overfueling?
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Junior User
Joined: Aug 2003
Posts: 53
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overfueling?
i have a 92 f150 302 which seems to have an overfueling prob. i have a new tank,pump,filter,pressure regulator, lines.
after running (rough) for about 20 min i get a large amount of gas in the oil. the engine runs smoother at higher rpms when i drive at higher speeds in low gear when it seems to be burnin the extra fuel.
only code to show was egr, had it sandblasted and tested and it holds vacuum fine now. kinda stumped here , any help would be apprieciated.
thanx
after running (rough) for about 20 min i get a large amount of gas in the oil. the engine runs smoother at higher rpms when i drive at higher speeds in low gear when it seems to be burnin the extra fuel.
only code to show was egr, had it sandblasted and tested and it holds vacuum fine now. kinda stumped here , any help would be apprieciated.
thanx
Elder User
Joined: Sep 2004
Posts: 941
Likes: 4
Hook up a fuel pressure tester to the Schrader valve. Pressurize the rails by cycling the key a couple of times. (Don't start the engine, just go from off to on to off to on) Pressure should build to about 40PSI. Now watch the guage. It should not drop more than 5 PSI in one minute. If it does, you likely have a leaking injector. Find it and fix it.
The next possibility is a problem with the CTS or IAT sensor. If the computer thinks the engine is "really really cold", it will over-richen the mixture. Furthermore, it will never get into closed-loop operation, and so will never be able to get feedback from the oxygen sensor to realize that the mixture is too rich and thereby set a continuous memory code.
The PCM should be able to diagnose this (and set some sort of code) if you run a KOER test. It should complain about unlikely sensor values (because it expects the engine to be warmed up) or that it couldn't get the correct response from the oxygen sensors (it forces the mixture towards "rich" and "lean" and watches for the appropriate response in the exhaust.)
Run a compression check and verify that you don't have one or more "weak" cylinders. Check the color of all the spark plugs while you are at it. Do any of them look much different than the others? A cylinder that does not fire due to no spark or poor compression will allow the injected fuel to wash down into the crankcase instead of burning it to provide power. The computer may consider the exhaust stream acceptable based on the output of the other 7 cylinders, but the engine will still run rough.
The next possibility is a problem with the CTS or IAT sensor. If the computer thinks the engine is "really really cold", it will over-richen the mixture. Furthermore, it will never get into closed-loop operation, and so will never be able to get feedback from the oxygen sensor to realize that the mixture is too rich and thereby set a continuous memory code.
The PCM should be able to diagnose this (and set some sort of code) if you run a KOER test. It should complain about unlikely sensor values (because it expects the engine to be warmed up) or that it couldn't get the correct response from the oxygen sensors (it forces the mixture towards "rich" and "lean" and watches for the appropriate response in the exhaust.)
Run a compression check and verify that you don't have one or more "weak" cylinders. Check the color of all the spark plugs while you are at it. Do any of them look much different than the others? A cylinder that does not fire due to no spark or poor compression will allow the injected fuel to wash down into the crankcase instead of burning it to provide power. The computer may consider the exhaust stream acceptable based on the output of the other 7 cylinders, but the engine will still run rough.
