90 engine dead tach

[lemonsy]

Hi,

I've done some searching and have seen this issue pop up but it has mostly confused me more, due to the number of variations there are.

I've got a 91 4G63 with the tach interference unit in the coil pack.

The engine is swapped in a 93 420A car and main harness, but the ECU is swapped for the original ECU.

The motor harness is from the 91 and has been repinned for the 93 main harness.

She fires up and runs, but no tach. Neither with the original dash or the 93 dash.

I understand that after 91 the tach interference isn't needed anymore, so could I change something in how the engine harness is pinned into the main harness so that the 93 dash tach would work? Or would that f*** with the signal to the original 91 ECU?

Thanks!

 

[ThunderChild]

Uh... what? 93 420a running on 90? Or 91??
Show pictures so we know what you're talking about, this seems strange...

 

[pauleyman]

are you sure you dont' mean 90? 91 up tach should be the same.
You need to clarify what you're saying. I'm guesing you had an NT 1g car (which is not a 420a) and you swapped in another 4g63 from a different year but you didnt' specify turbo, non turbo etc.
Need more information.

 

[steve]

There were two types of ignition setups on 1G 4G63 cars, the original 90 style where the tach interface is on the coil pack and the 91-94 type where the interface is in the power transistor. Perhaps you could explain again what parts you have?

 

[lemonsy]

Mmh sorry for the poor explanation.

Originally I had a 93 with a 420A, the 1.8L engine. We blew that engine due to poor fuel system and overheating.

I found a 1990 with the 4G63 naturally aspirated and got that to go in our 93 car. The 1990 ecu and engine harness came with it, but the main harness inside the car is still the original 1993 harness. Neither the 93 dash or the 90 dash work at the moment.

My friend did the repinning of the engine harness of the 1990 to the 1993 main harness, but something may have gone wrong there as it was all a bit confusing.

What would be a good next step to try and get the tach running?

The temp sensor and oil pressure sensor do work and I could swear I saw the speedometer work for a moment (with the 1993 dash), but no clue what happened there.

 

[ThunderChild]

You originally had a 4G37, not a 420A. You need to research the 1.8 non-turbo to 2.0 non-turbo conversion, I don't recall all of the harness differences off the top of my head, but I thought you had to add in connectors, or swap the entire dash harness.

 

[lemonsy]

Thanks for the correction.

I did research those, like this thread https://www.dsmtuners.com/threads/the-1-8-4g37-to-2-0-4g63-swap.166976/, but most of them make it sound straight forward in terms of plugging it in. I haven't found anything specifically there about the tachometer issue.

Whatever searching I have done it on it leaves me more confused. Would the advice from this post apply https://www.dsmtuners.com/threads/90-model-dead-tach.410779/ or should I try to trouble shoot it differently first?

 

[pauleyman]

I'm guessing you have a full 90 engine items, coil, power transistor etc. You need to choose if you are going to run 90 or 91 up electronics.
Let us know everything you have for sure.

 

[lemonsy]

Everything on the engine (coil, ptu, ecu) is from the 1990. The only thing maintained from the 1993 is the dash wiring and whatever trivial stuff is in the engine bay (windshield wiper motor, brake booster). The transmission is also from the 1990. The speed cable itself is from the 1993.

I really appreciate all the help btw.

 

[pauleyman]

So you have a 1990 cluster as well?

 

[lemonsy]

If by cluster you mean dashboard then I have both and I have tried both, with no luck.

 

[steve]

Make sure you have the wiring correct from the coil pack tach gate to the noise filter to the ECU to the cluster to start with. The 93 gauge cluster might not like the signal but the 90 should.