Dave WM

Clearly after market AC, back off on the pic with the circle spot not sure what I am looking at. Good thing is you don't have the expensive drier.

The best thing is to just read that EFI section a few times, keep in handy read several times, it will begin to sink in. On mine the temp sensor was reading low on the ohm for the given temp, this will make it run lean since the EFI unit thinks the engine is warm when its not (it works temp/resistance inverse relationship). there is a table in the EFI that will give you approx. resistance reading for given temps. check at the 36 pin connector, if not ok, check at the sensor, if still not ok then prob the sensor, if ok at the sensor then prob corrosion in the wire harness plug.

good point about being able to glue back. From the look of the pics, the bottom looks to be really tight on the sides so I was thinking it would not hurt to remove some foam there. I can tack glue some guides the sides and pull a very neat cut with the foam cutter.

I have a seat foam kit as well. 6'3" here, so after reading your post about lost cabin ceiling clearance I was wondering if you think it would make since to slice off 1" from the bottom of the foam before doing the install? I have a hot wire foam cutter but not sure how it would work on this foam, I used it for cutting Styrofoam for wing cores on model airplanes.

check and see if there is a Z club near by, could be a good group to contact.

Get lots of pictures under the hood so we can have a look at what you have.

Ok that is a good start (checking by pulling the wires) did that smooth things out? also does the replacement plug look the same as the others now? You could have a bad injector on that cylinder, oil fouling from a bad ring. A good baseline check of the cylinder pressure should be done. Checking the new plugs again will help confirm that the plug wire was the issue. I would have swapped the wire to another spark plug to see if the problem moved with the wire, but its ok to replace as long as you go back and make sure the plug is not re offending. If it looks fouled again you should listen for the injector to see if it sounds any different than the others (that's assuming the pressure test is ok). The problem you are likely to run into is you need someone that understands the EFI unit. As Zed and I both alluded to the #1 check would be the temp sensor checked AT THE EFI 36 pin plug. If you want to read the EFI book then you can follow along with the diagnosis, OR find someone that knows these cars. Again its not hard to learn I knew nothing about Z cars 8 months ago, some reading a few basic test tools are all you need. Since you are look for common problems Get the coolant system pressure checked to make sure you don't have any leaks. Check the condition of the fan clutch and water pump. Water pump failure will ruin your day. Warning if you do need to replace the water pump read up on how to try to avoid breaking bolts if stuck. I would not replace it if its ok, this is an item best left alone unless in needs replacing to avoid bolt breakage. Fuel tank, put a G-3 Fram fuel filter ahead of the fuel pump. It will allow you to see if you have junk in the tank (clear plastic filter). Check the fuel lines for pressure and flow capacity (they can rust from the inside restricting fuel flow) Mine were a bit stuffy (that's a FSM description BTW). I cleared up the fuel line with some evaporust and compressed air. Check the vent line that goes to the carbon canister, mine was completely blocked with rust. Does the fuel cap have suction or pressure when opening? Check all electrical connectors associated with the EFI Corrosion is a common problem. check all the Grounds associated with the EFI. Make sure you have GOOD battery cables and grounds to chassis off the negative lead. Check fuse links for corrosion where the plug in. Listen for valve noise. Valves will need periodic adjustment (easy). Make sure valve cover gasket is in good shape (can cause vacuum leak) Make sure Oil cap on valve cover has good gasket (vacuum leak) Brake booster, Listen for leaks, see if depressing brake causes idle to change (the booster can leak when pressing the brake). Oil dip stick firmly in place EGR working only when car is warmed up Vacuum gauge, get a base line vacuum at idle, report back. Start a service manual if you don't have one to document what was done and when. (I need to do this too). Sounds like a lot of but its really not, you just have to recognize its a 40 year old car, way past normal expected life of many of the parts so you have to be extra diligent about staying on top of things. Plus compared to modern day cars that are designed to go 100k with practically no service other than oil changes, the era these were made in assumed regular service intervals that were much shorter. Hang in there its well worth it once you get it sorted out.

As to the issue of the backfire, if the tank has sufficient fuel in it (good fuel)the fuel pressure checks out, I would start by checking the water temp sending unit (for the EFI not the temp gauge). This sender is responsible for fuel enrichment when the engine is cold, if its not working properly it could mess up the amount of enrichment, its all covered in the EFI portion of the FSM as well as hot to test it (you don't just install a new one, what if the new one is bad?). oh by the way how does the inside of the tank look?

fuel pressure check is next, sounds like its running lean. a little hesitation is ok, will never notice while driving it, but backfire thru intake is bad, can damage the AFM. oh and make sure you are not running out of gas. When I 1st got mine I was low on fuel and it started doing exactly that backfire thru intake, up until it completely ran out of gas. Your tank gauge may not be accurate. Everything with my Z so far has been simple dumb stuff (fuse blows cause I short out the VR while adjusting, fuse link blows due to shorted 40yr old alternator, back fire due to running out of gas). What you don't want to do is start messing with adjustments of things you don't understand. You should read the EFI bible and know it inside out and backwards. stuff like changing plugs, wires rotor all that is not the way to correct problems you must diagnose the issue and use a systematic way of checking things. The problem with replacements is you can introduce and new problem by not doing the fix correctly (like mixing up plug wires just as an example). the more variables added to a problem the harder it is to fix. Also modifying to fix a problem is not good either. These cars are very simple and in stock trim run very well. No need to replace the entire FI system with a modern after market unit. Bottom line is if you want to own a 40 yr old car you need to find a good mechanic or become a good mechanic (not that hard really) for your specific vehicle. Example why was the spark wires replaced? was there a mis fire, was it spark related, did you look for leakage and see/hear it? if not no reason to replace the spark wires to fix a problem. Now if there is no problem and you want to replace them cause they are old, fine, but do it when the car is running fine, and then if it does not run after the replacement put the old ones back. That way you can retrace your steps. If you are skilled at diagnosis you can get away with shot gunning parts (replace everything old just cause its old), and then if the car does not run right you can still diagnose the issues. But if you are not skilled this can lead to a near impossible to resolve issue without finding a skilled person to do the work of figuring out what the problem(s) maybe.

I know its been covered in the past, I did a search and found an old thread, but what the heck here is what I found. Mine would go well be low E and still have 4.5 gallons in the tank, and the low fuel light would not come on until I was about 2 gallons left IIRC from prior testing. 1st you can remove the sender without dropping the tank, just remove the one holding strap on the filler side (undo the j hook and let it hang out of the way. Remove the filler neck guard plate, then twist the retaining ring, remove and then fiddle the sender out. No need to jack or remove tire (removing tire makes it a bit easier but not needed). 1st I check the ohm range and made sure had free movement, all good. then I noted the bend angle (draw on top of the bench some ref lines while holding the wire on the bench), bent it just a tiny amount down, reinstalled now I have nearly 1/2 tank, yikes. so bent it back and try plan B, just this time rather than remove it I loosely attached the retaining ring and twisted the unit slightly clockwise. Voila now I am at about 1/8 tank (needle cover the vertical of the "F" in fuel) which is a lot better than completely below the E mark. This is with about 4.5 gallons, so say 2.0 gallon to spare before sucking air and having a bit of a safety margin I really have 2.5 gallons which is pretty close to 1/8. I tried to start out with it perfectly vertical (the sending unit) but if you are off only a few degrees it matters. Anyway just thought I would mention.

I don't think so unless it has a lot or corrosion on it. On the fuse links, you can buy them or make them (I have done both). They work fine IMHO I know there are a lot of folks that like to mod this area, but not sure why. I had one melt when my Alternator diodes short out, Fixed the alternator, put in a new one (after making one to get me on the road while waiting for a factory replacement) and have not had a problem since. I do have one fuse that runs hot (the AC fuse) not sure why as the current seems to be correct. Again just my opinion less mods are a good thing, as it makes you figure out what the problem is vs covering it up with non factory solutions. If everything is right, the fuse links and fuses should be fine.

sounds like gas that has turned to varnish in the carbs, indeed, how long did it sit

Nice cross flow. Yes the condenser is likely to have a rock strike. I see some new tube serpentine types that supposed to be a drop in replacement. If it was me I would do the least possible just to base line it, that would be pressure check to see if there is any R-12 in it now. If not pull a vacuum and put some R-12 in and see what happens. I really depends on how reliable you want it to be. Completely replacing everything and paying to do it will indeed cost a bundle just a rough break down in parts $400-600 for a new compressor $300 for a condensor $20 for a drier pray the evap and expansion valve are ok or $400 for new combo with modern expansion valve $60 for R12 so you can spend a $1000 in parts figure 400-500 labor and you are getting into the 1500-2000 for a professional job. OR pull a vacuum, recharge with R-12 and dye and see how long it goes $60 for the R-12 (get a can with dye) maybe 2 hours labor (mostly waiting for the vacuum to pull down) 150$. then see how it goes. On mine the only leak I have is a slow leak at the condenser, so that will be replaced in the future (I bought a used good one). My numbers are just ball park and I have no idea if my labor $ are even in the ball park, but I can tell you that I had a 92 ford explorer get all new stuff (stayed R-12) but for the evap and that was 1500$ at a AC shop. After that I decided I would learn more about it. Oh and HR369 is correct I would be all over it to help you get it going if you were close, but NW Ga is something close to 600 miles. Your best bet would be to take it to an AC shop that's been in bus for a while, and ask what would it cost just to check it out and try evacuate and recharge with R-12 if the compressor is not locked up. The biggest problem will be sourcing a OE drier, but they should be able to get an aftermarket to fit.

really depends on why its not working, if it still has Freon in it (gauges will tell) and If the compressor is not locked up then you would need to find out of the compressor cluch engages. If it does not that would be the 1st thing to sort out. More likely the Freon has leaked out (very low pressure if any on gauges). If that is the case AND the compressor is not locked up, then pull a vacuum, see if it holds. If it does then add some dye and R-12 and see if the compressor will work (checking gauges again). Prob will but may leak which is why the dye. run it for a few days and look for the leak with UV. After the leak is found (prob the condenser or shaft seal of the compressor) R&R it as needed, pull vac charge and you are good to go. The system is very simple just find an older mechanic, should be no problem.

If the amp meter is working and not showing charging then the 1st thing I would do is the power up to the F term to see if the alt will work with that VR bypassed (two prog plug out, jump lead from F to BAT). If that does it, then check for voltage at the N connector, should be about 6v (with the car running) You can also ohm out that N to ground should be a resistance there, not open but not low this is also in the FSM pic that Zed H attached. If that checks then I would suspect the VR charging relay is not latching completing the charge circuit. If you tried a new VR then I would suspect the wiring from the N term on the alt back to the round connector for the VR.

I may have missed it some where, but does the car have an amp meter or a voltmeter, and if so was it not showing discharge or low voltage before the car left you stranded? If it has an amp meter you should see it swing into the charging side right after startup at least for a min or two to recharge the battery from the starting process. If it has the voltmeter the voltage should go up after starting and I think it has a charging light that will tell if its charging or not (76 is when the amp meter went away in favor of the voltmeter/charge light). The best way to confirm charging if for some reason the amp meter or volt meter is not working would be to use a digital voltmeter (40$ at a lowe/homedepot/habor freight/radioshack) and measure the voltage at the battery terminal with the car off, then start the car and see if the voltage comes up, rev the engine some and keep checking. Besides the alt not working if your amp/volt gauge is not telling you about the issue then you have that system to look into as well. At a minimum you should be able to check the amp/volt gauge by just turning on the headlight with the car off, look for a discharge if amp or a drop in voltage if a voltmeter.

One thing I don't recall seeing, exactly how do you know the alt is not charging the battery? It should go without saying that you should have a good battery AND good cables with good grounds, and good clean contacts at the battery post. simple test would be to disconnect the FN plug (field coil and "signal wire) from the alt, start car, check the voltage at the battery. the alt will not be producing any charging current since the field is disconnected. This is the baseline voltage with no charging. You will hear the difference when you plug the FN plug back in as the alt loads if its working. Next plug in the FN plug check the voltage at the battery rev the engine up some see if the voltage changes. if it does then you need to find out why the charging meter is telling you its not (forgot to ask If voltage at battery with the alt hook up does not change (go up) with the alt FN plug hooked up then the alt is not working, either do to a fault of the alt or the regulator or the wiring or the fuses. to check the alt get a jumper (I used one with small alligator leads, insulated) hook from the F alt term (look at the alt to figure out which one is F from the photos above) to the BAT term. Oh and confirm there is 12v AT THE BAT term should be at all times, its directly hooked to the battery (thru a fuse link). Once you have the jumper in place start the car and see if the battery voltage is still at the base line. This is the FSM test Zed posted to bypass the regulator. DO NOT rev up the engine just a little above will show if the alt is working checking the voltage to see if it goes up. One last thing, the fuse box is not precise about what the fuse protects, so don't assume its only what it says. if you find a blown fuse replace it as the FIRST thing to do when trouble shooting. Also after replacing it and try testing check it again. Very possible its blown again in which case you must figure out why its blowing. I have found broken but not blown fuses I guess do to age/vibration etc... if the replacement fuse blows right away then you must figure out why before going any further. Make sure if you replace a fuse its the correct amp rating.

Zed head is right about making assumptions. I was assuming a running car that was not charging the battery. A few things to note the "signal" wire will not make voltage unless the engine is running, its used to tell the VR that the alt is turning and ready to charge.

IF the regulator is faulty, you can prob fix it. There is not much too it but points and coils. There are 2 relays, one is the charging relay (activated by the N lead from the alternator) It will latch if the N lead is generating any voltage (around 6-7v IIRC). for the 1975 its function is to prevent battery discharge I think, later models used that relay to operate the "charging" light on the voltmeter gauge (the 75 used an amp meter, so no charging light). The other relay is the one that does all the work of regulation, essentially duty cycle of the field coil of the alternator based on voltage output. as voltage rises it would open up to cut the field, as the voltage drops it would close the field circuit energizing the field coil. This happens very quickly so the points may be an issue. Make sure the VR cap (condenser) is in place to minimize the arcing that takes place from all the opening and closing of the contacts of the VR relay. This condenser is located up by the VR, there is also one mounted on the Alt this is more for noise suppression from the brushes of the alternator. If you do decide to buy a new VR (say the coils are open and burned out) I found one on ebay for about 35$ VR-159 I think is the part. There are SS versions of this as well, I opted for a mechanical unit. I really bought it just to see if that was the reason my autozone alt was barely able to deal with full load at idle. It was not. Don't know if its the reman alt (I took it back for another again just able to keep up) or maybe it was always marginal, but at idle with AC/lights/brakes/you can see the current move into the discharge side. anything above 1.1k rpm and its fine, and you are charging again.

my carpets have a rubber like backing, gotten hard and brittle with age. Too bad as the carpet itself looks pretty good. I am tempted to try to refurb the rubber backing, off to google land.

it looks like the one I got from auto zone, should only be able to plug in one way, and yes IIRC the F/N is noted on the case of the alt. That one like mine replacement has the diodes inside the case, not under a plastic cover. like the OE Htachi. Can the OP please confirm the fuse links? do you have 2 boxes or just 1? and I presume you have checked all of them (you have to check continuity of the fuse link, looking at it is not good enough). Also check all the fuses in the fuse box, IIRC I was adjusting the VR and shorted something (the adj screw was hot) with my metal screw driver. This popped a fuse in the fuse box, killed some other stuff as well.

If the alternator is not charging, you should check to see that the field coil is getting voltage from the regulator, the FSM covers how to do this, a simple jumper from the Bat to the field coil will fully energize, you just want to make sure you don't rev the engine up (with the field coil un regulated the alt will put out excessive voltage likely damaging the ECU). Monitor the voltage at the battery and if it starts charging with the field jumped then the regulator or wiring to the regulator is at fault.

I used the nylon tool which has a thin edge to get under the gasket where it meets the glass. Then I put the nozzle in that opening and started pumping and while moving the nozzle under the gasket, looking for a small amount of squeeze out. I started at the middle of the windshield and worked all the way around the bottom corner and up the side of the glass to the top corner. The gasket looks relatively new, but for some reason its just not a tight fit in that one area. This sealant is prob just a stop gap for now. I assume I will need to redo the gasket at some point in time and hopefully get a tight fit all around the glass.