A few Questions about AFM

[FastWoman]

Nothing looks suspicious in your numbers. You would expect #6 to look very different from 4 and 5, which would look very different from 1-3. Nothing looks that way. Your compression numbers are a bit on the low side, but not alarmingly so. They simply reflect wear on the engine. By comparison, the old marine engine on our boat -- a Chrysler 318 -- has compression numbers more like 100 and 95, and it still somehow runs quite well.

Your #6 just looks way too shiny. Maybe your #6 injector is blocked up, so that it ticks but doesn't spray. Does your exhaust make a regular chugging sound -- i.e. where the chugs are regular and evenly spaced? If so, that indicates one of your cylinders isn't firing. Also does your engine run the same if you pull your #6 plug wire?

[argniest]

Yeah, I triple and quadruple checked my compression and leak down test numbers...once I learned how to do them. So I think they are good numbers to go by, and I am not leading on a wild goose chase based on bum data Of course I know they would have been better hot (and with the throttle plate/flap open). I realized that now in retrospect. So I am just assuming my psi readings would be even higher if I did those things..

Well OK, its sounding like I could put my rocker cover back on, and then do some of these other tests. And hold off on the valve adjustments until later. Everyone is being so helpful with so much information!!!!!!! I think I should start it up and try some of these tests.

What are chances a brand new injector isnt working? I got them from my Z guy who has been working on these for 30+ years and only sells good quality stuff.

And you know what, I think the car IS making a chugging sound. I mean its so hard to explain coming from an apprentice like me, but yes, I would say it chug chug chugh chughs down the road. It seemed worse before those local mechanics changed the timing last week. now it seems less noticable. but still there somewhat. I dont know if changing the timing changed the chugging of if its just *ME*. And also, after they changed timing, I took off from their shop and the car had more power than ever before. But I know the engine is still all messed up. Im just saying...it had more power when taking off, it was smoother accelarating, more power up hill, definately more power available between 3000 and 4500 rpm's. In fact I never even heard the car sound that way before in the power band. But then, we have the bad looking plugs and bad gas mileage.

It seems I need to start up engine, pull #6 spark plug wire (NGK) and hopefully not get electrocuted when I do it. I have never touched them when it was running before. SCARED! But you know I think I saw those other guys pull them off when they were playing with the timing, etc. I would like to one by one, pull each spark plug wire, and listen to engine, and take note of if it changes engine sound. Also, shouldnt I do the same thing with the fuel injector connectors? I mean if I pull the electrical connection to each injector, shouldnt it make a very noticable change in the sound of the engine???

Edited April 17, 2011 by argniest

[FastWoman]

"Chug chug chug" indicates a nonoperative cylinder. I'm betting #6. You should be able to hear it when it's idling. Walk around to the rear of the car for a better listen.

Do be careful when pulling a wire. I think it helps to hold the plug wire with a rag, but you also have to be careful to keep the rag (and your fingers) away from any moving parts. A perfectly respectable alternative is to hook up your vacuum gauge, start your engine, note the vacuum, shut it off, pull the #6, restart, note the vacuum, stop the engine, plug back in the #6 and unplug the #5, start, note vacuum, stop, etc. If you've pulled the plug on an operating cylinder, your engine vacuum will become weaker, and you'll hear a difference in the "chug chug chug," which might become "ch-chug ch-chug ch-chug." If the engine runs the same with a pulled plug, that cylinder isn't firing.

Pulling the injector plugs one by one is another perfectly good approach, but you'll need to free up those little wire clips first. They can be a PITA. Also you might fail to diagnose an intermittently bad/dirty injector connector this way.

[240260280z]

Do all of your injectors have the same colour of plastic and same part numbers (if visible)? Something simple like mismatched injectors could be the problem.

My Z had 3 different types of injectors when I picked it up from the previous owner.

Did you have a chance to confirm that you have a spark on plug #6?

[argniest]

Yup all my injectors came from a recognized icon in the Z industry. Im not naming names but I am sure many of you know about this little company from the NW. The injectors are all the same. They are all new. All new orings, new hoses, new injectors. The only problem in this equation is "ME". Operator error.:tapemouth

As far as the clips on the injector electronic connections, well I aint got nun! They are long gone. Another thread I got going here, I am talking about replacing those wires for the injectors with these new white wires that have the quick disconnect clips on them. I havent done it yet, well, because I am running around like a monkey in a barrell of banana's right now....

And no I havent started car back up...was kind of waiting for a little more input (on another thread http://www.classiczcars.com/forums/showthread.php?41966-noob-valve-adjusting-on-1978-280z&p=361283&viewfull=1#post361283 ) about whether or not I realllllly need to adjust valves or not. Based on the data I collected last night. So right now the rocker cover is off, but if I get confirmation. I will put it back on and adjust valves later. And then I can do some of these other things you all are suggesting.

Edited April 17, 2011 by argniest

[FastWoman]

Without the wire clips, your #6 injector plug might have wiggled off.

I suspect you could bend some reasonably good wire clips out of paperclip wire. It would have to be a pretty small paperclip to give you a small enough wire diameter.

[argniest]

Well, I always check them, before doing a test drive. But who knows...the plastic on the FI connectors are all busted enough so it cannot accept any of the normal/original clips anymore. So I do think its connected, and remember I can hear #6 clicking like all the other ones. So I was assuming it was working. Of course I cant see what its really doing, but the spark plug that is basically clean and shiny in #6, seems to be telling us something is wrong.

I still have all the other FI's...they were mismatched too, I had at least two different kinds. But if #6 is truely dead, (I do find that hard to believe since its brand new but still) I could try to use one of the other ones, that I know at least was working....based on the spark plugs from the prior incarnation of my engine setup.

But that would require me removing the fuel rail again and all the other injectors, and i REAAAAAAAAAAAALY dont want to do that unless I am 100% certain that #6 is not shooting any fuel. So I guess I just simply have to start up the engine, and one way or the other run it with and without #6 spark plug and # 6 fuel injector, during different tests. And see how it sounds. If I am feeling brave I may just pull the plug wire off. I swear I have seen several people do this now when having it at local garage in past few weeks. If it doesnt make any difference to how engine is running, but the other ones do.........wellllllllllllllllll that to me, tells us we have a problem with #6. I could rap on it too, dont know how hard. If its stuck. but how likely is that also? hmmmmmmmmmmmm

Edited April 17, 2011 by argniest

[FastWoman]

I think since you don't have any injector clips, just pull the injector plugs to test the cylinders. No need to pull the plug wires.

Don't rap on the injectors. There's no need for it. If they're not opening, rapping on them probably won't help.

If your injector connectors are really that crumbly, I'd plan on replacing them. You can grab a set off of Ebay. I've dealt with this guy, and he puts together a nice set:

http://cgi.ebay.com/ebaymotors/injector-connector-kit-6pc-datsun-280z-280zx-300zx-_W0QQcmdZViewItemQQhashZitem43a04f8954QQitemZ290452375892QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

I'd suggest ordering 5 more of these for the following:

temp coolant sensor

thermotime switch

cold start valve

air regulator

1 spare for testing purposes. (Sometimes it's great to be able to plug something into a part to do a test.)

You'll need to know how to solder and work with heat shrink tubing. Instructions available on YouTube. (It's very easy.)

Edited April 17, 2011 by FastWoman

[argniest]

Yup I already have some of those kinds of connectors for my fuel injectors anyway. But havent changed them, well, because Im caught up doing so many other things. Its like what to do first, my head is turning to mush.

[FastWoman]

I know the feeling oh so well!

Even so, the crusty, crumbly connectors might be part of your problem. I'd go ahead and replace them sooner, rather than later.

Edited April 17, 2011 by FastWoman

[argniest]

The pictures shows #1 and #2 hoses that I disconnected for HVAC system and plugged them off and the intake hole I plugged off too. But the picture doesnt show that I also disconnected the brake booster vacuum hose too. I should have numbered that #3. But then you know where its at anyway.

I decided to remove the vacuum lines for the brake booster and the HVAC system from the equation (someone else was talking about HVAC causing vacuum problems. I unplugged the two hoses from he intake manifold, and then capped them off using a small section of vacuum hose with a bolt in the end of it. I also removed the hose from the fast idle actuator and capped it off. So basically, from a vacuum standing point, things were simplified a lot. If I understand correctly after looking at the system in the engine area, and also the FSM, that means I have effectively removed the HVAC vacuum from the system. So if HVAC was causing a vacuum problem before, after removing those hoses from intake etc...that it could not be contributing to a vacuum problem after removing them.

Is it possible the ECU is powering up the injectors (because I swear I can hear them clicking) but not sending the correct kind of a signal to the injectors to spit out the fuel ... or not at the right time, or not enough or too much of it?

I was also wondering about the dropping resistors, since they are the last stop from the ECU to the injectors. I see a test in the FSM for the Dropping resistors that I am going to try tonight.

I noticed those two hoses were sharing the intake runner for #6,5,4 cylinders (but mostly nearest #6 runner). Well after removing those vacuum lines, it had no effect on engine performance So that seems to tell me it had nothing to do with those systems. I thought maybe I had a smoking gun. But nope I guess not.

**************************

So what is VERY interesting to me is this, in the process of testing for HVAC vacuum problems, I decided it was time to also pull off the fuel injector (electrical) connectors, one by one, from 6,5,4,3,2,1. Well I cant believe what happened.

As soon as I pulled FI electrical connector for #1,2 and 3, the engine immediately took a nose dive, and plugging it back in, it went back to its normal sounding speed. But when I removed 6,5,4 fuel injector electrical connectors NOTHING HAPPENED. The engine sound did not change. I tested it many times last night and this morning earlier. Although one caveat, when I plugged #4 injector connector back in, the engine for about 1/2 second picked up speed, and then settled back down. And every time it was repeatable. Pull #4 off, no change, plug it back in, a small bump up in the engine sound and then back to original sound. Unplug #5 and #6, no change in engine sound. I waited like 30 seconds sometimes...still no change.

I dont know what this means yet, but if the engine isnt responding to pulling off the FI connectors for 6,5,4,, and combined with the spark plugs on 6,5,4 looking odd (#6 looks clean like its not doing anything, and 5 and 4 are black -even after 30 or 40 miles of driving) this cannot be a good thing for the engine performance. Any thoughts or ideas why 6,5,4 are acting like that, when 3,2,1 are acting how I would expect them to operate.

Also, someone else asked me about whether or not I have good spark. I had a technician hook up an oscilliscope/computer tablet screen last week, and I called him back today to verify and tell him what I found out about the FI connections, and he said based on what he saw with his 20 minute inspection with the computer/oscilliscope that we are not looking at a spark plug issue. He said the secondary ignition system firing pattern and burn time looked fine, and we didnt have any misses...except maybe a tiny little on #2

This makes me think we are having a fuel related problem, and that the injectors are not delivering fuel correctly. Also, I might be getting a fuel injector tester because someone has one I can borrow, or I can go there and have them tested while still on car by a technician, just to make sure the injectors themselves are working (they are brand new injectors and were not on the shelf very long). I would like to believe these new injectors are working in the sense that they are physically capable of delivering fuel, but its the ECU that is causing the issues or maybe the dropping resistors?

Edited April 19, 2011 by argniest

[240260280z]

You can feel if you have a spark by pulling each plug wire off one at a time while idling an noting how far away the plug wire is from the top of the plug when the spark jumps. Try to measure maximum distance on all plugs. Forget the tech with the tablet analyzer, these engines are very crude and easy to diagnose with your senses.