Need some help with a fuel issue, car dumping tons of fuel
07-21-2007, 12:56 PM
#1
Need some help with a fuel issue, car dumping tons of fuel We got a stinker that we just can’t get figure out… so any help is much appreciated.
Oh and as a disclaimer, we build suspension and chassis… not motors so please pardon any lack of knowledge
It’s a 2000. We just installed a set of Patriot 243 heads, Thunder Racing T-Rex cam, Fast 90 with a UMI throttle body and Racetronix fuel pump. Patriot recessed the valves .010 for cam clearance. The bottom end is still stock. The car is also still un-tuned. We assembled the car and I put 500 miles on it, car ran great, it ran rich which we expected but it ran good and even idled.
Now the problem… the car started to miss, or what we thought was a miss in the engine. It did it for a few seconds and cleared it self out so we didn’t think anything of it. After a few days the car begin to do it again and consistently, it would no longer idle and would barely even go with out full throttle, BUT above 3K and at WOT it is fine, just like it should be. We scanned it and there are no misfire codes. So the first thing we did was try plugs, we put a brand new set of plugs in it. The old plugs were black as black could be. We tried the new set and they did no good, the car ran the same. So we pulled the plugs to do a compression check. After only 2-3 miles of driving on the new plugs they are now black, covered in carbon. Every plug is the exact same, so every cylinder is burning the same way. We did a compression check and got 150psi per cylinder, so that eliminates a valve, correct?
After some playing around we found out is the car is dumping fuel like crazy, it burnt ¾ of a tank of fuel in 95 miles. You can smell it bad when it is running, the exhaust is not very black but you can smell un-burnt fuel coming out. What would cause the car dump this much fuel into the motor? And why would it start doing this after 500 miles? So we continued to try things, we checked the intake and there is no leaks there. We pulled the throttle body back off and it was fine. We checked fuel pressure and it is 62psi. We changed out the fuel regulator on the fuel rail and that did nothing. So we checked the fuel pump out and it is turning on and off as it should. We checked the ECT sensor and it is reading the correct temperature. The only codes we are getting are the typical EGR/AIR codes since it has all been removed. Every O2 is getting a code for poor heater performance. Now because of the O2’s it is running in an open loop. We are pretty sure these o2 codes were there before this all happened, maybe not all of them. We are thinking all the excess gas fumes may have caused them to read these.
Could this be a timing issue? The scanner reads 0 degrees timing, probably because it’s running in an open loop due to bad 02’s?
The only things we have left to do are a vacuum test and replacing the O2’s. Does a vacuum test sound appropriate? Could it be something with injectors?
Thoughts?
Thank you,
Ryan
Oh and as a disclaimer, we build suspension and chassis… not motors so please pardon any lack of knowledge
It’s a 2000. We just installed a set of Patriot 243 heads, Thunder Racing T-Rex cam, Fast 90 with a UMI throttle body and Racetronix fuel pump. Patriot recessed the valves .010 for cam clearance. The bottom end is still stock. The car is also still un-tuned. We assembled the car and I put 500 miles on it, car ran great, it ran rich which we expected but it ran good and even idled.
Now the problem… the car started to miss, or what we thought was a miss in the engine. It did it for a few seconds and cleared it self out so we didn’t think anything of it. After a few days the car begin to do it again and consistently, it would no longer idle and would barely even go with out full throttle, BUT above 3K and at WOT it is fine, just like it should be. We scanned it and there are no misfire codes. So the first thing we did was try plugs, we put a brand new set of plugs in it. The old plugs were black as black could be. We tried the new set and they did no good, the car ran the same. So we pulled the plugs to do a compression check. After only 2-3 miles of driving on the new plugs they are now black, covered in carbon. Every plug is the exact same, so every cylinder is burning the same way. We did a compression check and got 150psi per cylinder, so that eliminates a valve, correct?
After some playing around we found out is the car is dumping fuel like crazy, it burnt ¾ of a tank of fuel in 95 miles. You can smell it bad when it is running, the exhaust is not very black but you can smell un-burnt fuel coming out. What would cause the car dump this much fuel into the motor? And why would it start doing this after 500 miles? So we continued to try things, we checked the intake and there is no leaks there. We pulled the throttle body back off and it was fine. We checked fuel pressure and it is 62psi. We changed out the fuel regulator on the fuel rail and that did nothing. So we checked the fuel pump out and it is turning on and off as it should. We checked the ECT sensor and it is reading the correct temperature. The only codes we are getting are the typical EGR/AIR codes since it has all been removed. Every O2 is getting a code for poor heater performance. Now because of the O2’s it is running in an open loop. We are pretty sure these o2 codes were there before this all happened, maybe not all of them. We are thinking all the excess gas fumes may have caused them to read these.
Could this be a timing issue? The scanner reads 0 degrees timing, probably because it’s running in an open loop due to bad 02’s?
The only things we have left to do are a vacuum test and replacing the O2’s. Does a vacuum test sound appropriate? Could it be something with injectors?
Thoughts?
Thank you,
Ryan
07-21-2007, 03:20 PM
#2
On The Tree
Are you sure it is running in Open Loop?? sounds to me like it's closed loop and overfueling because you haven't tuned it. Running OK at WOT is probably the giveaway as that definatly drops it into Open Loop.
Best bet...get it tuned
Jim
Best bet...get it tuned
Jim
07-21-2007, 03:49 PM
#3
Thanks for the reply
Yes I know a tune is needed, that is next once we figure this out. If a tune would cure it, that would be great, maybe thats all it is. But what confuses us why did it run so good for so long and then all the sudden start this? If there is something wrong with it I would like to fix it so we aren't tearing it down at someone elses shop where it is being tuned.
Yes I know a tune is needed, that is next once we figure this out. If a tune would cure it, that would be great, maybe thats all it is. But what confuses us why did it run so good for so long and then all the sudden start this? If there is something wrong with it I would like to fix it so we aren't tearing it down at someone elses shop where it is being tuned.
07-21-2007, 06:48 PM
#4
You aren't trying to run the car with larger than stock injectors are you? Either way I'd be careful of it that rich, don't wanna wash out a cylinder or two.
If your O2 heaters are bad (or the circuit powering them) their outputs will sit low which will cause the PCM to hike the fuel trying to make them "swing". Eventually it will learn massively positive fuel trimming. This is the most likely case.
If your O2 heaters are bad (or the circuit powering them) their outputs will sit low which will cause the PCM to hike the fuel trying to make them "swing". Eventually it will learn massively positive fuel trimming. This is the most likely case.
Last edited by Frost; 07-21-2007 at 07:13 PM.
07-21-2007, 08:10 PM
#5
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Originally Posted by Frost
You aren't trying to run the car with larger than stock injectors are you? Either way I'd be careful of it that rich, don't wanna wash out a cylinder or two.
If your O2 heaters are bad (or the circuit powering them) their outputs will sit low which will cause the PCM to hike the fuel trying to make them "swing". Eventually it will learn massively positive fuel trimming. This is the most likely case.
If your O2 heaters are bad (or the circuit powering them) their outputs will sit low which will cause the PCM to hike the fuel trying to make them "swing". Eventually it will learn massively positive fuel trimming. This is the most likely case.
07-21-2007, 08:55 PM
#6
Originally Posted by Frost
You aren't trying to run the car with larger than stock injectors are you? Either way I'd be careful of it that rich, don't wanna wash out a cylinder or two.
If your O2 heaters are bad (or the circuit powering them) their outputs will sit low which will cause the PCM to hike the fuel trying to make them "swing". Eventually it will learn massively positive fuel trimming. This is the most likely case.
If your O2 heaters are bad (or the circuit powering them) their outputs will sit low which will cause the PCM to hike the fuel trying to make them "swing". Eventually it will learn massively positive fuel trimming. This is the most likely case.
The car was suppose to go in for a tune next week, but this came up and we wanted to figure it out first. The closest place to us to tune is 3 hours.
Thanks for the replies
