240Z, 260Z, 280Z Performance / Technical Discussions related to performance motor enhancements, upgrades.

Hello and Help with 280Z

Old 05-07-2015, 09:17 AM
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Hello and Help with 280Z

Hello all! I recently acquired a 1977 Datsun 280Z and had a mechanic do a lot of work to restore the mechanics (engine, brakes, etc.) to factory specs. However, there is still an issue. The car starts and runs great, but when it gets warmed up (about 15-20 minutes into a drive) it starts to stutter and then it shuts down. At this point it won't restart. Letting the car sit for about 5 minutes (not a long time!) seems to solve the problem - the car starts again and I can drive it until the process repeats.

Here is what has been done to the car so far:

- Fuel tank checked to see if getting clean fuel from it
- New fuel lines installed
- New fuel pump and filter installed
- New spark plugs
- Distributor checked
- AFM (Air Flow Meter) replaced
- Fuel rail replaced
- Air regulator valve attached (it was missing when I purchased the car!)

The fuel pressure was checked and the mechanic said it was good. So, my question is, what do I check next to see what is causing the car to stutter once it warms up? What other information do you need from me?

On a second note, when the car stuttered and stalled the first time I was driving it (a day out of the shop), I turned on my hazards. This caused my turn signals, hazards, and dash lights to all stop working. To clarify, my turn signals do not work at all. This means that they do not blink outside of the car, nor do the lights turn on inside on the dash. Neither do the hazards. On top of this, none of the lights on the dash come on when the lights are turned on and any electronic gauges (like the voltage meter) do not work any longer. The mechanical gauges (like the speedometer and heat gauge) work fine. The brake light for the emergency brake works. And a red light next to the voltage/charging meter briefly flashes when I start the car.

All external lights work (headlights, tail lights, brake lights), so this is not a dead bulb issue. Since all dash lights stopped working, I am assuming this is not a flasher unit issue. I've also checked fuses and fusible links and they all look good. Where do I go from here?

Thanks in advance for any help.
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Old 05-07-2015, 05:25 PM
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Originally Posted by SilverSurfer View Post
Hello all! I recently acquired a 1977 Datsun 280Z and had a mechanic do a lot of work to restore the mechanics (engine, brakes, etc.) to factory specs. However, there is still an issue. The car starts and runs great, but when it gets warmed up (about 15-20 minutes into a drive) it starts to stutter and then it shuts down. At this point it won't restart. Letting the car sit for about 5 minutes (not a long time!) seems to solve the problem - the car starts again and I can drive it until the process repeats.

Here is what has been done to the car so far:

- Fuel tank checked to see if getting clean fuel from it
- New fuel lines installed
- New fuel pump and filter installed
- New spark plugs
- Distributor checked
- AFM (Air Flow Meter) replaced
- Fuel rail replaced
- Air regulator valve attached (it was missing when I purchased the car!)

The fuel pressure was checked and the mechanic said it was good. So, my question is, what do I check next to see what is causing the car to stutter once it warms up? What other information do you need from me?

On a second note, when the car stuttered and stalled the first time I was driving it (a day out of the shop), I turned on my hazards. This caused my turn signals, hazards, and dash lights to all stop working. To clarify, my turn signals do not work at all. This means that they do not blink outside of the car, nor do the lights turn on inside on the dash. Neither do the hazards. On top of this, none of the lights on the dash come on when the lights are turned on and any electronic gauges (like the voltage meter) do not work any longer. The mechanical gauges (like the speedometer and heat gauge) work fine. The brake light for the emergency brake works. And a red light next to the voltage/charging meter briefly flashes when I start the car.

All external lights work (headlights, tail lights, brake lights), so this is not a dead bulb issue. Since all dash lights stopped working, I am assuming this is not a flasher unit issue. I've also checked fuses and fusible links and they all look good. Where do I go from here?

Thanks in advance for any help.
First of all, welcome to Z Driver! We're a small but mighty group.

Second, go to xenons30.com/reference and download the Factory Service Manual (FSM for short) for your car. It's a valuable reference document.

I'm only a 260Z owner so can't really help you with your first issue. No real experience with FI cars.

Electrical stuff is a bit more in my ballpark though. Congratulations on checking your fuses and fusible links. Many folk wouldn't even think of that. I do want to say that visual inspection, especially with the links, can be faulty. Test them with an ohm-meter to be sure. Often in these older cars, there can be corrosion, i.e. dirt, on the fuse holders. It's a good idea to pull each fuse and clean contacts of the fuses and the holding clips. Put the fuses back in and check continuity across them from the clips.

If this doesn't fix anything, at least you'll be sure you're in good shape in that area. Without breaking out my circuit diagrams, I'd hazard a guess (yes, pun was intended) you might have an issue with the combination switch under the steering wheel. Its design isn't that good electrically as it passes lots of current for headlights, instrument panel and marker lights. It might be another are to try some circuit cleaner spray.

Last edited by beg3yrs; 05-07-2015 at 06:14 PM.
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Old 05-07-2015, 05:50 PM
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Hello Beg3yrs! Thanks for taking the time to respond.

The fusible links are new, but I'd seen one blow before, which is one reason I checked them again. The 'look' good, but I did not test them. I will have to get my hands on a meter to do so (something else to purchase ).

I'll check all the other stuff (including wires and grounds, especially the grounds at the back of the car since once of the tail light units was swapped out.

As far as the engine stuttering, I think I resolved that one. The fuel line from the fuel filter to the fuel rail was pressed up against the engine itself. I think this was causing it to heat up and make vapor. I moved it off the engine and the Z is running great now. I drove it in city and on the highway for about an hour with no stuttering at all.

Thanks again for the help!
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Old 05-07-2015, 06:20 PM
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If your links blew, it's likely more things than your lights wouldn't work.

I'm really beginning to think combo switch. A Google search for "280Z combination switch" will be very informative.
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Old 05-07-2015, 07:11 PM
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Just FYI - The links blew when I first got the car because I did something stupid. The car had two black cables for the battery and when I replaced the old battery with a new one, I put the cables on the wrong way (positive to negative). Yes, very stupid. It blew a link and I replaced them. Everything was working fine after that, including the dash lights and signals. But, as previously stated, the dash lights blew after turning on the hazards. I just need to find out what is causing this (of course). So, it's off to the slow, methodical search.
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Old 05-08-2015, 08:02 AM
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A new red battery cable is probably less than $10.

Good luck with the search!
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Old 05-10-2015, 07:54 PM
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Oh, I replaced both battery cables with new ones, including one that was red. I did that almost right away.
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Old 05-11-2015, 06:17 PM
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I went to Advance Auto and had them check the alternator. The man ran the test two times and said the alternator is starting to fail. However, when I compare his results to what is in my Datsun 240Z, 260Z, 280Z, 1970-1978 Automotive Repair Manual, it does not look like it is failing.

The print out shows that the charging system voltage on test one is 12.81V. On the second test it is 12.97V. The man at Advance said it should be at 14V or so. However, in the Repair Manual it says the following:

"If it registers over 12.5 volts then the alternator is in good condition, it if registers below 12.5 volts then the alternator is faulty and must be removed and repaired."

Since both tests were over 12.5 volts, then according to the manual, the alternator is good.

What say you?
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Old 05-11-2015, 06:28 PM
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Perhaps I am reading the printed results wrong! The Starter Test reads "Cranking Normal" on both tests. However, the Charging System Test reads, "Results - No Voltage". Despite saying this, it show No Load: 12.81V, Load: 12.81V. If there is "No Voltage" does this mean the car is running off the battery?

Sorry for my ignorance on these things.
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Old 05-11-2015, 11:02 PM
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Alternators should be putting out something on the order of 14V.

12.6V is what a good battery puts out.

I think your test guy is likely to be correct.

Now, what about your lights?
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Old 05-12-2015, 12:37 PM
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Alright! Used a voltmeter and it shows the following when connected to the battery terminals:

Car off: 12.8 volts

Car at idle: 12.8 volts

Car under load: 14.8 volts (sometimes getting up to 14.9)

"Car under load" is the lights on, fan on high, and engine revving up to between 2000-3000 RPMs. As I release the gas pedal and the RPMs drop, the volt meter's reading drops. So, it looks to me like the alternator is doing it job.

By the way, I checked the alternator this way because someone on another forum said the following:

"I just recalled that there's one more possibility, common to the Z's - output at idle tends to be low. So, depending on what the machine measures, it may have seen no voltage because the the measurement was made at idle speed. Today's cars have ECU's that bump up the idle RPM to make sure the battery stays fully charged, and the testing machines are designed for them. Our old Z cars don't have that feature. One more reason to get a meter and check for yourself. It's not that hard to do."

I was checking the alternator first (before getting to the dash lights and exterior turn signals). Someone had said that a failing alternator could be or contribute to the problem. So, now I need to start checking the grounds and wires to see what I come up with.
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Old 05-12-2015, 04:37 PM
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Alright! Back onto the electrical issue with limited time this week.

I took the back panel off (the plastic cover you need to remove to gain access to the back lights and all the wires there). I checked all the wires, the ground, the connectors and bulbs. Everything looks good. So, now it's on to other things.

As a reminder, the following is NOT working on the dash:

- Turn signals and hazards (neither are they working externally on the car)

- The oil pressure gauge

- The volt meter

- The clock (though I don't think that was working before the dash lights went out)

The following is what is working on the dash:

- The speedometer (of course)

- The tachometer

- The temp gauge

- The fuel gauge (though the float in the tank gets stuck at 1/3 tank even on full)

Other things work like:

- The fan for the vent

- The center dash light (the one you flip down to turn on)

- The fasten seat belt light and buzzer

- The bright, red brake light at the bottom of the speedometer (in fact, for some reason this is on continuously)

I don't know if any of this information helps to pinpoint what could be the issue, but I thought I would post what I know so far. Again, I am learning about electrical, so any help would be appreciated.
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Old 05-12-2015, 05:41 PM
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I can see you put a lot of energy into your posts and they are precise. Always a good thing here

Not a 280Z guy - but I think all your current (hey, a pun!) problems started when you crossed your cables. That's more than just a no-no. Depending on the number of microseconds they were connected that way, you cooked and semi-cooked a variety of stuff, depending on how strong the stuff was before the shock came. They are all a bit older now - all over the place.

I think you are into circuit-testing territory now. You have your Elec Diags - if you print them out at 11x17 (print shop) and use colored pens, you can actually trace one circuit from A to B to C to D. Don't mind how 'good' it looks. Not useful info at this point. You have to use a circuit tester to see if each circuit is live at each leap. Get a tester that lights up and beeps when it hits a working circuit.

Go back to fuses, fusible links and relays, one a a time. All should be live and working. Get a 'working' signal from your tester for every one. Test the fused circuits at the fuse sockets (you slide your tester in to contact the socket at the fuse. Beep, light. Test heavy on the fuses and relays that handle lights/gauges of any kind. Something weak or dead has thrown your whole dash to wacky.

There is a video floating around on YouTube for removing and cleaning the light control stick on a Z31. It's gotta be a similar gadget to your 280 stick. Check that vid out.

The reason why you are doing all this is you decided you need OEM 280Z performance from your baby. There are a lot of us who do exactly the same thing for the same reason. We know we are right in that - and it pays. So keep up the good work and don't quit.

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Old 05-12-2015, 08:20 PM
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Thanks, zxguy1986! That's a great post, quite informative, and encouraging, too. I will get busy and report my findings.
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Old 05-12-2015, 08:39 PM
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Great. Also, some guys here swear that crossed cables will fry your ECU. Definitely worth a check - so if you ever get a chance to swap out your ECU with someone who has a 280Z ECU with the same part number (important, usually), go for it. A 5-minute swap could just show you where your fried eggs are.
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Old 05-13-2015, 05:23 PM
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Okay! As I am learning all of this, I went out and purchased a circuit checker (one of the ones that both lights up and beeps) and decided to do a test. I removed the covers to my fusible links, removed one of the links, turned the key to "ON" and used the circuit checker on it, connecting the one end to one 'peg' and touching the other. As expected, the light came on and it beeped. So far, so good. However, when I did the same to the second link, I got nothing.

Here is a photo to show you precisely which link (it is the red circled one):



I know the set on the right has a ground (the big black link), but does the back one on the left also serve as a ground of some kind? Or should it also produce a light/beep on my checker?
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Old 05-18-2015, 02:44 PM
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Okay. I learned that the circled link (above) is for the headlights and no current goes through it, even if the key is on, unless the headlights are on.

On a side note, the car was still stuttering from time to time and it was not heat related. So, I installed a fuel filter between the tank and the fuel pump. I drove the Z hard today and had no issues, either on the highway or in the city. The filter seems to be helping.
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Old 05-18-2015, 03:58 PM
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There are multiple kinds of circuit testers, even if you have one that beeps and has a light, not sure what you've really got.

A simple continuity tester has its own power source (like a battery) and two leads. If you touch them together you'll get the beep and a light.

A simple voltage tester typically has a wire with an alligator clip which is connected to ground and the other end is a pencil-like arrangement which contains the light and possibly a beeper. It usually has a metal probe at one end.

Try and describe your tester a bit better as depending on which one you've got, your test results mean different things.

BTW, I see you're duplicating your post on another Z forum. Not an issue here but if responders aren't following both forums, be aware you might get conflicting advice and the communication between responders between forums won't be there to help you out. Just be careful.
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Old 05-24-2015, 06:02 PM
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Hello beg3yrs,

Yes, I have been posting in a few places. I did not know which Z forums were actually active and helpful, so I figured I would try a few of them.

The circuit tester I am using is one that looks similar to a screw driver with a wire sticking out the top and something akin to an icepick where the screw driver head would be. The handle has the light that lights up.

Some small progress on the electrical side of things.

A rechecked the fuses and two of them were no good. One was for the hazard. Now my hazards work (both on the dash and outside on the car) as do all of my gauges on the dash (voltage, etc.). However, the actual dash lights do not work nor do the turn signals (neither on the dash nor outside on the car). So, the only non-working things are all my dash lights and my turn signals (internally and externally). All other dash components appear to be working properly.
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Old 06-02-2015, 04:09 PM
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Good news! Internal and external turn signals are working! Bad news is I am not sure why, actually. After having the front end aligned, and the steering wheel adjusted (it was a custom wheel the previous owner had installed and was all crooked), the turn signals just started working again. The mechanic who had worked on the car previously (the one that did all the engine work) had also done something in that area because the horn had not been working. I am wondering if something, like a connector, had been lose (and maybe still is) and when they adjusted the steering wheel it knocked it back into place?

Dash lights still are not working, but I have not had sufficient time to work through the harnesses, etc.
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Old 06-09-2015, 11:06 AM
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Well, I think we know what the stuttering/stalling issue is with the engine:





I replaced the inline fuel filter (between the tank and fuel pump) after only running about a half tank of gas. I definitely need to clean out the tank.
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Old 06-09-2015, 06:01 PM
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Okay! Here is what I've noticed the past few times I've run the car. I don't know if this helps at all, but I thought I would add it into the mix.

When I first put on the inline filter, I had filled up the tank to full. The car ran great for about an hour (on the highway and off). Then, as gas was used over time, I started to run into more and more trouble with the engine starting to run rough ... not continuously, but periodically. The more gas I used, the more I hit these stuttering and stammering spots (including a few times when I stalled out). Since my gas gauge is not working, I am using the tripometer to estimate how much gas is being used. In each case, the troubles start to increase after about 70 miles of gas use. When I get up to 95 or more miles, the car starts to have frequent stutters, especially under load (i.e. on the highway going over 50 MPH). Now, just to be clear, these miles aren't all put on the car at once. I am not driving 100 miles at one time, the car doing great for the first 70 and then slowly degrading as I drive. I am driving a few miles here and there (going to the store, going to pick up a part, going to visit a friend, or just going to take the car out on the highway).

Judging by the fill-ups and how much gas I had to put in compared to the tripometer, I am averaging about 15 MPG. So, after using about 5 gallons of gas (from a full tank), I start to get stutters periodically. After using about 6-7 gallons, the stuttering becomes a lot more frequent, making it hard to take the car anywhere.

Does this provide any useful information?

Edit: Here is something I forgot to mention above - I had filled up the tank twice after the previous inline fuel filter was installed. Both time I did it after running the car for about 90-100 miles worth of gas. Both times the car ran great on a full tank, but started to stutter and stammer more (periodically) as gasoline was used. This last time, I swapped out the inline filter (see images in my previous post above), but did not fill up on gas (I want to run the tank out so I can drop it and clean it). When I ran the car tonight on a fresh inline filter, I almost instantly had issues with stuttering. The car would run smooth at times, but would also stammer at times.
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Old 06-09-2015, 08:03 PM
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If you have the source and return fuel lines reversed, you will get a symptom like this. You can't use all of the fuel in your tank. Check the FSM or just try swapping them.
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Old 06-09-2015, 08:07 PM
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Hi beg3yrs.

I will check the lines, though it is my mechanic who replaced all the fuel lines and he was 'going by the book', trying to restore the mechanical side of this to stock. Yes, assuming is dangerous, I know, but I am assuming he got the source and return fuel lines right.

No, I am not trying to run through all of my gas, but I currently have more than half a tank. I'd like to get it pretty low before draining the tank the rest of the way via the drain.
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