Distortion Posted September 1, 2012 Share Posted September 1, 2012 Ok, I just purchased a 1978 280z. Its runs amazingly but does have a slight issue. The fuel pump seems to be running at full cycle whenever the key is in the on position. It is flooding out the engine and makes it difficult to start. I also feel that it is important to mention that one of the fusible links was burnt in half. Im not really sure where to even begin. Im wondering if its something in the ignition electric system but im not sure where to start. Quote Link to comment Share on other sites More sharing options...
calvin280zxt Posted September 1, 2012 Share Posted September 1, 2012 Service manual is a good place to start Quote Link to comment Share on other sites More sharing options...
OldAndyAndTheSea Posted September 1, 2012 Share Posted September 1, 2012 on the 280z the fuel pump is supposed to run at two different times. first, only when the motor is cranking once it fires the air flow meter controls the fuel pump being on. As long as the flapper is open the fuel pump will run, so if you wreck and the flapper closes, the car shuts off, without the risk of shooting raw fuel all over the place, or even worse, fire.... Maybe someone wired the fuel pump constant to the ignition on. But I'd investigate your AFM, physically push the flapper open, if the fuel pump doesn't come on, someone may have bypassed it. Also the fusable link problems are very common with these cars, search "maxi fuse" Quote Link to comment Share on other sites More sharing options...
Distortion Posted September 1, 2012 Author Share Posted September 1, 2012 I made a new fusible link. The guy said the afm may have an issue so maybe he did know what he was talking about. Ill check it out. Is it possible for it to be stuck open? Quote Link to comment Share on other sites More sharing options...
Distortion Posted September 1, 2012 Author Share Posted September 1, 2012 Would unplugging the afm with the key in the on position cause it to stop pumping if that was the problem? Quote Link to comment Share on other sites More sharing options...
OldAndyAndTheSea Posted September 1, 2012 Share Posted September 1, 2012 (edited) I made a new fusible link. The guy said the afm may have an issue so maybe he did know what he was talking about. Ill check it out. Is it possible for it to be stuck open? You said the car runs and drives, its just the fuel pump thats giving you problems, and by problems I mean constant running. The air flow meter actually has what is called a "Fuel pump contact point" built into the AFM that sends the signal to the fuel pump relay to trigger the fuel pump's power. That's where I'd start. Here's the Bible for the L28e system. http://www.xenons130.com/files/280zfuelinjectionbook.pdf Hopefully it works out. Edited September 1, 2012 by OldAndyAndTheSea Quote Link to comment Share on other sites More sharing options...
Distortion Posted September 1, 2012 Author Share Posted September 1, 2012 yes the car will run and drive but for a short time. then bogs down at around 2k and wants to die Quote Link to comment Share on other sites More sharing options...
BluDestiny Posted September 1, 2012 Share Posted September 1, 2012 If you think the issue is too much fuel, then get a fuel pressure gauge. check the fuel pressure before and after. Could just be your old fuel pressure regulator is stuck open or broken. Quote Link to comment Share on other sites More sharing options...
Distortion Posted September 1, 2012 Author Share Posted September 1, 2012 The fpr wouldnt cause the fuel pump to run when it isnt suppose to. It should only run if the motor is cranked or running not with th ekey just in the on position. It has to be something elctrical not mechanical. After reading the basic theory and layout of the fuel system it almost seems like the afm has to be at fault. Quote Link to comment Share on other sites More sharing options...
Distortion Posted September 1, 2012 Author Share Posted September 1, 2012 I will check the pressure though just in case Quote Link to comment Share on other sites More sharing options...
NewZed Posted September 1, 2012 Share Posted September 1, 2012 Combined, the statements made about the car don't really fit. It would be worthwhile to define the problems better, it will help you understand their causes. - runs amazingly - afm may have an issue - will run and drive but for a short time - bogs down at around 2k and wants to die And it is important that one of the fusible links was burned. Did you find the short that caused it, and fix it, and what kind of wire did you use to make a new one? Lots of ways to go wrong here. Quote Link to comment Share on other sites More sharing options...
Distortion Posted September 1, 2012 Author Share Posted September 1, 2012 (edited) Sorry for discrepency let me sum it up. The motor runs amazingly when you can get it started. It drives great( referring to the feel of the car going down the road) Bogs down from 2k-2300 rpm when driving but only occasionally It will run and drive fine until it bogs down then it tries to die(fixed by feathering the throttle) I used 10 gauge wire to make a new fusible link. the old one had been slightly cut at the top where it bends and arced over. Fuel pump runs when it shouldnt The fusible link that burned was the short green one. I used wire with a 60 amp melting point to replace it. It is the ignition switch fusible link i think factory it had a 40 amp melting point Edited September 1, 2012 by Distortion Quote Link to comment Share on other sites More sharing options...
NewZed Posted September 1, 2012 Share Posted September 1, 2012 (edited) The first thing that you should do is remove your home-made fusible link, read up on fusible links, and make or get a new one. Once your wiring burns up, you're in a whole new painful world, if the car survives. (Nevermind, you edited out your 10 gauge wire remark. Did you just switch from 10 gauge to 60 amp wire? You shouldn't use a higher capacity wire either, get some 40 amp). Edit - if it's the green one from the battery, it's the EFI harness power. Proper fuel pressure is key to the EFI system. Measuring that would be good. Intermittent problems are hard to diagnose though, so your occasional "bog" could be difficult to cure. And the pump running could be due to someone bypassing the contact switch in the AFM or actually bending it so that it stays closed all the time. You can pop the black cover off of the side of the AFM to see how it's working. Someone might have rewired the pump power also. Reading the Engine Fuel section in the service manual will save you a lot of time and money, in the long run. Edited September 1, 2012 by NewZed Quote Link to comment Share on other sites More sharing options...
Distortion Posted September 1, 2012 Author Share Posted September 1, 2012 I couldnt find a 40 amp fusible link so I improvised. i got a fuse holder with a 12 gauge lead and some 40 amp fuses. I just ordered the maxi fuse setup to replace it all. Looks like my AFM has bent connections to be always on (believe its the full throttle connection) But I cleaned it all and now the draw on my link isnt there and Im not blowing fuses. So i think THINK i have it fixed Quote Link to comment Share on other sites More sharing options...
Distortion Posted September 1, 2012 Author Share Posted September 1, 2012 Its is finally fixed. The relay was shorting out. Replaced it and suddenly no problems 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.