ISPKI

What was wrong with the AFM? Did you/he do a resistance test on all the pins? AFMs can be expensive, try testing it and fuel pressure before buying new parts. If the boot after the AFM is cracked open, then it could cause problems, maybe not what you are describing though. Also - There is a fella on here who sells harness plug kits for our system. His kit is very good, the plugs are top notch, sealed with little silicon grommets etc. I will try and find his user ID.

Not much of an update. One of the helicoils that I was putting in near the timing chain broke and fell down behind the front cover so I am now in the process of removing it to pull the coil out.

I do have a short video but I get an error 404 once it finishes uploading. The 1/4-28 thread is odd, it just feels like a PO cranked some 1/4-28 bolts into the holes and ripped them apart. The threads are not in very good condition to say the least and I cant tighten a couple of them down at all. I am in the process of drilling and adding helicoils to them all as we speak.

Thanks for the reply josh. I replaced the PCV and hose when I took the intake and exhaust manifold apart. I also replaced throttle body and manifold gaskets as well as almost all of the vacuum hoses in the engine bay and tested them with starter fluid. I noticed the other day that my valve cover studs are 1/4-28 thread and the threads on two of them are stripped out almost completely. The one closest to the firewall doesn't have a single thread left in the hole so I will helicoil them all and see how it runs after that. The engine is not burning oil from what I can tell but I can't really drive it either. The exhaust has no color to it

I pulled the vacuum advance off the distributor to check to see if it was stuck. Movement was smooth but firm, I dont have anything to replicate vacuum but it seemed to be OK. Question: this is a dizzy from a 1979ZX, my vehicle is a 1977 280z with an automatic transmission. I noticed Rockauto has a separate vacuum advance, one for automatic and one for manual. Should I pickup an advance for an automatic transmission and see if that works or am I looking down the wrong avenue?

I hooked up my timing light and started adjusting. At 15 btdc on the crank pulley, it is difficult to start and will idle for about 10-15seconds. The idle drops until it dies. at 20 btdc, it is easier to start, it idles very low (around 600rpm) but stays running. At 25 btdc, basically the same situation but it idles slightly higher and more stable. Vacuum gauge reading is around 10ish at the 15 degree mark, 12-14 at 20, and 15ish at 25, but it bounces around quite a bit. Fuel pressure is relatively steady around 35psi before fuel rail. The engine bogs hard if I give it any gas at all three timing settings. If I tap the throttle, it bogs and coughs out the intake, then picks up the RPMs to around 1200 and smooths out nicely after letting off the throttle.

The issue is that it wont run without advancing the timing very far (25~btdc), and I am questioning why the cam sprocket appears to be so far off when the crank is rotated to 0 and the distributor is at position 1. Also - when advanced that far, it runs very poorly and cannot be driven

Now, when I compare my images to the ones from Atlanicz It looks as though my cam sprocket is rotated about very far CCW.

Got around to checking timing. Everything seems to line up perfectly, except the distributor housing appears to be rotated CCW further than it should be. With Piston 1 at TDC, notch on balancer lines up very close to 0, Valves 1 and 2 are up, marks on cam shaft and sprocket are right on each other, and distributor rotor is pointing to position 1 (pointed towards the adjustment bolt). Vehicle runs poorly, gently surging idle between 500rpm and 1500 rpm, has no power and bogs out if I press thr throttle down. I can tap the throttle and it will pick up and sound ok while I do that, but as soon as I stop tapping the pedal, and just hold it down, the RPMs drop and it bogs out hard. Vacuum gauge bounces around in the low 10s with the idle speed too, it sounds sort of like a vacuum leak problem, but I cannot find any leaks and I did not think that it would make the engine bog down so hard

Hey guys! I purchased a new compression gauge (could not find an adapter for my vintage foxvalley gauge) and did a compression test on my 280z. I unplugged the high tension cable from the ignition coil, unplugged all the injectors and all spark plugs and my pops cranked it over for me. Tests seem good: Cyl1: 170 Cyl2: 165 Cyl3: 165 Cyl4: 170 Cyl5: 175 Cyl6: 175 This actually seemed sort of on the high side to me. The vehicle has 75500 miles on it, so it has not seen much driving over the years, or maybe one of the previous owners replaced the rings? Next on my list will be checking verifying timing marks, valve timing, etc. This vehicle does have a distributor out of an 81ZX with the matchbox ign unit. Also - What is the spark plug firing order? Mine is setup as 1-4-2-6-3-5. Also - My previous post was somewhat innaccurate. With the timing ADVANCED to about 25 degrees, it idles much better, but I cant really drive it. It moves, but when I give it some gas it just bogs and pops a little out the intake and barely makes any power. I pulled out of the driveway and up the road about 500ft before turning around and parking it again. I dont think it would be good for the engine to drive it like that.

Hey guys, I got my 77 280z running fairly reliably now and I just had my buddy over messing around with it. The vehicle has been having a vacuum issue where the vacuum pressure in the manifold is low (around 12ish). Also - It idles very rough and low and would bog out and die if I gave it any gas. We retarded the timing and measured timing with a light. By retarding the timing to about 25 BTDC it idled much nicer and the vacuum got up to about 16-17 at around 750RPM and was quite steady. Plus, I could give it some gas and actually drive it, although it still hesitates when I first gave it some gas. Now the issue is figuring out why it seems to run so much better with the timing that far off, I read that it is supposed to be either 10 or 15 BTDC? Any suggestions or insight or advice would be greatly appreciated. I am going to check compression on all cylinders as soon as I get an adapter for it as it is something I have not checked yet. Something else that my buddy pointed out is that the ring with the timing marks could have spun, he had that happen on an old truck of his and he was not sure if the ring is bolt to the crank/balancer or if it is like his where it just held in place by some kind of gasket ring material.

OK. Exciting update. I cut out the battery cables and replaced with new ones. Moved the battery back to it's factory location and wired everything back up and now the car starts. I put some fresh 93 octane in it and got it to idle, but it idles pretty poorly. I rotated the distributor clockwise and it started to smooth out the further I rotated it. It was very smooth at almost the max adjustment on the dizzy but if I gave it any gas, it would pop out the intake while revving up. When I rotate the dizzy counterclockwise, it wont idle. Also - I have a vacuum gauge hooked up to it and it is sitting at between 10 and 14psi depending on where I adjust the dizzy. More clockwise = higher vacuum, but I also noticed that the vacuum empties as soon as the car shuts off. Shouldnt the engine hold vacuum unless there is a vacuum leak?

I checked pin 1 continuity to negative coil post and it checked out. I also checked from negative coil post to ground to make sure the wire hadnt chaffed and was contacting the body somewhere and that checked out. I have continuity from ECU to injectors as that is actually how I was manually firing each injector, by grounding it at the ECU plug. I have the original ECU which was working previously and a brand new ECU that I swapped in because my testing pointed to the ECU being bad. However, new ECU did not solve the issue. Tony: Which wires from the Battery to the ECU are you referring to? There appears to be several according to the diagram on EF-25 factory service manual. 5, 16, 17, 35 all go to battery ground, while 4, 10, and 20 run through the power relay to the + battery terminal. I want to make sure I am reading this schematic correctly: On EF-25, the wires that provide power to the injectors goes first into the power relay (connection #70 at the power relay). They exit the relay as #43 and run to the dropping resistors which then divide 12v to each injector.

The wires that connect the fuel injectors to the battery and run through the dropping resistors had badly corroded fusible links. I replaced the links with glass AGU(?) Fuses. There is one connecting to negative on the battery and the other to positive.

I bumped the battery cable size from the original 4awg to 1awg and soldered new copper contacts. I will take some photos of the setup tomorrow. Pin 1 is going to negative coil post correct? I believe I had verified that it has continuity but was not sure if I could check the signal coming from the coil. Can I just leave the meter on the pin while cranking to see if it is receiving a signal?

Hello Hybrids!!! I am finally back after moving around throughout winter. Long story short, I now have my first house with a garage and will be diving back into my 77 280z. It has been a while since I worked on it so I will start a new thread and see where I get with it. I have narrowed my issue down to the fuel injectors. They do not fire on their own. The vehicle starts off the cold start injector and then immediately dies. Spark plugs are working fine. I am able to manually fire each injector. The car was driving before I took it off the road to do some exhaust work. I also replaced the fusible links with a midi fuse box and moved the battery to the cab and added fuse holders for the lines running through the dropping resistors. I have performed all of the tests from the Bible and replaced the ECU which did not help. I need to know what can prevent the injectors from operating while the car is running. J came up with a hunch when measuring voltage. The battery voltage has dropped below 12v (11.73v I believe) with the new electrical work so I am curious if the injectors will simply refuse to function when the voltage is that low. The battery cables are now much longer than they used to be and have a bulkhead connector for the injector wires. I am think that the connector may be creating a huge resistance jump in the system.

Yes, I tried starting with and without the BCDD plugged in. Made no difference. To give you guys an idea of the wiring situation I am dealing with here, the BCDD was plugged into the AC compressor when I first got the vehicle D: I havent been able to work on it in over a month, have it buttoned up for winter. I will be moving into my first house in about 1 month and it has a garage so I will be able to do some serious trouble diagnostics on it. The injectors are getting fuel, I can fire them manually and they shoot fuel out when I do, its just that the ECU is behaving as though it is not getting a signal to pulse the injectors, the injectors just sit with 12v all the time and they never ground when starting. It has continuity from the - post on the coil to the ECU (dont remember which pin, I think it was pin 1 from - coil post) but I never checked if there is actually a signal from the - coil post, I only checked continuity. Not really sure why it wouldnt pulse, perhaps the ICM on the dizzy is faulty? It is one of the few things I have not really checked.

Picked up a replacement relay from a gentleman on here. Tested it before putting it in the car, passed all tests from the FSM. Bolted it into the car and it still won't stay running. Starts for a second after sitting overnight and then won't start again.

You mean ones with brass contact points?

If your voltage is low when the vehicle is running then it is most likely the alternator as the alternator powers the electrical system when the engine is running. You can test just the battery voltage with a voltmeter when the car is off. It should read 12.7v BUT your battery could still be bad even if it reads 12.7v. An auto parts store can test it's cranking amps if you bring it to them. The battery in my Datsun was reading 12.7v but it was only holding about 250 amps which was barely enough to get the engine started. I would suggest getting a decent multimeter, they aren't very expensive and you will use it constantly when working on your car.

Hello Hybridz! I am troubleshooting my 77 280z and found that the EFI relay (the large double relay mounted above the ECM) is not functioning properly. half of it works, but the half that engages with the key in the "start" position is faulty. I am trying to find a replacement and found something on Rockauto that looks promising. They have two relays under the Switches and Relays > universal relays tab that both say "MAIN RELAY" made by standard motor products. One is a 6 pin, the other is a 5 pin which matches the double EFI relay (it also has 5 pins on one side and 6 on the other). Does anyone have any experience with these relays and would they work to replace my original double relay?

I pulled the Main Ignition relay out of the vehicle to run some tests on it according to page EF-55 section 7-1. I wired up a jumper wire from Pin 86c (+) and 85 (-) to a battery pack that I have for jumping cars. When supplied power from the battery pack, the relay passes the first test of having continuity between pin 88z and 88a, and has continuity between 88b and 88z. Moving down to the next test for the fuel pump, the relay fails to have continuity between 88y and 88d.

Got some testing done on the car today. Found some goofy wiring with the thermotime switch and water temp sensor wires. Straightened that out and I now have 2950 ohms from the water temp sensor with the ambient temperature being around 60ish so that seems to be passing. I continued on and performed the AFM circuit tests detailed after the power relay control unit tests. Tests 1-3a, 3b, and 3c. I was testing at the ECM plug and the resistance values were all somewhat high. I have 260ohm from pins 8-6, book calls for 180ohms. I have 225ohm from pins 8-7, book calls for 100. I have 145ohm for pins 8-9, book calls for very low resistance (no value). Again I was testing those at the ECM plug, not at the AFM terminals, so I would expect the resistance to be a little bit higher but those seem abnormally high, not sure if that would prevent it from starting but I will pull the AFM out and test the terminals at the AFM in the upcoming days if I get the time (doing brakes on my scion TC tomorrow so not sure when that will be). Oh, I did do the next test as well 3-(3): testing Pin 21 to ground, should have battery voltage within 15 seconds of key being in "start" position. That test failed, it stayed at 0 voltage. This is leading me to believe that there is something going on with the power relay or the ignition switch since power should be supplied through the power relay. I will test for power at the wire going in to the cold start valve next time I get to work on the car just to make sure that the relay is actually functioning, however, I have the cover off the relay, and the "start" side of the relay did not close when I held the key to the "start" position and when i have the wire to the starter solenoid connected, the "start" side of the relay clicks and sparks very quickly rather than staying closed. I supposed I could carefully hold the start side of the relay closed and try the test again to see if it works.

I havent done anything regarding the water temp gauge or the transmitter, I was only working with the water temp sensor. I was getting confused with the multimeter because the #13 wire from the ECM plug wasnt reading any resistance - or very very little. Then I found that the #13 wire had continuity to ground when disconnected from the water temp sensor which is telling me that the wire must be broken somewhere and contacting the body or other wires. I tried measuring it on the 200, 2000, and 20000 settings with the same results, almost no resistance. From what I read online, the "2000" setting should read anything in the 4-digit range, the "20000" would read anything in the 5 digit range.

OK. So I was walking through the EFI bible, went to test the water temp sensor resistance again (Pin 13 to ground). This has been really confusing because my AFM had zero resistance when I tested it and now the water temp sensor also has no resistance (should be around 3000ish). I went to test the wires at the sensor to see if they were connected properly which they did not seem to be. It looked like the wires for the water temp sensor and the thermotime switch were switched. Here is where it gets interesting. I switch the plugs to they appear to be going to the correct sensor, then I unplug one of the quick disconnects for the water temp sensor (the wire that has "13" printed on it) and test continuity from pin 13 on the ECM to that wire - should read continuity and it does. I then unplug the other wire and for some reason I decide to test continuity from the #13 wire at the sensor to the #13 pin on the ECM plug again - no continuity... I plug the opposite wire back in and retest #13 wire to #13 pin at ECM, and I have continuity... I then unplugged both wires going to the water temp sensor and the plug for the thermotime switch and then tested continuity from pin13 to ground and I have continuity... This is telling me that somewhere in this harness, the #13 wire is contacting ground which explains why I cant get a resistance reading from the water temp gauge.