2G No injector pulse good ECU & CAS

[Busdownthotiana]

Hey there everybody.

I’ve been trying to hunt down this gremlin for a good minute.

Was just cruising to a stop sign- she just shut off. Bust down thotiana. Rolled the car home since it was around the block, I started diagnosing everything I could think of.

Compression is 180 on all 4
Spark is good
Fuel is at the rail.

She’d just keep cranking.

Suspecting my ECU I brought that to ECMTuning and it checked out.

My next suspect was my CAS.

I have a 95’ and didn’t want to change my crank sensor located near the crank. Maybe I’m being preventative lazy, or my cam sensor so I opted to install a 91+ CAS.

I’m no diagnosing nerd but this car has made me have to become another person that curses a lot.

Wired up my own harness according to RRE’s tutorial I have both power and ground reading battery voltage at the power wire. Using my oscilloscope with my ground on the battery negative, it reads a good cam AND good crank sensor square wave..

I have spark, and fuel to the rail, no injector pulse. I verified that with a noid light from Autozone, some kit with 9 or so lights. Verifying battery voltage on all 4 injectors and using several varying pins that were capable of not ruining my injector harness- I verified with the 3 possible noid lights that I was not receiving injector pulse at the injector harness's via noid light.

Every test as far as for spark or for injector pulse has been possible by spinning the rotor shaft after unbolting my Cam/Crank angle sensor “CAS” while the vehicle was on the “ACC” mode or key in the ON position.

I read a thread talking about a TPS Throttle Position Sensor that was reading WOT during start up preventing flooding the cylinders with fuel. I verified this was not the case by disconnecting the TPS sensor and of course with the key in the ON position I spun the rotor shaft on the CAS and still no pulse.

I borrowed an ECU from another friendly DSMer who owned a 96’ GST same model and only off by a few serial digits. Same result, no pulse at the injectors.

Finally I’ve checked the ECU harness where pins I believe is 87/88 and also have verified signal on the scope for both good cam and crank signal right before the female plug goes into the ECU.

Both attached cam and crank signal readings are from two separate tests, one by the cam and crank harness in the engine bay and the other test was inside of the vehicle at the ECU harness.

If anyone has any suggestions please let me know. Also yes there is battery voltage at the injector harness.

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[Busdownthotiana]

Hey yall. I can keep you updated on the build thread I'm making. I'm attaching a log of me cranking INCASE this thread gets lost.. So far I've tested the CAS ECU signals (Cam and Crank), disconnected sensors 1 by 1, and am getting ready to check wiring from ECU to injector circuit, resistor injector module and the MPFI relay which is different on a 95 model. EPROM ECU with DSMLink v3 lite that just came back from ECMTuning.


I'll skip the bs here but you can find diagnosis steps in my build thread.

Posted log for a quick crank of the no start (no injector pulse) while cranking.

 

[Blinkyblinx9]

Accordingly to the diagram the injectors are fed a constant voltage from the MPI relay which is grounded at the ECU after the injectors to complete the circuit. Check for voltage at the injectors to make sure they are actually getting power. If not check for voltage into and out of the resistor pack (its up against fie firewall). Its not in the diagram for some reason but its there. If not that Check for proper operation of the MPI relay. Apparently that's where they get their power from.

 

[Busdownthotiana]

Hey blinx when you say diagram are you looking at a factory manual? I do have a manual somewhere…

I checked for voltage at the fuel injectors and am seeing battery voltage at each lead from the harness. At the resistor module I’m seeing within the specs, which is 6.45Ohms each resistor wire.

Also I’ll check into the MPI- on the 95’ there’s one relay- two in one. One side controls FP and the other side controls the injectors as you were saying. I don’t have a pin out of the relay though -_- I was kind of upset about that because the ones I’ve seen are for the 2 in one relay but the pin outs are different because the specific 95’ model has a different pin layout DSMWiseman Steve mentioned the difference in a post about the specific relay so I haven’t dug that deep into possible pin out diagrams.

For now, my ECU can communicate… which I believe- correct me if I’m wrong- since I can see the CEL for 5 seconds and off after 5 and my ECU and other important sensors runs off of the 20A engine fuse in the engine bays fuse box wouldn’t that suggest my MPI relay is functioning? I’m getting battery voltage at the injectors or is the relay in charge of the grounding control being sent to the ECU to send a ground?

I still gotta check what the voltage is coming out of the injector resistor module so I’ll check back with any other info after test results and after I’ve tracked down the closest diagrams so they can be in one place when someone has a problem with their MFPI relay and isn’t hopping around threads.

 

[Blinkyblinx9]

Each injector is grounded by its own transistor within the ECU. You can find wiring info here: https://www.dsmtuners.com/threads/2...ecu-pinouts-diagrams-tcu-diagrams-ect.528552/

Everywhere I have found it lists it as being relevant for 2Gs but I have noticed some inaccuracies. For instance section 4-17 shows the tach signal from the power transistor going to pin 31 of the ECU. Sure enough that pin isn't used on my ECU and no diagram I have ever found shows it as being used. You'll find the the rest of discrepancies I'm sure.

 

[steve]

Log says you have a huge injector pulse width and huge airflow while cranking which I find hard to believe. (7.5ms with 1000cc injectors?) Is this E85 Fuel? Charge up that battery too.
Hopefully one of the SD savy people here can comment on your sensor configuration and VE table. What's with the 3.1 global scaler on the MAF Comp tab.

What happens if you spray starting fluid in the intake?

 

[Busdownthotiana]

Log says you have a huge injector pulse width and huge airflow while cranking which I find hard to believe. (7.5ms with 1000cc injectors?) Is this E85 Fuel? Charge up that battery too.
Hopefully one of the SD savy people here can comment on your sensor configuration and VE table. What's with the 3.1 global scaler on the MAF Comp tab.

What happens if you spray starting fluid in the intake?

hi Steve! You’re the man I’ve seen on many a posts solve these dumb issues !

The tables that were edited were input by v8sareslow about 7 years ago when I got this thing tuned.

He moved some stuff on maf comp tab and the ve tables.

Not blaming him for anything, he dealt with a lot of issues I was having while he was trying to tune me up remotely.


I was going to spray some starting fluid in the intake but was trying to be a mcguyver before I went and cheated like that .


I had just asked Dave Mertz from ECMTUNING how to check inj pulse at pin 1.
"My question is would the same be possible on pin 1? Does pin 1 control the ground side to the injector? Where should I be measuring injector pulse if it’s not pin 1?"



The ECU provides ground on pins 1,2, 14 and 15 to the injector to activate (open) the particular injector associated with each of these pins. The ECU pins that are connected to the injectors should show 12v on them when the ECU is not activating the injector. The 12v passes as follows: MFI relay -> Injector resistor -> injector resistor -> ECU. With the ECU not activating the injector, no significant current flows due to the very high impedance of the meter, so there should be essentially no voltage drop through all of this wiring. With everything connected normally and the ignition on but without cranking the engine, the meter should show 12v on pins 1, 2, 14 and 15 of the ECU.

A noid light connected between 12v and the ECU pin should illuminate when the ECU attempts to activate the injector. I don't know if the 7ms pulse shown in the log would be sufficient to make the filament of an incandescent 12v lamp glow noticeably. When we test on the bench with an incandescent lamp we use a longer, more frequent pulse so the that filament will get hot enough to glow with the pulses.

Dave Mertz
ECMTuning, Inc.”



I will throw some fuel in the intake if I can find some brake cleaner, but for now I’m going to rig up a noid light up to 12v and pin 1 on my ecu and see if I can get a pulse on the noid light. I don’t see why it wouldn’t work!!?

Also I just did some research on the ASD relay. If that were an issue it would not create spark right?

Steve, I’m so glad you decided to give this post a view, always great to hear you chime in!! Also no it is 91 or 93 I haven’t driven this car in so long and when I put the new fuel pump and gas tank in I made sure to put new premium fuel in it and im not set up for e85.

I just need gopher to chime in now..

I’m going through full details of this diagnosis on my build thread if you’re interested in following me on the boring stuff.

 

[Busdownthotiana]

Alright so I did the mcguyver thing. I rigged up a noid light with one end on battery positive and battery negative on the other end rigged into pin 1.

I can actually verify now I have injector pulse at injector 1.

Don’t see the need to check the other 3 but I will, just to pretend I did something today.

I’m pretty much at a loss for words.. signal coming from ecu.. not making it to the end of the harness -_-

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Well now I feel like a mini Steve. Just without all the WHY IS IT WORKING figured out. The mcguyver ghetto rig mastery is almost tapped out.

Ok now that I have this info.. what can I do now

I’ll take it as a W BUT DANG WHAT THE HECK!

Also like I said I go into much MORE DETAIL on how I set this up on my car on my build thread. Here I’m just shooting the turd with some legends. Appreciate any input!

 

[Justin DuBois]

"+" BAT -> MPI relay -> resistor -> injector coil -> ECU "-".
Was the injector wired in-line with the light when you tested like that?

Injector coil test OK?
Resistor pack test OK?

 

[Busdownthotiana]

"+" BAT -> MPI relay -> resistor -> injector coil -> ECU "-".
Was the injector wired in-line with the light when you tested like that?

Injector coil test OK?
Resistor pack test OK?

Justin, thanks for replying man I actually was careful when rewiring my CAS and super impressed on your write up.

The “injector coil”.. you mean the resistance for ohms? I measured just under 3ohms on all 4 injectors. I actually read a post about a shorted injector causing a no injector impulse in another car. So I’ve ran some of the test with all injectors unplugged but am testing the circuit via noid light on injector 1. During this specific test, I plugged the harness into injector 1 and makeshifted the noid at pin1 and battery pos.

The resistor box is ohmed within spec as well.

I also verified 12v we’re going into the resistor box via the female harness side going to ecu, and 12 v on the resistor module side.

All 5 wires have 12v in and out. Idk if they are supposed to be less since it’s a resistor but I’m not exactly up to Steve’s knowledge and know exactly how the fairy’s work on hamster wheels to deliver the correct voltage .

For my simple brain and to explain as best as possible..

12v from EACH wire(including the white one) at the resistor box and back to the 4 wire harness leading back to I believe the ecu.

My relay I also believe is working since I can hear it clicking when I turn off the key. Also the fp is usually running while spinning the CAS and pressure is at the rail.

The injector was also connected while I ran this test.

So the injector plug usually has the noid light on it but was on the 1 injector while the noid light was make shifted on pin 1 and battery positive.

 

[Justin DuBois]

Justin, thanks for replying man I actually was careful when rewiring my CAS and super impressed on your write up.

The “injector coil”.. you mean the resistance for ohms? I measured just under 3ohms on all 4 injectors. I actually read a post about a shorted injector causing a no injector impulse in another car. So I’ve ran some of the test with all injectors unplugged but am testing the circuit via noid light on injector 1. During this specific test, I plugged the harness into injector 1 and makeshifted the noid at pin1 and battery pos.

The injector was also connected while I ran this test.

So the injector plug usually has the noid light on it but was on the 1 injector while the noid light was make shifted on pin 1 and battery positive.

Yes - if you can measure 12v at the ECU injector pins like the light bulb is indicating, that means the ECU is providing the ground, and you have +12v power all the way through from the battery - through the relay - through the resistor, and the injector coil, and the harness, all the way back to the ECU.

The only reason you would not have fuel is if the injector is clogged, pump makes no pressure, or the fuel filter clogged.

Justin

 

[Busdownthotiana]

Yes - if you can measure 12v at the ECU injector pins like the light bulb is indicating, that means the ECU is providing the ground, and you have +12v power all the way through from the battery - through the relay - through the resistor, and the injector coil, and the harness, all the way back to the ECU.

The only reason you would not have fuel is if the injector is clogged, pump makes no pressure, or the fuel filter clogged.

Well the thing is I have a new fuel filter, and new injectors and am trying to see why I don’t have injector pulse at the harness.

I understand why it wouldn’t work from the injectors I’m just trouble shooting this signal at the injector harness. Noid light works at the ecu but not at the point I need, which is any of the injector harnesses :/

 

[Justin DuBois]

Well the thing is I have a new fuel filter, and new injectors and am trying to see why I don’t have injector pulse at the harness.

I understand why it wouldn’t work from the injectors I’m just trouble shooting this signal at the injector harness. Noid light works at the ecu but not at the point I need, which is any of the injector harnesses :/

Did you test with the light wired serial like a Christmas tree light like this?
"+" Bat -> MPI Relay -> Resistor pack -> Injector coil -> Light -> ECU "-"

Do you get any codes from the ecu - like. "Injector Circuit malfunction"

I think you are saying that this below does not produce the same light result as above.
"+" BAT -> MPI Relay ->Resistor pack -> Light -> injector coil -> ECU "-"

 

[Busdownthotiana]

Did you test with the light wired serial like a Christmas tree light like this?
"+" Bat -> MPI Relay -> Resistor pack -> Injector coil -> Light -> ECU "-"

Do you get any codes from the ecu - like. "Injector Circuit malfunction"

I think you are saying that this below does not produce the same light result as above.
"+" BAT -> MPI Relay ->Resistor pack -> Light -> injector coil -> ECU "-"

“Did you test with the light wired serial like a Christmas tree light like this?”

Just are you asking me to do the same test with the noid light back on the injector harness with battery pos jumped to my MPI relay!? I think I might understand now.

Having a hard time understanding that sentence. Also to be a bit more transparent and make myself clear I hardly know what I’m doing here hehe.

After running this test with positive on the noid I did get an injector circuit malfunction code on DSMLink. Only for injector 1. The test I created was basically jumping battery positive all the way from the positive post with a long wire. I attached that long wire to one side of the noid and the other leg was also wired up to a jumper that went to pin 1 on the ECU. I was curious to see if I was indeed receiving pulse signals from my ECU.

Maybe what you’re trying to explain is the injector circuit.

I haven’t gone through the circuit just cause I’m having a hard time coming up with a step by step process on what to do. If there are any write ups you can link me to I’d be super grateful. At this point the only thing that makes sense is these wires aren’t making contact. But how can all 4 not make contact when I’m receiving voltage to the injector and also 12v at pin1.

I have not checked battery pos to the MPI. My MPI Relay is a 2 in one and I’m not exactly sure what the pin outs are since most manuals cater to the other style 2 in one. If you could let me know which pins to test on the MPI relay. I might just be misunderstanding you as well.

like I said I’m kind of noob still. I did a continuity test from pin 1 and injector 1 (harness unplugged)on the green wire and it’s showing continuity. However, what I’m curious about is, the ECU harness pins, are they actually making connection to the male pins on the ECU.

 

[Justin DuBois]

There are several ways to measure with a multi meter. Do you have something with a red + probe and a black - probe with a voltage display?

Here is the circuit diagram for reference:

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[steve]

The first diagram in my tech article on the 2G MFI circuit https://www.dsmtuners.com/threads/2g-basic-ecu-mfi-mpi-relay-circuit-function.497188/ has the correct pinout for the 95 all in one MFI Relay. The testing page 13A-229 also shows the pinout for relay in case you're confused as to which pin is #1.

The injectors get power from the other output pin (#2) than the ECU does (#3). This same pin feeds the Cam and Crank Position sensors, all the solenoids, and the injector resistor. The fact that the ECU powers up and you can talk using DSMLink to it indicates that at least part of the MFI circuit is functional. Measuring battery voltage at the injector resistor at the same time indicates that both pin 2 and 3 are switching the voltage from pin 4 to them.

The ECU doesn't send a signal to the injectors. It makes the ground connection that causes current to flow.

Following conventional current flow says then that the current flows from the battery positive through the MFI relay to the injector resistor, through the resistor to the injector coil and from there to the ECU where a transistor passes it to ground.

I never know if some random noid light is going to work with the injector resistor inline...

 

[Busdownthotiana]

The first diagram in my tech article on the 2G MFI circuit https://www.dsmtuners.com/threads/2g-basic-ecu-mfi-mpi-relay-circuit-function.497188/ has the correct pinout for the 95 all in one MFI Relay. The testing page 13A-229 also shows the pinout for relay in case you're confused as to which pin is #1.

The injectors get power from the other output pin (#2) than the ECU does (#3). This same pin feeds the Cam and Crank Position sensors, all the solenoids, and the injector resistor. The fact that the ECU powers up and you can talk using DSMLink to it indicates that at least part of the MFI circuit is functional. Measuring battery voltage at the injector resistor at the same time indicates that both pin 2 and 3 are switching the voltage from pin 4 to them.

The ECU doesn't send a signal to the injectors. It makes the ground connection that causes current to flow.

Following conventional current flow says then that the current flows from the battery positive through the MFI relay to the injector resistor, through the resistor to the injector coil and from there to the ECU where a transistor passes it to ground.

I never know if some random noid light is going to work with the injector resistor inline...

I started taking some notes about which pins have what voltage etc.

Pins 4,8 are both showing up with battery voltage with car off.

I jumped pin 6 to ground and heard the relay click. Was kind of scared to ground out my ecu.. but at this point I need to start dealing with the diagnosis part where you mess things up.

After hearing it click, I wanted to bench test it so I took the diagram from Steve’s post. Which is as follows.

************* read the diagram not the screenshot of the text!! The page saying
13-A-229 is where we’re getting the entire testing instructions from!!!

Vvvvvv screenshot below vvvvvV

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I placed the relay exactly how it is placed on the drawing and set up my leads carefully making sure to put the grounds where they have them placed in the diagram and same with the positive leads.

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First test is pins 5(-), 7(+)

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Next let’s check pin 1’s voltage with the negative lead from our meter on battery negative post( like the drawing in test 1)

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Holding my multimeters ground lead on the negative post and my red lead on pin 1 I am reading battery voltage ( sorry for not charging my battery I don’t have one!!)

Next part of this test involves removing the negative lead from the post.

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Not sure what this test is for, but here’s my reading 033.2 MV

So battery voltage with the circuit energized and
033.2 unenergized with one lead still on battery positive.

Next was a little more tricky since I can’t show my readings but I set it up basically the same.

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Pin 6(-) pin 8(+)
Now with test #2 we’re changing our meters to OHMS shown with an OMEGA SYMBOL
Placing our meter on
terminal pins 2 and 4
I’m reading continuity @.50
At pins 3 and 4
I’m reading continuity @.60

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And disconnected on the negative post I’m reading at pins 2 and 4
OL

Reading at pins 3 and 4
OL

This was my testing at the mpi/mfi relay
and of the bench test with the relay for a 1995 weird model relays.


Ok so now that this sucker is testing out, I believe my conclusion is, the relay is good?

Actually I forgot to check the first ohms check.

Moving the relay to a colder place than hell outside, I place the meter on OHMS and with the two leads on
Pins 5 and 7

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The diagram for the first actual test was a CONTINUITY TEST between pins 5 and 7.
approx. 90ohms.. PER FACTORY SERVICE MANUAL. P.s. in heat and cold the temp will change this reading so id say 92ohms is pretty good.

Ok and then 6 and 8 pins on continuity as well. Say ONLY ONE DIRECTION.

Like is that mean the leads ? Me being not the brightest crayon I checked it anyway.

I imagine the reading is for when the circuit is energized. Correct me if I’m wrong though maybe my test is being performed correctly and this is my problem? (Doubt it )

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Same test, leads reversed.

So just to clarify, I’m pretty sure leads don’t matter on a continuity test but I’ll admit, I don’t understand one direction thing. I imagine- it’s when the circuit is actually energized.


Welllllllllll at least I think my relay is working -_- idk where to go from here hehe but I’ll do some more digging around. Really would like to get this figured out and help some people.
It seems as if I’m not the only person who’s ever experienced this. And also Steve


“I never know if some random noid light is going to work with the injector resistor inline...”

I didn’t realize a noid should light up specifically for our car. Is there one you rely on? I barely saw a pulse. It was very difficult to spot.

 

[Busdownthotiana]

Following conventional current flow says then that the current flows from the battery positive through the MFI relay to the injector resistor, through the resistor to the injector coil and from there to the ECU where a transistor passes it to ground.

So I checked the relay wiring pins
#6 pin with ground jumpered energized the relay
Transferred power from
Pin 4 > pin 2 & pin 3
both read battery voltage at 12.08v

Fuel pump side
#5 jumped to ground
Energized the relay
Transferred power from pin 7 @11.7v
To pin 1 @11.7v

My question is, which direction do I go now? Where do I end up according to the schematic?

I want to see how I’m ending up from whatever pin on the relay to my resistor.

It’s actually quite satisfying performing these tests.

Jumping grounds was fairly easy, if you have a safety pin or even a paper clip, take some scrap wire from anything it really doesn’t matter it can be cheap wire too. Once you wrap the wire around the metal the stick a pin behind the connector and tap the other end of the wire to a bare piece of metal (ground).

This knowledge has seriously priceless and I am super thankful to be able to discuss this high level stuff with legends like Steve and Justin.

 

[Busdownthotiana]

There are several ways to measure with a multi meter. Do you have something with a red + probe and a black - probe with a voltage display?

Here is the circuit diagram for reference:

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Hey Justin the hard part about trying to read that is it’s like trying to read spaghetti I just want to eat it. Can you help me understand? I measured just within those specs at the resistor. 6.45ohms

 

[Busdownthotiana]

Alright y’all I could not for the life of me- figure out what to do next!! out of desperation I started trouble shooting the harness connector. I saw gopher had issues w pins not making contact on the connector. So I pierced my injector wire a couple of inches away from the ECU PIN to see if it was going to show signal. I hooked up a test light and could get a pulse. Pretty annoyed rn.

My wiring has to have something not wanting to let this signal pass from the injector wire to the injector harness. So I’m imagining how is this possible on all 4 injectors!?

I’d be much more pleased to say yeah my ecu has no injector pulse. But it does


Honestly at this point I wouldn’t mind 4 random jump wires and my hand tapping the ground signal myself

 

[Justin DuBois]

Best advice I can give is to check for 12 v at the resistor pack, then check at the injector, then check at ECU. I would start at the ECU. If you measure 12 V at ECU harness pin, then you have a complete circut without a break.

 

[Busdownthotiana]

Best advice I can give is to check for 12 v at the resistor pack, then check at the injector, then check at ECU. I would start at the ECU. If you measure 12 V at ECU harness pin, then you have a complete circut without a break.

Hahahahahahahahahahahahahaha

I’m laughing because I’m not alright!

I have 12v on each resistor wire, 12v on each leg at the injector harness.. 12v at the ecu wire harness…

Yeah this one has been an interesting diagnosis.

I’m receiving pulse signal at the ecu and 4-5 inches above the ecu pin on signal wire for injectors.


I’ll start inching my way up turning my signal wire into Swiss cheese.. let me know if you can think of anything else!!

 

[Justin DuBois]

Hahahahahahahahahahahahahaha

I’m laughing because I’m not alright!

I have 12v on each resistor wire, 12v on each leg at the injector harness.. 12v at the ecu wire harness…

Yeah this one has been an interesting diagnosis.

I’m receiving pulse signal at the ecu and 4-5 inches above the ecu pin on signal wire for injectors.


I’ll start inching my way up turning my signal wire into Swiss cheese.. let me know if you can think of anything else!!

And when it is all connected - and you check the DTC codes, can you reset them all? Does the injector circuit malfunction return?

 

[Busdownthotiana]

And when it is all connected - and you check the DTC codes, can you reset them all? Does the injector circuit malfunction return?

Injector circuit malfunction only seems to happen when I have a noid light test on the harness and I can clear it and not it’ll have it present anymore until.. I guess it feels like popping back up. All the tests it shows up on are my rotating of my CAS.

 

[Justin DuBois]

Injector circuit malfunction only seems to happen when I have a noid light test on the harness and I can clear it and not it’ll have it present anymore until.. I guess it feels like popping back up. All the tests it shows up on are my rotating of my CAS.

Key on - ECU Unplugged
The only way you can measure 12v at injector pins 1, 2, 14, and 15 in the ECU harness is if you have a complete circuit from the battery - through the MPI relay, through the resistor pack, through the injector coil and all the connected wiring harnesses up to the ECU. If you ground each pin (1,2,14,15) one at a time, you should hear the injector open and close. If you don't - then the issue is upstream from the ECU.

Since you are getting 12v at the ECU - and the ECU detection logic is failing, this tends to point to the ECU as the problem.

Did you have the ECU inspected and fixed by ECM Tuning? The capacitors on the boards leak and mess up traces on the board.