mikedick6969

Just got this 75 280. Went to go fire it up today, and it would not go. My brother drove it to the storage where it sits a few months ago. Now it will just fire up, and putter out. My cousin got it runnin for any period of time at all by tensing up the spring manually on the AFM. You guys think its AFM related, or maybe a fuel pressure issue? Plugs and wires are new, and I put new gas in it as well. I seen that write up about refreshing your AFM, and will probably try that tomorrow. Any additional tips on what I could look for would be appreciated.

jfairladyz

raising the tension on the AFM spring leaned out your mixture. Chances are something is causing you to run rich otherwise. Could be the AFM, but I doubt it since tightening the spring helped the problem.

naviathan

I agree, tightening the AFM leans the mixture, but if it's not running for long enough to get any real reading from the AFM then I don't believe that's the problem. You need to check your fuel pressure and also pull your plugs and see what they look like. If you're not sure you can snap a pic of the plugs and post it here and we'll read them for you.

mikedick6969

Alright. Ill have to see if my brother has his digi camera on him and go there tonight if time permits. Thanks for the responses guys. Ill let you know.

mikedick6969

Update: He said he opened it, not close it. So now he has me checking the fuel filter, and spark plugs. Also the filter in the end of the fuel pump. Any other suggestions. He says its super lean.

mikedick6969

Well, changed the plugs and threw a bottle of 104 octane in there for the hell of it. It runs for like 5 seconds then quits. When you punch the gas, it makes a whooshing sound from the air intake. My cousin thinks its the temp. sending unit
making the ECU think the car is overheating. He bypassed the unit and it ran ok.
Needs a little tuning. Anyone agree with this, or other thoughts perhaps??

EDIT: Looked through my stock of parts, and the head on my extra engine is an N47. The one on my car is an N42 and the extra is N42. Which of these are better and why?

mikedick6969

Also just wondered if there was a difference in the years for the ECU boxes. I have 3 of em total, and im positive 2 of em work. I have one from each of these years: '75, '77, and '78. Upon some reading, I found that the N42 head is better than the N47. Is this true?? That would be cool since I have 2 of the N42's, and one of em is on my car ATM. Thanks in advance!

ASA240z

Mike some people can make a good argument about which of the two heads is better.

IMO I believe from what I've read that the N42 is better. The N42 has large valves thus helping with performance, so does the N47. The N42 flows pretty good and on a L28 with flat top pistons pumps the compression to the mid 10's. A down side to this head although not really related to performance is that this have soft bronze valve seats for use with leaded gas.

In comparison, the N47 also also flows pretty good, but some may argue that there is a restirction in the exhuast ports. this is because the N47 came with emission liners in the exhaust ports which were designed in the hope of buring up any unburnt fuel. On the bright side these heads came with steel seats for unleaded gas. Just like the N42 when placed on a L28 with flat top pistons would pump compression to the mid 10's.

There is however a drawback to this as on flat tops piston these heads can easily lead to pinging, since the the low quench chambers in these heads were designed for dished pistons.

Look around the web to find the opinions of other Zdrivers about the various heads.

As for the the ECU question, I believe there is a simlarity between the N/A ECU's. Just ask on hybirdz.org and get a wiring diagram to look if they are similar. Verify this as I am not entirly certain...

You'll like this, this is a L6 engine calculator that is posted on classiczcars.com. It'll give you an idea of the specs of various compents in building a Z engine...
http://www.classiczcars.com/forums/s...&threadid=1292

Also look at bryan's site, Zgarage, it has alot of info on these heads and other Z related stuff.
http://www.geocities.com/zgarage2001/

Hope that helps,

Allen

PooFlinginMonke

There is a micro switch in the air flow meter that controls the fuel pump.

If you crank and die, this is what does this.

It can also show up as an intermittent stalling issue.