STILL having issues!!!

[mjr45]

This is about the 80th time I've posted with the same problem on this car its driving me stone crazy.

Problem: Stumbles and bucks above 4K under load. Runs great up to 3800. Occasional miss at idle. It ran great with very very slight stumble above 5200RPM after re-doing the fuel pump.

Whats been done: I've run all the checks and tests suggested by Zed Head, Fastwoman and others, kudo's to all for their help. Fuel pump rebuilt(new O rings and check valve) makes 37-38psi at idle, drops to around 30 under load, new injectors, new fuel line clamps, new fuel lines, new pressure regulator. No rust in the lines or at the pump. AFM calibrated per Blue at Atlantic Z. TPS adjusted. New CTS and Thermotine, checked OK per EFI Bible, new spark plugs and wires, new rotor and dizzy cap, timing at 10°. Has a 79 dizzy and ignition module. Vacuum is at 14.5", compression average 120 (this is at 9000'). New rubber boots on the intake. Spark plugs are black, tailpipe has lots of black soot, exhaust smells a little like fuel. Gas mileage is about 15mpg. You can see the miss at idle on the vacuum gauge( gauge is steady then drops about 1/2" then back to steady), doesn't happen with every engine cycle just occasionally.

My guess is ignition but at this point I don't really have any good guess's.

[siteunseen]

I put an Accel coil on my '77 when I was trying to figure out mine. That wasn't the problem though so I can't say it helped any, but that looks like the only part you haven't replaced.

[Zed Head]

Considering the time, effort and aggravation you've spent so far, maybe a trial of a GM HEI module would be worthwhile. $25 and some wiring versus $75 for a new ZX module. High RPM weirdness is a typical failing module sign.

It could also be the distributor though. Have you checked the gap between the iron rotor and the pickup points? Described n the 79 FSM. The rotor needs to be perfectly centered. The pickup coil magnet tends to break on the ZX distributors also. I've seen it but don't know if they still work when broken.

If you're not in to wiring or electronics, maybe $100 for a spare distributor would be worth the money. Or, maybe you could borrow a spare from somebody.

[mjr45]

site, I've got a new Accel coil on this b***h.

Zed, I've thought it might be the ignition module, so' I'll gladly spend the $25 for the GM HEI and give it a try. Up where I live there is only one other Z around and I've only seen it once last year. There are a few more in Colorado Springs, but no one I know. I've got an old(75) dizzy, but I'd have to hook up the old ignition module, ballast resistor etc., or could I use the old dizzy with GM HEI?

[mjr45]

Just a quick question, can I mount a GM module into the old 75 dizzy instead of externally?

[Zed Head]

The old 75 distributor will work great with the GM module. Here's a diagram that I spent a few days putting together. Connect the red wire to W, the green wire to G, and B and C as shown. Make sure that the mounting grommets are electrically grounded.

Missed the internal part. There's not enough room inside for the GM module. But, if I was going to do another one I might mount it in the cabin where the old ignition module was. The red and green wires from the distributor run all the way there, along with the old coil positive and negative wires. You might need to fabricate a mounting plate. It would take some time with the wiring diagram.

For a test though, it might be simpler to just run jumpers from your ZX distributor. You can take the ZX module off of the side and the two wires you need will be right there. Choices.

Edited April 25, 2014 by Zed Head

[mjr45]

Thanks Zed. I'll have to dig thru my boxes of Z stuff and find the old dizzy. What can I use for a heat sink and being real electrical savvy, how much of the module has to be covered by it?

Mike

Edited April 25, 2014 by mjr45

[Zed Head]

I edited my other post with a few more thoughts... In case you missed them.

[EuroDat]

Im having a problem with mine atm. It misses or more like hits a rev limiter when its under load. Starts and drives great, its only when you accelerate hard that it starts playing up. Its not the same problem your having, but its starting to be a pita.

I had problems with water in the fuel an thought it might have been something to do with the efi. Now starting to check the ignition system.

I checked the dizzy and noticed the dizzy shaft has a lot of sideways movement. About 2.5mm. It also has a compensating spring on the opersite side of the pick-up. Not sure what the purpose of this spring is.

Not sure if that can cause problems on an electronic ignition system. It can cause problems with dwell on points dizzy's. There is nothing in the 1977 FSM about sideways tolerences.

It will be interesting to see how you go with the 75 dizzy.

Chas

[mjr45]

Euro, I'll probably just stick with the 79 dizzy and wire in the GM module. The dizzy is so tight in the holder that to remove it I have to undo the bolts that hold it to the block. You're right, PITA.

[madkaw]

Mike

If you are interested I will send you my dizzy complete with coil module everything that worked perfectly before I took it off a month ago.

I would suspect your ignition, but this would eliminate that part of it.

PM me if you want to try it.

I believe my set up is from an 81

[mjr45]

madkaw, PM sent. Thanks.

Mike