94 No Start H2O Pump / Opti

[Steve 147]

I'm not new to this forum but have just registered and this is my first post.
I am working on a 94 for my friend Sharron and need some help.

Back ground - The car has set for 2.5 years. Fuel stabilzer was added to the fuel and new fuel has been added from time to time. The car has been started from time to time to keep the battery charged but hasn't been on the road but has been running fine. Except of the digital display, the connector has come loose from the glass plate and you get scrambled data.

The H20 pump went bad, bearing came apart, and water got on the opti spark and now the car wont start. I downloaded the trouble shooting procedures from this forum, thank you to whomever typed this up. Sharron gave me her Haynes manual to use but I don't have a FSM. Haynes is pretty much usless and rarely mentions the optispark.

I should tell you this is an OBD2 car. I replaced the opti with a Cardone new part. Sharron didn't have the money for the GM unit. I know, its suspect.

I followed the procedures, the fuel pressure at the fuel rail is 42.5 psi while the pump is running. when the pump shuts off it drops to 40 and stays there. It does not lose pressure. Each time the pump kicks on the pressure goes to 42.5.

I tested the coil and have the proper resistance on the primary side and between the primary and secondary. Power is being supplied to the coil. I also put my timing light on the individual spark plug wires and am receiving spark on the wires to the plugs while cranking.

I had to stop TS the Opti to replace the fuel injector Orings because they started leaking. Pulled the fuel rail off and replaced the Orings. Finished that and then found 2 of the spark plug wires were so brittle they just broke. So I stopped and replaced the spark plug wires making sure I got the wires back on properly.

Ok back to TS the opti. I checked all the fuses in the right side panel and the Maxi fuses on the left near the battery, all are OK.
Next I looked at the fuel injector connectors. 12 volts is present. I connected a Noid light and found no pulse, nothing while cranking most of the time. Sometimes the engine fires but doesn't start and at this time I get a good Noid light but its intermittent, sometimes its really dim not a good strong pulse.

Went to the connector at the opti which has a new cable and checked there. KOEO red wire has 12 volts. The red/black and purple/white wires do have 5 volts. The pink/black wire has continuity to ground but measures 3.2 ohms. Don't know if this is OK or Not.

I replaced the Cardone opti spark with another new one. Same condition, same test results only this time the engine never fires. Noid light never comes on, 12 volts to the hot side of the injector connector.

For grins I don't know if the optical sensor in the original GM opti is bad or not. After it got wet the engine would not start. I broke the original cap trying to get the V belt pulley off because it was rusted to the hub.

I took the new cap and rotor off the Cardone opti and put it on the GM original unit to see if at least I could get a pulse at the injector. The original cap and rotor are really worn. Still the same condition, same test results.

I must tell you I am doing this without the H2O pump installed and naturally the temp sensor and air flow sensors are not connected.

Scanning the OBD2 there are no ignition or fuel faults, there never has been everytime I have checked. The only codes are for the H2O temp sensor, naturally it isn't connected.

I suspect the Cardone Opti spark units are junk and I got 2 in a row that are bad for the optical sensor but at this point I am not confident that getting a GM opti would solve the problem. I feel there is something else going on here. You get to a point where you start second guessing yourself.

Can you all give me some guidance?

Steve

 

[Midnight 99]

Have you checked the ignition module? I had the same issues with my 94 Z28 and found the module was bad. The module for the Camaro was riveted to the coil bracket. I can't say where it is on the C4.

 

[Steve 147]

Have you checked the ignition module? I had the same issues with my 94 Z28 and found the module was bad. The module for the Camaro was riveted to the coil bracket. I can't say where it is on the C4.

It's in the same place on the C4 attached to the bracket with the coil. I considered it ok since I have spark thru the wires to the plugs. I'll take another look at it. I'm also going to look at a couple videos I found here in the forum about the Opti.

I took the original GM opti apart and found rust powder residue inside on the optical sensor and signs of water contamination on the optical disc. It's toast. It looks to be the original opti to the car or at least it has been in there a long time. The bearing in the Opti is rusty and you can feel sings the bearing is bad because it got water in it.

As a side note - I replaced the convertible top on Sharron's 94 with a Robbins top and put a power point presentation together on replacing convertible tops for our local car club. If anyone would like to have the presentation let me know and I'll send it to you. It has slides containing pictures of the 94 Corvette top replacement as well as a few slides on a 73 MB 450SL convertible top replacement.

I'm going to have to stop working on Sharron's 94 today and concentrate on Pat's 76 Corvette radiator replacement. But I'll still be thinking about what could be wrong with the 94.

Any advice finding the 94's problem would be appreciated. It maybe that Sharron will have to get the GM opti just to eliminate that as being the problem. This car needs a lot of attention as it has been setting a long time. I have warned her that this is only the beginning. The fuel system will need to be looked at and the digital display needs work. The passengers seat will not move so that needs to be looked at as well.

Thanks for reading my post,

Steve

 

[ecss]

Even if the water pump is not attached, you can still attach the electrical connector to the CTS and IAT.
Manually open the throttle body blades and spay some starter fluid into the throttle body.

See if the engine fires.

If the car sat 2.5 years and was briefly started, chances are there is rust in the tank. The sending unit
assembly is known to rust. Pull the sender and look inside the tank.

The 94 is what some people call OBD 1.5 It was not fully OBDII compliant. Many people have said a third party hand held OBDII scanner can log false codes and can't read CCM codes.

 

[Steve 147]

Thanks for the advice so far. I did a little more checking and rechecking my test results.

I rechecked the ICM according to the TS flow. The color codes of the wires don't match the flow but using it along with the manual I have, I was able to determine the following KOEO. Pin A pink/black has 12 volts. Pin D Green has 12 volts. Pin C is white/black and Pin B is white. but I do have spark to the plugs thru the wires.

My problem is no fuel injector pulse. Now I have 12 volts KOEO at the fuel injector connectors and it goes to 9.7V while cranking, but No ground while cranking. No Noid light.

Now I checked the OBD2 stats and see the following static and while cranking frame 5 on.

Batt Volts - 11.7
IAC Position - 146 (Idle Air control)
Inj L PW MV - 0 - goes to 36 at frame 5 (Fuel Injector Pulse Width Control)
Inj R PW MV - 0 - goes to 36 at frame 5 (Fuel Injector Pulse Width Control)
Loop Status Open
MAF - 0 (Mass Air Flow)
MAP - 29.10 (Manifold Absolute Pressure)
IAT - 40 (Inlet Air Temp)
Spark Adv -0 - goes to 13 at frame 5
TPS V - .63 (Throttle Position Sensor)
Coolant F - 70
Cyl ID - 0 - goes to 28 at frame 5 (Cylinder Identification)

I hooked up the sensors even though I have the water pump off, so the PCM is seeing the input. What it is telling me is that I have a fuel injector pulse starting at frame 5 this is while cranking the engine. On the other hand the Noid light will not pulse while cranking, maybe there is a high resistance to ground keeping the fuel injectors shut off?

It will fire if I spray fuel in the intake. So the electrical fuel circuit I think is the problem.
It's leading me to think the PCM maybe the problem but somehow I want to verify it. I don't want to start just throwing parts at it.

Also from your comments maybe my scanner TechScan 7000 isn't giving me the whole picture. OBD1.5?


Steve

 

[Steve 147]

Just found something. A friend of mine who knows the C4 told me to check PCM connector D (blue) pins 29 and 30 both are tan wires. They should be 2.5 v. They are 4+ volts KO as well as cranking. Seems there maybe a problem with the vehicle theft system. Maybe they shut down the fuel injector pulse when the theft system gets tripped.

Steve

 

[ecss]

Just found something. A friend of mine who knows the C4 told me to check PCM connector D (blue) pins 29 and 30 both are tan wires. They should be 2.5 v. They are 4+ volts KO as well as cranking. Seems there maybe a problem with the vehicle theft system. Maybe they shut down the fuel injector pulse when the theft system gets tripped.

Steve

The two tan wires are the serial bus and is the bus the CCM uses to communicate with the PCM, HVAC Programmer, ABS and Derm computers.

When you insert the key and turn the ignition key to On the Security light should be off.
If the Security light stays on solid it indicates the key pellet resistance wasn't read properly and
the starter enable relay will be disabled. (Engine won't crank) and there will be no pulsing of the
fuel injectors.

If the key pellet resistance is correct, the starter enable relay is enabled (Can crank the engine) and a message is sent to the PCM. The PCM decodes the message and replies to the CCM. The PCM will now pulse the injectors.

If there is a problem a CCM or PCM code is set.
I don't believe your hand held scanner can read CCM codes. As far as I know only a Tech 1 or Tech 2 can.

CCM codes can also be displayed on the dash cluster LCD when your short pin 4 or 5 to pin 12 on the diagnostic connector and turn the ignition On.

You did mention the data on the LCD is scrambled. The data comes from the CCM.

Are you jumping the starter or are you using the key to crank the engine?
If you turn the ignition On and press the Eng Met button on the DIC does the temperature display
on the HVAC control head change from F degrees to C degrees? (Assuming you have auto climate control).

This would tell you the serial bus is working.

 

[Steve 147]

I am using the ignition key to crank the engine. That has always worked. I don't recall about the security light going off when I turn the ignition to on, I will look.

The digital display was initially scrambled when I first got the car. That was several months ago. I had taken it out and following the procedures I found here on the forum, took the display apart and fixed the connector on the glass plate. Reinstalled the display and it had been working fine for several months. Just recently when the weather turned colder, the display started messing up again but the engine was running fine.

I will check the climate control head to see if it changes F to C.

One thing I noticed from my scan data is that the spark advance changes from 0 to to 13 while cranking the engine. This would seem to tell me the optical sensor in the opti spark is working. From what I have read, the PCM would have to receive signals from the opti spark in order to change the spark advance. In other words light shinning thru the holes in the optical disc. 360 holes in the disc for the timing and the other hole slots for crank position.

I'll get to spend some time with it today to see if I can figure something out. I may have to stop and fix the digital display in order to get the CCM data.

I'll have to check the diagnostic connector for the pins you suggest. Its a little hard to get at contorting the body to get under there and see clearly through my bifocals. Turning 60 isn't fun, but better then the alternative!

All the Best,

Steve

 

[ecss]

Now I checked the OBD2 stats and see the following static and while cranking frame 5 on.

Inj L PW MV - 0 - goes to 36 at frame 5 (Fuel Injector Pulse Width Control)
Inj R PW MV - 0 - goes to 36 at frame 5 (Fuel Injector Pulse Width Control)

MAF - 0 (Mass Air Flow)

I hooked up the sensors even though I have the water pump off, so the PCM is seeing the input. What it is telling me is that I have a fuel injector pulse starting at frame 5 this is while cranking the engine. On the other hand the Noid light will not pulse while cranking, maybe there is a high resistance to ground keeping the fuel injectors shut off?

Just noticed is the MAF attached to the throttle body when you did the test? I would think you would get
an airflow reading and not zero. If you disconnect the electrical connector from the MAF I believe the MAP sensor is used.

Also is the injector pulse width in millisecond and not millivolt?

 

[Steve 147]

Security light on when you open the door, insert key turn to On security light goes Off.

Pressing the Eng Met button changes the display from F to C, appears serial bus is working.

The PID on the scanner reports it as injector pulse width control in Mv. I assumed it was millivolts but since the OBD2 is not fully complient they maybe using that PID but it means something else.

Am looking into seeing the availability of a PCM. I read where the PROM does not come with a new PCM. You have to take the old PROM and install it into the new PCM.

PCM Serv No 16181333 868JSNK03271078N PROM number 22183. Just looking into the availability, have not decided to replace it yet.

Steve

 

[ecss]

Security light on when you open the door, insert key turn to On security light goes Off.

Pressing the Eng Met button changes the display from F to C, appears serial bus is working.

The PID on the scanner reports it as injector pulse width control in Mv. I assumed it was millivolts but since the OBD2 is not fully complient they maybe using that PID but it means something else.

Am looking into seeing the availability of a PCM. I read where the PROM does not come with a new PCM. You have to take the old PROM and install it into the new PCM.

PCM Serv No 16181333 868JSNK03271078N PROM number 22183. Just looking into the availability, have not decided to replace it yet.

The 16181333 uses a EEPROM (electrically erasable programmable read only memory. I'm pretty sure it's soldered on the circuit board. You reprogram the EEPROM by reflashing it just like you update the bios on a PC.

You save the binary file from the original computer then reprogram the replacement computer with that file.

If you buy a used computer some people will flash the computer with the proper binary file before they send it to you. Tunercat.com sells a cable and the software to do it yourself for around $180.00.

I beleive there is a knock module that is removable and maybe what you're referring to. There is a small metal plate held on by a couple of bolts and the module is behind that plate.

 

[Steve 147]

Thanks ecss, your input is valuable. I'm not at the point of replacing the PCM yet but reprogramming the EEPROM is nice to know.

It seems from all the test I have run the following is true.
The opti spark is working. I have spark to the plugs. The timing advance is working PCM receiving signals from the opti spark. Timing advance going from 0 to 13 during engine crank.

Spraying fuel into the intake will cause the engine to fire but not start.

The fuel pressure delivery to the fuel rail is working. 42.5 psi with pump on. The fuel injectors have 12 volts, 10 volts while cranking. However No ground pulse to the injectors.

OK now, the MAF and MAP sensors could cause the PCM to shut down the fuel injectors. Also I read in the book that the H2O temp sensor could cause the PCM to shut down the fuel injectors.

I could have compounded my problems by having the the sensors unplugged while TS because I still have the H2O pump off. No sensors = no start

Now since water was sprayed all over the front of the engine when the H2O pump went out I could have shorted out a sensor. The MAF sensor is the only one not reading anything on the scan. When I plugged all the sensors back in, if the MAF sensor is bad it could cause the engine not to start by the PCM shutting off the fuel injector ground pulse.

So now I'll try to start the engine with all the sensors plugged in except the MAF sensor. If the MAP sensor input will be used as ecss suggest in place of the MAF maybe the engine will start. (Or at least do something different)

Sounds like a plan, I'll see what I get.

VIN 1G1YY32P7R5103822

From a GM dealer the current parts numbers are
Distributor Ignition Control Module - 01103841
Electronic Ignition Control Module - 10483139
Body Control Module (CCM) 88999217
PCM 16181333 replaced by 88961148

Take Care Steve

 

[ecss]

The MAF sensor is the only one not reading anything on the scan. When I plugged all the sensors back in, if the MAF sensor is bad it could cause the engine not to start by the PCM shutting off the fuel injector ground pulse.

As far as I know the engine should start with the MAF and MAP sensor disconnected.
I believe the MAP sensor is backup for the MAF sensor.

I''m curious to know if you disconnect the MAF electrical plug what the air flow reading would be using your scan tool. Assuming the MAF was connected to the throttle body when you got a reading of zero for the air flow.

The disconnected 02 sensors should not cause the engine not to start but may eventually set a code.

Has any work been done on the transmission? Many of the ground wires are on a stud on the driver side
engine to transmission bellhousing.

Also the Camaro used PCM 16188051 which people have said will work on a Vette (programmed with a Vette
binary file).

The Camaro for that year didn't use a CCM but used a separate module to enable the PCM to pulse the injectors.

Here's a link that has some good info. It also has a bin file for a 94 Corvette with auto trans.

16188051 and 16181333 PCM Information $EE $EEB

 

[Steve 147]

Well crap, my plan didn't work. disconnected the MAF sensor, all other sensors connected. No change, No Start no injector pulse.

The MAF sensor has never read anything but 0, electrical plug connected or disconnected, rubber snorkel connected to throttle body or not. Heck I even connected the plug and shot air into the intake and no change to the reading. That can't be right. the sensor does show signs of water being on it. In any case the reading isn't right so I'm getting a new MAF sensor.

There is a burn off module located under the ECM. According to the book, It provides power to the MAF sensor and is used to clean off the sensing wire. Current is supplied to the sensing wire to maintain a calibrated temperature which in turn causes the MAF sensor to read a certain voltage. The MAF sensor is getting its power from the burn off module but it's not reading anything.

i have cleaned the sensor plugs up around the front of the engine to make sure of a good connection. The other sensors like the H2O Temp, IAC and throttle position, I can see the values change on the scanner when I disconnect them or move the throttle.

A tech at the dealership parts dept told me the MAF sensor if bad will definitely cause the engine not to start. Sometimes you can disconnect the MAF plug and the engine will start but not always. didn't get to talk with a service rep. He seems to think I have more then one problem which makes diagnosing more problematic.

I haven't done anything with O2 sensors and no work has been done to the transmission.

 

[ecss]

The MAF sensor has never read anything but 0, electrical plug connected or disconnected, rubber snorkel connected to throttle body or not. Heck I even connected the plug and shot air into the intake and no change to the reading. That can't be right.

.
The MAF sends a signal based on frequency to the PCM.
There are 3 wires at the MAF sensor. Pink wire is 12 volts when ignition is On.
Black wire is ground.
Yellow wire is the MAF signal to the PCM.

Simple test to check the wiring to the MAF.
Disconnect the 3 pin plug.
With a DVM set to DC
Ignition On
Red meter probe on Yellow wire.
Black meter probe on Black wire.
Should measure 4-6 volts DC This voltage comes from the PCM.

Red meter probe on Pink wire
Black meter probe on Black wire
Should measure 12 volts with the ignition On.

This will tell you the wiring and voltages to the MAF are good.

I verified in the service manual a disconnected or bad MAF will cause the PCM to use
the MAP sensor to start the vehicle so no need to buy a MAF

I don't recall a 94 having a MAF burn off module but I will investigate further. :ugh

Remember free advise from anyone is just that. No guarantee the information is accurate.

Right from the Helms service manual.

You are not getting a PCM DTC 48 but it indicates a MAF problem
DTC 48 will set if the PCM detects engine reference pulses without detecting a frequency signal from
the MAF sensor.

When set the Service Engine Soon will light.
Speed Density will be used for fuel management.

When the ignition switch is turned to the On position (before engaging the starter the PCM energizes
the fuel pump relay for two seconds allowing the fuel pump to build up pressure. The PCM first checks
speed density, then switches to the MAF sensor. Engine coolant temperature, Throttle position sensors
MAP sensor are also used to determine the proper air fuel mixture ratio for starting.
When the engine is first started the 02 sensors are ignored while in open loop.

 

[ecss]

Here's something else to try.

The PCM continuously monitors the voltage of each injector driver circuit. When the PCM
detects a voltage that is out of range, (grounded circuit or open circuit, a circuit shorted to voltage
and injector is open or has low resistance a DTC 18 will set and the driver will be disabled.

DTC 18 will set when the PCM detects the wrong voltage potential on any of the injector driver
circuits for 4 seconds or more.

Action taken the PCM will disable the injector driver on the particular injector that had the fault.
DTC 18 will be stored by the PCM and will NOT turn on the Malfunction Indicator Light.

If you disconnect all of the injector connectors and turn the ignition on and crank the engine for more
than four seconds. Use your scan tool and see if DTC 18 eventually sets. (Probably the engine doesn't need to be cranked but try it that way for the test).

 

[Steve 147]

Here's something else to try.

I will try this to see if I get a code. I haven't been able to fix this no start problem and had to temp stop working on it and devote time to restoring a 57 Buick Century 4 dr Ht.

I'll get working on it again and try this test. Maybe this will allow me to look at the 94's problem with fresh eyes.

Thanks Steve

 

[ecss]

Since you have multiple problems it's difficult to say if any are related. One problem is the car sits a lot.

LCD scrambled data prevents you from pulling CCM codes.

Are you positive you have the optispark drive shaft installed properly. Some people say you can force it in wrong but people have. This causes the timing to be off but shouldn't cause the injectors not to pulse. :L

You said the injectors are not pulsing. The noid light will dim when you crank the engine because of the battery load from the starter. You said you measured 12 volts on the wire at the each injector plug which would indicate the injector fuses are good.

PCM should pulse the injectors by grounding one of the injector wires.
You can verify the PCM has a good ground by using a ohm meter.

Unplug the Red, Blue and Gray connectors at the PCM.

Connect Black meter probe to negative battery terminal.

Use Red probe on the following unplugged connector wires at the PCM.
All should measure zero ohms to the negative battery terminal.

Red connector
Pin 2 Black/White wire
Pin 18 Black/White wire

Blue connector
Pin D Black/white wire

Gray/Clear connector
Pin 32 Black/White wire

If you read a high resistance, clean the ground wire that goes from the negative battery terminal
that goes to the engine block near the oil filter

Here's a picture of what a fuel pump assembly looks like when it's exposed to the air for a long
period of time.

 

[Steve 147]

Would you believe it! The car sat in the shop for almost 2 months with the battery disconnected while I was working on other projects. Sharron is not in any hurry.

Anyway had some time to look at it. Unplugged all the injector connectors. Connected the battery, and cranked the engine over for 3 to 4 seconds. Used my scanner to pull the OBD codes as you suggested. The result was no codes logged. The one thing i noticed was that the digital dash display was working perfectly.

Disconnected the battery, plugged all the injector connectors back on. Connected the battery hit the key and the engine started right up. Didn't let it run long cause I still have the water pump off and the serp belt is off.

I thought crap! Engine heal thyself!

So now I am installing the water pump and putting it all back together. Then I'll connect the battery and see if she starts up again.

Possibilities; The PCM had some error stored in it that wouldn't clear and letting it set for a long period of time with the battery disconnected cleared it (possible but not probable).
Or there is some connector or connection that is marginal. The warm weather we have been having (mid 80's) has caused a marginal connection to become stable. The digital display is now working - Probable
Or maybe all the times I tried to start the engine while TS, connecting and disconnecting the battery, connecting and disconnecting sensor plugs screwed up the PCM.
Or maybe flooded the cylinders and it took awhile for them to dry out.

I'll see if she starts again when I get everything back together.

GEEZE! Steve

 

[Steve 147]

Well got it all back together and it started right up.

I don't know, maybe it should have stayed broke so I could have been confident I found a problem and fixed it. Its probably a bad connection somewhere.

Really the only thing I did between the time it would not start and this last time when it did start is to leave it set for a long time with the battery disconnected.

You're right the car setting a lot is bad on it and I have told her that. Fuel injection, pump, sending unit, electrical connections, seals, gaskets, battery and so forth.
Yup the next thing to go wrong will probably be the fuel system. I have been keeping it consistently at 3/4 of a tank and add stabile once in a while.

Yes if a person is not careful you could get the opti installed wrong. The shaft is keyed both on the crank and on the opti. the trick is not to force the opti on. The aftermarket opti has the shaft permanently attached. Get the shaft set up close to the keyway just have to be patient and turn the opti shaft a tooth at a time until they go together smoothly.

By the way the MAF sensor reads 10 when the engine starts.

I am going to try to pull the CCM codes now that the digital display is working.

I have worked on some of the other newer vehicles and they sometimes have a computer glitch and have these kinds of problems. Sometimes disconnecting both the positive and negative battery cables from the battery and letting them sit or connecting the two cables together for awhile has solved some computer problems.

Anyway, thanks for all the advice and help. Maybe this discussion can help someone else.

Steve