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| Fuel system breakthrough!!; Runs great with fuel pump disconnected | |
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| Tweet Topic Started: Oct 4 2012, 04:17 PM (1,748 Views) | |
| triketrash | Oct 4 2012, 04:17 PM Post #1 |
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Vince
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I'm impatient for some input so I thought I'd start a new topic to avoid people having to slog through a long thread BREAKTHROUGH!!! Ok today, I was going through some of mwebb's algorythm to test the fuel system. I had connected a tester light to the FI connectors and was going to see if it would blink with key off, cranking engine. Well I though I should probably disconnect the fuel pump, so as not to flood the already wet cylinders with fuel while cranking. After removing the fuse, and craning my neck to see the light under the hood while cranking, she fired right up!!! About the time I was considering just driving around without the fuel pump connected- problem solved- it died, obviously starved of fuel. I re-installed the fuse and it fired up and ran for about 5 seconds before quitting again. Further cranking was not helpful. I repeated the procedure a couple of times, removing the fuse, cranking it over a few times and it would fire up; install the fuse and it would quit again- I'm pretty sure it's flooding out. Another observation, and herein lies my question- when the ignition is turned on, I notice what looks like a half an ounce or more of gas pour into the throttle body. There is no further dripping after that, but each time you cycle the fuel pump, a pretty big quantity of fuel shoots in there. Is this normal, or is my injector letting this past when it shouldn't? thanks, Vince |
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| starscream5000 | Oct 4 2012, 04:25 PM Post #2 |
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Got 70 MPG?
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That doesn't sound right. The fuel injector is supposed to only put a small amount of fuel in, enough to make the butterfly plate look wet, but not dripping wet. Have you checked your fuel pressure? |
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| triketrash | Oct 4 2012, 04:27 PM Post #3 |
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Vince
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I haven't done that yet- I have to go into town to get a fuel pressure guage- so you think the injector could still be ok, but just too much pressure there? |
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| clarkdw | Oct 4 2012, 04:32 PM Post #4 |
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Fuel injector should not let any fuel through till the engine is turning over. Key on engine off the fuel injector is not being energized just the pump. Your injector is not closing or the o-rings that seal the injector are leaking by. Replacement refurbished fuel injectors. |
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| charlesufarley | Oct 4 2012, 04:56 PM Post #5 |
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Grease monkey
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I would suspect an ecm issue or a short in the wire from ecm to injector to ground. Injector has power whenever the key is on, and ecm grounds it to fire the injector. Try shorting across the terminals going to the coolant temperature sensor. This will trick the ecm into thinking the engine is 300F and will all but shut fuel off to engine. |
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| charlesufarley | Oct 4 2012, 04:59 PM Post #6 |
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Grease monkey
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Just reread your post. Riddle me this, Batman: If you connect a test light between the terminals feeding the injector, is it on constantly when the key is on or does it flash when you crank it? If it is on all the time, there is a short in the injector driver wire or the ecm itself is shorted. |
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| triketrash | Oct 4 2012, 05:40 PM Post #7 |
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Vince
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can you tell me where to find the temp sensor and I'll try that first test- on your second post, I was in the middle of the test you're suggesting when the car started to run and I didn't go any further with it. Blew my mind that I had BOTH the fuel pump AND the fuel injector disconnected and away she ran- go figure- |
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| charlesufarley | Oct 4 2012, 09:04 PM Post #8 |
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Grease monkey
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Coolant temp sensor is near the thermostat, on the housing, but the second test is probably more important. It can run for a few seconds on what fuel is still laying in the bottom of the intake manifold, even with injector and fuel pump disconnected. |
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| triketrash | Oct 5 2012, 12:31 AM Post #9 |
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Vince
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OK Charlesufarley- I'll check for the flashing tomorrow- I tried to measure the fuel pressure at the outlet on the throttle body, but for some reason I couldn't get a reading- I think the mickey-mouse gauge setup I had was the problem. |
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| cpalz | Oct 5 2012, 04:55 AM Post #10 |
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Advanced Member
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I would check fuel pressure first, as mentioned. Excess pressure can flood it out. THe reason it ran when the pump was disconnected, was the engine was clearing itself out. No more fuel entering the cylinder, and it finally cleared itself out to a mixture it could burn. Years ago, when fuel injection first came out, people were not used to not touching the pedal while cranking. They would flood the cars, especially in the winter. When they were towed into the shop, we would pull the fuel pump fuse, floor the pedal, and crank it. Then they would start. Same principal here, but yours is flooding sor some other reason. Not to sure what these use as a regulator, or if they even have one, but on cars with a regulator, if it gets stuck open, it will flood the engine immediately. Good Luck! |
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| Woodie | Oct 5 2012, 06:29 AM Post #11 |
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No, it's not. And the coolant temperature has nothing to do with the fact that his injector is leaking. He either needs his injector rebuilt, injector O ring replaced, or Fuel Pressure Regulator replaced. |
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| triketrash | Oct 5 2012, 10:38 AM Post #12 |
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Vince
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does anyone have a link to the FPR- ie a diagram or photo? |
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| Jittney | Oct 5 2012, 01:11 PM Post #13 |
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Anchorage 92 XFi
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Gmpartsgiant.com has the diagrams |
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| triketrash | Oct 5 2012, 04:28 PM Post #14 |
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Vince
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thankss Jittney- well I went to work with the test light this morning to try to rule out an electronic problem before ordering a fuel injector. I was following mwebb's protocol: connect test light to either injector pin and the other lead of the test light to battery POSITIVE crank starter , does the light BLINK ? if NO connect to the other injector pin crank starter , does the light BLINK ? if one injector pin blinks with respect to battery negative while cranking the starter ... the PCM and engine speed sensors and circuitry is good , What I observed was that when connected to one side the light turned off completely while I was cranking and to the other side, it dimmed, but did not go out altogether. Doesn't really fit with his description.... no blinking, just turned off. I also gave another shot at measuring fuel pressure at the inlet- I didn't get any reading, which makes sense because the fuel just dumps into the throttle body every time I cycle the ignition. I had a look at the fuel pressure regulator but don't see any tears in it, although after drying somewhat, the two layers of the rubber separated somewhat. I'm figuring the fuel injector is my best bet, but am thinking it wouldn't hurt to change that FPR as well. On a bad note, I believe I may have stripped the threads on one of the screws that hold the cap on the injector- we'll see abou that. |
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| starscream5000 | Oct 5 2012, 05:12 PM Post #15 |
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Got 70 MPG?
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Just get some a2 stainless hardware to replace them with
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