280zWraith

I bought a 1977 280z one and a half months ago. On the drive back (2.5 hours) the only problem was a split small heater hose connection under the fuel rail which I repaired. Since then I've been able to drive it normally. It had a bad exhaust leak to the passanger compartment and it was running rich already (strong fuel smell from exhaust and wet spark plugs). Felt like it was low on power too.

Two weeks ago I decided to do a small tune up on it. During the process I cleaned the sides of the engine that were covered with dirt and oil. Basically I wanted a "clean" engine to see where the leaks were coming from. I was careful to remove the electrical connections (alternator, oil pressure sensor) and avoid the ones I could not remove. I replaced the following items (all purchased from zcarsource, minus the plugs and the hoses):

-Water pump and gasket
-Thermostat and gasket
-Fan belt
-Spark plugs (new are NGK B6ES-11 straight from dealership, all gapped correctly to 1mm)
-Spark plug wires (R-8 NGK, blue colored)
-Fuel filter
-Valve cover gasket (not yet installed, waiting to fix the rest and do a valve adjustment)
-All vacuum hoses in engine compartment (thermal vacuum valve, EGR, PCV, air flow sensor, fuel canister, etc.), minus the vacuum hose for the fuel pressure regulator

I reconnected all the electrical components and made sure that all the hoses were tightly clamped. Upon inspection, the valve cover gasket bolts were only finger tight (guess this explains the oily leak streak down the side), so I tightened those up too. Afterwards, the vehicle would stall out after 10 secs. During which time it would climb to about 800 rpms and run very rough. The exhaust smells VERY strongly like fuel. If the car sat for hours, only then would it start for a few minutes. Still rough, and over time it seemed like it was bogging down. Also, small black droplets are being spit out from the exhaust.

I have performed the following tests (I am using the FSM):

-Fuel pressure is at 38 psi (spec is 36 psi) with key on/engine off. Fuel is running clear and solid through bleed hose. Afterwards, it drops to 34 psi with key off/engine off. 5 minutes later it has dropped to about 26 and keeps dropping thereafter.
-Using a spark tester, all 6 wires produced spark.
-Compression is at 170 average between all cylinders (spec is 162-178).
-All injectors ohm out to 2.5 ohm (no spec for this as far as I could see).
-Tested air flow meter according to FSM. Only problem found was with pins 36 and 39 test. Continuity should exist only when flap is opened 8 degrees or more. Anything else is bad. Upon testing, continuity exists all the time regarless of flap position. Cleaned braket/meter connections. Verified continuity with body ground.
-I tripled checked all the hose connections and locations.
-Spark plugs 1,2,5, and 6 were black and wet with fuel. 3 and 4 are clean.
-Wanted to check EFI Control Unit, but I couldn't find the pin numbering anywhere. So pretty much when the book says "check pin 20", I can't know which one it is since the numbering isn't in the book or on the harness/unit as far as I could see.

So is the fuel pressure supposed to stay close to spec all the time? Is it supposed to drop? Is the fuel regulator supposed to hold pressure?

My best guess is that some injectors may be flooding the cylinders, and/or the fuel regulator is bad. I just don't see where I could have jacked the car so much to cause this. Any help is appreciated. Thanks.

280zWraith

Finally found the time to put into getting my beast back and running. I decided to do somewhat of an overhaul and tackle some other problems that were already present:

--Removed gas tank and had it cleaned. Replaced all fuel/breather hoses and installed a clear fuel filter inline between gas tank and gas pump.
--Replaced radiator (original one was very corroded and hose necks were deformed) and hoses. Also installed a new water pump and seal since I didn't want to deal with a possible dry seal from the car sitting for all these months. When I performed a pressure test on the cooling system I found a few leaks: on the thermostat gasket, thermostat housing to head gasket, and in the heater core area (couldn't make out if it was at the core or hose attachment points.) Replaced both gaskets with ultraflange sealer and removed the hoses that feed the heater hose (on the right side of the engine) and plugged the ends. Retested system and everything checked out.
--Replaced the ignition coil (had the original on).
--Removed the fuel rail with injectors. I placed the assembly (still connected)on top of a catch tub. The goal was to run the engine with the injectors off the vehicle to see if they are firing correctly. Upon inspection, injectors 3 and 4 weren't even firing!! That explains why the spark plugs were clean (in original post). I verified that current was flowing to the connector. Then I applied direct power to the injectors and they opened which lead me to bad connections at the connectors. There was a bit of corrosion so I cleaned them all VERY well. Bought Deoxit D5 (this works awesome!!!) and used a flat needle file to remove all the corrosion from terminal ends. Also used a small pick the clean the connectors.

Reinstalled connectors and rechecked system. All the injectors are now working properly. On another note, while the system was pressurized I noticed fuel droplets exiting the vacuum port on the fuel regulator (possible pierced diaphragm?). Disassembled rail and cleaned all lines with carburetor cleaner. They weren't bad at all, but wanted to be thorough. Reassembled rail with new hoses and a new regulator. Also placed new injector seals. NOTE: now is a good time to replace the small coolant hoses underneath the rail!!! I did that too and finished rail installation.

At this point the car started, but it was stumbling at around 300-400 rpms could only go up to around 1000 before stalling out. Verified that timing was correct with FSM. Ok, at this point I'm still scratching my head, and decided to search for videos and hit on one that really helped. The engine ran exactly like mine until he wiggled the electrical harness. Basically it was bad connections. So I went and cleaned ALL the harness connections in the EFI system the same way I did the injectors.

--Tested the AFM and noticed that the resistance to ground was way to high (about 7.5 ohms). Managed to make a wire connection to the plate it bolts on to and lowered the ohms to around 0.2. Also, the hose between the AFM and throttle body was previously patched with tape. I removed the tape and to my horror almost the entire hose was split with holes. Being late in the night, I taped over the entire hose (already ordered a new hose). The plate which connects to the AFM got a thorough sanding as well to ensure a good connection.

After installing the AFM the car fired right up and reached 1400 rpms!!!!! Then it lowered to 700-800 to idle. It sounds amazing!!! Still missing a little bit but nothing like before. It actually sounds better than when I bought it.

Ok if you're still reading this, THANKS for sticking with me this far. By the way, the test on the AFM that failed in the original post appears to be linked with the fuel pump operation. The AFM is supposed to take over energizing the pump after the car starts (thus the 8 degree test. A full explanation of the operation can be found in the EFI bible.) in case if the vehicle stalls, the pump shuts off. So, not a crucial circuit for operation at the moment I believe.

In conclusion, LOTS of gremlins got hammered. Although I know more will eventually arise. Be warned, they will be dealt with . Again, thanks and looking forward to reading your replies.

skittle

One of the main causes are vacuum leaks, the AFM boot is a big culprit.