Project Boondoggle (or, so I went and bought a Z!)

[charliekwin]

So fuel tank restoration is the newest entry on my list of Things I Never Want to Do Again.

 

One of my failures on the smog test was an EVAP leak, and since my garage had been smelling like a gas station, that wasn't a surprise.  I dropped the tank, and it was pretty obvious why (I hope, at least): the sending unit o-ring was missing, there was a hole punched in the top of the tank, and a previous owner had put on a patch of unknown quality.  Great.  Better go learn how to deal with this.  Thanks to the helpful posters here, the other Z boards, and across the internet for all the tips and how-tos that have been published.

 

First started rinsing with water, and the rust started coming out.  Had I known how much there would be, I would've done a better job trying to catch it.  This is maybe half of it.

 

Followed by throwing in 88 nuts and getting my workout for the day.  All 88 came back out.  Then rinsed with muriatic acid and followed that up with some diluted naval jelly.  Flushed with water and acetone and it looked pretty good inside.  I thought I took more before pictures of, well, everything...guess not.  Here's the after.

 

I debated for a while about what to do with the inside.  Heard good things as well as some warnings about using Red Kote, but decided it was worth the risk.  I made a point of blowing out everything with compressed air and draining thoroughly.  It looked nice when it was all done (take my word for it; the photo got corrupted).

 

On to the outside.  Wire wheeled all the old paint off and filled the holes with JB Weld, which I hope will hold.  Then tried brushing on some Eastwood primer.  The instructions say to spray it, and it looked kinda lousy, so I went to Harbor Freight, picked up the $15 HVLP gun and set up my very makeshift spray station.

 

For my first time every spraying paint, I think it came out pretty well.

 

But I maybe just got lucky, the finish coat didn't look quite as nice.

 

Washed all the rubber bits with soap and water and hit them with some silicone spray.  Sending unit (with gasket!) was cleaned and reinstalled.  Tank is ready to go back in.

 

With everything torn apart,I figured it was prudent to replace all of the old fuel and EVAP hoses and cleaned up years of accumulated gunk.

 

And then everything came to a halt, when I couldn't find the drain plug. I'm pretty sure my 3 1/2 year-old helper absconded with it.  Thanks for the fast shipping zcardepot!

 

So everything went back together with a minimal amount of cursing and I put a gallon or so of gas back in.  It started and ran, so hooray for that.  There's a gas station a little less than a mile from my house, so I went to fill it up and promptly ran out of gas a 1/4 mile in to the trip  ::

 

Next up is a new cat so I can hopefully pass smog, get a title and actually drive the car.  Then maybe the dash, because this whole mess of harness that isn't connected to anything just fell out of it.

[bratliff]

Nice! Spent the day doing basically the thing to my tank. Haven't started cleaning the inside uet. Next weekend.

[charliekwin]

The smog testing adventure continues.  Took it in for a pre-test today and failed again with similarly awful numbers.  Good news is that at least the EVAP leak was fixed by all the work on the fuel tank.  Also had a new cat put on, so at least that's legal, but not fixing my emissions issues.  Plugs, air and fuel filters as well as a couple hoses have already been replaced.  It runs very rich, which the sniffer confirmed as well.

 

 

Earlier in the week I checked the coolant temp sensor, and the resistance across the terminals looked pretty good.  The connector looked bad and fell off when I touched it, so I replaced that as well, but apparently that wasn't the quick and easy fix I was hoping for.  I'm working my way through the bible now, starting with checking the fuel pressure.  I know the AFM has been opened before (it's been re-sealed), and knowing how other work on the car has been handled, my suspicion is that it's wildly out of adjustment.  Any of the gurus out there have additional suggestions?

[Zed Head]

 

Earlier in the week I checked the coolant temp sensor, and the resistance across the terminals looked pretty good.  The connector looked bad and fell off when I touched it, so I replaced that as well, but apparently that wasn't the quick and easy fix I was hoping for.

 

This here is your main hurdle.  You have to measure and get real numbers at the ECU connector.  And there is almost never a quick-easy fix.  Just a collection of small fixes that add up.

 

Those numbers aren't that bad.  Mine were similar, but they only check idle up here.  I lowered my fuel pressure and made some other adjustments.  But I have a modified system that allows that.  

 

The first three things that I would do are:  measure resistance across the cooling circuit pins at the ECU connector and compare it to the chart, measure fuel pressure with and without the vacuum hose connected and with the engine running, and examine the AFM gear with a magnifying glass to see if you can find the original glue blobs and put it back to where it was.

[charliekwin]

Thanks for the insight Zed Head.  I checked resistance at the ECU and the numbers are at least in the right ballpark.  I have to hunt down a thermometer to get actual coolant temps and will check again to confirm, but considering the ECT is $13 and an Amazon Prime item, I may just get a new one.  Engine temp gauge never seems to go more than about an 1/8" or 1/4" past the 120 degree line, which -- if that's low -- I guess could also point to a problem with the sensor (or a stuck thermostat).

 

Fuel pressure gauge is also on the way after a goose chase in which I learned that none of the major auto parts stores carry those.

 

And finally, I cracked open the AFM, which was...interesting.  I've done some looking around, and I think I might have a 280zx and/or a remanufactured unit, because the counterweight doesn't look like any of the pictures I've seen of other 280z AFMs.

 

 

Fingering the AFM helped lean it out, but didn't seem to make it otherwise run much better.  Pushing it towards the rich side immediately made it worse so I must be on the edge with the mixture right now.  I won't make any adjustments to the AFM until addressing the other things, though.

[Zed Head]

 I have to hunt down a thermometer to get actual coolant temps and will check again to confirm, but considering the ECT is $13 and an Amazon Prime item, I may just get a new one.

 

 Engine temp gauge never seems to go more than about an 1/8" or 1/4" past the 120 degree line, which -- if that's low -- I guess could also point to a problem with the sensor (or a stuck thermostat).

 

Fuel pressure gauge is also on the way after a goose chase in which I learned that none of the major auto parts stores carry those.

 

And finally, I cracked open the AFM, which was...interesting.  I've done some looking around, and I think I might have a 280zx and/or a remanufactured unit, because the counterweight doesn't look like any of the pictures I've seen of other 280z AFMs.

 

 

Fingering the AFM helped lean it out, but didn't seem to make it otherwise run much better.  Pushing it towards the rich side immediately made it worse so I must be on the edge with the mixture right now.  I won't make any adjustments to the AFM until addressing the other things, though.

If you measure before you drive it, everything should be at room temperature.  Often it's not the sensor but the 6 connections between it and the ECU circuitry.  Each one can add a little resistance, showing a cold engine to the ECU and causing added fuel.  Clean all of those connections.

 

The temp. gauge doesn't use the coolant sensor.  It's separate.  There's a sensor and a sender.  But a cold engine will be a big problem.  Often people have overheating problems and remove their thermostats.  A new Nissan thermostat would definitely be worthwhile.  Your local dealer might have one, or Courtesy Nissan.  Nissan quality is worth buying for that part.

 

Are there numbers on the AFM, either the cover or body?  A11-xxx-xxx.  That will tell you something.  Idle circuit is separate from running circuit, there's a switch on the throttle body.  So fingering the vane will only show gross problems.

 

 

I'd focus on getting the engine hot first.  You can't pass if your ECU is adding fuel for a cold engine.

 

I think that 78 is A31-604-000 for the AFM.  And you're right, that AFM does not look like my old 1978 AFM.

Edited May 10, 2015 by Zed Head

[Captain Obvious]

I agree with the above. Those numbers don't look that bad.

 

You know there is an idle mixture screw on the AFM don't you? It allows for more or less air to go around the AFM vane hence affecting mixture under low lower load (idle and light cruise) conditions. Before you go tweaking the AFM, you might want to try opening that idle mixture screw up a little. Counterclockwise for lean. Clockwise for richer.

 

Adjust the idle mixture screw while you have the sniffer up the pipe. There's some description in the manual about how it should be adjusted. IIRC, you're looking for CO numbers which will indirectly tell you mixture.

 

Sorry if I'm telling you stuff you already knew, but stating the obvious is part of my contract.

[charliekwin]

The quick recap on the last week or so, in which little may be going my way toward the end.

 

First the good stuff.  My current garage work/storage area has been pretty pitiful, so I got a little something for my birthday to help with organization.  Thanks dad!  Also, the battery ground was in terrible shape, so I dug up some old 0 AWG welding wire and some lugs I had leftover from the audio install in my G and redid that.

 

And that's about the end of the good stuff.  Moving on.  When I went to replace the thermostat and coolant temp sensor, I found that the housing had been cracked and epoxied back together with the same stuff that was used on the fuel tank.  The housing is discontinued, but it doesn't seem to leak, so I guess it stays for now.  A previous owner had also removed the thermostat entirely.  Replacing that and the sensor seems like it's getting the engine up to a better temp and (based on smell and fingering the AFM) I think it's leaned out a bit.

 

 

Now for the ugly.

 

I ran a compression test.  From 1-6: 75, 70, 55, 70, 70, 65 psi.  I think I need someone to hold me.  I've never done a compression test before, so there's a possibility I did it wrong or maybe the gauge is off, but those numbers seem outlandishly low.  It puts out smoke at higher (~4k) RPMs, but seems to pull pretty well.  I put a bit of oil in #5, which bumped it up to 100, and went on to valve adjustment.

 

After pulling off the valve cover, I found a whole mess of sludge up there.  I'm tempted to try to clean it up, but my gut says it might be better to leave it alone so it doesn't get dislodged.  Thoughts?  I'm going to re-run the compression test after the valves are done and hope to see better numbers.

 

[Zed Head]

Did you use an adapter with your pressure gauge?  They add a lot of volume and will lower the numbers quite a bit.  Better to take the numbers on a warm engine also.  Plus, if the oil is gas-thinned from running rich you'll get a poor seal.  Cylinder pressure tests are mainly good for comparing quality between cylinders.  You're looking for consistency.

 

The 30 psi bump with added oil and the sludge do suggest high miles and wear though.  But you'll probably be able to get it to run well and pass emissions, it might just burn some oil and smoke a little bit.  The valve adjustment might have a significant effect, since it's possible it hasn't been done while all of that sludge was building up.

[charliekwin]

I used the pressure gauge that Pep Boys loans out (http://www.pepboys.com/parts/tools) and did check while the engine was warm.  With the exception of cylinder 3, they all test pretty close, so I won't fret too much about the low numbers, but the increase after adding oil is disappointing.  If I can still pass smog with the engine in this shape, I can live with it for a while and swap or rebuild sometime later.

 

Valves (somewhat surprisingly!) were well-adjusted,  Only two of them needed adjustment, and both were only off by 1 thou.  What of the sludge?  Leave it or clean it?

[Patcon]

Doesn't the intake have to be open somehow? On carbureted carbs I believe you hold the throttle open so the butterflies don't restrict the intake of air.

[Zed Head]

If you have a shop vac you can rig up a hose to get in to the crevices.  I would just worry about dropping a chunk of sludge where it could do some harm, trying to spoon it out.  It's not going anywhere otherwise, unless you plan to hit some bumps at high speed.

 

My old engine had worn valve seals that leaked oil in to the intake runners.  If you're looking for work, new seals might clean up emissions a bit.  I still passed though with my old seals.