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Bigworm

Urgent help needed!!! Voltage problem

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Oh i though you just diconnnect the battery and drain all the power from the electrical system, or leave it unhooked for a period of time.

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Later computers that self learn, like the Ford EECIV and EECV computers will reset themselves and self learn, but the L28 computer was very basic and didn't really do much in the way of adjustments on the fly

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ok i tried re-setting the computer by draining it but that didnt seem to work, then i managed to grab another one the same and put that in and still no difference so i think that there may be an issue with the actuater thing near the fuel pump letting too much pressure through the line to the front. maybe i can find some sort of aftermarket fuel line regulator to fix the issue??? it seems like my fuel pump is contantly cranking when ignition is on and someone told me that it should only run for about 5 seconds then cut out so maybe thats a part of the problem with mine?? any thoughts on this theory guys???

thanks

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Going back to the battery connection/test light discussion.

 

There doesn't necessarily need to be something turned "on" to have a draw. Many items will have a draw when turned "off", to keep any volatile memories alive. Things such as radios (with clocks and electronic presets) have volatile memories that will draw a small amount of current. Clocks, especially mechanical clocks, will draw current, security systems will also draw a small amount of current when turned "off".

 

Moving up to the current discussion...

 

Before replacing anything, I would look at the AFM. From what I read, these can go out of adjusment and because of thier switch design, if it doesn't close almost fully at idle, this can cause problems. Also check your Throttle Position Switch. There are two switch points, not a range of voltage in the L28 EFI system. Closed throttle and Wide open throttle. If the closed throttle switch side is not adjusted properly or your throttle linkage is binding up and not allowing the throttle to close fully, that can also cause idle issues.

One other thing that seems to be common is the flexible tube between the AFM and the throttle body can tear and this will cause inaccurate readings of the AFM, since unmetered air is allowed to enter the engine this way.

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Going back to the battery connection/test light discussion.

 

There doesn't necessarily need to be something turned "on" to have a draw. Many items will have a draw when turned "off", to keep any volatile memories alive. Things such as radios (with clocks and electronic presets) have volatile memories that will draw a small amount of current. Clocks, especially mechanical clocks, will draw current, security systems will also draw a small amount of current when turned "off".

 

The current draw of things like a radio memory, alarm sensors and a clock would produce only the tiniest of sparks.

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well i have replaced the AFM yesterday (before i swapped the computer) to see if there was any difference but it did nothing, so maybe it could be the TPS, i will have a look when i get a chance. and from knowledge the air hoses on my car seem in good condition but ill check them out aswel.

cheers

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Try unpluging the cold start fuel injector; it may be stuck open. From memory its located near the throttle body.

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The current draw of things like a radio memory, alarm sensors and a clock would produce only the tiniest of sparks.

 

:facepalm:

 

I never mentioned anything about sparks, besides "tiniest" is relative.

 

The current draw form those items is more than enough to cause a test light to turn on, used as a ground connection.

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+1 on cold start injector... I hear they a frequently dysfunctional in zx's... Clamp off the fuel if you have to (jammed open?)

Test all injectors are firing? place a flathead screwdriver against the body of the injector and hold your ear to it.. listen for the "click click"...

Check your plugs (are they black and wet?)

Another thought: check your coolant temp sensor. A faulty sensor or bad connection will read VERY cold to the ECU which will rich-out to compensate.

 

Good luck.

-pete

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Is it just me, or do old fashioned carbies sound really good about now?

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Is it just me, or do old fashioned carbies sound really good about now?

No way... you couldn't pay me to take my MS off me. EFI is far superior to carbs in almost every aspect except simplicity for troubleshooting. Carbs are a metered leak, EFI gives superior atomization without the need for comprises in manifold air temperature, flow and port design required to maintain atomization in carburated systems.

 

Don't blame EFI... the zx ecu is 30 years old and not built for user interface. That said, I don't think it sounds likely that the ecu is the source of failure, it would just be nicer if you could plug the laptop in and see the ECU readouts for troubleshooting like in a aftermarket system but that's how it goes.

 

Keep us posted on progress... there are lots of simple tests you can use to track down the problem if you think about it logically. I also have HEAPS of zx efi spares that may help if you need.

 

-Pete

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thanks pete, i think when i get over there today im gonna get the multimeter out and test all the electrics on the wiring harness and the component switches and relays just to eliminate it being an electrical fault (thus eliminating a faulty ecu) and also i have tried running it without the cold start valve plugged in to no effect, but i might have to pull it out completly and have a look if its jammed or something.Also i did adjust the TPS yesterday but that didnt seem to do anything really either.

 

 

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nws.

If you're not sure about reading plugs swap in some brand new ones, run them for a bit (10 mins+?) and then pull them out and take a photo straight away, also note if they are wet (is it thick grimey wet with oil, liquidy and smells strongly of octane, or watery with a bit of green... dab it on paper if you have to) ... It will really help with troubleshooting if you know exactly what the problem is. Fuel plus spark plus air = bang... one of those is the problem so work out exactly which first then we can work backwards through EFI if nessecary.

 

Although the normal instinct is to change things untill you find the problem it can stuff with you ability to locate problems by adding complexity... think about it like this:

1. If it was working and now isnt, something has changed.

2. It is probable that there is only one point of error

3. The probable source or error is the last thing that changed (what have you changed recently?)

 

 

If you started fidling with wires and changing things stuff without following a logical process you may be introducing new errors - cables can come loose, short etc.

The probability of finding two errors is exponentially greater than finding one because you only have one source of information output (does it work? - yes/no)

 

I cannot recall the number of times i've changed a relay or wire and then had to adjust it afterwards because i'd let somehting sit loose or connected incorrectly. Without knowing is you've made a mistake you could potentially introduce a plethora of new problems :(

Start from basics would be my strongest advice.

 

 

 

-pete

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I find EFI to be more simple than carbs.

 

Just FYI, there are a number of OEM EFI systems that have datalogging capabilities, the Z and ZX ECMs are not able to though. The GM ECM I use in my 240Z has an ALDL (Assembly Line Diagnostic Link) connector that has all sorts of info sent through it. :D

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ok an update on whats goin on. I have sorted out the problem with the excess fuel pressure (seems my uncle who was helping me with the car had unplugged the sensor on the block next to the oil filter for some reason and forgot to plug it back in :-[)but as soon as i plugged it in all was well with the fuel system it builds up pressure and then shuts off after a few seconds and keeps it at the correct pressure so the fuel system is fine! :D Now the car kicks over and idles but it is still lumpy and blows a bit of smoke, i took the rear cover off the afm so i could monitor it and the potentiometer thing is flapping a bit and if i gently hold it shut it runs nearly perfect, making me think there is some kind of airflow or vacum problem. also what is the easiest way to tune these systems to get them running nice?? i have tried a combo of timing/idle speed adjuster/AFM bypass screw but it doesnt seem to do much (maybe it has something to do with the air problem??)

thanks

 

Jesse

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getting it idling then worry about the finer details... set timing at stock, idle screw conservative 800-1000 rpm

You have 2 afm's yes? swap them and look for the same phenomenon... if it doesnt resolve with a different unit my instinct  would be to start looking for vacuum leaks (sorry my knowledge on the AFM function is very limited).

You might find it runs alot better after you work through undoing alot of the fiddling you've done trying to track down the earlier problem

 

Is the cam stock? A aftermarket cam would make it "lumpy" or is it missing a cylinder? change your spark plugs and photograph them!!!!!!

What colour is the smoke, how does it smell, how much is there?

(basics basics basics)

 

-pete

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Jesse, I have a PDF of "280-Z Electronic Fuel Injection -Theory -Troubleshooting".  Also have 1978 FSM and the 1979 wiring diagram, between these I was able to methodically diagnose and fix my 1979 280zx.  If you want a copy PM me your email address, it's about 3.8Mb.

I also highly recommend replacing it with megasquirt.  I did MS2 on mine, learn't a lot about EFI making it work and went a hell of a lot better too.

Mike

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There may just be a heap of unburned fuel in the engine; get it hot and hopefully that should clear all the fuel from the motor. If it still does it, start checking all the other sensors.

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alright i have got it running fairly well now what i did was replaced a few air/vacum hoses and put a small spring on the potentiometer counter-weight to restrict how much the flap moves which sounds bad, but it works a treat. if i dont do this the flap moves too much and sends too much fuel into the engine flooding it. so if i leave the spring off and try to run it it wont start and then i pull the plugs out and there black with carbon and fuel but if i then clean them and put the spring on to restrict the flow it runs fine. im still having a bit of a play arond with the idling settings and timing as it runs nice but seems pretty gutless for some reason???

and p.s mike i have that same manua aswelll its what i have been using to diagnose this problem aswell its a really good document to have!!! but thanks anyway

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lol come on its not that bad :-[

also after i took it for a test drive yesterday i noticed it was extremely loud but i thought it may have just been the way that engine sounded, but i put it up on ramps and stands and found the exaust just before the first muffler had a massive split (around 3/4 of the diameter of the pipe!!) so i took it off and welded a cover plate over it and that sealed it. so now its nice and quiet and runs a lot smoother i guess there wasnt enough back-pressure, but it still needs the spring to run

P.s i only thought of the spring because the original AFM is supposed to have an inbuilt recoil type spring inside the potentiometer cover and mine doesnt (from the photos i have seen anyway)

thanks to everyone who helped me out with this whole debarkle, the advice advice was very helpful!!

 

Jesse

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