engine giving me issues... movies and photos included

[crazyoctopus]

Alrighty lets get to it.

 

car: 10/1972 240z with an L24 and an E88. completely stock engine.

 

I have recently been able to get my car to move under its own power, but it seems that problems keep coming about. Yesterday while taking her out for another test drive she drove fine for about 1/8th of a mile then she started to sputter, i gunned it and once i got past 3kish rpms the car pulled like I was hoping this car would be capable of. but as i started a to do some normal driving, 2k rpm cruising and 3krpm shifting the car started to sputter, lean pop, and backfire again and again.

 

brought her back into the drive way and started testing there. she revved fine and it seems that whatever the problem was it was gone. and then after i let it idle for awhile it came back. so i came back here and started looking at what to do. This is what I have done in hopes to stop the problem.

 

cleaned both of the carbs, replaced gaskets where needed

checked float - 10.31mm

checked timing - 0deg

set valve clearance - with engine warm .012 exhaust .010 intake

checked carb air balance - unisyn at idle

checked carb fuel - tried colortune on cyl. 1 and 5, but it kept acting up and resorted to the SU carb tuning tech on classiczcar

checked timing again - 0deg, and jumps to 20+ when at high rev.

 

then I let the car sit for a night because it was getting cold and damp. double checked all of my info and found that: the timing should be at 7-10 deg not 0, i should balance the carbs at 3k rpm not idle, and colortune at 3k rpm on cyl 2 and 5.

 

started the car up this morning, in hopes that it would all be sorted out with the inproper set up, but it obviously wasn't.

 

here is a vid of the first start up

 

 

that pop at the end is both backfire and a lean pop. awesome.

 

So I started to re-tune everything.

 

timing now set to 8ish deg

 

[crazyoctopus]

synced the carbs with unisyn, backed down all of the screws equally and set idle to 650-700 rpm. turned off the car, and then pulled the #2 plug

 

 

looks normal, and they are less than 20 miles old. stuck the colour tune on and here is what it is at idle

 

 

and then i set the idle to 3k and tuned it.

 

 

movie doesnt show it well, but color that I achieved, bunsen blue with hints of orange.

 

turned off the car and pulled #5 plug

 

 

tuned the rear carb at the same rpm and finally got the same color that I got in the front.

[crazyoctopus]

then I checked to see if my needles and nozzles were binding.

 

 

the rear piston is a bit harder to pull up than the front, so I am planning on dunmping the ATF and using some 10w30. To see how the carbs were actually balanced I used the lifting pin to see how the engine ran on only 1 carb.

 

 

from what I have read about the pins, the carbs look to be too rich, but according to the colourtune they are at their best. So meh.

[crazyoctopus]

Then I checked to see how the car revved through the power band. All of the jumping around is me playing with the throttle.

 

 

It seems that all of my problems were solved! So I took a photo of my temp gauge to show you all what "normal temp" is on the car, to see if that is what everyone else sees.

 

 

and while i was doing that the car started to act up again.

 

 

so i checked to see if both carbs were actually working, twice. and showed you the difference in nozzle richness.

 

So yeah... I have no idea what is wrong. please someone give me some advice. The only thing that I think it could be are the needles and/or nozzles, but why would it only happen after the car was warmed up, or under load?

[Pomorza]

I cannot help you on the running issue but it sounds to me it is running rich. The temp gauge is high for my standards. In my Z (280) the gauge usually sits under the midway point even on the hottest days here in Arizona. It looks as if you car is running hot for some reason.

 

Jan

Edited March 9, 2010 by Pomorza

[ozconnection]

I'm impressed by the amount of effort you went to to document your problems. Well done!!

 

Your timing is perhaps a little retarded at 8 degrees. I would like to see at least 12 degrees to improve your engines performance at idle and on the throttle. Your current timing could also cause your temperatures to be registering as high but it can also be influenced by other things such as thermostat temperature opening point and the condition of your cooling system. My guage shows the same as yours and I know my cooling system to be in good working order!

 

As for setting up your carb's, I can't help you with that. I'll let others who know these things better chime in.

 

Cheers

[yetterben]

Trash in the carbs, plugged filter, weak pump. When i had my 3 screw's i had to have a electrical pump dont ask me why but the stocker was not doing it.

[crazyoctopus]

i'll check for crap in the carb system again, hopefully that'll be the case. I did just clean everything when I pulled them apart 4 days ago, but i'll go back and look at the float as well as re-clean the nozzles.

 

i changed the fuel filter a couple of weeks ago, maybe i'll replace it with a clear one so that i can see if it is getting dirty.

 

and as far as the pump goes, it was replaced a couple months ago with a brand new one, i'll take it out and clean all the insides to see if there was any gunk that has been stuck in it. as far as the electrical pump goes, did you just get a universal 5-7psi pump and put on a pressure regulator? or just have the pump set to what it needed to be set to.

 

i'll make the correction to the timing after i get the morning's coffee, and then i'll start pulling things off and cleaning where need be.

 

thanks for the input hopefully this will help me get this thing finally running right.

[crazyoctopus]

okay so I replaced the fuel filter with a clear one, re-cleaned my needles, piston, and nozzle; set my timing to 12 not 8, the richness to 2.5 turns down; then tried to start her up again.

 

with the lack of every bit of emmisions it takes a bit of work to get her running, but once she does start she is quick to turn over. once i got her running she was lean poping here and there so i made adjustments to both of the carbs and within about 5 min she was running normally.

 

I checked to make sure that the carbs were synced, and there were a hair off so I made the adjustment. checked the richness of the carbs by the method decribed in classiczcar, and then sat in the car and this is what is going on.

 

this is probably one of the best examples of what happens.

 

 

I am making a run to the parts sotre and picking up some brake cleaner to see if there are any vaccum leaks after i post this, and then check the float level (forgot to check while i was cleaning).

 

I am almost damn positive that it is a fuel at this point, and I am pretty sure it has to do with the rear carb. The reasons why I am moderatly sure that it is the rear is due to it needing a ton more richness. then again, it could be that vaccum leak and it needs a crazy amount of richness just to get the right mixture.

 

On a related note, I think, I am occationally hearing rod knock sound coming from the rear of the engine, cyl 5 & 6ish. This is my first pistoned car and am not really used to sounds like this, but from what I have gathered does this mean that the rear is running lean? it doesnt happen all the time, and I have yet to really pinpoint when it exactly does.

 

hopefully this will bring more light, and spark more ideas in your heads to help me figure out this issue.

[Daeron]

Wish I could help more, but one thing you can confirm is adequate fuel supply from the pump. Disconnect the output of the pump from the carbs, and find a safe way to pipe it into a clear container. Pull all the spark plugs, (to make it easier on the starter motor) and run the starter for a moment to monitor the output of the pump. It has been so long since I've done this, *I* wasn't even the one doing it (it was my dad and I was 12 and ignorant) so I can't tell you off the top of my head how much fuel you should get, in how much time, but the FSM may well have a figure for that test, or someone here may chime in.

 

Although, after watching that video, an intermittent bad pump seems doubtful.... However, the fuel lines may well benefit from being blasted out.

[Xnke]

Check the oil levels in the carbs, and check for vacuum leaks. That is almost pinpoint dead on what my engine ran like with a vacuum leak on the front carb, and no oil in either carb.

 

Of course, my lack of oil is probably just superfluous, and it's just a vacuum leak.

[crazyoctopus]

daeron - i doubt it is the pump, that thing is way new, and the frequency that i have been replacing fuel filters (whether i needed to or not) it should be more than fine.

 

xnke - the oil in the carbs have never been more than a month old, and they currently have fresh 5w-20 oil in them. I tried to find if there was a vacuum leak, but the car never raised rpm wherever i squirted carb cleaner or brake cleaner. If anything it kinda died a little bit, which is completely backwards to what used to happen on my old 7 (rpm goes up when you spray and there is a leak).

 

 

 

I cleaned and made sure that both of the floats were at 24mm through the blow through method; blow through the inlet tube and once it stops the air that is where it'll sit, measured twice with calipers. the float needle, or whatever it is called, is the one from thezstore and stamped with 1.7, the older ones that i has were both 2.0; dont know if that could help.

 

After i did this it seems that the car is running worse... i re-synced the carbs, adjusted richness on both carbs, and the rear is still much lower (near complete bottom) than the front.

 

noticed that i am spitting some white smoke out of the back of the car, so I am sure that i am running rich somewhere. Also noticed that the engine slows down its RPM whenever i turn on the e-fan, would this also mean that the spark plugs are getting less juice, and therefore not getting enough to explode all of the gas in the chamber? I have been planning on the GM alternator as well as the 280z HEI mod, but was kinda waiting to get this problem sorted out before i went crazy with that stuff.

 

all the signs, especially xnkes comment, point right toward a vacuum leak. but without the engine revving up like i am used to i have no idea; I'll head to the auto parts store and pick up some starter spray and see if that does anything at all for tomorrow's attempt.

[Xnke]

Check your brake booster; they can be a vacuum leak too, internally. Won't show up with the spray unless you get it inside the booster; hard to do

 

Pull off the brake booster line and cap it off, see if it fixes it.

[crazyoctopus]

i have a fresh can of starter fluid so, pardon the fps cliché, i'll be spraying and praying.

[yetterben]

make sure you check around the throttle shafts.

[70 Cam Guy]

make sure you check around the throttle shafts.

 

agreed, my first set of SU's had bad leaks around the throttle shafts and made it impossible to balance. Actually my first set was so bad that I repaired the rear carb only to find the front carb was leaking too. Vacuum leaks were so bad on the rear that the front went undetected until the rear was ok.

 

In my recent experience, carb clean or brake clean does not raise the idle but you can stall the engine with it.

[crazyoctopus]

hmm kk. well i am going to let the car/back rest and see if I can get it to stall while spraying carb cleaner in those areas again. I did try something else though. I ran the carbs lean, so as to get lean pops, and check if there was any bit of smoke sent out anywhere but the main inlet. low and behold there was a spurt that came out of the throttle bushing. I dont know if this proves that there is a lean right there, but i am going to try to reproduce it, as well as try to stall the car with some spray repeatably.

[crazyoctopus]

cant get her to even start right now, so i am going to wait until tomorrow to see if that is where the final problem lies.

 

and if it is the case, i have searched and am unable to find carb throttle bushings anywhere. the only way that i have seen the possibility of getting one is by sending the carbs in to get rebuilt...

[rags]

Simple way to find out if you are running out of fuel is to put a fuel pressure gauge in the fuel line after the fuel pump. My guess is you will see very low fuel pressure. Once the bowls run dry the stumble will start. Bowls fill up and the car will idle fine. Quick, free check for peace of mind. If that all pans out, hit the throttle shafts with a blob of axle grease to see if that makes things better before tearing the carbs apart.

 

Joe

[crazyoctopus]

i did the check earlier today and i am hitting a solid 4psi right out of the pump. also did a compression test (cold) and they were avg 120 +/-5 across all of the cyl. i'll try that gob idea tomorrow before i start the engine up, makes sense.