cpark_12 Posted October 15, 2012 Share Posted October 15, 2012 (edited) I've had my 83 ZX for about 2-3 months now, and my FI problem is really getting old! I bought the car knowing it had a problem, but it's progressively gotten worse. The previous owner put the fuel pump on a switch. I don't know why, I didn't ask. Anyway, every now and then I'd go to crank the car, flip the switch on, turn it over and it would crank, but would run way too rich. Black smoke and smell of gas, so I flip the fuel pump switch off and it would idle normal for about 5-7 minutes and eventually run out of fuel. Then flip the switch on and it would run like a champ. How in the world it runs that long without the fuel pump on is beyond me! Anyway, that would happen maybe once a week. Now it happens about once a day! I can be driving down the road and all of the sudden I lose power and just pour black smoke out of the exhaust. I did a little test with the CHTS when it ran good: I unplugged it and it acted like it did when it ran bad, so I replaced the CHTS. Now with the new sensor in, it will never run right. It just sends way too much fuel. I'm looking into going to a carburetor now, but if someone can help me figure this out, I'd love to keep it like it is. My biggest thing is why it's just an intermittent problem...if it's a sensor, I would figure it would be bad all the time. Edited October 15, 2012 by cpark_12 Quote Link to comment Share on other sites More sharing options...
NewZed Posted October 15, 2012 Share Posted October 15, 2012 Almost impossible to diagnose without measuring the basics, like fuel pressure, CHTS resistance versus temperature at the ECU plug, etc. Someone may have "tuned" your AFM to make up for a different messed-up part. Maybe someone installed high flow injectors in a misguided attempt for more power. Many possible causes for the "running rich" problem. Quote Link to comment Share on other sites More sharing options...
BluDestiny Posted October 16, 2012 Share Posted October 16, 2012 (edited) Highly doubt its a sensor. Before you explain nay further, we need to know if this is a stock car or a modified one. Did the PO tell you anything at all that was either changed or modified in the engine bay? Did he tell you of any parts he replaced? Can you get in contact with him and find out why he is using a switch for the fuel pump? Are there any modification in the fuel system other than the switch to power the fuel pump? Could be something as simple as a broken FPR or even the injecotrs being stuck open, or it could be your ECU is fubar. We need more info. I'm banking on a more mechanical problem, such as stock injectors or the FPR being crap. Edited October 16, 2012 by BluDestiny Quote Link to comment Share on other sites More sharing options...
cpark_12 Posted October 16, 2012 Author Share Posted October 16, 2012 Highly doubt its a sensor. Before you explain nay further, we need to know if this is a stock car or a modified one. Did the PO tell you anything at all that was either changed or modified in the engine bay? Did he tell you of any parts he replaced? Can you get in contact with him and find out why he is using a switch for the fuel pump? Are there any modification in the fuel system other than the switch to power the fuel pump? Could be something as simple as a broken FPR or even the injecotrs being stuck open, or it could be your ECU is fubar. We need more info. I'm banking on a more mechanical problem, such as stock injectors or the FPR being crap. Motor is stock with 220k miles. No other modifications other than the fuel pump switch, exhaust system and a k&n cone filter up front. I have replaced the intake/exhaust gasket and changed plugs twice. The p/o said the pump was on a switch because the pin that controlled it on the ecu was bad. Injectors are okay, we checked those via the FSM. The p/o had replaced the ecu with an 81 model. I can't think of anything else... Quote Link to comment Share on other sites More sharing options...
BluDestiny Posted October 16, 2012 Share Posted October 16, 2012 I would suspect it may have something to do with ECU. I know the 83 is finicky and that they have a specific ECU only for an 83. That could be a reason why the fuel pump is hooked up to a switch because either it doesn't have the correct pin or he swapped the AFM out and it doesn't have the correct pin. read this: http://www.zdriver.com/forum/280zx-s130-forums-77/83-280zx-starts-stalls-right-away-help-32091/ I would personally still check the FPR and fuel lines for proper pressure so make sure your not killing them with fuel pressure. One more question how long have you had the car? like when you got it it was having this problem once a week, but now it does it every day. How long did that take? months or weeks of owning the car? Quote Link to comment Share on other sites More sharing options...
cpark_12 Posted October 16, 2012 Author Share Posted October 16, 2012 I've only had the car 3 months or so. It never did this when I first got it. Maybe about a month into it started doing it and has progressively gotten worse Quote Link to comment Share on other sites More sharing options...
NewZed Posted October 16, 2012 Share Posted October 16, 2012 (edited) With the EFI system you really have to be able to identify and separate the various issues if you want to get things running right. In your first post you said that you bought the car knowing it had a problem and it's gotten progressively worse. Now you're saying that it never did this for a month, then started and got worse. So it's either an old problem that maybe a PO tried to fix, or it's a totally new problem. Plus, you changed the intake/exhaust gasket for some reason. Maybe you fixed a problem, maybe you created a new one when you changed the gasket. It's easy to get the various symptoms and potential solutions mixed up. That's why taking measurements, even of components that you're positive are good, will help you determine what's really wrong and get all of the parts working together. Edit - don't forget to check your TPS. If it's stuck on wide open, the ECU will dump fuel. Maybe you banged it when you removed the manifolds. Best to sit at the ECU plug with the FSM and take all of the measurements you can from the connector, with a friend to move various parts like the AFM vane and the throttle. Edited October 16, 2012 by NewZed Quote Link to comment Share on other sites More sharing options...
cpark_12 Posted October 16, 2012 Author Share Posted October 16, 2012 The car didn't do this when I bought it. Maybe the p/o did something as a temporary fix and didn't tell me...I changed the intake/exhaust gasket because it had an exhaust leak that I couldn't take. So, maybe I did something, but what it is, I can't for the life of me figure out. I'll check all the components I can and see what's up. What irks me the most about the whole deal is that it's an intermittent problem. I would figure if it was a problem, it would never run right, but that's not the case at all. This morning it ran good as gold all the way to work.This afternoon on the way home, it cranked up fine and I drove for about 5 miles and it started acting a fool again... Quote Link to comment Share on other sites More sharing options...
Domzs Posted October 17, 2012 Share Posted October 17, 2012 I don't see how the engine can run for that length of time without the fuel pump running . When problem occurs again , pull the vac. hose off your fuel press. reg. to see if any fuel comes out . It's poss. you might have interm. problem with a leaky reg. . Good luck . Quote Link to comment Share on other sites More sharing options...
280Zhunter Posted October 17, 2012 Share Posted October 17, 2012 HEllO, I agree with BluDestiny about the ECU. Before you make yourself CRAZY put the PROPER ECU back in the car. The early Z cars only had 2 ECU's I know of but the ZX's seem to have a different ECU for each year they were made. The switch could have been put in as a theft deterent or instead of buying a new relay or the lack of the control pin in the 81 ECU. Are you SURE none of the injectors have been changed?? Are they the original set?? My car the PO had only changed 1 and it ran pretty decent until I noticed the cold start valve leaking. I bought a set of SK? injectors on Ebay for $160 and you can probably find an ECU for about the same. Make sure the numbers match the original 83 ECU, ask the PO if he still has the original or if he copied the numbers off the original. Also make a checklist of everything you do check and the results(feed and return fuel line pressure,resistance of each the injectors/sensors, etc.) If you give up and go with the carbs use the WEBER DGV's due to the high mileage but you will have to change the fuel pump as well so it should be an ABSOLUTE LAST RESORT. Quote Link to comment Share on other sites More sharing options...
cpark_12 Posted October 19, 2012 Author Share Posted October 19, 2012 Update: The past 2 days, it hasn't given me a lick of trouble. It ran just as pretty as you please! I'm gonna check the ECU and injectors with the FSM this weekend to see what I can find out and/or narrow down the problem. Quote Link to comment Share on other sites More sharing options...
cgsheen Posted October 19, 2012 Share Posted October 19, 2012 WIRING!!! The connectors in these cars are way past their "sell by" date. Much of the copper wire in your harnesses will be oxidized. The ECU is in a place prone to be dripped on by windshield leaks. The first thing to check and clean (and check and clean again) is wiring and connectors throughout... (especially when you have something "intermittant") Quote Link to comment Share on other sites More sharing options...
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