No RPM signal...what to check?

[!^3]

I just installed an AEM EMS. Here is the timeline of events:

August: Installed new race motor

September: Drove car around with race motor but with old parts (SAFC, 16g, 550's, etc.) Ran perfectly.

Beginning Late September: Installed AGP 50 trim turbo kit, AEM EMS, 5-bar MAP sensor, GM IAT, AEM UEGO wideband O2, FAL slimline fans, 720's, all stainless lines, AEM fuel rail, AEM FPR.

Today: AEM EMS is not receiving any RPM signal when the car is cranking. There is no voltage being sent to pinout 21 on the EMS (crank signal, same one used when the SAFC is installed for RPM signal). I don't know what would have happened between when the race motor was running and right now that would have affected the RPM signal.

Bad igniter?
Wire splitter that is still attached to the RPM signal for when the SAFC was installed is causing trouble? (it is just attached to the wire and not connected to anything else).

Anyone else had lack of RPM signal problems? What things should I check on? Thanks!

 

[jott5555]

check for the tach noise filter unit.. its a small silver box and origionally it was located on the rear of the intake manifold on the drivers side.

that is one thing.. keep in mind this is a 90 only unit. on 91-94 the unit was intergrated into the ignition module.

good luck

 

[4g63swap]

I assume that you still have a power transistor pack check the white wire in the middle of it if its loose you wont have any tach readings. had that trouble with mine come to find out that the tach wire came loose when relocating the power pack. it an easy fix thats where i would check first. let us know what you find out.

hope this help
4g63swap

 

[!^3]

Thanks for the tips.

It turns out that the groun on my CAS harness was hot so I have a short somewhere that must have come around when I took the old turbo kit/ECU out and before I installed the new turbo kit/EMS. Hopefully tracing the ground to the short and a quick re-ground will fix the problem.

 

[JamiesTSI]

Couple of items. Does "stat sync'd" go to on when cranking? If not check to see if the crank signal and cam signal switch on and off. AEM needs both signals to work.
Do you have 5 volts on two of the CAS wires, battery voltage on one of the wires and continuity on, I think pin number four, on the wire harness?

 

[!^3]

IT RUNS!!!


I feel like the biggest idiot...there are four harnesses in the dash area...three go to the EMS and one goes to a relay thingy. Well, to make a long story short, the relay harness somehow became disconnected which carries things such as fuel pump signal, cam/crank grounds, etc. Plugged that in and she purrs like a charm...kind of. Won't idle less than 1600rpm, but the car was doing that before the EMS/turbo changes so I am thinking there is some mechanical problem; either a boost leak or something of the like.

This is the happiest day of my life

Thanks!

 

[coolnick]

check for the tach noise filter unit.. its a small silver box and origionally it was located on the rear of the intake manifold on the drivers side.

that is one thing.. keep in mind this is a 90 only unit. on 91-94 the unit was intergrated into the ignition module.

good luck

I have a 90 AWD with no tach signal and I just removed that noise filter because the intake manifold support is broken. Where should I mount the noise filter, and does it need to be pointed in any particular direction?

Thanks, sorry for the hijack....

 

[jott5555]

im just lettin it dnagle.. just zip tie it to something.

 

[coolnick]

I was baffled for a minute there, thanks jott!

 

[Mike1992]

I have a 90 AWD with no tach signal and I just removed that noise filter because the intake manifold support is broken. Where should I mount the noise filter, and does it need to be pointed in any particular direction?

Thanks, sorry for the hijack....

Before my turbo car overevved and floated 2 valves I had no tach signal either. I thought this was caused from a bad part on the coil pack. I got another coil pack, should I replace the noise filter to? Doing a full rebuild here and dont have a way to test anything right now.