irocdaddy

O.K. I PUT IN A NEW MODULE LIKE WE DISCUSSED EARLIER IN THIS FORUM. THE CAR STILL WON'T RESTART AFTER RUNNING SOMETIMES. SO AS NOT TO CONFUSE OTHERS, THIS IS NOT DO TO THE VATS SYST. MY STARTER DOES CRANK. ALSO, I ADDED A NEW CAP AND ROTOR WHILE I WAS IN THAT AREA. ANYMORE IDEAS?

turbo497

Check wiring harness that pugs into ECM.

Drop computer, start car and gently give each wire in the loom that plugs in the computer a tug.... When the harness is made if the machine over crimps the wires you can have an intermittant open in a circuit.

GMTech

Hmmm, thats very odd, because Johns car was doing the very same thing, and when it wouldn't start, we did what we told you to do (carb cleaner), I think you remember the story. Anyway, the reason it wasn't starting was no injector pulse. When John manual triggered the ECM (replicated the signal from the Distributer) the injectors would then fire. So it definatly sounds like its the distributer (assuming yours is doing the exact same).

Its just that the ignition module fit the description so well with the RPM window like we discussed before. I am curious if maybe its a pickup coil or reluctor wheel problem.


Turbo, I know good and well about the problems you are refering to, and I thought that about Johns car (who I mentioned earlier) but we never could find any type of problems there. But you could always get the car started with carb cleaner and then it would run fine all day (several days for that matter), w/o ever touching any of the wires.

It shouldn't be ECM related, because we tried two new ECMs, no change. Its real hard to say.

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If you live in Southeastern US, check us out!
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ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey, 22# injectors,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE

irocdaddy

My Chilton manual says to check for spark at the plug during the no fire cond. If no spark or weak spark, this is Distributer related. Also, The coil must be tested at the BAT terminal to see if thier is an open circuit running from thr ignition switch. Knowing these things, once I determine if it is an open circiut before the Distributer or a problem within the distributer I will know where to look. Which terminal on the coil is BAT? Also, if problem is within distributer, how can I test the pick-up coil?

GMTech

Yes, if there is no spark during the "no-start" then it is safe to assume that it is in the distributer as long as we do have power going to it, BUT... If you can start the car by adding starting fluid, than it wouldn't make sense to have "no spark". Understand?

Obviously we have a lack of fuel, either getting to the injectors or the injectors not spraying. If you had a "noid" light, you could test and see if the injectors are indeed trying to fire during the "no-start". The problem I have with it being the pickup coil is that the car shouldn't have spark either, since the Ignition Module uses it to know when to fire the coil.

My reccomendation is: Go to a part store and ask for an injector "noid light" for your car. It should only be about $10 (I have seen whole sets for $17). Then next time it doesn't start, unplug an injector and plug it into the noid light and have somebody crank it. If the light flashes, then the ECM is trying to fire it. Do that and let us know.

------------------
If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey, 22# injectors,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE

irocdaddy

GMTECH-I can't thank you and everyone else on this board enough for the help that has been provided. I will test the signal to the injectors and get back to you.

irocdaddy

GMTECH- I got a noid light and determined there is pulse at the injectors during no fire. Also, we do have spark at the plug during no fire. Here's something odd though....when the car is coooold, you can restart with no problem,but after about 100deg. no fire again. This isn't operating temp,but it was something I noticed. Like I said before, this thing has been going on for years! With patients, we should be able to narrow this some more? What about my coolant temp switch? would this explain the cold start success?

[This message has been edited by irocdaddy (edited January 11, 2001).]

GMTech

OK, so lets get this straight:

When the vehicle won't start:

• The injectors DO pulse
• There IS spark getting to the plug
• The vehicle CAN be started with some sort of starting fluid

Is all of this correct?
Does your car have the "cold start valve"?

------------------
If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey, 22# injectors,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE

irocdaddy

All the above is correct. I do not have a cold start valve. The following is what we know about fuel pressure at the rail:
-engine idling no load=35lbs.
-no load wot=45lbs.
-no start at 40lbs.
-did start once at 30lbs.
-still will fire w/starter fluid.
The injectors are stock and were cleaned and flow matched a few years ago (7000 miles ago).

[This message has been edited by irocdaddy (edited January 13, 2001).]

GMTech

Something is just not adding up.
We know you have spark, all the time. And you also have injector pulse w/ sufficient fuel pressure at the rail during the no-start, and yet starting fluid will get it started meaning a lack of fuel.

I wonder if maybe there is a "dead spot" in your coolant temp sender for the ECM. You said it starts cold all the time, every time, it only acts up when its slightly warm. Maybe that "warm spot" is the "dead spot" and fooling the computer into thinking its way hotter than it really is and is leaning out the mixture enough so that it won't start? Don't confuse the ECM temp sender w/ the gauge temp sender, they are different. IF you had a scantool, you could look at the CTS value when it won't start to verify. If you don't, I hate to tell you to throw endless parts at the car, but it may be a CTS problem.

------------------
If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey, 22# injectors,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE

irocdaddy

I have no problem putting a new CTS. Once it is in, I will let you know.

TunedPort350

Have you actually pulled out a plug and checked for presence of fuel during the no start condition? Is it wet?, or completely dry?

As for the starter fluid on a flooded engine it is just possible because engine starting fluid is comprised mainly of Diethyl Ether. Ether in a gaseous state has an auto ignition temperature of 180 deg C. When the air and ether vapor mixture is introduced into the engine combustion chamber, ignition will take place as the heat of compression reaches 180 deg C. As the piston nears the top of the compression stroke, if the heat generated by compression plus the added heat from the burning ether is sufficiently above the auto ignition temperature of 360 deg C, of gasoline, the cylinders will "Fire" and a successful start is achieved.

If you do try holding the pedal to the floor (WOT) the ecm will see a clear flood condition and will not inject any more fuel. If it does start at WOT the next thing is to figure out why there is too much fuel being supplied. It definately could be a bad CTS fooling the ecm into thinking the engine is colder than it actually is, thus supplying too much fuel.

[This message has been edited by TunedPort350 (edited January 14, 2001).]

irocdaddy

I am pretty sure the plugs are dry during the no fire cond. I will test this today to confirm and get back to you.

GMTech

Tunedport, don't be offended, I wasn't saying the either one of us was "wrong" or "right", hell, if one of us was "right", then this car would be fixed already. I just had a hard time seeing how a flooded engine could be started by adding more "fuel". Your explination may be possible, but then you need to account for the fact that "starting fluid" is a loose term, that can range from ether, to carb cleaner, to the "old" style WD-40.

------------------
If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey, 22# injectors,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE

TunedPort350

GMtech, no offense taken
I understand your point. I am also just trying to help, and rule out other possibilities.

Tim Burgess

If this is a tuned port motor, it is possible that the fuel pressure diaphragm has a small tear in it & is slowly flooding the engine through the vacuum reference tube, after the engine is turned off. Also, it is possible for a fuel injector or injectors to be leaking. If the ECM detects a flooded condition, it will disable the fuel injectors for a period of time. If a scanner is used to determine when the injectors are firing, it may miss the initial onset of the fuel injectors, when the engine is initially cranked, due to the event occuring in between scanner sample periods. Pull the reference tube from the regulator & look for fuel after the motor is hot & turned off & sits for a while. If that's OK, then check the injectors by doing a leakdown test with a pressure gauge on the fuel rail or pull the fuel rail assembly & inspect the injectors while they are under pressure.

Tim

irocdaddy

I WILL CHECK WHAT YOU'VE MENTIONED. THANKS

GMTech

Tim, thats good thinking, except the computer doesn't automaticly go into the "clear flood" mode, the operator has to put the throttle past 80% while cranking. Hooking up a pressure guage will definatly help rule a leaking diaphram/injectors.

------------------
If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey, 22# injectors,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE

irocdaddy

I put in the new CTS,no change in starting cond. I am out of ideas. Since the car runs fine, it can not be a constant condition.What does the term "vapor lock" mean?can I be experiencing this? What about the fuel pump or relay? how can I test these?

[This message has been edited by irocdaddy (edited January 18, 2001).]

Tim Burgess

GMTech, what other ECM condition would cause the injectors to be shut off during cranking? I'm just curious - I had a hard start problem a while back & thought it was electrical, since the Auto Xray was showing no injector pulse for 3 to 4 seconds of cranking - and then when the injectors were finally enabled by the ECM, the car would finally start - it turned out to be a leaking regulator that was flooding the motor - the flooding condition was some how detected by the ECM & I did not touch the gas pedal during cranking. I guessed that the reason the ECM shut down the injectors for 3 - 4 seconds was that the ECM did not sense an RPM increase with the application of fuel at the onset of cranking, after a certain period of time. I also hypothesized that the injectors may have been enabled for a short period of time, initially, but it happend between sample periods on the Xray - which is why I never saw it. Any ideas on why the fuel injectors were held off for 3 - 4 seconds with a flood condition without any throttle applied? ('92 VIN F TPI)

Tim

GMTech

Tim, the ECM has no way of knowing that the engine is flooded. Remember, the O2 sensor is to cold, so it is reading 450mV regardless of how rich/lean the exhaust is, so the computer has no way of knowing. It may be that it just took 3-4 cranks for the excess fuel to evaporate, or it may have taken that long for the oil pressure switch to turn the pump on, since the "2 second prime" has leaked down already. As for the injectors being turned off, that may just be coincidence, or it may be that the scanttool was just real slow, hard to say. Maybe it just wouldn't register untill the car was running?

Irocdaddy, don't know what to tell ya, bud. Try what tunedport said. Next time it won't start, see what the plugs look like. If you have a fuel pressure gauge, see if you don't have some sort of fuel leakdown problem. Anything is possible at this point.

------------------
If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey, 22# injectors,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE

Tim Burgess

GMTech, the fuel pressure was normal during the entire cranking period of 3 to 4 seconds during a hard start condition. I took data on several "hard" starts, and several normal starts, and the data was repeatable - on easy starts, the engine started when the fuel injectors were enabled, which was right after cranking commenced, where as on hard starts, the engine started when the fuel injectors were enabled, as well - it just took 3 to 4 seconds of cranking - a long period of time - until the injectors were enabled. I agree that the O2 sensor is useless at engine start time, as it is an open circuit when cold, but there has to be some algorithm in the ECM software that disabled the injectors for that excessive period of cranking time - every time the hard start occurred. It seems to me that the algorithm would have to be based on the derivative (rate of change) of rpm while the engine is cranking.

Tim

irocdaddy

Hey Tim/GMTECH-
I guess now everyone here know's why I have had this condition for years. This IS very hard to diagnose. I love my IROC, but at times like this, thoughts of selling enter my mind. Of course I couldn't sell her! After all the car did get towed 7 times in one year after the dealer installed the ZZ4. Oh ya, there was also that time the iroc rolled off front ramps pinning me until the fire dept. got it off me! Yes my friends this is the history love is made up of. The car had 28k miles when I got her in "95" Today, actual mileage is 67k. O.k. enough of that. Upon no start cond. there is no presence of fuel on the plugs. Fuel gauge shows no drop in pressure during no start. What do you guys think would happen if I let my local G.M. Dealer have a stab at it? Should I put in a new regulator before giving up? Since the car will burn a flammable substance sprayed into the TB, can we be sure this is definately fuel problem?

Tim Burgess

What year TPI? '90? Did you pull the vacuum line off of the fuel pressure regulator & see if fuel comes out of the steel tube after sitting for a while when the engine is hot?

Is it true that during a hard start if a test light is put across both wires of a fuel injector plug, it will blink, and fuel pressure is in the 35 - 45 psig range, yet starting fluid will start the motor?


Tim

irocdaddy

TIM-
1989 IROC.
NO GAS PRESENT IN VACUUM FROM REGULATOR.
FUEL PRESSURE IS STEADY AND WITHIN RANGE.
SPARK PLUGS ARE DRY.
I USED A "NOID" LIGHT TO TEST INJ. PULSE,WHICH WAS NORMAL.

DAVE.

Tim Burgess

I wonder what the output of the MAF looks like at startup & I wonder if the fuel pressure drops off fairly fast after the motor is shut down.......Maybe it's time to invest in an AutoXray - $150 from Checker - and if you want the ability to download & graph the data on a PC, get the EZlink kit for another $90.

Tim