1G Injectors Not Pulsing.

[LostCauseZ06]

alright, i have searched my butt off for hours....


i have a 1990 GSX. just did a head gasket/timing belt/balance shaft removal/ac removal, so forth so forth. running 560cc injectors, maft w/ blow through, safc, AGP L2r bb turbo, fmic, ported 2g exhaust mani, evo 3 housing, and full 3" exhaust.




Alright. i got the car back together and went to start it. nothing. trouble shot everything i could search for.


I have concluded that my injectors are not firing. there is no gas in the cylinders after cranking nonstop. i am getting power TO the injectors, but they are clearly not grounding to fire. Timing is set up perfectly CAS has been verified to work as well as swapped out just to be sure. TPS is reading correctly.


im just not getting the signal for the injectors to open up. Every connector is plugged in. every bolt i tight.



The only option i can think of is the ECU. are there ANY other possibilities before i try and track down a wonderfully fun to find 1990 ecu locally?


are there ANY other sensors that control whether or not the injectors are allowed to ground on a 1990 GSX?


thanks for any help you guys can give me.

 

[steve]

What happens when you first turn the ignition switch to run?
Does the CEL light up for five seconds and then turn off?
Does the boost gauge move to 0 and sit there until you start cranking?

If you spray fuel into the intake does it start?

What is your compression?

 

[LostCauseZ06]

i havent tried starting fluid or anything of the like. i have had the timing checked by a second party who build these cars every day. they said timing is perfect.


when i turn the ignition key to run the CEL turns on, stays on for 5-6 second, then turns off. then the open door beeper stops beeping.


the compression (checked this morning) is 131 135 133 132.


the motor is in GREAT shape for the mileage. the new head gasket seems to have solved the lower compressioni had before (110-120 range)

boost gauge moves to zero and stays there.

im stumped.... all the local dsm guru's are stumped.


i also removed the ECU. all caps look to be in great shape. ill probably end up trying another one anyways because you never know.

 

[slowstang]

If your able to I'd change the caps anyways. I just got done troubleshooting some problems I had with my ECU which included the injectors not firing for startup or the computer not coming on at all. The problem started intermittently but quickly became a everyday event. I just put new caps in 6months ago and found one was already shot even though it visually looked ok. New caps solved all the problems.

Good luck

 

[Loewen21]

If there's anyone in your area with a car simliar to yours (turbo, same gen) try running the ecu in their car if they're still running a factory ecu. Should tell you whether or not thats the problem pretty quickly.

 

[steve]

So the ECU is turning on and running. That's a good sign.
Compression is ok but not great might be because it's cold. Somewhat supports that the mechanical timing is good.

Since you have a second CAS, try connecting it and see what happens when it's connected and turned by hand. If the ECU sees the CAS the fuel pump should turn on and you may hear the injector clicking.

There are a couple of connectors on the 90's that can get swapped like the resistor pack and ISC or something like that.

Try spraying some starter fluid and let us know if it starts for a second.

 

[Dragon TalonTsi]

You should be getting some kind of P code with these problems. Your PCM is responsible for the injectors, through proper timing inputs and various other sensors (TPS, FPS, CAS, CKP, etc.) If any of those are out of order, the PCM will try and compensate for that, but its causing several different problems. A misfire is either through ignition, fuel, or compression. Either way, air, fuel and spark are the culprits for making any gasoline engine work (with the proper combination). I would get either a PCM test light or a noid light test to see if the signal from the PCM is correct or not. The PCM grounds the injector to make it work, so the ground side is susceptible to most common faults (ie, open or shorted ground, high resistance.) I would also do a leak down test, just to be safe... ANd when you did your compression test, did you do it wet and dry?

 

[Dragon TalonTsi]

What happens when you first turn the ignition switch to run?
Does the CEL light up for five seconds and then turn off?
Does the boost gauge move to 0 and sit there until you start cranking?

If you spray fuel into the intake does it start?

What is your compression?

I could see why you ask about compression, but why would you ask him about a PCM 5 second test (drive cycle/MIL test)? And the vacuum source on the boost gauge will read 0 until you crank, after that, even during cranking, it will fluctuate, until you reach a steady idle, then it will read properly. 18 in/Hg is the spec for our engines... He should be getting a code 12, 22, 23, something along that line, that's dealing with the input sensors the PCM uses for injector timing, since his CAS is both his crank and cam position sensor.

 

[LostCauseZ06]

compression was done dry after the car had sat for a week.


i am confused why you guys are saying the compression isnt great? this is a 1g and i was under the assumption 135-140 was perfect for this car. it was in the 120's and 110's before the head gasket.


the car ran GREAT before it was taken apart. it just had a tiny head gasket leak that was pushing pressure into the coolant system.



Steve, we have tried turning it by hand. when we turn the cas by hand the spark plugs fire, the fuel pump turns on, but no injector pulsing...


literally after searching i have tried every single trouble shooting besides a new ECU. i have never had problems with this ecu up until now if it is indeed the ECU.


i am getting no codes at all. thats why this is so confusing and frustrating.



i am , however, 10000% positive that the problem is the injectors not going. there is no fuel getting in the cylinders but i have fuel pressure and power to the injectors which i measured with a multimeter as well as a test light.


i also hooked the test light up to the negative injector connector terminal and the 12V source, then cranked it... light never lit up

 

[ezz-e]

Sounds Like the Caps on the ecu are gone, try testing the car with another 90 ecu

 

[LostCauseZ06]

wow....



just tried another ECU. no dice. car still wont fire.

 

[steve]

I could see why you ask about compression, but why would you ask him about a PCM 5 second test (drive cycle/MIL test)?

Simple, I didn't ask about PCM 5 second test (drive cycle/MIL test). I asked him to confirm that the ECU was powering up and running. As part of the bulb test the ECU turns on the CEL and if the ECU is still running after 5 seconds it turns it off.

If the MPI fuse is popped or the MPI relay is bad the ECU won't get power and neither of the checks I asked for will pass. If the caps leaking have killed the ECU then they would pass either.

I always ask because it's a common problem.

And the vacuum source on the boost gauge will read 0 until you crank, after that, even during cranking, it will fluctuate, until you reach a steady idle, then it will read properly. 18 in/Hg is the spec for our engines... He should be getting a code 12, 22, 23, something along that line, that's dealing with the input sensors the PCM uses for injector timing, since his CAS is both his crank and cam position sensor.

There isn't a vacuum source for the factory boost gauge. It's all faked by the ECU from the airflow/rev input from the MAF and CAS. Watch the factory boost gauge and you'll note what it normally does when the ECU powers up and once you start cranking. Also watch what happens if you don't let the engine start vs if you do. These are useful diagnostic tool on DSM's that you won't learn at a trade school.

If the CAS is bad would would expect to get a 22 or 23 DTC but once you read the ECU software you'll see that the tests are very basic and it's possible for the CAS to be dead and not throw a DTC.

compression was done dry after the car had sat for a week.

i am confused why you guys are saying the compression isnt great? this is a 1g and i was under the assumption 135-140 was perfect for this car. it was in the 120's and 110's before the head gasket.

The service limit is 114 psi or more than 14 psi between high and low. I get 160 psi from my 135k engine and have since new.

the car ran GREAT before it was taken apart. it just had a tiny head gasket leak that was pushing pressure into the coolant system.

Steve, we have tried turning it by hand. when we turn the cas by hand the spark plugs fire, the fuel pump turns on, but no injector pulsing...

literally after searching i have tried every single trouble shooting besides a new ECU. i have never had problems with this ecu up until now if it is indeed the ECU.

i am getting no codes at all. thats why this is so confusing and frustrating.

i am , however, 10000% positive that the problem is the injectors not going. there is no fuel getting in the cylinders but i have fuel pressure and power to the injectors which i measured with a multimeter as well as a test light.

i also hooked the test light up to the negative injector connector terminal and the 12V source, then cranked it... light never lit up

How much did you disconnect to take the head off? The fact that the plugs fire and the fuel pump run are more indications that the ECU is operating. It's possible that it's injector circuits are damaged but I'm guessing you connected some wiring back up wrong. Like I said, more than a few 90 owners have done that when putting the car back together.

Please spray some starting fluid into the intake and crank the engine over.

 

[Dragon TalonTsi]

Simple, I didn't ask about PCM 5 second test (drive cycle/MIL test). I asked him to confirm that the ECU was powering up and running. As part of the bulb test the ECU turns on the CEL and if the ECU is still running after 5 seconds it turns it off.

If the MPI fuse is popped or the MPI relay is bad the ECU won't get power and neither of the checks I asked for will pass. If the caps leaking have killed the ECU then they would pass either.

I always ask because it's a common problem.



There isn't a vacuum source for the factory boost gauge. It's all faked by the ECU from the airflow/rev input from the MAF and CAS. Watch the factory boost gauge and you'll note what it normally does when the ECU powers up and once you start cranking. Also watch what happens if you don't let the engine start vs if you do. These are useful diagnostic tool on DSM's that you won't learn at a trade school.

If the CAS is bad would would expect to get a 22 or 23 DTC but once you read the ECU software you'll see that the tests are very basic and it's possible for the CAS to be dead and not throw a DTC.



The service limit is 114 psi or more than 14 psi between high and low. I get 160 psi from my 135k engine and have since new.



How much did you disconnect to take the head off? The fact that the plugs fire and the fuel pump run are more indications that the ECU is operating. It's possible that it's injector circuits are damaged but I'm guessing you connected some wiring back up wrong. Like I said, more than a few 90 owners have done that when putting the car back together.

Please spray some starting fluid into the intake and crank the engine over.

I was assuming he had an aftermarket boost gauge in his car... My bad for not reading his mods list either, I should've checked. Either way, a mechanical vacuum source will fluctuate during cranking, until its steady idling, it will staty stagnant. If there are problems, it will fluctuate at a steady idle (bad rings, valves, etc). That's not the only thing, in my work, ignition and fuel misfires are alot more common that compression misfires. From those 3 symptoms, ignition and fuel combined are like 70:1 compared to compression.

Now for OBD1 diagnostics, yes, on certain makes and models, the OBD1 monitor cycles do not always check for sensor outputs, but they do for inputs, like timing, that's a major control input for DISTRIBUTORLESS ignitions. So it has to be monitored, otherwise, the car would stay in open loop and limp in mode and have hard starting and never leave to closed loop and proper opertaion. Regardless of ECT and 02 inputs, but thats another engine performance issue.

On his car, I would be more worried about the injector/PCM circuit, and see what is wrong. If the fuse is popped, there is a short to ground somewhere in that circuit, if the relay is bad, well, the relay is bad, replace it. Since we are on the subject too, I would check out your ignition circuit (plugs, wires, coils, transistor, etc.) just to be safe. Not only that, if his CEL bulb is blown, you will never know what the PCM is doing, so, take that into consideration when you do engine performance diagnosis. And since this is a 1st gen, I would also recommend like everyone else is to get the capacitors replaced, or at least checked out and replaced. Just for the simple satisfaction of it. Capacitors can be diagnosed, but not with acid all over the PCM. Its obvious at that point. And if he doesn't get any fuel, 8 times out of 10 on most makes and models he will not get spark, or his spark timing will be off. One or the other...

 

[Dragon TalonTsi]

wow....



just tried another ECU. no dice. car still wont fire.

I just read you said you checked the ground side, and nothing lit up? Well, its obvious just throwing parts at the car will not work, this takes some knowledgable engine performance diagnostics. I would look at the entire injector circuit. You said fuel pressure is good, 37 PSI at idle is the spec, no kinks in your lines, fuel pump is working, so that leaves the electrical aspect. You have a short, high resistance, or an open in the ground side of the circuit. Most injectors are controlled through the PCM's ground circuit. When the PCM sets the spark timing, it also sets the injector timing as well, to coincide with the spark for proper operation. It grounds out each injector either by individuals or in a group, hence multi port or sequential fuel injection. I would start by looking at the (black and yellow) (yellow and black) (light green) and (light green and white) wires coming from the PCM, then the (black and yellow) (black and blue) (black and white) and then (black and red) for the ground side. You said you had a DVOM, I would place the meter in parallel with the ground side, and check the resistance of the path. It should read less than 1 Volt, if there is 1-11 Volts, that ground path has high resistance, but if the ground side reads a full 12 Volts, then the ground is open, so start looking for open wires or bad/misaligned components.

 

[Dragon TalonTsi]

compression was done dry after the car had sat for a week.


i am confused why you guys are saying the compression isnt great? this is a 1g and i was under the assumption 135-140 was perfect for this car. it was in the 120's and 110's before the head gasket.


the car ran GREAT before it was taken apart. it just had a tiny head gasket leak that was pushing pressure into the coolant system.



Steve, we have tried turning it by hand. when we turn the cas by hand the spark plugs fire, the fuel pump turns on, but no injector pulsing...


literally after searching i have tried every single trouble shooting besides a new ECU. i have never had problems with this ecu up until now if it is indeed the ECU.


i am getting no codes at all. thats why this is so confusing and frustrating.



i am , however, 10000% positive that the problem is the injectors not going. there is no fuel getting in the cylinders but i have fuel pressure and power to the injectors which i measured with a multimeter as well as a test light.


i also hooked the test light up to the negative injector connector terminal and the 12V source, then cranked it... light never lit up

Okay, its difficult cause it takes knowledge and time to diagnose these problems. I would look at the basics, clogged fuel filters, kinked lines, etc... Just because it could be one thing or another, and sometimes it is the basics, most times its not. I would also look at the MPI relay, but also the components it controls. From both factory service manuals I have, the relay controls the Fuel pressure solenoid, the fuel injectors (1-4), the fuel pump, and the ignition suppressor/resistor block. I would look at all thos components, and see if they are working properly. Both electrically and mechanically... Since they FPS, FP and INJ are basically solenoids and a motor, they are both mechanical and electrical in both aspects, so they need to be checked fully...

 

[LostCauseZ06]

i agree completely.


the problem , no questions about it, is in the ground circuit on the injector clips.


EVERYTHING else checks out. there is nothing else wrong with the car.



are there ANY other sensors that could be reading bad that could tell the ECU "dont let the car start" im pretty positive that is what i need to look for.



likelihood that ALL 4 of the ground wires coming from the injector clips got broken in the harness, and NO other wires, is basically impossible. None of my injectors are firing, no fuel is entering the engine. I have fuel pressure, i have no CEL.



so i guess my question is... what other factors control the ground circuit ONLY of the injector clips. The pcm gets its signal from the CAS and its clearly getting that signal because its firing spark plugs and toggling the fuel pump on with each turn.


there has to be another sensor that controls whether the PCM is allowed to ground the injectors.

 

[LostCauseZ06]

alright i think i just made a big discovery.


i just tried to jump the power on the clip, into the injector, and then manually ground it with another wire.

injector didnt open... looks like my resistor pack is bad.

 

[LostCauseZ06]

also.. .the resistor pack gets so hot that it will physically burn your finger after about 15 minutes of the key being in the run position in the ignition...

im sure that cant be good.

 

[LostCauseZ06]

car started... looks like it was a bad resistor pack

 

[steve]

Reviewing this thread I wonder if the OP didn't mix the ISC and injector connectors. That will cause the resistor pack to overheat and if left long enough burn out several of the resistors. The connectors are interchangible and in the same general area. It's happened several time before to guys with 1990 cars.

 

[Sarge32]

Thanks Steve,

My injectors were not firing since I installed the engine back in. I had a code 41. It appears I as well swapped the connectors between the ISC and the inj resistor. Fired right up after switching them correctly