Ga_Z Posted July 18, 2009 Share Posted July 18, 2009 have a problem, my 76 280Z will not keep running. It will rev good when it is first started but then bogs down when you give it gas. It had sat for years before this but I have taken off & cleaned the fuel tank, new Walbro fuel pump, new fuel filter, replaced the AFM, the fuel pressure regulator and Seafoamed it. I know the water temp sensor needs to be replaced but I don't think it would cause this??? If you rev it at idle once it is fine but then it will barely keep running. Doesn't idle long either. I have downloaded the FI Bible and read it but I'm ready to pull my hair out. Any hints would be appreciated. Thanks Quote Link to comment Share on other sites More sharing options...
280zjoel Posted July 18, 2009 Share Posted July 18, 2009 have a problem, my 76 280Z will not keep running. It will rev good when it is first started but then bogs down when you give it gas. It had sat for years before this but I have taken off & cleaned the fuel tank, new Walbro fuel pump, new fuel filter, replaced the AFM, the fuel pressure regulator and Seafoamed it. I know the water temp sensor needs to be replaced but I don't think it would cause this??? If you rev it at idle once it is fine but then it will barely keep running. Doesn't idle long either. I have downloaded the FI Bible and read it but I'm ready to pull my hair out. Any hints would be appreciated. Thanks If you start the car and let it idle by itself will it run for about 5 seconds and then cut out? I ask because i had this happen to my 280z before and i checked everything, like you everything seemed fine. After lots off searching through the forums, I ended up finding a thread with some info that helped, it turned out that there is a relay under the dashboard near the steering wheel that ended up being the problem. I dont even remember what type of relay it was but i changed it and my car ran fine. Quote Link to comment Share on other sites More sharing options...
Ga_Z Posted July 18, 2009 Author Share Posted July 18, 2009 It will run for as long as 30 seconds sometimes. I think you may be talking about the fuel pump relays. Mine are okay as near as I can tell. Quote Link to comment Share on other sites More sharing options...
ModernS30 Posted July 18, 2009 Share Posted July 18, 2009 Have you tried to hold your foot on the gas at a higher RPM, maybe it will stay running. If so it could be your low speed fuel injection tune. It might be filling up with to much fuel and flooding off. You did check your injectors right? They arn't gummed up or anything. Quote Link to comment Share on other sites More sharing options...
rk2334 Posted July 19, 2009 Share Posted July 19, 2009 Check maybe intake air senser (clock), it happned with once do you see black smoke when you press pedal? Quote Link to comment Share on other sites More sharing options...
jasper Posted July 19, 2009 Share Posted July 19, 2009 What is your fuel pressure at idle? What is your fuel pressure when you open the throttle? What are your compression readings. Posting specifics and test results will enable others to help with educated experience,,..rather than guess. Quote Link to comment Share on other sites More sharing options...
Ga_Z Posted July 20, 2009 Author Share Posted July 20, 2009 My injectors look okay, not gummed up or anything. I have no way to check the fuel pressure though. I changed the fuel filter and it ran okay for a few minutes then started acting like it was starving again. I'm starting to think that my nain fuel line is the culprit. It will rev ONCE then it is hard to keep running, like it uses all the available fuel to rev and then runs out. If it dies then I restart it, it does the same thing. I thought about disconnecting the line at my pump and at the filter and blowing it out with air??? Quote Link to comment Share on other sites More sharing options...
Pharaohabq Posted July 23, 2009 Share Posted July 23, 2009 yeah, sounds like your fuel filters. there's 2 of them one in the back and one in the front. you might pull loos your fuel line at the front and run some gas through it to be sure there's no crap in it. then replace the filters again... Quote Link to comment Share on other sites More sharing options...
Guest Rolling Parts Posted July 23, 2009 Share Posted July 23, 2009 I have no way to check the fuel pressure ...then started acting like it was starving again... You've replaced a boatload of parts but still have not even tested your fuel pressure? Why not buy a gauge for $18 (http://www.jegs.com/i/JEGS/555/41012/10002/-1) and SEE what you need to do next? Just put it in-line after the fuel filter. If there is a blockage, YOU'LL SEE IT. That will tell you if it's fuel. Also look for AIR LEAKS between the AFM and the intake manifold, in vacuum lines, and in the air-bypass hoses at the throttle, the vacuum advance hose, and the brake booster hose. The engine just may be leaning out too far when the cold start injector cuts off. The old L-Jetronic is VERY sensitive to air leaks since there is no O2 feedback and air leaks are just not "seen" by the ECU. If the 33 year old rubber hoses are OK, then get some contact cleaner and clean the 33 year old electrical contacts at the AFM, the TPS, and the ECU. This is probably not the cause of the intermittent problem but it costs only $4 for a can of spray contact cleaner and it needs to be done anyway... Quote Link to comment Share on other sites More sharing options...
Ga_Z Posted July 26, 2009 Author Share Posted July 26, 2009 You've replaced a boatload of parts but still have not even tested your fuel pressure? Why not buy a gauge for $18 (http://www.jegs.com/i/JEGS/555/41012/10002/-1) and SEE what you need to do next? Just put it in-line after the fuel filter. If there is a blockage, YOU'LL SEE IT. That will tell you if it's fuel. Also look for AIR LEAKS between the AFM and the intake manifold, in vacuum lines, and in the air-bypass hoses at the throttle, the vacuum advance hose, and the brake booster hose. The engine just may be leaning out too far when the cold start injector cuts off. The old L-Jetronic is VERY sensitive to air leaks since there is no O2 feedback and air leaks are just not "seen" by the ECU. If the 33 year old rubber hoses are OK, then get some contact cleaner and clean the 33 year old electrical contacts at the AFM, the TPS, and the ECU. This is probably not the cause of the intermittent problem but it costs only $4 for a can of spray contact cleaner and it needs to be done anyway... Thanks for the info, I'll order the gauge Monday. I already cleaned ANY connections I could find with contact cleaner. There are several things that do not work so I thought I'd clean everything. I figured grounding because of the time it had sat. I am going to check again for air leaks & blowing out my line today. Quote Link to comment Share on other sites More sharing options...
Ga_Z Posted July 27, 2009 Author Share Posted July 27, 2009 OK, I could not find any vacuum leaks and the fuel coming from my line is crystal clear, no particles at all. I am ordering a fuel pressure gauge and just to be safe, I am replacing all my vacuum lines. I forgot to mention that I had a friend hook up his meter that measures air fuel ratio. When it is first started it is around 11.8 -12.0 but after a minute or so it jumps to 32.0or higher. Anyone else have any suggestions???? Quote Link to comment Share on other sites More sharing options...
trippintl0 Posted July 27, 2009 Share Posted July 27, 2009 Just FYI, you can rent a fuel pressure test kit at AutoZone from their Loan-A-Tool program. It contains a "tee" with hoses and hose clamps to attach the gauge into the fuel line. You pay like $150 deposit, and they refund 100% when you return it (must return it within 90 days). Quote Link to comment Share on other sites More sharing options...
Daeron Posted July 27, 2009 Share Posted July 27, 2009 http://forums.hybridz.org/showthread.php?t=135748&highlight=efi+bible+step as for specific guesses, I would be wondering about the Throttle Position Switch (not a sensor, this switch ahs three positions: idle, cruise, and WOT, and between them they each occupy roughly 1/3 of the throttle travel) or the Thermotime Switch. As for your AFR reading... 32 would be stupid lean, something seems out of whack there, and AFRs aren't the tree to start barking up to solve this problem. What do your spark plugs look like? Fouled out with too much fuel, or what? Quote Link to comment Share on other sites More sharing options...
pbagchi Posted July 29, 2009 Share Posted July 29, 2009 I had a very similar problem with my '75 280 for a few months. It had been sitting for almost 20 years, so I went through the fuel system...painstakingly restored the tank, new filter, new pump, new inline fuel filter in front of the tank, new injector connectors, thermotime switch connector, removed a spider web of an alarm system, made sure it had enough gas, and it would still be starved for fuel at times...FRUSTRATING, to say the least. BUT then I went after the fuel interlock relay. I was about to bypass it when I decided to check my coil. I believe the coil readings were a little low, so I replaced the coil out, and the problem disappeared!! I believe the interlock relay gets a signal from the coil, and this may have been fluctuating due to a bad coil. Not sure, but it worked for me. Hope it helps! 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.