Dave WM

when its left open (like testing water temps or the leak test for gas) it like to burp. If I just leave the cap on all is fine, no recovery tank, but I have one, maybe will hook up just to see what happens. Temps look good, stays right at 185 per meat thermo which is right in the middle of the gauge, does not move once its there. no milkshake under oil cap, Oil on dip stick looks ok. I need to flush out the rad and start over again, there is something mixed with the water, but could have been there from when I was hooking everything up. lots of brown yuk came out with the burp. I am prob over worrying about it since I don't have any other sign of a head leak. only the one test, chem blue, that I want to repeat with some fresh water. Rained last night so I have some nice distilled water.

More testing this time a leak down test. engine was cold (well never cold in Florida, lets say not hot) rad cap off, tested very well, 90/85 (about 6%) psi on each cylinder and not a hit of a bubble from the rad. Sounded like most of the air was escaping past the rings. (could hear it from the dip stick or down the cam chain area). Running the engine has helped in this regard as it was much worse when I 1st got the engine on the stand (and it had not been run in some time). I am going to pull the thermostat out and test run it again, try the exhaust gas in coolant test. Wil remove the thermostat in hopes of not making a mess when it burps. Then will follow up with the leak down and look for bubbles with a fully warmed up engine. I noticed in the power test pulling the #6 injector seemed to have a much smaller effect during running, but that cylinder test fine in both compression and leak down. I can hear the injector clicking, will prob put the color tune plug in there to see what is going on with respect to the combustion.

I wonder if its possible for the head gasket to just fail due to age, and not other underlying factor (that would need to be addressed before just replacing). Any will check. I am going to conduct a test with the chemical leak detector on my running 75 just to see if it will pass the test. Will start with the cap off to see if it wants to burp up water when 1st started as well. I did not have any big compression test fails, everything was between 165-170 warm test so was kinda surprised to see the fail. I had assumed if the HG was bad there would be some compression problems.

while messing with the spare engine on the test stand I noticed some odd behavior of the cooling system. very soon after starting way before the water temps rise, if I leave the rad cap off it will start puking water up, a lot of water (quart or more), then as the temp rises and I presume the thermostat opens (the water getting puked is cold) everything settles down (after adding water back) and the temps stabilize at 180f per the meat gauge, no more puking water running thru the rad. Next I drained off a little water and tried my napa head leak tester. This is the one that pulls air from inside the rad thru a mesh screen bubbling the blue chemical. It had a tinge of yellow, def lighter color than the dark blue it started out with. I am pretty sure this is conclusive testing but for fun I plan to try using the leak down tester with the rad full up, engine warm, and pressurize the cyl one at a time to see if the water level in the rad moves up (like it did when I was running it and it was cold). the 1st test should be enough but I like to try stuff. anyway it looks like I may be getting a chance to pull the head off. I don't know if you always have to skim them, but will test it with a straight edge when I get there.

I would like a very nice condition mid 90's 300zx, I think they are the best looking of all the Z's (including the S-30 for that matter), but I appreciate more the simplicity of the S-30 with its straight 6. anyway IF I get a bigger garage I would be all over a 90's 300zx, heck even the 2+2 model of that car is snazzy, prob stay away from the TT just cause I don't want the hassle. I believe in buying what you want and taking other opinions of value with a grain of salt.

its not a lot of money, if you have the space to keep it from the elements, AND you want something you can drive right now then Go for it. If you get too much blow back, or need to free something up, sell the 300 purely from an investment point of view. Mainly I want to see you on the road, so a ready to drive vehicle sounds good to me :) Its all about space IMHO. I just think you deserve a driver right now. I suspect you would get much less blow back if you had the driver vs the torn apart 300zx, so move it into long term storage, and get this one in the garage.

I will help you load it up Jeff! lets go

I am ready for you my friend, I will be done testing soon, can my motor and bring it over for you!!

well you can see large sections with carbon deposits, prob best to not mess with it, Italian tune time. I don't know how well my borescope will do as far as trying to photograph what is on the screen. water temp and oil pressure hooked up, all looking good. Starts instantly now, will invest in some proper wire and clean up the harnessing. Funny how I was so sure it was the EFI, but should have known better due to the conflicting info (fouled plugs/leaning did not help). I saw a nice wire selection at HF last time I was there, assortment of sizes and colors IIRC. I would like to get some of the connectors to really make it a nice test harness for the ign etc... Jeff, about time for you to hook up your turbo on the run stand!! the next big question will be what next? take it all down and store as a spare, look for turbo stuff, build my own go cart?

Bingo, and the award goes to polarity. started this morn right up, swapped polarity , back to chuga chuga, swapped back , smooth again. Clearly the smoking gun Next up will be to hook up the gauges, color code the distributer wires, work on the vacuum advance, get some new plugs, just refine the over all status. I would like to do something about the carbon build up on the pistons, not sure if I buy all the hype of sea foam, don't want to hydro lock with water. Don't want to pull the heads right now. I am sure they needed it even before the rich running the borescope showed a LOT of build up. Maybe use the CSV hooked up to a bottle of water under pressure then some very short burst? that CSV real atomizes well which may help with avoiding hydro lock. some before and after picks to show the effects?

could be pinhole leaks, or leaking from somewhere else and working its way to a low spot. I pulled my tank and had it professionally cleaned out and sealed. pretty expensive, IIRC he cut it open over the center of the tank to sand blast it clean (no other access) then coated inside. Other problem areas can be a bad sock or what ever is connected to the pickup tube, holes in the pickup tube sucking air. IIRC it was a franchise "tank re nue" or something like that. No leaks or any other issues since then. I also install a Pre filter, it was a large metal type that was designed to be used in front of the fuel pump.

you know I was thinking of the wave form from something else, a square with trailing oscillations. have to go back and review. ok I remembering the wave form at the neg side of the ignition coil...

possible smoking gun! guess that is what happens when you start hooking up things from scratch. So the working theory was it was trigging on one of the trailing positive going bounces, and not the larger square wave (neg going with incorrect connections).

and that is how I have it :) testing tomorrow will include switching those around to reverse polarity to see if I get the chuga chuga chuga jungle juice effect.

So if I read this right the large eye off the distributor is the Green lead per ZH attachement so that connects to G lead on the module in the attached PDF and either of the small eyes would go to the red on the module. think I got that right. could not figure out how to get the pdf to show an image for clarity.

1978 ign module.pdf

I did not realize that. thanks for the heads up.

yea the coil hookup seem to have little effect, not really sure what happened that it seems to be working much better. Will tidy up and get some more instrumentation. The vacuum advance is connected but the diaphragm is clearly leaking (will not hold a vacuum). I could swap it for a spare, but one change at a time. Timing light next, but I have to go read up on it. Could not find an old school fixed light, now they have some adjustment that you have to dial in. I think delays the firing so you always just look for TDC and then read the degrees of advance. Seems overly complicate to me. Maybe worth it if you did not have the scale built into the pointer I suppose. I really wish I had a smoking gun to point to, but lets see how it goes tomorrow on a cold start before declaring victory.

next project will be to hook up the oil pressure/water temp and tach if Jeff has a spare. Still need to check the timing, I did notice the dizzy vacuum servo is leaking. I assume the mech advance is ok since it can be turned and springs back (the rotor). Weld up the exhaust to quiet it down a bit more. Those alligator clips are prob not the best way to hook up the distributer so will work on a better connection there as well, Once I am happy with the setup. guess I could but a SPDT switch an manually select it. More tidy up coming too, only thing left connected to the power strip is the EFI, need to get some more big spade connectors that talk to the EFI fuse links and wire that directly to the battery AUX leads off the cables. then can tidy up the excess wire lengths now that the form is settling down. Really glad I invested in getting the alt to work, don't have to worry about the battery anymore.

running kinda cool how the stll pic of the video captures the distributer wires.

hmmm ok single either coil or coils in series seem to have no effect, and it starts right up and runs much better now. This morning it was giving me fits before the pickup coil fix, now I cant get it to chug. It still not perfect, but considering the quality of the plugs I am not surprised. Wish I had a clue. Going to give it a rest and start over tomorrow on a cold engine.

I have a backup single coil distributer, but the reluctor is damaged from impacting something (I presume the coil) and its not mounted so I would have to transfer the bottom parts that bolts to the engine to use it. It did spark the coil in my early test, but I was not sure if all the reluctor tangs were firing it. Would be nice either way if I could confirm this as a ign problem, and not a EFI or injector problem.

1.5k on the leads I am connected to where it works, so working on the dual coil in series (not correct hookup) I will give it another try after it completely cools down. then will try the single coil (750 ohms read on small eyelet and large eyelet )correct per diagram and see if it acts up again.

I am going to check the distributer wires and see if they are color coded.

started right up no need to monkey with WTS. Think ZH was on to something about the signal to ign module. Going to have to hit up Jeff to see if he has a tach laying around, I would like to know I have that part of the circuit working right. I don't want to just assume I have the resistor hooked up right. Curious about the RPM anyway as I would like to see if its idling correctly. Will get video later, but it started instantly from a warm start. I am reading about 40 ohms on the water temp gauge sender which I have previously check as 185 on the gauge. Jeff, I will be hooking up that oil pressure and water temp gauge later.