Loss of Fuel Pressure, Flooding Behavior
#1
08-07-2019, 08:24 AM
Loss of Fuel Pressure, Flooding Behavior
Hi everyone... I need some troubleshooting advice on this one...
I have a 1998 Camaro, 3.8 V6 automatic with 173k. No check engine light or codes. The car recently developed a kind of flooding issue that resulted in hard starts after sitting for a few hours and fuel is getting in the oil. The analysis report stated 6.6% gasoline when I had it tested at 950 miles on the oil.
I replaced all 6 injectors, assuming at least one was leaking. When that didn’t fix it, I found that the fuel rail wasn’t holding pressure and that the vacuum line to the fuel pressure regulator smelled like gas when disconnected (no liquid fuel noticed). For good measure, I changed the fuel pressure regulator too, since I assumed the fuel smell indicated a leaky diaphragm. That didn’t solve the problem either.
First thing in the morning, the car starts fine. When I get in the car at lunchtime, 4-5 hours later, it cranks but doesn’t want to start unless I press the throttle while cranking. It doesn’t have to be more than 1/3 throttle to start it, but it fires right up when the pedal is pressed. Once running, there are no drivability issues. It never stalls, hesitates, or misfires. It just seems to either be leaking gas into the intake after shutting off the ignition or dumping too much fuel while running. It does it every time I drive it and let it sit for less than 6-8+ hours.
I haven’t checked fuel pressure because A) all or most pressure bleeds off after about an hour, and B) it runs and drives fine once it’s started. I might blame the fuel pressure loss on a bad check valve in the pump, but that doesn’t explain how the engine is flooding. It’s definitely getting enough fuel with the pump running.
But again, no codes are showing up. I tuned it up last year with AC Delco plugs and wires, but not the coils. I haven’t pulled any plugs yet (cuz they’re so much fun on this engine), but I would think that it would run rough or throw a code if one or more cylinders weren’t firing properly.
I’ve checked various threads on different sites and found similar issues but not quite what my car is doing. Do you guys have any ideas? Could a fuel return issue cause flooding?
PS- I also replaced the IAC valve...no change. It just seems to be getting too much gas or leaking it in the intake. Fuel economy has predictably deteriorated too.
I have a 1998 Camaro, 3.8 V6 automatic with 173k. No check engine light or codes. The car recently developed a kind of flooding issue that resulted in hard starts after sitting for a few hours and fuel is getting in the oil. The analysis report stated 6.6% gasoline when I had it tested at 950 miles on the oil.
I replaced all 6 injectors, assuming at least one was leaking. When that didn’t fix it, I found that the fuel rail wasn’t holding pressure and that the vacuum line to the fuel pressure regulator smelled like gas when disconnected (no liquid fuel noticed). For good measure, I changed the fuel pressure regulator too, since I assumed the fuel smell indicated a leaky diaphragm. That didn’t solve the problem either.
First thing in the morning, the car starts fine. When I get in the car at lunchtime, 4-5 hours later, it cranks but doesn’t want to start unless I press the throttle while cranking. It doesn’t have to be more than 1/3 throttle to start it, but it fires right up when the pedal is pressed. Once running, there are no drivability issues. It never stalls, hesitates, or misfires. It just seems to either be leaking gas into the intake after shutting off the ignition or dumping too much fuel while running. It does it every time I drive it and let it sit for less than 6-8+ hours.
I haven’t checked fuel pressure because A) all or most pressure bleeds off after about an hour, and B) it runs and drives fine once it’s started. I might blame the fuel pressure loss on a bad check valve in the pump, but that doesn’t explain how the engine is flooding. It’s definitely getting enough fuel with the pump running.
But again, no codes are showing up. I tuned it up last year with AC Delco plugs and wires, but not the coils. I haven’t pulled any plugs yet (cuz they’re so much fun on this engine), but I would think that it would run rough or throw a code if one or more cylinders weren’t firing properly.
I’ve checked various threads on different sites and found similar issues but not quite what my car is doing. Do you guys have any ideas? Could a fuel return issue cause flooding?
PS- I also replaced the IAC valve...no change. It just seems to be getting too much gas or leaking it in the intake. Fuel economy has predictably deteriorated too.
#2
08-07-2019, 11:19 AM
There are a lot of things that could cause this. I would still want to check fuel pressure to be sure its not to high. Just about every thing else will need a scanner. You need to check to make sure your sensors are reading right and the MAF senor is not dirty. I would focus on coolant/air temp and barometric pressure. Also it sounds like you O2 are not reading right. That could be just age or a bad cat causing it.You should pull one plug and see what it looks like to verify a rich issue.
#3
08-07-2019, 07:41 PM
Thanks for the reply. I’ll get a fuel pressure gauge by the weekend and see what kind of pressure I get.
Concerning what you said about sensors, I’ll have a friend with a good scanner help me check stuff out. But what should I check that to figure out how the fuel pressure is bleeding off?
Concerning what you said about sensors, I’ll have a friend with a good scanner help me check stuff out. But what should I check that to figure out how the fuel pressure is bleeding off?
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