'72 240Z quit...

[Mr.Woof's72z]

I feel terrible posting in this section for my first post but it needs to be done...First off this is my first car (dreams come true), never thought it would be possible, but I picked up a '72 240Z with 83,550kmi, triple webers w/ k&n filters, rear sway bar, Monza Exhaust(I think, can't find the name right now...guy gave me 2 to be exact), 15 inch rims/tires, whaletail, urethane front, plus extra goodies like nice new fuel lines, new wiring harness, performance springs (unsure what make or spring load) and a few others here and there. Problem is the guy who sold it to me had inherited it from a friend meaning that he knew nothing about what his friend had done to it previously. Anyways, I picked it up for $3,250...fair deal in my opinion seeing as it ran beautifully, EVERY gauge, light, electrical piece worked and the body was the best I've ever seen...white with red accents (hood lines, sideskirts). Now that you guys have an idea of the car...

About a month ago it started fowling the plugs, typical sign of running rich. I called up the mechanic who had done work on it for the previous owner, he mumbled something about jets being changed and I haven't been able to get in touch with him since...no good. I know very little of what they had done to the car before besides what I see with my own eyes, foolish on my part I know but in the excitement of me possibly owning my dream car I overlooked that issue as the car ran perfect for 3 straight months.

2 weeks ago I drive the car a round trip total of about 300 miles. Upon returning home my Z started backfiring, running rough at anything below 2,500rpm (and later anything below 4,000), and generally just running like, well...crap. I had noticed this pulling onto my road dropping down from 60 MPH to about 30. By the time I had reached my driveway the car would not run below 4,000 RPM so I decided to coast in. It has not run since. Checked the spark plugs, uber fowled, brought out a brand new set, still nothing. Well school finals got in the way and I could not get around to anything else before I went home for break...now I'm at home while my poor Z is sitting in CO while I'm in NY.

I've done research for a few days on here trying to figure out the problem without asking. Seems to me most people say to check the fuel filter, lines, tank, making sure there is no gunk, debris, etc. This doesn't seem to be the case though since I turn the car over and will flood the engine if I keep going. On top of that it ran great for 3 months prior, right up until the last few miles home. Are my Webers crapping the bed? Am I not getting a spark? It seems weird that everything ran fine up until that road trip and since then the car has gone belly up...

I do live in high elevation (Steamboat Spings, CO...I know, not ideal for a Z but come on, $3,250?!?!?!) and have heard of the jets needing to be replaced, though people also say that adjusting the carbs will work. Any input is greatly appreciated, I don't have access to the car until a week from now but I would love to get a laundry list of things to do/check/change etc before I head back west. Hope you guys can help me get her going like she was before, it's a dream to drive and almost as good as that are all the looks I get when people see a 19 year old driving a '72 240!

[Cethern]

First welcome to the site.

My first thought would to lean it out with some new jets. Was the car always in Steamboat? Look for vacume leaks, was the car sitting for awhile? Could be some bad gas...

Do a search for Webber carbs see what turns up, I have not messed with them so I'm not much help. But the car could be ready for a good tune up.

If you get around Denver there are a few members along the front range I like the rest enjoy meeting other Z owners.

Eric

[jerryh]

My 2 cents on your sick Z

Back firing through exhaust, look at carbs or fuel supply.

Back firing through carbs, look at ignition system.

Runs good one day then bad next day, fuel problems, supply, fuel lines, dirty jets, bad gas.

The first thing I do when I have a problem with decreasing performance is change fuel filter and perform volumn check at supply line to fuel rail (carbs).

Good luck

[Mr.Woof's72z]

The car was in Steamboat for some time, probably not it's whole life but the original owner was building it up in Steamboat, not quite sure what for but that is beside the point. After the original owner passed away the car was sitting for some time (I want to say 5+ years but I'm not sure) not running before the guy I bought the car from finally got the title. Once he got the title he had a mechanic take a look.

Now this only happens in small towns but I happened to meet the daughter of the mechanic because she recognized the car and I up at college. She told me that her father, the mechanic, had taken the entire motor out, cleaned everything out (very vague, but it's word for word), and added the front spoiler/body kit. That would lead me to believe that he had taken apart the entire fuel system since he did put the new gas lines on. So I'm assuming it's not bad gas and since I've bought it I've only put in 91 (no 93 in Steamboat or the majority of CO and it's killing me).

It does back fire through the carbs, though there is also a low, muffled backfire that comes almost right where the headers meet up with the exhaust, leading me to believe there's a leak somewhere and the gas ignites once it hits O2. I could feel it when I drove because it was right underneath the pedals. ***I also have 3 into 1 headers, older headers so I don't know the brand. Thanks for all the help so far, especially the vacuum and the difference between backfiring. If it does just happen to be through the carbs what should I look at in the ignition system? What would have changed in 3-4 months that would be a good candidate for the source of the problem? I've also heard gapping the spark plugs to .040 instead of the .030 or .032 that is recommended helps with rich systems, any truth to this?

[Mr.Woof's72z]

I forgot to ask earlier but where is the fuse box? I lost my tail lights but not my brake lights, I'm assuming its a simple fuse change but I couldn't find it to save my life once I found out my lights were out (thank you CO State trooper). If anyone can help me out with that as well that'd be great.

Also I was wondering how to post a classified ad for all the spare, original parts I have like air box, original springs, hub caps, headers, exhaust, etc. I know there might be a rule like I must have __ many posts before I can but I figured I'd ask. I have no need for them and I am not looking to restore to original condition (I can't drive a slower, less performance-oriented car now can I?) and I'm sure there is someone that is looking for 80kmi-condition original parts (best I can describe them).

Cethern- where do you live in Denver? I would love to meet up with some other Z owners. There is a guy up here who used to race automatic Datsun's back in the 70's (lost his left leg) and I've been trying to get in touch with him concerning my car. Funny story though: I had some guy at a stop light in downtown Steamboat jump out of his car and run up to mine, knock on the window, and as soon as I had rolled it 2 inches he yells "I've got a 1973 240Z!" and then run back into his car before the light turned green. I guess Z owners are a different breed...

[hls30.com]

lift the panel in the console that is below the radio and contains the defroster switch. The fuse box is in the area it covers.

Will

PS http://www.classiczcars.com/classifieds/index.php

[240jetjoc]

Mr.Woof's72Z,

Many Z owners with triple Webers comment on their Webers being very finicky because of seasonal weather changes - humidity and temp changes. What's changed in three or four months is the weather. Your problem could very well be carburetor jetting not being appropriate for the season. Find a good mechanic experienced in Weber jetting and tuning.

If you're going to run Webers, I would recommend buying a couple of books on Weber carburettors and doing some reading. One book that I have is the SpeedPro Series "How to Build and Power Tune Weber & Dellorto DCOE, DCO/SP & DHLA Carburettors". The author is Des Hammill. Also, go to the HybridZ Nissan L6 forum and read the "sticky" on Weber carburetors. It's well-written and very informative.

Welcome to this forum and enjoy your 72 240Z. I'm a big fan of the 240Z and currently own three of them, including a nice 1972. You'll find folks on here to be very knowledgeable and eager to help.

[Mr.Woof's72z]

Thanks for the fuse info, wouldn't have ever found it just by looking...And thank you very much 240jetdoc for pointing me in the right direction. I've been eyeing that book for a while, now I have a reason to buy myself a Christmas present. I forgot to mention that I was under the assumption that weather played a huge factor and my next post was going to ask who, if any, run their Z in colder climates. I already feel terrible about having the Z in a cold weather climate so please don't make me feel worse than I already do. I'm transferring this year to a place nice and warm where I can work on my car and follow my other passion: paintball.

So, does anyone run their car in high elevation, cold weather, humid/dry weather, or any combination of the 3? I would love to find someone who has figured out a good setup for higher elevation/cold weather conditions. Thanks again for all the info, I've figured out more in one day than I did in a week of trying to find info online. I guess that's what these forums are for...

[EScanlon]

There is an often over-looked and common problem to the Z's ignition system that will also produce many of the same symptoms you've described.

The Vacuum Advance Slide Plate under the main plate of your distributor, is simply two sheets separated by ball bearings held in plastic holders. Over time the plastic ages, gets brittle, and the ball bearings fall out and the vacuum advance will not operate smoothly. Sometimes the vacuum is enough to shift the plate, and then with vibration will return or not...all depending on the vaguaries of chance.

Simple enough to test for: Remove the distributor cap, and disconnect the vacuum hose at the intake manifold or simply connect another hose to the vacuum port on the distributor. As you apply vacuum (whether with a pump or simply by sucking on it) you should see the point plate move AND return smoothly. If it does not, or if by peering past the point plate you see little ball bearings rolling around, you need another slide plate.

2¢

E

[Mr.Woof's72z]

In doing some more research I found this...

"6. The DCOE and IDF ultimate performance family of carburetor are not compatible with a vacuum advance distributor system. You will need to recurve your distributor or adjust the timing to compensate. You may also want to purchase a performance mechanical distributor."

It came from http://www.webercarburetors.com/ppw/html/aplication_guide/important_things_to_know.htm

Could this be a problem? Do people that put the DCOE (Triple Webers for Datsuns, etc) use the mechanical distributor or adjust their distributor? I guess what I'm asking...is it general knowledge that you should change your distributor or at least adjust it accordingly when you put Triple Webers on? I'm kicking myself now for not doing more research on the car while it was still running great but I suppose that's why I didn't...

[Mr.Woof's72z]

p.s. anyone looking for new distributors should look at www.centuryperformance.com ...cheap

[Mr.Woof's72z]

Upon reading more in the HybridZ forum on Webers I realized I forgot to mention I get a flat spot/no power if I'm at low RPMs (below 3k) and I floor the car. Seems to be a common but I figured I'd throw that out there.