johnny haywire

Just a quick update - I bought some new hose, gave the AAR a better cleaning with some carb cleaner (opens and shuts freely now), cleaned the contacts and popped it back in. The car fired up fine, but with no real difference since it was around 100 degrees yesterday (and it was stuck closed when I pulled it, so I didn't expect much to change after seeing that). I didn't have time to drive it to see if the high idle issue was still there (it seems to like to hover around 1,400 RPM and occasionally drop to about 900). I hope to test the cold start valve tomorrow and will keep you guys posted.

Hi Wade, I pulled the AAR last night and it was basically the same situation as with yours (thanks so much for the link to your post on the AAR, it really helped me understand how it works). So, my valve was stuck shut, I was able to pop it open with the pick, cleaned it out, did the freezer test, and it appears to work. A bit sticky still, though, so I'm going to clean it out some more before installing it. Also need new hoses, the split as I was removing them. Next up...the cold start valve, which I think is my culprit. Looking at temps up to 104 today in Chicago, though, so I think I'll hold off on that for a few days... Thanks again!

Many thanks for pointing me in that direction, Wade! I'm going to pull the bugger off tonight and give it the same run-through you did. I suspect mine is jammed wide open. I've been reading the FI bible (the window has been permanently open on my browser for about two weeks), but didn't have a .pdf version, so this really helps (I bring my laptop to the garage while I wrench on the Z, but no wifi there). Looks like I owe you two beers, sir! I'll keep you guys posted on what I find.

A friend on the west coast picked up a set of gauges out of a 2+2 280z, I believe a '78, and before sending them out to me, I was wondering if there is a quick way to test them (and thus make it worthwhile to ship). After searching the forum, I found that you can do a quick test on the oil pressure/voltage gauge by using a 9V battery (if the needles rise, they are most likely good), but I just wanted to ask before sending any potentially risky voltage through the other gauges. Thanks in advance for any help on this!

I think the rate of the speedo is specified by a gear in/on the trans for the speedo cable that is replaceable and color-coded. I read about it somewhere a while back, maybe for calibrating different rear-end ratios. Hopefully someone else will chime in on this. As for pulling the speedo, I just did the tach and it wasn't too bad (except for having to trim back the dash cover), but the speedo looked a bit harder to get to. Keep us posted, eh?

Thanks guys, and duly noted. As soon as I can get someone to the garage with me, I'm going to test the AAR and the cold start valve. To test the valve, I'm just going to pull it and place it in a container and see if fuel is still coming out after the car starts (with someone else starting the car). Is this what you guys do? One other odd thing I've noticed about this Z is that the throttle doesn't settle very quickly after a rev, especially when it is in its high-idle mode. Not sure if that's a clue to an issue with either of these devices. Thanks again for all your input, it is very appreciated! I'll be sure to update the post once I've performed some tests.

Just a quick update - the new tach is installed and working! That was a bit of a chore, but it worked out in the end. So, I got the car warmed up and then played with the TPS and I was able to change the idle speed by adjusting its position, so I'm thinking that the TPS is working fine. I have yet to pull the cold start valve to check if it's leaking (I suspect it is), but I did verify the connections on the thermotime switch and the water temp. sensor (I just received my color wiring diagram in the mail today). They seem to be connected correctly, and I even tried reversing them. With the connectors reversed, it would hardly start, and then would die immediately. Once back to proper position, the car fired right up and went into its normal (or what has been normal since I've owned it) high idle for 5 minutes. Someone suggested that I pull the water temp sensor and clean it. Is it common for these to build up corrosion and not work properly? The pins on the sensor were crusty but I cleaned those and the pins on the thermotime switch. Still running rich, though. Would the air regulator have an effect on richness? Sorry to be so needy, but is there a way to bench or quick test the air regulator? I still don't have a good voltage tester, but that is up next on the list. Thanks again for all your help!!

Just wanted to update this post. I picked up a replacement tach last week, taking the gamble on the previous owner's word that it did work when the car was parked (3 years ago), but it wasn't too expensive, so I went for it. The needle on the new tach did bounce around before I set about installing it, whereas my stock tach was frozen at 700 RPM. I have a full dash cover, though, so getting the old one out required some major surgery. I had to make a cutting scribe out of a wooden block with an X-acto blade screwed to it to trim back the dash cover. Just ran it around the rim to cut it back. Took about 20 minutes, though. This was the easiest route, since my dash cover has some damage near the glovebox already. It didn't come out too badly, though. I'm somewhat pleased with my work... And so, with a bit of luck, some Model Especial, and some patience, I was able get my old tach out. Then the new one went in...and it works!! But I forgot to change the bulbs beforehand. Talk about a pain in the arse. And there was no way that baby was coming out again. Note to self: always change to new bulbs beforehand. The problem with changing the gauge bulbs when installed on a '78 (and probably all Zs), as many of you know, is that you need two hands up there, one to hold the bulb socket, and the other to push in the bulb and twist. But there is little room for that, especially with my hands, so I set up a 1/4 screwdriver handled socket driver with a 8" extension and a small socket (maybe a 10mm, I forget) lined with bicycle tire inner tube that allowed it to grip the bulb and twist it while holding the socket with the one hand that could get up there. The Sylvania 53 bulbs are sadly just as dim as the stock bulbs, but they all work now... So, to sum it up, in my case, the frozen needle was a sign of a dead tach. And thanks for the tip, Andrew, my color wiring diagram from Prospero's Garage is on its way! - Paul

Thanks for all the excellent advice - I love this forum! I'm going to check my BTDC vs. the original mark and remark it just to get the timing correct for now, but a replacement pulley has now moved to the top of the list. Any tried and true methods to test if the replacement pulley has spun at all (before installing it)? Perhaps orientation in relation to the key slot?

Sorry to wake up an old thread, but to the original poster - did you ever determine if your pulley had slipped? I just installed a working tach on my '78 280 and was excited to finally check the timing on the car tonight...only to find that with the 'strib all the way advanced, it left me only at the 0 degree mark. I'm suspecting a spun pulley and will check for TDC before doing anything else.

Thanks again, FastWoman, I'm going to check the connections on the temp sensors tomorrow and I'll let you know what I find. Good point about the vacuum leak corrections making it run richer. I hadn't thought about that. The temp gauge works properly at present and I remember cleaning the thermotime switch contacts last year, so the connections are probably (but possibly not) correct. I kind of suspect my cold start valve may be leaking or my TPS is stuck in WOT mode. Well, all the sensors are suspect at this point. The previous owner's techniques to get it running were a bit dubious. I'll have a look at the air regulator as well when I do that. But I did get a tach over the weekend! Excited to install that and get the car timed properly, then I'll test the TPS to see if it's working properly, and then on down the line with the rest of them. But first the battle of getting the dead tach out of a dash with a full cover (that overlaps slightly onto the gauge bezel).

Thanks, Arne. I ended up deciding to go the proper part route. I'm probably going to go with the KYBs but still figuring out what else I'll need. I'd prefer to keep the stock springs, but at 34 years old, I'm not sure if they are any good and would hate to do the same disassembly twice. Only 92K miles on her, though. I'd rather not go with lowering springs, if possible...

Hi FastWoman, Many thanks for the clarification on the tach signal and the tips on where to start. I was curious as well about the O2 sensor (I hadn't noticed one). The car definitely doesn't know it's running rich ; ). My plan of attack will be to replace all vacuum hoses first (and use the yogurt cup test for sure). I did a few of the hoses already, but not all. And then go through the sensors, starting with your suggestion - the coolant temp sensor. It may well be the cost start valve as well (or both). The fast idle on the car does not like to settle into low idle once it's warmed up. It will on a very hot day, but not until well after the coolant has reached operating temperature. Does that sound like a coolant temp sensor symptom? The temp gauge seems to be accurate, but that comes from a different sensor, right? I'm also going to do the test on the TPS once I throw the new tach in (it's arriving tomorrow) so I can determine engine speed more accurately for the test/adjustment. Getting the old one out is going to be tricky as there is a full dash cover and it's overlapping the tach bezel a bit. My particular Z is a California car - it's indicated on the under hood sticker (I should probably check the altitude sensor as well while I'm at it). I did change the plugs/wires/cap and rotor the other day and she runs stronger (mismatched plugs, worn rotor), but still very rich and the old plugs were sooty when I pulled them. Thanks again for your tips and advice, very much appreciated. I'll be sure to post a follow-up on what I find! Should get a little wrench time in over the next few days.

Not sure if you found one yet, but perhaps try placing a "wanted" ad in the classifieds on this site. I've had some luck there.

Hi Wade, I'm reading your mail - I own an FSM and have been going through the "EF" chapter and also reading up on the Atlantic Z tech pages regarding the FI system, but I'm still unclear about the tach signal relevance vs. actual tach needle operation. If the dead tach is affecting the loop, that needs to be done first, right? Because it could be sending a low or 0 RPM signal to the ECU? I have no plans to rip anything off of the car; I hope to do the opposite, really. I don't want to start removing or replacing sensors (or using Atlantic Z "tweaks" to bypass a replaceable sensor) that don't need replacing. I want her to run right stock before any mods come into play. What I'd like to know the most is if the tach needle not moving is affecting the rest of the system. As for the exhaust, I assisted with the cat removal, even bought the parts to patch in, and the guy did a solid job, I was 3 feet away from him the whole time, even set the lift arms to protect the frame before she went up. No leaks from the exhaust, just no cat, and I feel like I have a few sensors are stuck "on" that shouldn't be. I just want to start in the right place and I want to be sure that if the tach needle not moving is screwing up the baseline for the system, then that needs addressing first. Thanks for your thoughts - I owe you a beer!

Hi Wade, Thanks for the info. Here's what confuses me - my tach needle is frozen at about 700 RPM. From what I understand, the TPS has three settings, idle, 1400+ RPM and WOT. If it is relying on the tach signal to make these changes, then perhaps the signal for the tach is still being sent, just not registering on the tach itself? I was thinking the same thing, that the car wouldn't run if there was no tach signal. The fumes in the cockpit are when the windows are open, I should have mentioned that. The car is running very rich and I had the cat removed while I was driving it home to Chicago from California due to the converter getting too hot (due to the rich mixture), so...even more rich fumes as a result of that. The car only has 92K on it, but I think the O2 sensor wouldn't be a bad thing to replace. i guess my thinking right now is that I should fix the tach before moving forward on other tests, but perhaps all the wiring is fine and the tach itself is just shot (so signal is being sent to ECU and sensors, just not showing on the tach). I'm just wondering where to start. With the tach, then?

Just a quick question for you FI gurus. I've got a few issues with the FI on my '78 280z (manual). She chugs a bit starting up when it's over 70 degrees F, then settles into a high idle, then comes down to what I believe is about 750 RPM, but this can take a while. She runs pretty well after being warmed up, no sputtering or front/back fires, but runs very rich. The exhaust is always very fumy and the fumes get into the car with the right type of breeze. But before I go about testing different FI bits, I was wondering, since my tach currently doesn't work, does the TPS (or ECU) count on a tach signal for its operation? I'm hoping that getting my tach working or replaced might save me some digging around the FI system. Many thanks in advance!

Will do - thanks!!