240Z with 280ZX Engine Swap Goes to WOT When I Start Engine

[cruisedirector]

I'm hoping to get some help and I'm new to the forum.  I've searched this site as well as the web to find the answer to my problem and I haven't found it.  I recently purchased a 70 240Z that had an engine that wasn't running well because of valve and rocker issues.  

I bought an engine from an 82 280ZX and installed it this week.  I took the SU carbs (which were working fine) and intake from the 240Z and installed them on the 280ZX engine.  The engine came without a distributor so I purchased a rebuilt Cardone to install.

My problem is that when I start the engine, the RPMs immediately start climbing even though I am not pressing the gas pedal.  I started it 6 or 7 times and then had to shut it off almost immediately because the RPMs just kept climbing.  Here's what I know and what I am thinking:

I installed an electric fuel pump to replace the mechanical pump on the 240Z.  It's a low pressure pump designed for carbureted engines.  It seems to be working fine.

When I installed the new distributor, I noticed 2 things:  First, I can't tell if I have an E12-80 or E12-92 ignition module because where it is stamped on the outer case of the module it has been scratched or gouged so I can't tell if it says 80 or 92.  It has 2 connectors on top and doesn't have a connector or a little "ear" sticking out on the side like the E12-92's I've seen pictures of.  Second, my rotor was not pointing where it should have been when I installed the distributor but since the distributor slot is offset I didn't think there was any way I could have installed it wrong.  But, when standing on the driver's side of the car looking at the distributor, the rotor was pointing at approx the 3 o'clock position when I had #1 piston at TDC.  From what I have read, the rotor should actually be somewhere around the 7 o'clock position.  The distributor wouldn't go in any other way so I installed it the way it was.  Then I read a couple of posts on one of the forums where guys said they had the same problem but the engine still ran fine.  Others said they had to change the spark plug wire connections on the cap to match where the rotor was.  So, I did that.  I put #1 spark plug wire on the distributor cap where the rotor was at TDC and then continued the firing order.  Didn't work.  It backfired like crazy, so I went ahead and put the spark plug wires in the "correct" positions, with the #1 wire at the 7 o'clock position.  It fired right up but the RPMs immediately started going way up and I shut her down.  Same thing every time I've started it.  

I also followed the instructions in several forum threads for wiring the 280ZX distributor into the 240Z harness.  I removed the ballast resistor and connected its two wires together.  I connected "C" on the ignition module to the "-" side of the coil and used a "y" connection to connect the "ignition on" lead from the harness to the "B" side of the module and also to the "+" side of the coil.

I'm thinking maybe I do have an E12-92 ignition module and this is causing the problem.  Does that make sense?  I can't think of what else would cause something like this.  I haven't been able to time the engine because I have to shut it down almost immediately after I start because of the rising RPMs.

Edited December 1, 2013 by cruisedirector

[Josh280z]

Get yourself a timing light and tune your carbs, maybe even rebuild them. You might even be running too much pressure with the fuel pump.

Edited December 1, 2013 by Josh280z

[NewZed]

The only thing that keeps any engine from destroying itself is control of the air supply.  If you have too many RPM then you are letting in too much air.  Check all avenues for air in to the cylinders.

[cruisedirector]

Thanks guys.  Before installing the engine, I took the fuel injection and intake off and replaced it with the intake and SU carbs from the 240Z motor.  I used a new intake gasket and torqued it properly, but I've read that there is a section of the cylinders of the 280ZX head that are not covered by the 240Z intake but the gasket is supposed to cover those sections to prevent a problem, but maybe that's not the case so I will investigate.

 

I have a timing light but can't time the car because I can't leave it running.   As soon as I start it I have to turn it off so I have to fix the run up RPM problem before I do anything else.

 

Thanks again for the replies.  I check for any air getting into the engine.

[dexter72]

As has been suggested, check for a vacuum leak at the intake manifold and cylinder head.

 

Make sure you didn't catch anything like a line or bracket, in between the intake manifold and cylinder head as well.

 

I have seen that before.  

[9/73-E31-260z]

Did you have the choke on? I started my car with the choke sort of stuck on and it did what your engine seems to be doing, I turned it off and fiddled with the choke and then it started fine.

[cruisedirector]

OK, I went out this morning and without changing a thing, I tried to start the car.  No go.  I can smell gas so I know the fuel pump is working.  I tested the coil and I have 12V going to the "+" side of the coil but the coil didn't seem to be firing.  Since this coil was designed for use in a system with a ballast resistor, which I bypassed when I put the 280ZX distributor in, I bought a new coil designed to be used without a resistor.  Still the car wouldn't start, so I checked the coil input and output again.  It was same as with the old coil - 12V going in but the coil isn't firing.  So, I'm thinking I may have a bad control module on the distributor.  

 

And after more research, I'm pretty sure I have the E12-80 control module.  It was late at night on a long day when I ordered the distributor but when I looked back at my emails I realized I did order the distributor for a 1980 280ZX and not a 1982 so it is supposed to have the E12-80 module.  Just wish I could read the numbers on the outside of the module to be sure.  At any rate, I'm leaning towards either getting a new control module, or buying an HEI module and doing the conversion.  Any thoughts?

[Fuzzydicerule]

Two Things i can think of

 

-Choke stuck open,  make sure the linkage is not pulled tight

 

-Throttle linkage is not installed properly,  unhook it and make sure the butterfly valves are fully shut,  also make sure they have their return springs.