Crap! What did I do??

[Biker_Trash]

1978 280Z that has been sitting. Boiled & sealed tank, cleaned out lines, new filters and hoses. Running pretty well. Bled clutch and now she's able to move on her own. That brings us current.

Had low oil pressure reading so I bought a new factory sending unit. While screwing in the new unit, it didn't seem to go in very far (I didn't realize my crescent wrench was hitting something so the sending unit wasn't very tight). Started the car and was getting spotty reading from the gauge (no surprise!). Ran it for awhile then shut her down.

Later same day, put 5 gallons in the tank from a can. Went to start the car and it just turns over. Hmm. Wondered whether my new sending unit was bad so got out (forgot I left the ignition on) and pulled the sending unit plug - heard something buzzing from the other side of the engine which stopped when I plugged it back in). Shut the ignition off, then pulled the sending unit plug again. Checked the sending unit I just installed and realized it was still hand loose. Put a wrench on it and snugged it up real good. Plugged it back in and went to start the car. It just turns over but doesn't fire. Hmm.

Pulled the line to the fuel rail and I have plenty of gas. Pulled a wire and connected it to a spare plug and I have spark. So . . . what gives?? I understand the sending unit will kill the fuel pump if no pressure, but I have gas so I wouldn't think that's my problem. Did I zap something when I pulled the sending unit plug with the ignition on? Something tells me this is a simple fix but I'm stumped (doesn't take too much).

All help appreciated. Thanks in advance.

Jeff Woodard

Richmond, VA

[Zed Head]

It's not clear if you meant fuel was flowing in your fuel lines, or you just saw that lines were full of gas. Residual pressure remains in the lines after they get pressurized, so the fuel pump may not actually have been energized.

Maybe you know this but you could pull the wire to the starter and listen for the fuel pump when you turn the key to Start. It's the small wire with the female connector made to be pulled off and pushed on easily. The electric fuel pumps can usually be heard from inside the car. Pull the wire (make sure it's not touching a ground), turn the key to start, listen for the pump.

[Biker_Trash]

Thanks for the reply. Sorry, yes fuel is flowing through my fuel lines. Cranking the motor over causes fuel to flow freely. I do hear my fuel pump power on, too, so I think it is okay. Any other thoughts?

Jeff

[Biker_Trash]

New day, same issues. Spark is good and fuel supply is good to the fuel rail. Is there a point in the fuel rail where I could be losing fuel to the cylinders? After I crank it over, there appears to be some buzzing from the fuel pressure regulator. Could the fuel regulator be bad and redirecting all that fuel back to the tank? Should the fuel regulator "buzz"? If it is bad, will a Napa one due or should I get OEM?

Jeff

[Jeff G 78]

Get a fuel pressure gauge and T it inline between the filter and the rail. The Oil Pressure Sender sends a signal to the fuel pump in the '78, so if the sender is bad, you might not be getting fuel. I believe it should be reading around 36psi.

As a quick and easy test, try shooting starting fluid in the intake elbow under the air filter. If it briefly fires, you know you have a fuel problem and not an ignition problem.

BTW, don't throw parts at it. Most of the time, you will just frustrate yourself and waste money.

[Biker_Trash]

Used some starter fluid and the car fires/runs, so I'm looking at a fuel problem. I've got good flow into the rail and flow out of the rail, though not as strong coming out as going in. I'm going to pick up a fuel pressure gauge first chance I get. Until then (and assuming my fuel pressure is fine), what are my culprits?

> bad fuel pressure regulator redirecting the fuel to the return line?

> injectors not injecting (electrical? would they all go dead at once?)

I'm not sure what else could be the problem. Open to suggestions.

Thanks.

Jeff

[Jeff G 78]

You can use a large screwdriver to determine if the injectors are firing. Hold the tip of the screwdriver against the first injector and hold your ear tight against the the end of the handle while cranking the engine. You should hear a click each time the injector fires. Repeat for all six injectors. If all six click, the problem is likely fuel pressure. If either only the front three or only the rear three fire, the problem is electrical. If random injectors fire, either the electrical system or the injectors are the culprit.

Id suggest downloading the FSM and the EFI Bible from www.xenons30.com With that, you can check each and every system as needed.

[JimmyZ]

Silly question but did you pull and check the plugs? A friend of mine with a 280Z had a similar problem. I asked him if his plugs were fouled and he said they were fine. He NEVER actually checked them! (Since he had JUST replaced them he "ASSumed" ) After driving 100+ miles to visit and assist the first thing I did was to check the plugs. (Black/fluffy RICH) It turned out his ECU was bad and somehow causing the car to run super rich. Things were so bad a set of fresh plugs was fouled in less than 5 minutes.

Edited February 16, 2010 by JimmyZ

[Biker_Trash]

I just downloaded and read the EFI bible (280Z/ZX Electronic Fuel Injection Guide, right?). Good stuff. Will try the screwdriver & injector trick. I did pull a couple of plugs and they look fine. They are new and have about 20 minutes run time.

Still stumped that I went from starting fine to no fire, just like that.

Jeff

[ezzzzzzz]

www.richmondzcar.com Contact this club. Join the club (great people!) Someone there should be able to assist you. IF you were down this way I'd suggest the Tidewater Z Car Club or Todd at Tidewater Z Auto Service.

[ZCurves]

Jeff,

I have a '78 and what you are going through is similar to what I experienced when I "woke" my car up. Your problem is not with the Sender, so scratch that one off the list...Did you change the Fuel Pressure Regulator? Earlier, you mentioned that you heard Buzzing coming from the Fuel Pressure Regulator, that is ok, it should do that. What was happening was the system was building pressure and the spring inside the Fuel Pressure Regulator was being compressed. Did you check the wire harness to the Oil Pressure Switch? When you Unplug the Oil Pressure Sender, can you hear the Fuel Pump buzzing (With Key on)? Try to start with the Oil Pressure Sending unplugged. If it starts, does it shutdown when you plug it back in?

Just as a Sanity Check, check the following: Did you make sure the AFM is functioning and plugged in securely? Is the brain (ECU) plugged in and screwed tight to the body? Have you re-checked the Fusible Links? Is the HOT lead (White Wire) from the battery to the EFI system Clean, Tight and have good integrity?? Post back with your findings. We can lick this one, it is something obvious....(I hate those...)

[Biker_Trash]

Everyone - thanks for the ideas.

Update -

I did not change the fuel pressure regulator.

Pushed the car into the garage this morning and looked for any problems in the wiring but found none. Cranked the car for a minute and she started up. Yeah! But, now I don't know what might have been the problem. As you'll recall, it fired on starter fluid before so it still strikes me as a fuel delivery issue. Any further guesses on causes are appreciated.

Need to pull the radiator to deal with a small leak now.

Question - I was getting good oil pressure reading and as the car warmed up, the temp gauge was looking good. The car settled on a nice idle. I then noticed that the oil pressure gauge and temp gauge were "pulsing" together . . . up some, then down some. Also, the amp gauge is high at 15. Any ideas? Is the alternator/regulator going south?

Thanks to all!

Jeff