78 280Z - Finally got it driving - High Idle, will occasionally die (but restart), sound like it has a misfire

[NocturnalEmber]

Well, a major update I suppose you could say.

I drained enough gas out of the main tank to fill up my two gallon, placed both feed and return lines inside the two gallon can, and started it up. By my watch, the car ran for twenty minutes and sounded significantly better, with fuel pressure being about 34 PSI the whole time. It did abruptly die once at the end of the twenty minute mark with absolutley no warning, just completely died.  Though it did restart right away with no issues and continued to run fine.  Idle was at 1,500~ RPM, and I adjusted it down to about 1,000 via the set screw.

 

I only attempted to rev it once due to how late it is, it seemed to rev mostly okay but stumbled as the RPM's dropped to around idle speed, though it did settle back into its idle shortly after.

I did notice after I crossed over the twenty minute mark and restarted it after it had abruptly died, the fuel pressure did drop down to about 32~. If I unplugged the vacuum line on the FPR, it would get to near 40 PSi.

 

It wasn't 100% by any means, but it sounded like it was actually running rather than missing and stumbling while trying to run.

 

So, I'm assuming the elephant in the room must be the gas tank?

 

[siteunseen]

I would have bought 2 gallons of new fuel. Drain the tank fuel into a clear plastic tub and see how it looks. Mine looked like Sunkist when the tank was fuel of crud.

[siteunseen]

Good read here.

https://www.atlanticz.ca/zclub/techtips/fuel/gastank/index.htm

[NocturnalEmber]

51 minutes ago, siteunseen said:

I would have bought 2 gallons of new fuel. Drain the tank fuel into a clear plastic tub and see how it looks. Mine looked like Sunkist when the tank was fuel of crud.

 

47 minutes ago, siteunseen said:

Good read here.

https://www.atlanticz.ca/zclub/techtips/fuel/gastank/index.htm

 

I did drain the fuel a few times. What caught me as odd is that it never looked dingy, dirty, or full of rust flakes.  There was one time when I went to perform this test last night or the day before for the initial time (when I left the return line connected to the gas tank) that I saw a rust flake about the size of a pinhead sitting in the fram inline filter. The fuel had a slightly yellow tint to it, but I didn't think anything of it as the fuel wasn't visibly contaminated with sediment.

 

But with the car holding steady fuel pressure with its feed/return lines connected to the gas can, I honestly don't know what other culprit there is at this point, I would think it points in the direction of the tank being suspect. As a result, that means i'll be placing an order for a "new" tank. That link does provide some good info to be mindful for when the tank gets here, much appreciated!

Edited March 8 by NocturnalEmber

[Yarb]

Wix 3003 3/8 fuel filter is clear. Fram used to be but not anymore.

[Zed Head]

There is a "can" or cylinder inside the tank, which has the fuel pickup point inside.  That's where the crud would be.  There is a screen or "sock" at the end of the tube to block particles from passing in to the pump.  If your tank has been sealed in the past it might be that some of the sealant has come free.  A borescope might tell you something.   You can find quite a few pictures around the internet of the inside of the tank but for some reason people rarely take a picture inside the can where the end of the tube is.  It's strange.

https://atlanticz.ca/zclub/techtips/fuel/gastank/index.htm

 

 

[Zed Head]

Here's another link.  They say that there's a fine screen around the pickup area.  I've never seen a clear shot of it.

https://forums.hybridz.org/topic/96315-por-15-fuel-tank-repair-question/

[siteunseen]

I dropped and refurbished my 1st tank on the '77 I still have. Honestly it was a waste of time and a little money, the car didn't run any better. At the end of the very "long day" it was the coolant temp sensor resistance to the ECU. It could be your fuel pump? 

Now the '72 240Z I bought was a whole different story. That tank was like a porta-john's tank minus the big breath mints.

This isn't rust, wouldn't stick to a magnet, just old fuel and sediment. The car sat for years with fuel in the tank, eventually turning to pretty much dirt.

 

 

 

[NocturnalEmber]

Well, the new tank is ordered. I have no idea how long S30 world will take to get it here, but they say they have a warehouse in the US, so maybe not too long.

 

I'm hoping that based on how smooth and stable the fuel pressure was (for the 20 minutes I ran the car for) with the feed/return line coming out of my red gas can as opposed to the gas tank itself, that I may have found the culprit. 

Of course I'm still looking at other issues, too, since I doubt this was a cure all, but the engine did sound like the closest to a normal happy engine I've heard since I bought it (though like I mentioned, it did stumble and recover after I revved it once.)

Feedback on next steps in the meantme?

While waiting on the tank and fresh engine harness I plan on :

- Cleaning contacts

- Replacing vacuum hose

- Adjusting valve lash (It was listed in the FSM as something to check/verify during the troubleshooting process.)

- re sealing valve cover

Edited March 9 by NocturnalEmber

[NocturnalEmber]

9 hours ago, siteunseen said:

I dropped and refurbished my 1st tank on the '77 I still have. Honestly it was a waste of time and a little money, the car didn't run any better. At the end of the very "long day" it was the coolant temp sensor resistance to the ECU. It could be your fuel pump? 

Now the '72 240Z I bought was a whole different story. That tank was like a porta-john's tank minus the big breath mints.

This isn't rust, wouldn't stick to a magnet, just old fuel and sediment. The car sat for years with fuel in the tank, eventually turning to pretty much dirt.

 

 

 

That..is an enormous amount of sediment/dirt, etc.

If the temp sensor wasn't brand new (I still do need to perform the test at the ECU though) and if the car didn't run and hold normal fuel pressure for the 20~ minutes I had it running when the fuel feed/return lines were connected to my red gas can I'd be more skeptical that it could be the temp sensor, or that the temp sensor might have something major to do with it.

I do still plan on testing it though, just to be safe. But I'm hoping the major culprit was that the tank has some sort of blockage in it considering how my fuel pressure went right to normal levels and the engine ran mostly fine when I took the fuel tank out of the equation.

 

 

[siteunseen]

Most folks just leave the valve cover gasket dry without any type sealant for the off and on you'll be pulling it, until you get it right then just once a year or so to check valve lash. I run those cover bolts down with an electric drill set to the lowest possible strength setting, that's always tight enough for mine. No leaks. Have you read about using ant-seize thread lube on everthing? It helps.

 

[NocturnalEmber]

Well, it's been awhile, but the tank finally arrived. Unfortunately, S30World no longer has a warehouse in the states and sent it NLPost/USPS, so there was a bit of a tracking black out until it got to/cleared customs. They also just didn't use packing material on one side of the box, so the seam on the left side of the tank wore through the cardboard and got bent. I'm really hoping this tank doesn't leak because of how close the seam is to where it bent. They seem open to working with me though if there is a problem, so that's ideal. Hopefully that stays the same if I end up needing a replacement.

 

I managed to get the factory tank dropped and stopped there for the night.  Somewhat difficult to see in there, but it looks like there's sediment on the bottom, but it doesn't look too bad. I'm hoping the pickup screen inside that cylinder that I can't see inside is where the problem lies, because when I used the gas can as a makeshift fuel tank, that seemed to solve the problem (and when I crimped off the return line, the fuel pressure stayed the same, so I'm hoping its a clogged tank being that the pump and filter and rubber lines are all new.)

 

I've got the tank mounting bolts soaking in brake parts cleaner, they were caked with dirt/grease, and I didn't want to damage the threads.

 

Does anyone happen to know if its safe to use fuel injection clamps on those two vent hoses on top of the tank?

 

The clamps that were on there weren't rusty at all (or the one on the filler neck either now that I think about it) but I did somewhat disfigure the head getting them out, so if I can replace them with EFI fuel clamps that I happen to have a surplus of, that would be ideal.

 

Edited April 5 by NocturnalEmber