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I cannot get the 91 to start. It does seem to be ignition related. Here is the info to work with;
I replaced the regular battery with a smaller battery/ 220cca motorcycle (AGM) battery.
The starter will turn over and the fuel rail pressurizes via the oil pressure sensor instead of the fuel pump relay. I have a fuel pressure gauge hooked up and that is how I know. The fuel pressure will not come up at key on, it takes a few seconds after the engine is turning via the starter and then pressurizes via the oil pressure switch. Just like the manual says it will. But, there is no ignition. It will just crank and crank but will not fire.
The sys symbol in the dash display, where the speedometer is, flashes and the battery light in the center console info display is illuminated.
My thought is that there is just not enough amps from the smaller battery to get the ECM to fire injectors or to send power to fuel pump relay.
I know some other C4 owners out there have used these smaller batteries. Is there something I am doing wrong?
From: Las Vegas - Just stop perpetuating myths please.
Easy test for spark is to pull a plug wire, stuff any spark plug in it and lay it on the manifolding somewhere it can connect to ground. U should observe a spark in the plug electrode when cranking. They do sell lights that install inline with the plug/plug wire and will lite up on cranking but u can choose which for yourself. BTW they sell "node" lites for the injectors too. Dont use one of those sharp pointed "stab" lites on your ignition plug wires or u will have ruined them by 1 pierce.
U can always try a batt from your other car or even a jump with cables will make the difference.
I did hook up jump cables from another vehicle but still had the battery light and sys flashing in gauges screen. I guess I will try another battery, but I know some other guys are running these batteries so hoping it is something I need to do.
Also, I did replace the steering wheel and removed the SIR system. I didn't see anywhere that the SIR was connected to Ignition System so don't think that could be my problem.
Easy test for spark is to pull a plug wire, stuff any spark plug in it and lay it on the manifolding somewhere it can connect to ground. U should observe a spark in the plug electrode when cranking.
That test can also be done with a screwdriver; observe the length and color of the spark.
Someone familiar with VATS on a '91 might tell if the SIR removal has affected it.
Frankly, I am surprised that such a small battery could deliver enough power to prevent the voltage from dropping to a point where the ECM won't function (around 10vdc?).
That test can also be done with a screwdriver; observe the length and color of the spark.
Someone familiar with VATS on a '91 might tell if the SIR removal has affected it.
Frankly, I am surprised that such a small battery could deliver enough power to prevent the voltage from dropping to a point where the ECM won't function (around 10vdc?).
This could be a possibility. I just did a CCM diagnostic test and it is giving me code C41 and H41. Which according to the manual is a failure to acquire an ECM serial number communication which I guess is saying there is no communication with the ECM. I wonder if this is due to the smaller battery not supplying enough amps for the ECM to power?
This could be a possibility. I just did a CCM diagnostic test and it is giving me code C41 and H41. Which according to the manual is a failure to acquire an ECM serial number communication which I guess is saying there is no communication with the ECM. I wonder if this is due to the smaller battery not supplying enough amps for the ECM to power?
First, you still need to know if there is any spark.
You need spark before anything else will happen. The ECM uses the reference pulses from the ignition module in the distributor to synchronize the firing of the injectors with the rotation of the engine. Without those pulses your injectors will not fire.
You could have a bad ignition module or pickup coil. You can have the ignition module tested at most auto parts stores. Be sure to put thermal grease under it. It gets VERY hot. You can test the pickup coil with an ohmmeter. It should read around 800 ohms (or 0.8 if you're on the Kohms scale).
You might want to make sure the distributor is getting power. The wire on the BATT terminal should measure around 12 volts when the ignition is on.
Thanks for all the input. I am going to just put a auto (car) battery in and see if that remedies the issue. I think I am just short on amps for the complete system to function. Hopefully this is the only problem.
Okay, I put the standard auto battery in and no change. I also pulled the number one spark plug and cranked the engine; no spark at the plug. After this I pulled the ecm off the mount so I could verify all the wiring going into it were snug and no signs of bad wiring and all looks good.
From: Las Vegas - Just stop perpetuating myths please.
No spark out the plug then next step back is the coil. If u are sure the plug was in contact with bare metal to make ground connection then u can measure voltage at the coil where the positive side sees 12VDC but is trigged off as the dist shaft rotates. Oops this is an HEI with coil in the cap isnt it?
Ok, ok, ok no more guessing around and i got out the '88-'90 chiltons (assume the '91 same TPI as '90). Code 41 for the corvette is called "cylinder select error". If u turn off the ignition - which should clear the code - and code 41 sets again when turned on then the "Mem-Cal" is installed wrong or faulted. Check pins on the Mem-Cal and ECM. If replacing Mem-Cal doesnt fix it then its the ECM.
There is a test for the ign module and coil but its too extensive to post here. But i found a good link for testing the HEI ign: http://easyautodiagnostics.com/gm/4....ed-icm-tests-1.
Well, finally figured it out. The issue at least and now I need some serious help with a repair.
I removed the complete SIR System. I did not have any indication that the SIR was tied into the ECM. Well it is. Section 6e3-a-14 under drive ability and emissions (Chart A-1). No service engine light, which I do not have illuminating says under test description; The SIR system Diagnostic Energy Reserve Module must be connected to the I/P Harness or switched ignition voltage will not be supplied to the ECM and his will not allow engine to start. Dammit.
Your going to have to figure out with the FSM/Electrical Supplement and determine what input the SIR provides and then provide it to that pin. Sorry I have an '85 and no SIR so I cant help with that.
I am going to connect the yellow 1139 to the radio hot wire and that should hopefully get the power to the ECM.
I will provide an update once I get it done. Pulled the passenger side of dash apart this evening and will try to finish up by this weekend. Going to be busy for the next few days.
Your going to have to figure out with the FSM/Electrical Supplement and determine what input the SIR provides and then provide it to that pin. Sorry I have an '85 and no SIR so I cant help with that.
Ask Cliff Harris!
I have an '86, so no SIR in my car. I am not familiar with the SIR wiring.
Originally Posted by chevyowner
You can try jumping B3 to B9.
I don't see any connections between the DERM and the ECM. It looks like the "ECM fuse" gets power from the ignition switch (through the splice next to "C") whether the DERM is there or not. Maybe this diagram doesn't apply in this case?
I know in my car the only usage for the ECM fuse is to tell the ECM that the ignition is on.
Last edited by Cliff Harris; Dec 17, 2014 at 01:32 AM.
I have an '86, so no SIR in my car. I am not familiar with the SIR wiring.
I don't see any connections between the DERM and the ECM. It looks like the "ECM fuse" gets power from the ignition switch (through the splice next to "C") whether the DERM is there or not. Maybe this diagram doesn't apply in this case?
I know in my car the only usage for the ECM fuse is to tell the ECM that the ignition is on.
Somehow I overlooked the splice.
PS
The fuse block diagram shows that the ECM fuse gets power from the SIR module.
Last edited by aDigitalPhantom; Dec 17, 2014 at 08:47 AM.
Starting/Ignition Issue
