Serban Posted January 9, 2014 Share Posted January 9, 2014 Quick background on the car. Its a '75 CA model. I recently replaced the stock injectors and fuel rail with a custom top feed o-ring style rail and Ford 19lb injectors. This setup has been been problem free for over a month. On to the problem...3 days ago as I was getting my A/C charged (its Florida, we need it year round), the car just stalled, which I thought was weird. Try to start it, and it will not fire. Spark is good, the engine just floods before you can even start the car. If I unplug all the injectors and crank, it'll run until it burns the residual fuel in the cylinders, as soon as I connect the injectors and try to start it, same problem. Pinching the fuel line will get the car started, but fuel psi gauges shows 0 psi for pressure. As soon as you give it a little gas, it runs very lean, maxes out the wideband at 18. I disconnected the battery cables and left it like that for 24 hours, once I connected them, and cranked the car, it fired right up, and idled great. Fuel pressure was mid 30s. I let it run for 15 minutes, revving the engine a few times during that time, even turned the A/C on to see if it would replicate the problem, but it ran fine. I decide to shut the car off start it again....same problem, floods the engine before it can fire. Could the ECU be the problem? If it was an injector issue, it would be one or 2, I've ran into that problem before. And it wouldn't just all of a sudden work again. Maybe the AFM is the problem? Anyone ever experience this before? I'd like to pick up another ECU and try that. Is there any difference in the 75 or 76 non CA ECUs, or even the 2+2? Quote Link to comment Share on other sites More sharing options...
Serban Posted January 9, 2014 Author Share Posted January 9, 2014 (edited) Also, I know a couple of those sensors on the thermostat housing communicate with the ECU and affect fuel delivery until car is up to temp. I've had them disconnected before to see if it would affect startup or warm up in the past, but even with them disconnected, the car would always start. So I doubt my problem is there. Edited January 9, 2014 by Serban Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted January 9, 2014 Share Posted January 9, 2014 Sounds like your pressure regulator diaphragm may be leaking, allowing fuel to get in your intake manifold through the vacuum line. Get a pressure gauge and measure your fuel pressure. Quote Link to comment Share on other sites More sharing options...
sq_creations Posted January 9, 2014 Share Posted January 9, 2014 2 ideas come to mind. first it could be a temp sensor gone bad making the computer think its really cold and adding a ton of fuel. look at water temp and intake air temp to the computer. 2nd idea would be the injectors stuck open. That would account for the lack of fuel pressure too. You could put noid lights on the injector plugs to varifiy if the ecu is pulsing the injectors or just full on. Quote Link to comment Share on other sites More sharing options...
Serban Posted January 9, 2014 Author Share Posted January 9, 2014 Sounds like your pressure regulator diaphragm may be leaking, allowing fuel to get in your intake manifold through the vacuum line. Get a pressure gauge and measure your fuel pressure. Regulator is fine. I do have a fuel pressure gauge mounted on the fuel rail, and when it runs, the pressure is right where it needs to be. Plus I've tried disconnecting the vacuum hose from the regulator to see if that affects anything, no fuel comes out. 2 ideas come to mind. first it could be a temp sensor gone bad making the computer think its really cold and adding a ton of fuel. look at water temp and intake air temp to the computer. 2nd idea would be the injectors stuck open. That would account for the lack of fuel pressure too. You could put noid lights on the injector plugs to varifiy if the ecu is pulsing the injectors or just full on. I haven't checked the air temp sensor, but the water temp sensor is new. Guess I'll find a noid light to try the injector plug trick. I pulled the manifold off, and cranked to see if the injectors are firing, they were, none were stuck open. And pressure remains in the line once I shut the car off. On a side note, can someone with an EFI setup chime in on this...once the car turns off and the ignition is still on, after a few seconds, I get rapid clicking from the injectors, like they are being energized. Is that normal? Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted January 9, 2014 Share Posted January 9, 2014 Regulator is fine. I do have a fuel pressure gauge mounted on the fuel rail, and when it runs, the pressure is right where it needs to be. Plus I've tried disconnecting the vacuum hose from the regulator to see if that affects anything, no fuel comes out. I haven't checked the air temp sensor, but the water temp sensor is new. Guess I'll find a noid light to try the injector plug trick. I pulled the manifold off, and cranked to see if the injectors are firing, they were, none were stuck open. And pressure remains in the line once I shut the car off. On a side note, can someone with an EFI setup chime in on this...once the car turns off and the ignition is still on, after a few seconds, I get rapid clicking from the injectors, like they are being energized. Is that normal? Doesn't sound normal to me, what does the fuel pressure do after this? Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 9, 2014 Share Posted January 9, 2014 Quick background on the car. Its a '75 CA model. I recently replaced the stock injectors and fuel rail with a custom top feed o-ring style rail and Ford 19lb injectors. I'd like to pick up another ECU and try that. Is there any difference in the 75 or 76 non CA ECUs, or even the 2+2? I've seen it described that failing ECU's will sometimes flood the engine. I had one fail and the guy that helped me push said he smelled gas from the tail pipe. I was too busy trying to figure out how to avoid a towing fee to check for sure. I replaced the transistors on that ECU and it worked, so my guess is that the two big transistors that control the injectors can fail just like the igniton module transistors do, causing erratic and excessive cirrent flow (when igntion modules fail you'll see high RPM readings and poor igntion after they get hot). What's the impedance (resistance) on those Ford injectors and did you keep the harness resistors? Maybe you're running too much current through the ECU transistors and you've damaged them. Nissan used several ECU models on 75-78 280Z's. They deem to differ by CA vs. Fed. and auto vs. manual. You just have to check the numbers. 75-78 Fed. manual all seem to be the same model. Quote Link to comment Share on other sites More sharing options...
Serban Posted January 9, 2014 Author Share Posted January 9, 2014 Doesn't sound normal to me, what does the fuel pressure do after this? After the rapid clicking, sometimes it maintains fuel pressure for a few seconds, then it drops to 0, other times it holds it longer I've seen it described that failing ECU's will sometimes flood the engine. I had one fail and the guy that helped me push said he smelled gas from the tail pipe. I was too busy trying to figure out how to avoid a towing fee to check for sure. I replaced the transistors on that ECU and it worked, so my guess is that the two big transistors that control the injectors can fail just like the igniton module transistors do, causing erratic and excessive cirrent flow (when igntion modules fail you'll see high RPM readings and poor igntion after they get hot). What's the impedance (resistance) on those Ford injectors and did you keep the harness resistors? Maybe you're running too much current through the ECU transistors and you've damaged them. Nissan used several ECU models on 75-78 280Z's. They deem to differ by CA vs. Fed. and auto vs. manual. You just have to check the numbers. 75-78 Fed. manual all seem to be the same model. Thanks for the info, I will look for the transistors. Are they inside the ECU, or outside of it located in the kick panel? The injectors are high impedance (I believe 12ohms) vs the stocks which are low impedance. I've been told going with a higher impedance injector is fine, its when you go lower, you need resistors. Quote Link to comment Share on other sites More sharing options...
NewZed Posted January 9, 2014 Share Posted January 9, 2014 I'm not suggesting that you replace the transistors. It's just an example of what can go wrong, and replacement is kind of difficult. Plus, an exact spec. match for the original transistors is not available. You didn't say if you bypassed the dropping resistors or not. You can measure resistance of the injectors with an ohm-meter. I don't know how much resistance it takes to cause a no-open problem. If I swapped injectors, I would try to match impedance for the whole circuit since that's what the ECU was designed for. Quote Link to comment Share on other sites More sharing options...
Serban Posted January 10, 2014 Author Share Posted January 10, 2014 Got home tonight and decided to give it another shot. The car started fairly easy, ran rough for a few seconds, but eventually cleared up and idled fine. Let it idle for a while, turned it off and on several times, and everything seems ok. Could it be the ecu just needed to be reset? I'll check it over the next few days, and see if I can replicate the problem, but as of now, it seems to be ok again. Quote Link to comment Share on other sites More sharing options...
Serban Posted January 22, 2014 Author Share Posted January 22, 2014 A week later, and the car is still ok. Not sure what to make of this whole thing, but whatever it was, disconnecting the battery overnight cured it. Quote Link to comment Share on other sites More sharing options...
BluDestiny Posted January 23, 2014 Share Posted January 23, 2014 I would grab a spare just in case it happens again to make sure it's the ECU. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.