mjtjnj Posted October 26, 2008 Share Posted October 26, 2008 Hey Guys, I had an interesting day. I had access to a DRBII scanner, and my friend, who is an ASE mechanic (Ford) came over to figure why I'm running so rich. The scanner gives pulse width, operating temp, barometric pressure, TPS output, advance and open/close loop, among other things. I'm not coming out of open loop, even when it reaches operating temperature and beyond! My friend suspects that the fuel pump, which I had a mechanic :ack: install (see threads on stalling), is probably pumping too much fuel into the TBI. What is the right fuel pressure? Guess I'm going to have to pressure test it. If it's too high, it's going back to the shop for the right fuel pump and 4 new spark plugs :headpop: Tom Link to comment Share on other sites More sharing options...
Randy in Maine Posted October 26, 2008 Share Posted October 26, 2008 I have only worked on one of these ever, but I was thinking that the TBI ran about 14-15 psi and that the fuel pressure regulator was adjustable. The pump just puts out volume, it is the regualtor that keeps it at the correct pressure. If the pressure is really too high and adjusting th eFPR doesn't help, be looking for a clogged up return line that goes back to the fuel tank. Suggestion: Make sure you have no vacuum leaks in the system or they will drive you nuts. Link to comment Share on other sites More sharing options...
mjtjnj Posted October 26, 2008 Author Share Posted October 26, 2008 Randy, I hear ya on the vacuum leaks with a Renix. None that I know of. And why won't it come out of open loop? I wasn't aware that the 2.5 had a fuel regulator. Where is it?? Link to comment Share on other sites More sharing options...
Randy in Maine Posted October 26, 2008 Share Posted October 26, 2008 OK I had to get out my Haynes manual to see. Chapter 4 Photo 3.31 is the photo and they also say to test the fuel pressure at the rail to ensure that it is at 14-15 psi at idle. Be sure to use a FI pressure gauge (mine that I mostly use for Bosch L-tronic goes 0-60 psi). 0-30 psi is the range you are looking for. I appears that the FPR is attached to the TB on the left side of the TB and sort of looks like a small round fuel bowl with the adjustment screw on the bottom of the bowl. CW is higher pressure. Link to comment Share on other sites More sharing options...
mjtjnj Posted October 26, 2008 Author Share Posted October 26, 2008 huh! I'll have to check that in the AM, but thanks! But I know I don't have a fuel rail, it's just a 2.5 throttle body, not multi-point. Link to comment Share on other sites More sharing options...
Randy in Maine Posted October 26, 2008 Share Posted October 26, 2008 Correct, you have no fuel rail, just a little test port on the fuel line just as it goes into the TB. Link to comment Share on other sites More sharing options...
FxRacing282 Posted October 27, 2008 Share Posted October 27, 2008 open loop refers to O2 sensors. which would cause you to run super rich. my clamaro has that going on right now Link to comment Share on other sites More sharing options...
mjtjnj Posted October 27, 2008 Author Share Posted October 27, 2008 Not exactly, as I understand it. If I'm flooding the fuel bowl with too much pressure, it could run rich and then the 02 sensor reads that and doesn't flip it into closed loop. Right? :dunno: Link to comment Share on other sites More sharing options...
Eagle Posted October 27, 2008 Share Posted October 27, 2008 Not exactly, as I understand it. If I'm flooding the fuel bowl with too much pressure, it could run rich and then the 02 sensor reads that and doesn't flip it into closed loop. Right? :dunno: Wrong. First, you don't have a fuel bowl. Second, the O2 sensor doesn't flip into closed loop mode, the ECU does. And it does so when the operating temperature reaches the "normal" range, which is around 165 to 168 degrees, as reported by the temp sensor in the side of the block (not the one on the back of the head ... that one only feeds the gauge). If you aren't getting into closed loop mode, your ECU is simply ignoring the O2 sensor and running in "warm-up" (open loop) mode all the time. You most likely either have a bad temp sensor or a bad ECU. Start by checking the wiring between the temp sensor and the ECU to be sure you have a circuit. Link to comment Share on other sites More sharing options...
mjtjnj Posted October 27, 2008 Author Share Posted October 27, 2008 Not exactly, as I understand it. If I'm flooding the fuel bowl with too much pressure, it could run rich and then the 02 sensor reads that and doesn't flip it into closed loop. Right? :dunno: Wrong. First, you don't have a fuel bowl. Second, the O2 sensor doesn't flip into closed loop mode, the ECU does. And it does so when the operating temperature reaches the "normal" range, which is around 165 to 168 degrees, as reported by the temp sensor in the side of the block (not the one on the back of the head ... that one only feeds the gauge). If you aren't getting into closed loop mode, your ECU is simply ignoring the O2 sensor and running in "warm-up" (open loop) mode all the time. You most likely either have a bad temp sensor or a bad ECU. Start by checking the wiring between the temp sensor and the ECU to be sure you have a circuit. OK, thanks. If the DRBII scanner is telling me that the coolant temperature was 200-205 degrees (before my fan kicked on), shouldn't it have come out of the open loop? Wouldn't the fact that the sensor is putting out the data mean that it (coolant temperature sensor, which is brand new) is operating properly? So you're saying that operating temperature is the only thing that flips the Renix system into closed loop operation? How would you proceed? Swap the ECU with another one to test ? Link to comment Share on other sites More sharing options...
KillerCOM Posted October 27, 2008 Share Posted October 27, 2008 to adjust the fuel pressure on the 2.5 TBI you must remove it from the intake. that's just four 13mm nuts at the base and 10mm bolt in the side that hold it to the manifold. you'll see a cylindrical object with a "nipple" off to one side. take a drill bit and drill the inner part of the nipple out. its extremely soft. and there should be a Torx style fastner (T-30 if i remember). :cheers: Link to comment Share on other sites More sharing options...
Eagle Posted October 27, 2008 Share Posted October 27, 2008 OK, thanks. If the DRBII scanner is telling me that the coolant temperature was 200-205 degrees (before my fan kicked on), shouldn't it have come out of the open loop? Wouldn't the fact that the sensor is putting out the data mean that it (coolant temperature sensor, which is brand new) is operating properly? So you're saying that operating temperature is the only thing that flips the Renix system into closed loop operation? How would you proceed? Swap the ECU with another one to test ? Which coolant temp sensor was the scan tool reading? There are three, if you have an auxiliary fan. The one on the back of the head only sends data to the gauge; it has nothing to do with operating the engine. The sensor in the radiator tank only controls the auxiliary fan; it also has nothing to do with controlling the engine. The temp sensor that feeds the ECU and actually affects operation of the engine is located down low on the driver's side of the block, near the knock sensor (and sometimes mistaken for the knock sensor). Yes, it is basically just temperature that controls when the Renix system switches from open loop to closed loop mode. Don't discount the possibility that you may simply have a broken wire, so the information is not getting from the temp sensor to the ECU. I would verify that the temp sensor is reading correctly and that the signal is reaching the ECU before I swapped in another ECU. Link to comment Share on other sites More sharing options...
mjtjnj Posted October 28, 2008 Author Share Posted October 28, 2008 There's only one coolant temp SENSOR. I know what the gauge sending unit is, and my truck didn't come with an aux fan from the factory. The sensor is telling the ECU what the temp is. I know this because we had the DRBII hooked up and it said "coolant temperature: whatever degrees." The DRB was plugged into the diagnostic connectors under the hood. This is why I'm having the confusion: according to the DRB, the truck warmed up into operating range, and beyond, but never left the open loop. See what I'm saying? It was getting temp readings from the coolant temp sensor. So I imagine it's working. It happened to correlate with the gauge as we were running the diagnostics on the idling engine. From that, I'm concluding that it's not only operating temp. flips the truck over into closed loop. :wall: :D Tom Link to comment Share on other sites More sharing options...
Eagle Posted October 28, 2008 Share Posted October 28, 2008 All you have proven is that you have a temperature signal from the sensor to the diagnostic plug under the hood. Unless you're leaving something out, you haven't verified that the signal is actually reaching the ECU. The switch from open to closed loop IS based on operating temperature. If the signal is reaching the ECU, then you may indeed have a flakey ECU. Link to comment Share on other sites More sharing options...
mjtjnj Posted October 28, 2008 Author Share Posted October 28, 2008 Hmm -- OK, I see what you're saying. I didn't think of that; I thought the diagnostic connector was a reading of what's going to the CPU. It makes sense to me that signal goes sensor-->CPU-->diagnostic connector, but I have no proof of that. I was tooling around under the hood last night and found a crack in the vacuum line to the MAP sensor. I electrical-taped that up and it ran a LOT less rich. Driveability is still kind of poor - it hesitates pretty badly, almost like it's running lean now! Tonight, planning on hooking up the DRBII again to see if I'm now getting into closed loop. Also going to test fuel pressure at the TBI and adjust, if necessary, after the fuel pump was changed. I played with the volt/ohmeter a bit last night. I'm getting battery voltage to the 02 sensor, the MAP, MAT, and temp sensor are getting the correct voltage (4.x volts). I tested resistance on the MAT and temp sensors, and they dropped after warm up. I didn't write anything down LOL -- kind of helter skelter. But nothing was wildly abnormal. Here's one of those dumb questions JUST TO MAKE SURE: there are two similar looking sensors, the CTS (coolant temp) and MAT, both on the intake, one on top and one in the side. Which is which? I'm sure I put the right ones where they go when I had the intake off, prior to install, but I'm just re-tracing all my steps! Thanks! :dunce: Link to comment Share on other sites More sharing options...
mjeff87 Posted October 28, 2008 Share Posted October 28, 2008 MAT is on top of the manifold, behind the TB. CTS screws into the side of the manifold. Jeff Link to comment Share on other sites More sharing options...
mjtjnj Posted October 28, 2008 Author Share Posted October 28, 2008 Thanks, Jeff. Wondering if I put the right sensor in the right place! I'll check my wiring diagram LOL :oops: Link to comment Share on other sites More sharing options...
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