Blue driver scan tool.
I notice my LTFTs are always 0, Im guessing the tuner didnt use them. The STFT and 02s are reading well and adjust accordingly when I pump the brakes at idle to simulate a lean condition.
02s Read lean when I pump brakes and then stft went up to 10% to compensate and ltft stayed 0. Things go back to normal when quickly after I stop pumping
Question is, cruising around and logging, what would be a red flag on the stft to possibly be too rich? Should stft not go greater than +/-10% crusing around town. If let's say, short terms read 20% or more, I should mark down when and what I was doing while driving and go from there?
I have a question on what to look for when data logging on my Blue driver scan tool.
I notice my LTFTs are always 0, Im guessing the tuner didnt use them. The STFT and 02s are reading well and adjust accordingly when I pump the brakes at idle to simulate a lean condition.
02s Read lean when I pump brakes and then stft went up to 10% to compensate and ltft stayed 0. Things go back to normal when quickly after I stop pumping
Question is, cruising around and logging, what would be a red flag on the stft to possibly be too rich? Should stft not go greater than +/-10% crusing around town. If let's say, short terms read 20% or more, I should mark down when and what I was doing while driving and go from there?