RonK Posted July 13, 2012 Share Posted July 13, 2012 75 280z manual Fuel Injectors Pulsating Too Fast and Flooding Engine Fuel pressure is 30-35 (appropriate) When fuel line is clamped off, engine will run til existing gas is depleted. However, when fuel is allowed to be injected at the rate the injectors are pulsating, it floods the engine. ECU? Quote Link to comment Share on other sites More sharing options...
Six_Shooter Posted July 13, 2012 Share Posted July 13, 2012 Is the AFM adjusted properly? Idle switch (Throttle position switch) adjusted properly? Coolant sensor within spec? Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 13, 2012 Share Posted July 13, 2012 The injectors should only "pulse" once every three sparks. How do you know that yours are pulsing too fast? Quote Link to comment Share on other sites More sharing options...
RonK Posted July 13, 2012 Author Share Posted July 13, 2012 The injectors should only "pulse" once every three sparks. How do you know that yours are pulsing too fast? My mechanic was comparing the pulse rate with a 6 cyl Jeep in his shop and noticed that the Z injectors were "lighting continuously" Noting that the Fuel pressure is 30-35 (appropriate) and that when fuel line is clamped off, engine will run til existing gas is depleted. However, when fuel is allowed to be injected at the rate the injectors are pulsating, it floods the engine. Quote Link to comment Share on other sites More sharing options...
RonK Posted July 13, 2012 Author Share Posted July 13, 2012 Question... do you think that putting on a new alternator on this z that has been driven 200-400mi a year for the past 10yrs could have "spiked" the ECU, causing this malfunctioning of the injectors. Note: mechanic was given by Identifix (a trouble shooting service they subscribe to) all the electrial specs to check regarding the fuel system and they apparently checked out correct. Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 13, 2012 Share Posted July 13, 2012 (edited) Actually, flooding the engine is a symptom of a bad ECU. Some people have found that the solder connections to the circuit board were faulty and that tweaking the connector or even banging on the ECU would fix the problem. I had one go bad, flooding the engine, but didn't try the beating approach, I just swapped ECUs. The one that went bad on me had no apparent cause. I was testing it to make sure it was good and it took me a mile down the road before crapping out. It would restart and drive for a short time but then die again with lots of gas smell. It had also been on a car that sat for ten years. These Zs seem to be a "use it or lose it" kind of car. Only a bad alternator should "spike". A new one shouldn't cause problems. Edit - your mechanic must be using a scope. If he compares events at the coil negative, or blue wire from coil negative, with the injectors, he should see a three to one ratio, three sparks to one injection, for a properly functioning system. Edited July 13, 2012 by NewZed Quote Link to comment Share on other sites More sharing options...
RonK Posted July 13, 2012 Author Share Posted July 13, 2012 Actually, flooding the engine is a symptom of a bad ECU. Some people have found that the solder connections to the circuit board were faulty and that tweaking the connector or even banging on the ECU would fix the problem. I had one go bad, flooding the engine, but didn't try the beating approach, I just swapped ECUs. The one that went bad on me had no apparent cause. I was testing it to make sure it was good and it took me a mile down the road before crapping out. It would restart and drive for a short time but then die again with lots of gas smell. It had also been on a car that sat for ten years. These Zs seem to be a "use it or lose it" kind of car. Only a bad alternator should "spike". A new one shouldn't cause problems. Edit - your mechanic must be using a scope. If he compares events at the coil negative, or blue wire from coil negative, with the injectors, he should see a three to one ratio, three sparks to one injection, for a properly functioning system. Thank You, NewZed ... Bad ECU - Makes Sense! Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted July 13, 2012 Share Posted July 13, 2012 (edited) You have to be careful when someone says "bad ecu" since about 90% of the nissan ecus sent in to me at blue streak for a rebuild tested ok. In your case, it sounds like the the car experienced a "wrong polarity incident" that has fused the injector drivers. You can test this by simply turning on the key and checking whether the ground side of the injector is being continually grounded. I would do all testing with the fuel pump unplugged to keep the engine from being filled with gasoline. Edited July 13, 2012 by HowlerMonkey Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 13, 2012 Share Posted July 13, 2012 Note that I said it was a symptom, not a certainty, and gave a good diagnostic, for a good ECU anyway. There is anecdotal evidence for ECUs causing flooding. To be more clear. What is "blue streak"? Do you guys offer a rebuild service for individuals? Sounds interesting. Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted July 14, 2012 Share Posted July 14, 2012 They rebuild and test ecus. I used to be general manager at the testing and rebuild facility which probably has 40,000 ecus in the warehouse which are used for "critical core" program in which they simply replace your ecu with a tested unit on the shelf. If you want testing, it would be "R & R program" in which you send in the ecu for testing or repair in the interest of getting your old unit back once fixed or tested ok.........or they tell you it is unfixable and will provide a new one. Blue streak/standard motor products only deals wholesale through most every parts store chain as do "A1 cardone" and a few others. Most of the "others" like BWD are reboxed blue streak ecus. Try a local chain you trust to give you pricing options if you go that route or simply get another ecu. Quote Link to comment Share on other sites More sharing options...
RonK Posted September 17, 2012 Author Share Posted September 17, 2012 Long Story Short.... looks like the Temp Sensor (not "Switch", which btw only pertains to automatics which have dual pickup distributors and rely on the temp "Switch" to control the retarding and advancing of the distributor... My Z is a Manual, hence, the temp switch had nothing to do with my problem)...as I was saying, looks like I bumped the Temp Senor lead while changing my distributor wires. Apparently, the senor "tested ok" but after fixing the lead the sensor then needed to be replaced. Car is running well but still working kinks out...such as I'm noticing that, after shutting off engine for awhile(to run into the store for 10-20mins)AND if the engine temp gauge is reading well toward the hot side(Before Starting),the engine is difficult to start...acts as if it is either flooded or can't get enough fuel initially and slowly ramps up to normal operation. After it has time to cool down, it has no significant problems starting.... Ideas??? And Don't Say "It's the Temp Sensor"!?! LOL ...Kidding Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted September 18, 2012 Share Posted September 18, 2012 (edited) You are experiencing vapor lock and it is unrelated to your previous issues. The fuel is boiling inside the injectors and the short distance from rail to injector after a hot soak. This is why nissan put a cooling fan on the 280zx turbo all the way up to the Z31 300zx ending in 1986.....which is when they went to dual feed injectors. The dual feed injectors circulate fuel through them so any boiling fuel is sent out the return line. Some people have no issues running without the fan and I have on a few cars but I did have to install a fan on 3 of my L engine turbo cars. 1984 nissan maxima L24e with turbo 1982 280zx turbo 1991 infiniti M30 with L28et. You can either live with it or install the fan though some who went with aftermarket rails might be getting around the issue. Edited September 18, 2012 by HowlerMonkey Quote Link to comment Share on other sites More sharing options...
RonK Posted September 18, 2012 Author Share Posted September 18, 2012 Interesting ... Thank You! Quote Link to comment Share on other sites More sharing options...
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