77 280z Water Temp Sensor Issue, Runs Very rough

[Captain Obvious]

At the injector connectors on both pins it showed power when It's suppose to be power and ground, correct? Therefore its shorted somewhere in my wiring?

No. Measuring +12 volts on both sides of an injector is not necessarily a problem. The way the system works is this...

One side of each injector is always connected to +12 through a "dropping resistor". You should always measure about +12 on that side of the injector.

The other side of each injector is connected to the ECU. Inside is the ECU is a switch (a transistor) which, when closed, connects that side of the injector to ground.

When the transistor switch is open, no current flows through the injector and you will measure +12 on both sides of the injector. When the transistor switch is closed, current flows through the injector (which causes the injector to open), and you will measure +12 on one side of the injector, and ground on the other.

However... The amount of time that the transistor switch is closed is very short, and your typical voltmeter will not pick it up. Your typical voltmeter will average the signal in some way, and since the amount of time that the injector is connected to ground is such a small amount of time, it will essentially average out to +12.

Does that help? Does that make any sense?

I'm not sure that your mechanic is familiar with fuel injected systems.

[Samson]

Coincidentally, today I was looking at a few ECU's I've collected to see if they had the "altitude compensation" pins. All of them are A11-600-000 and they come from cars from 76-78. While checking the FSM's I saw that only the California cars came with altitude compensation. I wonder if the -601- ECU's have the altitude compensation circuit? Samson is in CA, Eurodat, where did your car, or ECU, come from?

The switch is described and shown in the Engine Fuel chapter, it drops the fuel supply through the injector duration by 6% when the switch closes due to low pressure from high altitude. It wouldn't affect operation unless the switch was shorted, causing a lean condition.

Samson, your mechanic doesn't understand how the injection system works. The injector connections have 12 volts on both sides due to the way the transistors operate (I confess that I'm not clear on why that is either, but it is). The injector solenoids don't activate until current actually flows when the transistor circuit allows it to. 12 volts on both sides is good.

As I said in an earlier post, you're pretty close. I had to adjust my idle air screw and install some new plug wires on my last DEQ (our emissions checkers) visit here in Oregon. A miss will spew unburned fuel (bad), and the idle air screw can lean up the idle. I wouldn't do anything major and I would find a mechanic who knows old EFI.

My 77 is a NON-CA car therefore there is no altitude switch aswell as a catalytic converter.

I now understand what you all mean thanks for the enlightment.

Also went over the car today and noticed that the vacuum routing for charcoal canister dist vac port aswell as the ported vacuum switch were hooked up wrong.. from the charcoal canister it went straight to the nipple under my throttle body. Then goes Vac advance>port vacuum switch>other nipple of vacuum switch goes to this "thing" next to the egr sorry I don't know what It's called.. could this affect the mixture?

Edited January 11, 2013 by Samson

[EuroDat]

Coincidentally, today I was looking at a few ECU's I've collected to see if they had the "altitude compensation" pins. All of them are A11-600-000 and they come from cars from 76-78. While checking the FSM's I saw that only the California cars came with altitude compensation. I wonder if the -601- ECU's have the altitude compensation circuit? Samson is in CA, Eurodat, where did your car, or ECU, come from?

.

Hi Zed,

My car is originally from Redlands 92373, California.

Chas

[EuroDat]

If you are loking for an ECU, there is one on ebay that might be ok.

Datsun Z L28 Computer | eBay

[Samson]

Update: Just got my EFI harness in aswell as the computer the other day. Found pallnet's fuel rail cheap on craigslist and picked it up, thought to myself if i'm going to be changing out the rail why not do the injectors too right? It's going to be right there anyways? So i'm still debating on that. Checked continuity on the whole harness and it all checks out ok. I have an appointment with a state referee on tuesday because in order for a shop to install a catalytic converter on the car, it needs to be signed off (i think that's pretty dumb) so at the moment i'm just going to leave the car how it is now and not touch any of the wiring till then, afraid something else may go wrong right before the appointment, missed my first appointment last tuesday because i thought i may as well change out the plugs since they're all fouled and #5 cylinder's threads decides to cross thread. FML right? I have that all sorted out now tapped the hole and installed a new insert.

[Samson]

Another Update: Installed the new EFI harness, ECU and dropping resistors all from a 76 280z. Replaced the injector connectors that were on the new harness since they were all old and dying. I'm not sure if i fixed the Rich mixture part yet given i don't have no Gas Analyzer to look at the numbers but i do have pictures of the plugs, anybody here pretty good with examining them? Much Appreciated.

Here are 2 plugs side by side. Left one is the new plug how it looks right now. Also one point these plugs were installed on the car before the whole EFI electrical part was replaced, i'm not sure if that has an affect of the left over carbon fouled burn the car used to produce?

Just a better picture of the new plug's burn.

Thanks all! I feel like i'm getting close on fixing this problem! Also i have new fuel injectors on hand but have not installed them yet.

[EuroDat]

The plugs are looking better. Looks like your almost there.

If you have new injectors, I would use them.

Have you checked your AFM? If the spring tension has weakened the ecu will think its getting more air and give more fuel.

You can follow these instructions to check it and do some field adjustments.

http://atlanticz.ca/zclub/techtips/afm/calibration/index.html

http://atlanticz.ca/zclub/techtips/afm/index.html

If you follow those tips, you can then use a temp. sensor resistor to richen the mixture after making it leaner in second tip.

Chas

[darom]

Hi Samson, any updates? Did you re-test your car? I would assume that catalytic converter should have helped you pass.

Regards!

[rcb280z]

Samson, I'm not sure why you have to have a ref station tell you it's okay to put a cat on your car. When I moved back to CA (Ventura) I just had a local shop install one. It was that easy. Unless your county is weird about things like that. Also if you haven't figured it out by now CA smog stations will fail you unless your cat has the production date and a serial number if I remember correctly, but don't quote me. Reputable shops know this already. I would also recommend using NGK plugs. I'm curious also as to the results of your smog test.

[Samson]

Sorry about not updating the thread, totally forgot about it.

But the Z passed smog! My injectors were dripping aswell as the FPR. Had those replaced and aswell as the cat installed. The CO% on the 25mph barelyy passed. Max was 1.16 i measured 1.15. Phew! Close one.

Couldn't have passed without any of your guys help. Thank you all!

[bryand2]

Sorry about not updating the thread, totally forgot about it.

But the Z passed smog! My injectors were dripping aswell as the FPR. Had those replaced and aswell as the cat installed. The CO% on the 25mph barelyy passed. Max was 1.16 i measured 1.15. Phew! Close one.

Couldn't have passed without any of your guys help. Thank you all!

Just curious, which plugs are you using now, they look like ngk iridiums, if so whats the number on them?

[bryand2]

Hmm okay, I will try to bypass the ignition but I mean the car did turn over about a month ago just not doing it now since after I changed all the stuff.. at one point the car turned over but at super fast idle and it died, noticed a super loud hissing noise aswell. My afm has that fuel cutoff switch if I move counter weight i can hear a click

If your hearing a click when you move the counter weight then it is either your fuel pump relay, because that contact causes to fuel pump to kick on, or it is your fuel injection relay. The fuel pump relay is above the fuse box on passenger side, fuel injection relay is up under the dash on the drivers side above your left knee