Intermittent Loss Of Power-1972 240Z Stock

[bartsscooterservice]

I used to have that problem to, it turned out the carbs where worn out, basically it got to much fuel, and fooled the plugs after a while and it started bogging etc.. misfire. But since your carbs are rebuilded..

 

Maybe the coil is burning the points, or there is something wrong in the distributor..

Edited April 15, 2015 by bartsscooterservice

[AWAUDIO]

Hi all, once again thanks for the thoughts and suggestions.  As the problem is intermittent, points are new, coil voltages look ok, plugs look good (front 3 and back 3 the same) and it pulls like all get out when it runs, I'm going to try the tank and then filters screens on carbs. I think the fact it was bucking so bad last time, cleared the debris so I could get home.  The first time it happened I replaced all the stuff mentioned above, it ran great.  2nd time it happened, I replaced points, rotor, condenser, ran great, then failed.  So I'm hitting the tank first.  I've looked at dropping it, any advice along those lines?  I have both FSMs/Chiltons/and yet a 3rd manual, but pointers from those who "have been there, done that" are always appreciated.  Thanks again for your time and suggestions.  Andy

[siteunseen]

Here's a step by step with a lot of pictures for a 280 tank removal,  http://atlanticz.ca/zclub/techtips/fuel/gastank/index.htm

 

240s are a little harder because of all the evaporation tank lines.  I replaced everything though so I just cut them at the tank and got it out of the way.  Spray the straps bolts and all the hose clamps the day before.  50/50 ATF and acetone in a trigger spray bottle works better than anything I've ever used and for the price you'll get a lifetime supply, at least for me.  1 quart transmission fluid, 1 quart acetone is less than $15.

[AWAUDIO]

@siteunseen  THANKS  I use the same 50/50 solution (I also have a Jeep I'm working on), so absolutely that is what I do before starting.  BTW I've found for frozen bolts, if you heat them up, and squirt the solution on them hot, it will wick into the threads.  Do it a couple of times and bingo…breaks free.  Also, first thing I'm doing is the pressure test which should be at 3.41 lbs, and volume test, which should put out 3.71 quarts of fuel, at 1k idle in under a minute (per FSM).  Then to the drain plug, cheap slosh and look for debris.  FSM says there's a gas strainer in there.  Thanks for the the tank reference.  Andy

 

PS  are you on BAT?

Edited April 16, 2015 by AWAUDIO

[AWAUDIO]

@blue  I'm going to check those filters as Bruce sent me a bunch of gaskets!  Thanks, your posts are always spot on.  Andy

Edited April 16, 2015 by AWAUDIO

[siteunseen]

 

 

PS  are you on BAT?

I don't know, what is it?  If it's "Bring a Trailer" then no, I'm a buyer/hoarder of Z stuff as long as I can afford to.  Someday my heirs might be but they've been instructed to post here 1st.  I've added my username and password to my will, with a stapler not an attorney. 

[AWAUDIO]

Researched cleaning and dropping the tank.  It appears some folks just pull plug and flush the tank in place.  One person said they did it with a garden hose in the tank.  Stuck it in thru fuel filler and pressure flushed.   Kept flushing until no more debris came out.  Not sure I want to use water, but if I let it dry out I don't think there would be a problem.  Vent lines are all up higher.  As long as I don't damage fuel float sending unit, and only fill it with a gallon or so of water,  it looks like a good first try before dropping tank.  Would not be offended if someone pointed out this is a bad idea….   Andy

 

PS  Yes, I know, no sparks or flame source anywhere near an empty tank.  There are still enough fumes to easily ignite.  And yes, disconnect the fuel outlet line at the tank to prevent water from getting in the lines.

Edited April 16, 2015 by AWAUDIO

[rossiz]

two reasons to flush the tank: 

 

1) get rid of the crud that's in there

2) protect from the same thing happening all over again

 

drop it, have it hot-tanked and coated and you'll never have to mess with it again. dropping the tank is done in an hour or less depending on if you run into frozen fasteners. you'll also have the opportunity to blow out your hard lines and replace soft ones, both of which will need to be done if they are original.

 

another cheap, stop-gap alternative is to put a clear filter between the tank and fuel pump. i did this to tide me over until i do a full tank refresh. i've had to replace the $3 filter just about every couple of months. i installed an in-line shutoff gate valve between the clear filter and the tank so i can do the swap with little drama in about 15 min. but it's still a PITA and not a permanent fix.

[Patcon]

I don't like the water idea. The volume of fluid is a good idea and the water is safe, but if your tank doesn't have rust in it now. Flushing with water is very likely to remedy that...

Charles

[AWAUDIO]

Ok sports fans, It's NOT the tank.  My tank had fresh drain plug and washer.  Looked like it had been dropped.  Straps all clean and threads very clean.  Drained the tank completely.  Drained it and filtered gas thru 2 screens to check for any debris………there was none, zilch, nada.  Refiltered it thru finer mesh before returning it to the tank…….nothing!   That gas was so clean it looked like spring water (kinda).  For future drainers, drain with gas cap on, it's slower, but lets you control the outflow so you can switch cans. So now I'm going to clean line between engine filter and rear flex hose to tank.  I'm also going to check tank hose for cracks, as air leaks could be sabotaging me.  Keep the comments coming.  Andy

 

PS  Have fuel pressure gauge coming from Amazon.  Do Not buy the Napa version, it's set up for vacumm, not 3/8" fuel lines.

[Patcon]

If the vacuum advance was jamming or hanging up, would it cause this?

C

[AWAUDIO]

From what I understand, you can disable your vacuum advance, and run it that way.  It's also intermittent, which compounds the problem:  runs perfectly for x amount of time, then loses its mind:  lurches, bucks, will not accelerate, but will idle along ok.  Will also rev and idle and look good in driveway w/o a load.  On the road, either perfect or perfectly disgusting.