What we have done/tried:
Engine has been totaly rebuilt to STOCK specs. Total of about 1 hour on new rebuild.
MAF has been both swapped and cleaned
All emissions have been removed. Unused Vacum lines capped off.
Plugs, wires, Cap, Rotor have all been replaced.
Injectors swapped
ECU Swapped
Power Transistor swapped
Distributor swapped
Fuel Pump replaced with a NEW Walbro 255LPH High Pressure pump
Fuel tank replaced with a Racing Fuel Cell
Fuel Filter replaced with a stock filter
New TPS
Exaust is removed after the collector
Transmission Wireing and Speed Sending unit are NOT connected.
Dash has been removed
O2 Sensor has NOT been changed
FPR was Swapped
Belts, Hoses are new along with new Radiator

Best we can determin is that the ECU is cutting fuel flow by turning off the injectors but this is hard to confirm. We say it is a fuel cut off because when the engine fires again thare is no smoke from a fuel rich condition that would occur if spark was cut.

With so few sensors giving input to the ECU why would it cut fuel? We are not even getting close to the 6000 rpm area that one would expect for a rev limiter.

Sorry for the long post but I want to give a complete picture and hope that someone can give an answer. There are other simalar posts but none that either say what was finaly replaced to correct the problem or we have allready replaced what they did.

PS: Please do not sugest swapping to a DOHC or SR20 etc. We race a stock class and must run the original motor type. Turbo etc also not allowed.

Thanks in advance for your thoughts and ideas.

Dirt is for Racing, Asphalt is for getting there. Have fun, Play in the Mud.

I did try running the car at 5000 (after cleaning) and it held RPM fine. I then unpluged the MAF and it cut out just like it did on the track. I think we are on the right track. We will know more after the next race (next Saturday)

Thanks for the sugestion. I will post more when we know more.

Basicly nothing changed. We did replace the MAF Connector and did not fix it. We dis find a frayed wire going to the Power Transistor and repaired that but it made no diferance.

One other thing we found out is that we can run up to about 4500 in second WITHOUT the engien cutting out but only upto about 3000 - 3500 in 3rd (the gear we need to race in.)

Can any body tell me under what conditions the ECM will decide things are so bad that it must shut down the engine? We think that the ECM is getting confused and is eather getting a signal at the wrong time or not getting a signal it is expecting and it decides that all heck is breaking out ant to sut down as an act of self preservation. Seams a little advanced for this gen of ECM but thats is all I have right now.

Any othr Ideas guys? (and gals if you are around) We are stumped.

1974 KA24DE Powered Datsun 610 coupe

I don't think it is Fuel Pressure as we did swap the FPR with another one from our non-running doner car. If fuel pressure was low, I would expect the engine to slowly die off as fuel required exceded supply. That is not what is happening. In this case it is like throwing a switch. But only under load. We can run 5000 all day long as long as we are not in gear.

THEN.....
we went to mode one to check just hte O2 and expected to se flashes 5 or 9 every 10 seconds depending on which referance you use

BUT....
We say NO flashes. No error code but an O2 that is not working. Went and picked up a new O2 and we now have flashes. We are going to go to a dry lake bed on Saturday and see how it runs.

We swapped the MAF and it made no differance. Our best guess now is that the ECU is not getting the MAF signal for some reasion. We hafe checked the obvious and now are going to start striping doen the wire harnesses lookin for either hidden damage or an old repair that has failed.

Any thoughts or sugestions?

Could it be the transmission? How does it run in 5th? You mention some wireing is not hooked up... is there a reason for that?
What about timing? Have you taken it to any knowledgable people in the auto business?

It seems to me that your having problems with your tranny. Not the mechanics, just the wiring I suppose. You enjoy free reving under no load, but are having trouble when travelling. Was the car running before you made it a track car? If so, I would suggest you consider the things that you have changed first.

When we swapped the trans we found out that the wiring for the trans was torn and cut out. We just left the wiring dissconnected.

We have not tried the car in 5th gear as we don't have the room. This is a total race car. If we take it on the street big trouble.

I understand your thoughts but what I don't get is that when you look at the wiring, other than the speedomiter output of all of the switches are "open" unless you are in reverse, 4th or 5th. If it does not "know" what gear you are in why does it effect the problem?

Right now I will probably reconnect the trans wires just because they are not connected and should be but I don't expect a big change. I hope I am supprised.

Thanks for the input and keep the ideas coming.

After re-wireing some parts of hte harness (none of the injectors) I fired up the car and it was not running right. I pulled injector wires one by one and found that we were only running on 2 cylinders! (2 and 3)

I had been working with the ECU so I double checked the connection and all looked well. When I moved the wires the idel smothed out etc. Thought that was odd so wiht the ECU sitting on the floor I just flicked the wires with my finger and the engine died. Re-started it and tried it again. Flicked it again and the idel would change etc.

So it lookes like we have bad wires at the ECU connector even though they look good. We are going to try to swap engine harneses with one from our doner car and see what we get. I think the ECU being exposed to the eliments in this race car took its toll. Once I get it working right I am going to build a cover for hte ECU.

We did swap the ECU Harness last night. We now are running on 3 cylinders. A 50% inprovemnet #4 is not working so we have to swap that injector out and then head to the dry lake bed to test it this weekend.

I think we are getting close. When we get it fixed and win a race then I will post a picture

Ok most recently we found that the #4 injector was not firing. We had swapped injectors before to fix this and ASSUMED it was fixed. Everyone knows what happens when you assume. first time we swapped all four but this time we swapped just #4. Still not working. Seeing as we had changed the injector and the wiring harness (for differant problems) the only thing left was to swap the ECU.

Low and behold #4 injector starts working. Reset the timing and things run great (we think). The car seams to have a lot more power (duh!)

No time for testing so we head to the track.

Start of the Heat Race my son hits the gas and to make a long story short it took the entire front stright for him to crash

Broken left front strut bearing (aka Strut Mount) and lots of fender damage for me to fix. Oh, well. Thats Racing.

Also the car still falls off above 3500 RPM. Has to be MAF. Nothing else left. Changed ECU and Harness.

I will update when I have more to report.