ZCar Forum banner
Status
Not open for further replies.
1 - 11 of 11 Posts

· Registered
Joined
·
6 Posts
Discussion Starter · #1 ·
I have a 76 280z that has a FI or timing problem. I beleave it is electrical. The enigne is not getting any gas or at the wrong time(such as when the intake valve is closed). If I use starting fluid it runs ok. I don't know how the computer knows which injector to fire. Computer, fuel pump, injectors, and regulator all test fine. I had to change the dist. and now have this problem. I have checked the crank and cam timing. Any help would be great.

Rob
 

· Registered
Joined
·
103 Posts
Distributor off 360 degrees?

You changed the distributor and "now have this problem"? It would appear that your problem would then be related to the ignition system. Your hypothesis that the engine must get getting gas at the wrong time ("when the intake valve is closed") would appear to be not valid, since the fuel mixture can only enter the combustion chamber through the (open) intake valves. A common mistake is to install the distributor with the rotor pointing to the Number one plug wire when the timing mark is on Top Dead Center. There are TWO top dead centers....one for the compression stroke and one for the exhaust stroke. I would suggest that you pull the distributor, turn the engine (crank) around one full revolution (360 degrees) to the OTHER top dead center, and then reinstall the distributor.
 

· Registered
Joined
·
600 Posts
Rob,
The FI fires all the injectors at once. It is not a sequential system as you seem to be thinking. If you are getting fuel pressure at the injectors then your hook-up with your new distributor is probably at fault. The FI (EFI unit) uses a pulse signal from the distributor to fire the injectors. You can also "listen" to your injectors for a clicking sound by putting a long screwdriver to the injector body and the handle to your ear to make a crude stethescope. If they aren't clicking, they aren't firing.
Retro
 

· Registered
Joined
·
1,351 Posts
I am curious. HOw can the computer fire all of the injectors at once, since the pistoons must be at different positions around the circle at any one time? THis is probably a sfq, but I am not a trained mechanic. Thanks.
 

· Registered
Joined
·
972 Posts
This is called batch firing as opposed to sequential firing. Although we have 6 injectors they operate more like a modern Throttle Body Injection system then typical Multi-Port Injection. Although some cylinders get a "fresh" charge of fuel and others get fuel that has been in the intake runner for 5/6'th of the cycle, the burn difference is neglegable.

The performance increase that modern engines have over our L28s have less to do with the injection method and more to do with "smarter" fuel mix and ignition timing control.

ConorP
 

· Registered
Joined
·
6 Posts
Discussion Starter · #6 ·
Re: Distributor off 360 degrees?

I pulled the #1 Plug and removed the valve cover. I set the piston to tdc after the intake vavle closed. Is this correct? The dist. only goes on one way. Does the Dist. only make 180 deg while the crank makes 360? I can get a good run with starting fluid. There is no back fire through the intake or exaust.
Thanks for the help, Rob
 

· Registered
Joined
·
6 Posts
Discussion Starter · #7 ·
Should the injectors have 12v + on both wires going to the injectors when not being fired? Does the system only fire once for each 360 deg revolution of the distributer? If so what fires the injector. Or does it fire with every spark
Thanks for the help Rob
 

· Registered
Joined
·
600 Posts
I believe the ECU fires the injectors by grounding them, so you should be able to read voltage on both injector leads. I believe that the injectors fire once for every revolution of the distributor.
 

· Registered
Joined
·
3,207 Posts
Your approach is wrong....

Hi r5sims.
You should begin a problem such as yours by starting at the basic's and working out to more involved systems from there. The fact that you even mention your distributor makes me suggest this. First, start with readjusting your valve timing. If you don't know how to do this then Mr Haynes and Mr Chilton are good sources for information as well as here at Zcar in the ' Archives ' section. My 02 from this distance would be valves way too tight and a possible vacuum at the distributor not connected properly.Goodluck. shane-
 

· Registered
Joined
·
4,289 Posts
The '-' side of the ignition coil is connected to pin 1 of the ECU in your car. This acts like a tachometer input to the ECU and serves as a precise way to time the moment of injection. The ECU sees this as a negative going pulse and after every third pulse the injectors are fired.

The ECU fires all the injectors at the same time, once per crankshaft revolution.

Wayne Monteath
Masham, Quebec.
 

· Registered
Joined
·
6 Posts
Discussion Starter · #11 ·
Thanks for the info. It explained alot. I am now wondering if someone has monkeyed with the cam timing. When the #1 piston is at tdc my timing mark is about 8oclock.? Shouldn't this be on the measurement scale at tdc? The v on the cam and the oblong hole are 180deg out but perfectly alligned. My manuals say this is all wrong but it was running before??? Could the engine run with just the cam 180deg out? I set the #1 piston to tdc after the intake intake valve closed. and aligned my dist. to fire on that point. IF I retard the dist. it fires through the exaust and if I advance the dist. it fires through the intake????? Sounds like the dist is 180 degrees out but the cam seems right? Could the high and low side pickups on the dist. effect this? Thanks For the help in advance. ROB
 
1 - 11 of 11 Posts
Status
Not open for further replies.
Top