Zed Head

Or your local high school auto shop might take a measurement for you for free. Although you might be too close to having just got out to want to go back and visit.:sick: Just a thought. Your car would be a great example of the basics of fuel injection.

Thought I would put this out there for future searchers who are hearing noise from the vicinity of the water pump. Check your AC idler pulley first, if you have one. The external heater core to engine hose sprung a leak on my 1976 280Z and sprayed half of the coolant out as I drove home one night. I replaced the hose, refilled with coolant, then soon after (days), I started hearing what sounded like bad bearings from the front of the engine. I thought for sure that my water pump bearings had cooked themselves after the hose had burst. But before I got too deep in to it, I remembered that my AC idler pulley had made some noise in the past, fixed at the time (apparently temporarily) with a drop of oil and some WD-40. I took the AC belt off and was back to quiet running. Winter's coming and it need charging anyway, so it's a spring project now. Just putting it down for the record. It's easy to loosen the AC idler pulley and remove the belt, to see if that's the source of the noise.

I have to ask, just to satisfy my curiosity. Are you avoiding measuring the fuel pressure because the gauge is expensive? I know that I did not want to pay $45 just to measure something once or twice and then put it on the shelf. Or did you measure it and it checked out okay? If you're not going to measure it, it would be nice to know why. You can't have good fuel injection without proper fuel pressure. As far as the ECU swap, be careful, you could end up in this guy's boat - http://forums.hybridz.org/index.php/topic/95747-z31300zx-ecumaf-to-280zxt-problems/page__p__900526__fromsearch__1#entry900526 Plus you'll never get any help from the SU guys then...

Dave, you seem like a very helpful, knowledgeable guy. But I have to say that it is ironic that the "Electrical Hero Wanna Be" says to ditch the electronics and go back to mechanical. I'm just sayin'. It's funny.

The BCDD is not designed to "hold the idle" at low RPM. It is designed to maintain a certain pressure in the intake manifold at high RPM, throttle closed operation. I have read that they can get stuck but giving a high idle, not a low one. And the AAR is on its own circuit, designed to hold the idle up for a short while after starting. You could take it off and test it or disconnect the hose and block both ends to see if it has an effect. The BCDD is described in the Emissions section of the FSM and the AAR in the Engine Fuel section. 15 mpg is still pretty bad. How's the fuel pressure? Don't forget to get a new low pressure fuel pump or low pressure regulator if you go carbs. Otherwise, you'll really be running rich.

2nd edit - So, it sounds like you can buy a new cylinder, take it and your key code or the key you want to match to a good locksmith, and get back to brand new, one key operation. I didn't realize that it was that simple. I didn't fully understand Unkle's Option #2...

Is replacing the wafers a locksmith job or a DIY? That plus a new code-cut key seems like it gets you back to brand-new, with a single key for locks and ignition. Minimizing the number of keys. Everyone is happy.

I had a new key cut for my car using the code number on the glove box door. More accurate even than measuring with a micrometer, I assume. The old key would barely work on one door lock only, not at all on the other. But, unfortunately (or not depending on perspective), the new key still easily comes out of the ignition switch at any point in its rotation. Just one real-world experience with a new key on a 1976 car. I added a fuel pump cutoff switch because of this, mainly to stop joyriders since my car wouldn't be worth extended effort to steal.

Are you II, III or IV? What is a 500Z? Ford 5.0 engine?

It looks like someone removed your fusible links and mounting fixture entirely. Here are a picture of fusible links from a 76 and 78. The 76 is the full engine shot. The 78 is the closeup from the top. Your 77 should look very similar. The red/white wires in your picture probably used to run up to the bottom of the fusible link fixture. The links are under the two white plastic covers in the full engine bay shot. You should probably re-protect those wires while you're finding and fixing your short.

Did you have the oil changed at one of the name brand quick oil change shops or the local mechanic? Maybe someone took a joyride. 32 psi is below the 36 psi recommended in the FSM. But your black plugs suggest rich running so that doesn't really fit your picture since low pressure should run lean. You didn't put a number on cylinder #6 - "The 6th one has on it." ???? You say the car will run until it warms up. Do you mean it will actually drive down the road like a normal car when cold, then lose power when it gets warmed up? Or it will run in the driveway, then backfire when you give it gas after it warms up?

The sound of "valves about to jump out of the motor" while climbing an incline might actually be "knocking" or detonation, which could be from incorrect timing. It's very bad for the engine.

You don't want to "pump." Press down, hold down while releasing the bleed screw, tighten bleed screw, then release pedal. That's why an assistant helps. If you let the pedal up with the bleed screw open, air will suck back in to the lines, whether working at the master or the slave. Things will get worse because you pump fluid out and let air in.

I had a slight steering wheel shimmy that went away after I tightened the wheel bearings.

I've seen this topic come up several times but never found a good description of how to tell. I realized today that I've seen one distinct difference between an early 280Z four speed and a 280z five speed. So I took a couple of pictures for the record. One is a 1976 four speed, the other a 1978 five speed. The difference is in the straightness of the housing across the bottom of the speedometer drive gear mounting area. The five speed is essentially straight while the four speed diverges at the housing. The old timers probably know how to tell at a glance, but I have not been able to find a good writeup of how to tell them apart visually. Both are mounted. The 76 4 speed is first, not in use, but mounted in a car. The 78 5 speed is second, currently in use.

It looks good in concept. But I think you'll find that when you tighten the nut down the top plate will pull down until it's edge (front or back, can't remember which) contacts the "diff mount front member" (cross member) lip. Effectively giving you a solid mount (metal on metal). The "clunk" will be gone but you might get more vibration. If you don't crank it down, you'll need a self-locking nut or similar to keep it tight. Not trying to be joy-killer, just something to watch for when you tighten it up. I have stared at that edge for quite a while trying to figure out how to work around it. the designers made it so tight, it only sits about an 1/8" above the lip normally.

I hate to ask, but have you or Mike's measured the fuel pressure? Sounds like you're a little low, maybe a clogged inlet screen, clogged filter, or bad pump. If you have good pressure, then you'll know to look somewhere else, like timing or vacuum leaks. And it sounds like they might have swapped in a used AFM? You didn't say "new." Coughing at part throttle is what my bad AFM was doing. But it went pretty well at open throttle. Idle - good, part throttle - stumbling and bucking, open throttle - goes fast. I would check fuel pressure first, check timing and make sure it advances properly, and look for vacuum leaks. I've been talking quite a bit out here on classiczcar. Hope no one minds. I don't want to monopolize the conversation.

Choke?

I was getting about 18 also before I put an aftermarket regulator on. Now I get a consistent 20 (at least 6 fill-ups calculated since I put it on). I have a 76. jthill3 - Just for my own personal interest, what fuel pump and regulator are you using? I'm still wondering about these high rate, high pressure pumps that the auto stores sell as replacement pumps for the Z cars. Edit - I agree on FP measurements. A little disappointed that Z Tyler Z didn't measure before replacing parts but good luck to him.

There is one other possibility for high pressure. It might be that some of the aftermarket fuel pumps push too much fuel for the stock regulator to handle. I realized that I have had three stock regulators give high pressure using aftermarket pumps. Two were with a new Carter fuel pump, giving 43 and 40 psi on two different regulators, on a 78 engine. The other was with an Airtex E8312 on a 76, giving variable high pressure depending on temperature. Just a possibility. I tried to experiment with a 6 volt dry cell to compare but it couldn't put out the juice. I don't have any way to confirm and can't find any data on flow rates. More and more aftermarket pumps are ending up on the Zs because they are quite a bit cheaper and that's what the auto parts stores sell. I wonder if it's one more reason that so many people have the "running rich" problem.

The FPR can fail open (low pressure) or it can fail (clog) closed (high pressure). The stock fuel pumps have a bypass that kicks in at 43 psi. So you can have a clog in a return line or a failed (clogged) FPR and the car will still run, just really rich. If you have an aftermarket fuel pump, you could get some very high fuel pressures, since many don't have a pressure bypass.

Fuel pressure is key. It affects everything.

The fact that your car runs fine when cold suggests that the fuel system can "keep up" with demand. You should have mentioned this in the beginning. If you can confirm whether or not the fuel pressure drops before or after the engine dies, you'll be way ahead in figuring out your problem. In post #3 I see that you did remove the vacuum line from the regulator and saw no change, sorry I missed that. You should have seen the pressure increase to 36 psi when you removed that line. 30 psi is fine at idle, but the ECU and injectors expect more when the throttle is opened. You have many odd bits of information scattered around. The answer is in there somewhere.

I got side-tracked with the focus on fuel pump, fuel filter, etc. 30 psi is not too bad at idle, it's actually a little high (for idle). But with your car idling, if you take off the small vacuum hose from the center of the regulator that is connected to your manifold, your fuel pressure should jump up to 36 psi. Don't pinch that one, take it off. You'll hear it hissing and the idle rpm should jump a little bit. Plug the end of the hose with your finger to stop the vacuum leak to the manifold. When you put it back on, the fuel pressure should drop. Anyway, sorry I couldn't be more help. Another video, showing the car actually idling, with a shot of the pressure gauge as you press the throttle linkage, might give some clues. If your FPR and fuel supply is working correctly, then the next fuel supply component in line is the AFM. When the throttle is closed , the AFM is not adding much, it has a bypass to let air through for idling. When you open the throttle, the AFM flap opens and signals the ECU that more fuel is needed. The Engine Fuel section in the FSM will tell you a lot.

The symptoms seem to point to your regulator. If the valve in the regulator is stuck at a certain flow rate, then the pressure reading would be constant and unaffected by the removal of the vacuum line. You can test your pump by pinching the return hose off the regulator. The pressure reading should go up. If you have an OEM pump it should go up to about 43 psi. But be careful if you have one of the generic pumps the auto stores sell, they usually can go up to 90 psi. If pinching the line causes the pressure to increase it suggests that your FPR is not doing its job (assuming everything is plumbed correctly). The other possibility is that your new filter or a clogged line somewhere is causing so much back pressure that the pump is maxed out and only 30 psi worth of flow is getting through. I would pinch the return line (slowly and carefully while watching the gauge) first and see what happens. If it increases, take the return line off and run it in to a container to make sure you're getting good fuel flow. If you are, then your FPR is probably bad. If you just get a trickle, you might have a clogged line.