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Help No start condition

Parrothead

Well-known member
Joined
Jul 23, 2003
Messages
63
Location
Lakewood, Washington, United S
Corvette
Quazar Blue 92
Well Merry Christmas to me. My baby will not start this afternoon. She turns over fine but won't start. Here is a list (yea it's a list) of symptoms:

Flashing Service Engine soon light

A clicking sound (like a relay) from under the dash, sounds like just to the right of center.

Flashing Security light

Flashing SYS light on the Speedo: flashes 3 times then displays a LO

Service ABS light stays on as well

Over the last couple of weeks while driving I have had all of the same indications happen as well as a sudden miss but never had a no start or the ckicking sound and they always reset when the car was turned off. I wasn't able to get into a shop until after the Christmas Season but now it l guess I don't have much of a choice unless I can figure it out with your help.


I read some of the other posts about some of the same conditions but my Battery is less than a year old, my aftermarket stereo has been installed for over two years and the guy was experianced with installing in Corvettes. I also didn't see any threads about the LO on the speedo. Sorry if this is rehashing old stuff.

Thanks for any advice you can give.

God Bless those in the Military during this Holiday Season..........:pat
 
Parrothead said:
Well Merry Christmas to me. My baby will not start this afternoon. She turns over fine but won't start. Here is a list (yea it's a list) of symptoms:

Flashing Service Engine soon light

A clicking sound (like a relay) from under the dash, sounds like just to the right of center.

Flashing Security light

Flashing SYS light on the Speedo: flashes 3 times then displays a LO

Service ABS light stays on as well

Over the last couple of weeks while driving I have had all of the same indications happen as well as a sudden miss but never had a no start or the ckicking sound and they always reset when the car was turned off. I wasn't able to get into a shop until after the Christmas Season but now it l guess I don't have much of a choice unless I can figure it out with your help.


I read some of the other posts about some of the same conditions but my Battery is less than a year old, my aftermarket stereo has been installed for over two years and the guy was experianced with installing in Corvettes. I also didn't see any threads about the LO on the speedo. Sorry if this is rehashing old stuff.

Thanks for any advice you can give.

God Bless those in the Military during this Holiday Season..........:pat
I am not going to be much help but you need a bump!
To start off I have skimmed the manual, and I haven't found a LO in my manual either.
However, the sys indicator flashing 3 times every 15 seconds is an indication of a current DTC malfuncation. Can you go into diagnostic mod and pull the codes?
You mentioned the battery; what's the voltage displayed on the dash before you try to start it?
Hopefully it is something simple like a dead battery or dirty contacts on your key's resistor!
Good luck!

Mike
 
Aboatguy, Thanks for the reply,

I will have to check the volts displayed but yesterday it was 14.4 which is what I normaly see when engine is running. Is there away to pull codes without a scanner? Just not sure how to do that. Also and pardon the ignorance....what is the DTC?
 
Parrothead said:
Aboatguy, Thanks for the reply,

I will have to check the volts displayed but yesterday it was 14.4 which is what I normaly see when engine is running. Is there away to pull codes without a scanner? Just not sure how to do that. Also and pardon the ignorance....what is the DTC?
I'm sorry I have spent too much time with the Helms manuals and tech forums (Diagnostic Trouble Code/s) DTC/s.
Go here for info on your car you have a vin P
http://www.troublecodes.net/GM/
 
Parrothead said:
I read some of the other posts about some of the same conditions but my Battery is less than a year old,:pat

I would recommend still checking the battery. I had the clicking sound and the car had problems where it wouldn't start. I too had Iinstalled a new battery just this summer and it turned out that was the culprit. Put a new battery in and it started up just fine.
It's worth a shot.
 
Confused even more now,

So I go out this AM (the rain finally stopped) to check for codes and she starts right up and doesn't show any cods other than 12 which is for diagnostic mode. It flashed that over and over.

I am going out to get a new battery as advised and see if that fixes it. I am also keeping my paperclip handy so if it happens again I can see what is there.

Thanks for the advice, if it comes back I'll post the codes displayed.....
 
When something fixes itself as you describe, it's all but guaranteed that it will occur again.

Next time that it turns over but will not start, check for fuel pressure and spark. That divides it into one of two categories and you then go from there.

Given all the things you described the probably is almost certainly electrical but that is resulting in either the fuel pump not running or the ignition not sparking. Once you've narrowed it down to one of those two, then you can keep troubleshooting from there.

Good luck,
 
L-98 Engine Start Sequence

When you start an L-98 engine Corvette, a series of events take place that causes the engine to run. Knowing the sequence will help you troubleshoot no start conditions.

Fuel Rail Pressurization:

When you first turn the key to the “on” position, the fuel pump will run for 2 seconds pressurizing the fuel rails. There is a Shraeder valve on the passenger side fuel rail near the rear of the engine and if you measure the pressure there after the pump runs, you should see between 40-42 pounds of pressure. The reading will go to 38-40 pounds nominal once the engine is running.test by attaching a fuel pressure gauge to the fuel rail at the shrader valve, on TPI and LT1 engines its located on the pass side fuel rail

Initial Crank Action:

If you then rotate the key to the start position (assuming the anti-theft system has not disabled the starter), the engine will rotate.

Once the oil pressure has reached 4 PSI, the oil pressure switch will close allowing the fuel pump to run. (Note that you should have a black oil pressure switch/sender. It is mounted behind the distributor on the driver’s side and if it is not black, it is suspect due to a run of bad units that stayed in the GM parts pipeline for some time).

The distributor will send a string of pulses to the ECM (Engine Control Module) in response to the engine being rotated by the starter. These pulses continue as long as the engine turns (both starting and running) and if they are not present, the engine will not run.

ECM Reaction:

If the ECM sees oil pressure greater than 4 PSI and the reference pulses from the distributor, it will energize the injector drivers which will begin pulsing the injectors on for 4 ms (milliseconds) periods. (In the L98, all injectors on one side of the engine fire at the same time followed by all injectors on the other side firing at the same time. On the LT-1, the injectors are fired individually at the appropriate time).

The ECM will also pull in the fuel pump relay in effect paralleling it electrically with the oil pressure switch. (If the fuel pump relay fails, you can still normally get the car to start and run unless you can’t make at least 4 PSI oil pressure. This is a “limp home mode” feature put in place to allow for a fuel pump relay failure).

The ECM also monitors the TPS (Throttle Position Sensor mounted on the throttle body assembly) and wants to see .54 volts at this time. If it sees appreciably more than 0.54 volts, it will assume the engine is flooded and the driver has pressed the accelerator to the floor to clear the flooded condition and restrict the fuel flow as a result. (.54 volts during start and at idle from the TPS is very important to both starting and run performance.)

Assuming the ignition module is good (meaning there is a spark of sufficient intensity to ignite the fuel), the engine will “catch”.

Engine "Catches":

When the engine catches, the MAF (Mass Air Flow sensor mounted just ahead of the throttle body) sends a signal to the ECM advising that air is flowing and also just how much air is being pulled through to the intake manifold. The ECM takes note of the amount of air being consumed and adjusts the injector pulse width to around 2.2 ms nominally so as to attain a proper air/fuel mixture to insure combustion. (This is how the 1985 through 1989 L-98 works. For information on the 1990 and 1991 L-98 variant, see the Note below).

The engine should show an initial idle speed of around 900-1100 RPM and then slowly diminish to 600-700 RPM unless the air conditioner is on in which case it will run at around 800 RPM.

If this does not happen, the Idle Air Mixture valve (located on the throttle body) may be misadjusted. Alternatively, there may be a leak in the intake manifold or another vacuum leak may be present. Listen for hissing sounds---there should be none.

ECM Mode:

The engine will now be in Open Loop mode meaning that the ECM is controlling the air/fuel mixture by referencing values stored in memory.

Once the Oxygen sensor (mounted on the exhaust pipe) reaches operating temperature of several hundred degrees, the Manifold Air Temperature (MAT) sensor shows an intake air temperature of more than 140 degrees and the Engine Coolant Temperature (ECT) has reached 160 degrees, the computer will switch to closed loop mode meaning the Oxygen sensor’s output is examined along with the MAT and ECT outputs and the ECM adjusts the injector pulse widths (more “on time” or less “on time”) to constantly strive for a 14.7:1 air/fuel mixture which is the best mixture to hold down pollution.

Note that prolonged idling can force the computer back into open loop mode.

Note: In 1990, the MAF was eliminated from the engine in favor of a speed/density system. This system uses a sensor called the MAP sensor which measures the Manifold Absolute Pressure (hence the name MAP) and compares it with the atmospheric pressure outside the intake manifold. This information, coupled with the Manifold Air Temperature, Engine Coolant Temperature and Engine RPM is used by the ECM to determine the amount of air entering the cylinders. It is a different way of reaching the desired 14.7:1 air-fuel mixture ratio but functionally is like the MAF system in that the ECM uses the feedback to control the "on time" for the injectors.

Corvette used this approach in the 1990 and 1991 L-98 engines and in the 1992 and 1993 LT-1 engines. With the 1994 model C4, they went back to the MAF system. Note that MAF based systems are far more accurate since they measure air flow directly whereas the MAP system infers air flow indirectly. A multitude of things can throw the calculation off and Corvette returned to the MAF system beginning with the 1994 C4 (with a MAP backup). From a troubleshooting standpoint, the MAP operation comes into the sequence the same place that the MAF does.

Summary:

If you have a no start condition or if the L-98 starts and then dies, check the above items in sequence to see if all the events are occurring as required.

A Scan Tool makes this job much easier and is a highly recommended troubleshooting aid for these sorts of problems.


Most of the C4 Corvettes used a MAF (Mass Air Flow) sensor to determine how much air is being pulled into the intake manifold. The exceptions are the 1984 Corvette that used a speed density system--a sort of predictive method of measurement---and the 1990 through 1993 C4 models which were also speed density based. In 1994, Corvette went back to the MAF based system but used the speed density approach as a back up. (1989 Bosch MAF installation shown at right).

A Mass Air Flow sensor has an extremely fine wire inside its bore. The 1985 through 1989 C4 engines used a Bosch MAF sensor that heated the wire to 100 C. The 1994 and later C4 models used a AC/Delco MAF that heated the wire to 200 C. The amount of current required to reach the temperature is measured in each case. (Note: the LT-5 engine used in the ZR-1 used a speed density system and continued to use that system in 1994 and 1995 since the engines had already been made prior to the last two years of production. The ZR-1 therefore has no MAF even after Corvette went back to the MAF based system).

Theory of Operation

As the air travels past the heated wire enroute to the intake manifold, it will cool the wire and additional current is added to again heat the wire to the design temperature. Since the amount of air moving past the sensor is directly related to the amount of cooling experienced by the heated wire, a feedback condition is established whereby the exact amount of moving air is directly related to the amount of current passing through the wire and the intake air is therefore precisely measured.

Once the amount of air is known, the computer controlling the engine can add or subtract fuel as required to maintain the magic 14.7:1 air-fuel mixture resulting in the cleanest burn possible from an emissions (pollution) standpoint.

It does this by varying the "on time" of the fuel injectors. The injectors are pulsed on and off and the width of the pulse is lengthened or shortened as required. When you first start a typical engine, the pulse width is around 4 milliseconds but as soon as the engine "catches" the pulse width is shortened to about 2.2 milliseconds for idle. During operation, the measured air flow through the MAF will cause the computer to increase or decrease the pulse width as explained above.

MAF Operating Conditions

The Bosch MAF is more complex than the AC/Delco version. Both measure the air flow but the Bosch MAF has a circuit called the 'burn-off circuit' that cycles on for about 2 seconds when you shut the engine down. This circuit heats the wire to a high enough temperature to burn off any residue that may have collected on the wire during operation. If you are in a quiet area, you can hear the relays click on and then off on a 1985-1989 C4 as the burn-off cycle occurs.

There are two relays involved with the Bosch MAF: A power relay that passes current to the MAF wire during normal operation and the burn-off relay that provides the current for the cleaning cycle. Both are located on the firewall in the engine compartment, just behind the battery on the drivers side. Bad MAF power and burn-off relays can cause hard starting problems and should be changed periodically as preventative measure and any time you experience hard starting conditions.

The AC/Delco MAF has a power relay but no burn-off relay. For this reason, you should pay even closer attention to the condition of your air filter on a later model C4 than normal since a contaminated wire in a AC/Delco MAF is going to stay contaminated for the most part and cause false signals to be passed to the computer.

Also, the Bosch MAF outputs its information as a analog signal to the computer but the AC/Delco sends its signal as a digital component of varying frequency. For this reason, you cannot measure it's operation directly.

A scan tool is generally the best way to troubleshoot engine problems and with the 1994 and later Corvette, it is virtually mandatory. (An oscilloscope will also work on the AC/Delco MAF but a regular test meter will not).

MAF Problems

Faulty MAF sensors will normally light the check engine light on the drivers information center if the problem is constant and store a trouble code. If intermittent, a trouble code will still be stored as long as the battery is not disconnected.

Normally, the problem is a poor connection at the sensor and wiggling the wires, unplugging and reinserting the connector will often cure the problem.

A faulty MAF will normally cause a no start or difficult start condition and although you can eventually get the car into the "limp-home" mode in most cases, you need to attend to the problem ASAP.

AC/Delco sensors can become intermittent or give false readings if the wires become contaminated as explained above.

The MAF is a critical part of the emission control system and as such will cause the computer to react to problems very quickly, setting trouble codes and reducing performance in ways that cannot be ignored for long.

MAF Mods

The Bosch MAF is often modified by removing the two screens that are present in the front and rear of the cylinder. Removing these screens significantly increases the air flow through them and this results in more horsepower. Removing the screens is an old trick from the Corvette Challenge days in 1988 and 1989. It does work but is illegal in many states so be advised not to do anything that will get you arrested for a pollution violation.

The AC/Delco MAF is not readily modified. It is what it is but since it is a larger diameter than the Bosch, it responds well to changing the air filter to a free flowing type such as the K&N filter.
Welcome to C4 vette codes it is very ....repeat very
important that if you are not savvy of working on your
vette ...you would be better off - taking your car to a
dealership for repairs on your trouble codes.
However if you feel that you want to dive right in ..than you
have come to the right place.First locate your car's alcl
this component is located just below the instrument panel and
to the left of the center console. Remove the plastic cover
the first two slots to your right are the A & B slots for a drawing of
the alcl module's picture is added below.
The A slot is the diagnostic slot and the B slot is the ground
slot. insert the computer key into these slots (with the engine
off) this is very important...now only put the ignition key
to on ( not start !!!) the check engine light will display a
code 12 which is one flash followed by two flashes.
this code will be flashed three times ..followed by the
trouble code stored in your car's computer.
what ever the code is it will be flashed three times.
have a paper and pencil ready and write down the
code .

code 13 =1 flash followed by 3 flashes =>oxygen sensor
code 14 =1 flash followed by 4 flashes =>coolant sensor
code 15 =1 flash followed by 5 flashes =>coolant sensor
code 21 = 2 flashes followed by 1 flash =>throttle position sensor
code 22 = 2 flashes followed by 2 flashes=> throttle position sensor
code 23 = 2 flashes followed by 3 flashes=> manifold air temp sensor
code 24 = 2 flashes followed by 4 flashes=> vehicle speed sensor
code 25 = 2 flashes followed by 5 flashes=> manifold air temp sensor
code 32 =>egr system
code 33 =>map sensor
code 34 =>maf sensor
code 35 => idle air control
code 41 => cylinder select error
code 42 => electronic spark control
code 43 => electronic spark control
code 44 => lean exhaust
code 45 => rich exhaust
code 51 => PROM
code 52 => fuel calpak
code 53 => system over voltage
code 54 => fuel pump circuit
code 55 => ecm
code 62 => oil temp
please remember that if you have the computer key installed
in the alcl and you start the engine ( you will ruin the engine's computer
)
only put the ignition to on (not to start)
If you should get a check engine soon display.. you can use
the above procedure and codes to buy the right part
or at the very least to keep from getting taken for a ride
and be made to pay hight prices for some inexpensive
module that you could have installed yourself.
You never ask a barber if you need a haircut ..
so you have to be on guard they will see you comming
a mile away.
If your engine displays a trouble code ... your engine will
go into limp mode ..it will still run but very poorly.
you might be able to reset the computer if it will not start
( just to get home ) by disconnecting both battery cables
and re-installing them ...this is not recommended ..but if
you are stranded it might help unitl you get your car home
or to a repair shop..good luck

--------------------
just because a 650hp big block was not a factory option in no way means I CAN,T INSTALL ONE!!
 
Just a little tip for not so computer savy members. You can highlighting text you wish to save and copy-paste it to a wordpad file. Name it so it is easy to find. This way you can print it anytime you need it for use in the shop.

Glenn
:w

PS I make a point to do this with Grumpyvette's information post. Thanks Grumpy.
 
Back to no start again,

This time I was ideling and it stalled out. I thought great, now I can get the trouble codes.......

What I did: Turned ignition off, inserted jumper into A and B ports, Turned ignition to on (not start :)), and wall la, I just get the service engine soon light quickly flashing and the clicking sound under the dash and no entering Diagnostic mode :hb. Isn't that just duckey.........I am on my way to get a new Battery (haven't made it that far yet) and will see what happens after that.

Grumpyvette, great explination of the start cycle, I felt like I was in school again :) Does the whole explination go with both L-98 and LT-1?

Thanks again for all the help............
 
theres very little differance between the two as far as diagnostics
you really can,t effectively play mr-fix-it with out the correct tools


https://www.etoolcart.com/index.asp?PageAction=VIEWPROD&ProdID=4047

while it appears to be expensive, it saves you a good deal of money in the long run compared to dealing with the local chevy dealers mechanics, and makes diagnostics far faster, I bought this for the shop and it seems to be a good investment, since between a dealers diagnostics and swapping parts that don,t need changing you could easily spend close to that on just a few problems getting sorted out
youll also want a few basic diagnostic tools

https://www.etoolcart.com/index.asp?PageAction=VIEWPROD&ProdID=4417

https://www.etoolcart.com/index.asp?PageAction=VIEWPROD&ProdID=6688

https://www.etoolcart.com/index.asp?PageAction=VIEWPROD&ProdID=2597

https://www.etoolcart.com/index.asp?PageAction=VIEWPROD&ProdID=8108

and a book or two

http://www.amazon.com/gp/product/08...103-1721776-8382206?s=books&v=glance&n=283155

http://www.amazon.com/gp/product/08...103-1721776-8382206?s=books&v=glance&n=283155

http://www.amazon.com/gp/product/07...1776-8382206?_encoding=UTF8&v=glance&n=283155

in no time youll be the area wizz kid on chevy injection diagnostics

guys are guessing at whats wrong on systems that have self diagnostic software that would tell them where to look if they understood the trouble codes AND THE BASICS of EFI and how engines function.

if the engines not running correctly its usually bad sensor function or a mechanical problem, yes its true that ignitions and minor adjustments can be the cause but in most cases the trouble codes or reasonable obvious clues to the cause are there if you know where to look,and can step thru the potential causes.

guys, don,t guess, step thru the probable causes one bye one, eliminate each carefully then move to the next only after TESTING,(that takes KNOWLEDGE, understanding the basic functions and some EQUIPMENT)
 
grumpyvette, what is the difference between the 6000 and the 5000/4000 series scanners? Is the difference in price worth the additional features?
 
Etoolcart Price: $349.99
http://www.etoolcart.com/index.asp?PageAction=VIEWPROD&ProdID=4048


Etoolcart Price: $439.99
http://www.etoolcart.com/index.asp?PageAction=VIEWPROD&ProdID=4047


the main differance is the ability to load the diagnostic software in your laptop and watch the data change as it comes in, with the ability to print off your computers printer ,is it worth an extra $100 or so, I said, yes but its up to you, keep in mind the ability to print out the data, make changes and keep the records of the results and keep EXACT records of those changes as your tuning/trouble shooting comes in VERY handy


Graph Drivability Capture Data
Achieve Scan & Capture information
Print reports
Export Capture Data in Spreadsheet Format
 
I agree with Grumpy. Dataloggers make trouble shooting intermittent faults much easier. I can upload my datalogs to my desk top and watch it over and over, checking the different parameters until I see/understand what happened.

Mike
 
grumpyvette said:
Etoolcart Price: $349.99
http://www.etoolcart.com/index.asp?PageAction=VIEWPROD&ProdID=4048


Etoolcart Price: $439.99
http://www.etoolcart.com/index.asp?PageAction=VIEWPROD&ProdID=4047


the main differance is the ability to load the diagnostic software in your laptop and watch the data change as it comes in, with the ability to print off your computers printer ,is it worth an extra $100 or so, I said, yes but its up to you, keep in mind the ability to print out the data, make changes and keep the records of the results and keep EXACT records of those changes as your tuning/trouble shooting comes in VERY handy


Graph Drivability Capture Data
Achieve Scan & Capture information
Print reports
Export Capture Data in Spreadsheet Format

Thanks for the reply! I guess I need to save my nickles and dimes.
 
No start update, not good

Well I finally was able to replace my battery but the problems continued so into the shop it went. The computer was intermittantly sending out bad data or no information at all to the diagnostic competer at the shop. If you wiggled or tried to shake the computer you could change the output data. The connecters appered to be fine so they replaced the computer. I got the car back and it ran great for 1 day.

After the first day I went out for a drive. First thing I notice is the digital water temp gauge reading over 200 degrees (when the car was cold) and fluctuating up and down by 30 to 40 degrees. Checked the Digital oil temp and it was doing the same thing. Don't remember the temp though. The analog water temp gauge was working fine. After a few minutes it started to develope a miss and I had way low engine power. No Warning or SYS lights this time. Took it back to the shop and now they report it is back to a no start condition and getting bad data from the computer again.

Does anyone have any idea what might be going on? Oh yea, the fuel pressure was good as were all vacume lines.

Thanks for the info so far........
 
I'm no expert in this matter, but could it possibly be a bad ground? These cars seem to be pretty finicky when it comes to being grounded. Just a thought.
 
my vote is bad ground or grounds. Normal computer reaction to bad connections or grounds is everything but normal.
Glenn
:w
 
Ground help

Thanks for the repy's.

Is there a "most likley suspect" in looking for a bad ground? Or a list of where the magor ground points are? I guess what I really need is a wiring diagram for the car. Does anyone have one in electronic format?


Thanks again for the help...............
 
I don't know how different 93's are from 94's but I can take a look at my Helms tonight if I have time and try to figure out where those are. There should be/is one near the back of the engine/transmission on the drivers side. I would remove clean thoroughly and then reattach. From what I have read and understand there are several ground points and any one could be the culprit.
 

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