EJ swap running w/ noisy injectors and tach bounces

[Mr. Brat]

I think I have this all hooked up right. I am positive that the injectors did not make this pulsing/rattling noise before I pulled the motor. Also I hooked my tach up to the yellow wire from the black connector under the dash. When the key is on and the motor is not running sometimes it bounces with the pulsation of the injectors. Wierd... Any ideas?

[Mr. Brat]

Also I didnt hook slpice in the check engine like wire from the ECU. Should I wire that in, and if so what wire do I tap it to?

[GeneralDisorder]

I seems easiest to run the tach using the yellow wire from the coil - that way you don't have a stray wire hanging out in the engine bay and no splicing for it under the dash. Worked fine in the '85 Brat I just did.

 

GD

[renob123]

I noticed a little bouncing with my tach, and it's hooked to the yellow wire in the engine bay next to where the ignition coil was. I think it's remarkable that it works at all, so I'm happy with it.

 

Yes, you should hook up the CEL. I wired mine to a new light sorta down by the fuses. It's on quite a bit, so I didn't want it somewhere directly in my field of vision during normal driving. The wire from the ECU is the ground, so you need to get switched 12V from somewhere. I tapped into the power for my MP3 player.

 

Jacob

Edited April 13, 2010 by renob123
Re-read original post.

[GeneralDisorder]

Bouncing tach is often a sign of a bad alternator - have you seen it bounce since you replaced it last night?

 

I just replaced the alt in my woman's EA82 sedan - all of a sudden we were driving and the ignition went to hell (no power) and the tach started bouncing like 1000 RPM throughout the range. Limped it home (3 blocks) and replaced the alt which had some bearing noise and about .5v of AC current comming out of the VR. Problem solved.

 

GD

Edited April 13, 2010 by GeneralDisorder

[renob123]

Bouncing tach is often a sign of a bad alternator - have you seen it bounce since you replaced it last night?

 

I just replaced the alt in my woman's EA82 sedan - all of a sudden we were driving and the ignition went to hell (no power) and the tach started bouncing like 1000 RPM throughout the range. Limped it home (3 blocks) and replaced the alt which had some bearing noise and about .5v of AC current comming out of the VR. Problem solved.

 

GD

 

Mine never bounced by that much. It went up and down about 2-300 RPM, if that. I haven't noticed a big difference so far, but I only have about 30 minutes of driving time with the new alternator. Most of that time was spent looking at the voltmeter and checking the coolant temp.

 

Jacob

[Mr. Brat]

Spliced the tach wire at the connector under the dash (no stay wires in the engine bay). The alternator is good and charging at 14 volts. I know this sounds bad but before I ran the wires threw the gromet behind the strut tower the tach and the injectors were fine, not noise nor bouncing. Before I ran the wires and relumed everything I striped out more wires the I had thought were not used. Cound this problem be a common ground that be hae been jepordized when things were moved. I came up with only 2 grounds for the EJ harness, which both came out of the harness that runs to the cooling fan. This seems like the only thing that makes sence to me. Should there be a common ground out of the ECU itself?

 

When the key is on and tach bounces it ranges from 200-800 rpms. Holds solid when the motor is running.

[Mr. Brat]

Did lot of checking tonight. found with the key being on and the engine off. When the injectors are clicking and the tach is bouncing, the coil is rapid fireing to the spark plugs and the injectors are dumping fuel. The only thing that I found that would stop all of this (besides turning the key off) is unplugging the alternator. Everything is quite. I cut the yellow wire, which is the signal to charge and plugged the alternator back in. No noise, no tach bouncing!

 

Any ideas?

 

Everything should work fine if I could find a wire that has a engine running voltage to wire to the alternator to turn it on. With this wire cut my volt gauge in the cluster is reding about 10 volts. If I hook that yellow wire to the positive side on the battery the alternator will charge and everything is fine.

[GeneralDisorder]

Give the yellow wire from the alt a new 12v ignition switched source.

 

GD

[Mr. Brat]

I tried that. Went to the key on position of the headlight relay under the dash. It still back feed and didnt change anything. If the alternator or the diode was bad you think this would cause the problem?

[Mr. Brat]

Went to the junk yard today and pulled another engine harness. Stripped it down and tried over again. BAM!!! it worked. I must have clipped a ground on the old harness and it all went down hill from there. So I took extra care and faness when stripping down todays harness. It works great and the fuel pump relay works the way it should be also.