OldS10

Have installed a 98 LS1 into an 89 S10. Time to start it up... 2 symptoms.
1. Turn key to "on". bright "MIL" light. engine starts up & runs smooth for 3-5 seconds, then dies.

2. Turn key to "on". dim "MIL" light, engine fires & immediately dies. No trouble codes.

We are using OBDcom interface with a laptop. No trouble codes, but it "connects" and can read O2 sensor voltages.

Our only 2 ideas are:
1. VATS not "turned off" in the PCM. Checked the PCM - VATS turned off

2. Oil pressure sensor reading low pressure? (We hooked up the original S10 oil pressure gauge to the LS1 oil pressure sending unit. Could it be loading the sending unit output enough to cause it to read low in the PCM?) Replaced the oil pressure sensor and disconnected the gauge.

have put a timing light on 1 plug wire just to see if spark is there while cranking...and it is.
Have monitored the fuel pump signal and it looks OK when it runs, and when cranking.
Have tried to monitor the ground side of an injector with a meter and an led to see if it is getting the grounding pulses...it appears to get them when it is firing or running, but not when it dies, or when cranking and not firing.

Have not had consistent DTCs.

For every time it runs for a few seconds, it fires & dies (probably) 10 times. It seems that if we wait awhile to try to start again, it does the run for 3-5 seconds.

We tried to be very careful & thorough when integrating the 2 systems together and modified the Corvette engine harness and the original S10 harness to integrate them.

Any ideas?

Thanks

ls1nova71

iTrader: (4)

Sounds exactly like VATS isn't off. I would check it again, and if you have the means to do so, turn it off again. I've heard of people turning it off, but it still being on.

Oil pressure should have nothing to do with it.

OldS10

Thanks for your input!

The guy who flashed the PCM checked the settings and said that it read "turned off". He then reflashed it "to be sure". I wonder if we need to pull it again and have somebody else check it with a fresh pair of eyes and another programmer. Also, in looking through the shop manuals for the Corvette, it appears that the data line out of the PCM ties to the body control module via a "star(??)" connector. Since the body control module was removed for our application, is there a way to put an input on that line to simulate the input that the BCM would send to the PCM to tell it that "everything is OK"? The thought here is that even if the VATS were NOT turned off, we could trick it into thinking that "all is good". If that were so, then maybe we could also "flip a switch" to remove the input and have it do what it is doing right now (thus our own anti theft device)???

Thanks again for your time.
PS-Nice 33. 33 & 34 are my favorites! (in cars)

aknovaman

iTrader: (7)

Unplug your MAF to force it into speed density mode. See if it fixes the issue (no cost). I bet it is going bad or dirty. You need to scan the car using HPTuners to see if all the sensor data is good and solid. I have seen bad maf and cam position sensor not fully plugged in. Need data or you are pissing in the wind and flushing bux down the drain.

OldS10

Thanks for the ideas. We unplugged the MAF and got a P0102 DTC. Otherwise the symptoms stayed the same. Reconnected the MAF and after several cycles, the DTC went away. Checked the cam position sensor connection and it is clipped on solid. You mentioned scanning using HPTuners. Excuse my ignorance, but what is that?

Thanks again!

cdk4219

Sure sounds like VATS

pdsq98gt

Check your grounds. The dim MIL light sounds like a bad ground problem

aknovaman

iTrader: (7)

Hp tuners is one of the software packages that is used to tune ( kill vats as well and timing, fuel and trans controls) and includes a scanner that allows you to look at all the sensor data as well as the coil and injector data. It is essential to troubleshooting issues like yours. First and foremost you need to see what the PCM is reading from the sensors and telling the injectors and coils to do. Find someone local to you that has hp tuners or efi live and have them datalog the car while cranking and brief run times. Also check your grounds and power to the PCM, maf, cam and crank position sensors with a reliable volt meter.

psiconversion

iTrader: (5)

For check engine light.... are you using an LED or a Bulb? If LED, you have to put a resistor in line for it to function properly.

Regarding start/stall issue, is this a 98 PCM or have you upgraded to the 99-NEWER PCM?

Jon
PSI

OldS10

THANKS, Guys for your time!
I will respond to each reply here.

Sure sounds like VATS

1. That is the most common input that we have gotten & makes the most sense. We have had the guy who flashed the PCM check it & reflash it with no change in symptoms.

Check your grounds. The dim MIL light sounds like a bad ground problem

2. We checked all 4 ground wires for the PCM, and even jumpered the ground wire for the splice pack that the PCM wires go to, to the cylinder head. We have tried to be thorough with our grounds, as we heard that this could be a big problem. Used a Fluke DMM for all electrical checks. Ground checks on the 2 ohm scale read less than 1 ohm. I did consider that the transistor circuit inside the PCM that pulls the MIL line to ground may not be pulling it “solidly”, but am not sure how to check that.

Hp tuners is one of the software packages that is used to tune ( kill vats as well and timing, fuel and trans controls) and includes a scanner that allows you to look at all the sensor data as well as the coil and injector data. It is essential to troubleshooting issues like yours. First and foremost you need to see what the PCM is reading from the sensors and telling the injectors and coils to do. Find someone local to you that has hp tuners or efi live and have them datalog the car while cranking and brief run times. Also check your grounds and power to the PCM, maf, cam and crank position sensors with a reliable volt meter.

3. Found them at Summit...Thanks! I will check around for somebody local that can help here for less than purchase price. Otherwise will have to buy one. Will also check the power & grounds on the sensors.

For check engine light.... are you using an LED or a Bulb? If LED, you have to put a resistor in line for it to function properly.

4. We are using an LED bulb. When the instrument cluster was out for accessing the old cruise control module & wires, we replaced as many bulbs with LED bulbs as possible. They are supposed to be a direct replacement for 194/174 bulbs. I didn’t think that an inline resistor was needed??

Regarding start/stall issue, is this a 98 PCM or have you upgraded to the 99-NEWER PCM?

Yes, it is a 98 PCM. When we bought the engine, we got the engine harness, cabin harness, all emissions equipment, the exhaust system, and anything else we wanted. We also got to hear the engine run, before he took it out of the chassis.


Again, Thanks for your time and expertise. It IS appreciated.

Denny

ealvarez11

i have exact same problem with my lsx....everyone kept telling me VATS...like you i triple checked removal of VATS...still can't get it to fire...hoping you find a solution

psiconversion

iTrader: (5)

LEDs need a resistor (unless they built the 'bulb' with one included). If you dont have one, it is almost like a short to ground.

Regarding the no start, as some have suggested, I would get a scanner on the car and watch the crank signal/maf signal when engine is cranking and running.

Jon
PSI

garys 68

iTrader: (1)

I'm running a 12V LED, what ohm resistor is needed?

OldS10

I'm guessing that you had a reason for asking whether the PCM was a 98. Did that PCM have some weird things that the newer ones did not?

Thanks!

psiconversion

iTrader: (5)

Gary do you have a dimming issue with the Check Engine Light with Key on or engine running? Typically if someone has a 12 volt LED it has circuitry built in to provide resistance.

Based on the OLDS10 'Dimming' Issue, I was recommending that a resistor be put in line as a dummy load.

Jon
PSI

psiconversion

iTrader: (5)

Just getting my bearings on what the situation was electrically as they are pinned out differently than the 99-newer setups. I dont think the fact that you are using a 98 PCM is causing the issue.

Jon
PSI

garys 68

iTrader: (1)

My CEL is always on with the key, just VERY dim. Never been a problem though.
Much brighter when a code comes up.

OldS10

Hi Jon,
Thanks again for your reply. In thinking about the PCM, it occured to me that since the serial data line on the PCM was tied to the serial data line from the body control module, the PCM might be looking for a signal from the BCM, even with the VATS "turned off". We removed the BCM from the harness as we weren't using it, but wonder if we need to hook it up somehow to simulate the "all is good" signal to the PCM on the serial data line.
In your experience, have you successfully "turned off" the VATS in a 98 PCM?
Not sure where we're going here yet, but .......

We have also been looking at some tuners/programers. The HP and Hypertech don't specifically say that they can turn the VATS off, so more research is in order.

Thanks for the input on the PCM pinouts. I thought that they might be the same. We bought the GM LS1 conversion manual that they used to sell for their kit, but I hadn't looked at the pinout closely since we also had the 3 part Corvette service manual.

Thanks again,
Denny

psiconversion

iTrader: (5)

Sounds to me like the LED you are using does not have enough resistance. It may not be a problem in your conversion, however, I have had customers call telling me that the fans will never go off. First question I ask is 'Do you have the check engine light hooked up?' answer is typically 'No, I didnt get that far yet, or yes, but it is glowing dim.' I follow up that it must be hooked up or the PCM can go into a limp mode as it THINKS there has been a check engine light failure even with the LED which acts like a short to ground (no/minimal resistance) if no resistor is put in line.

psiconversion

iTrader: (5)

Denny,

Yes i have turned the VATs off on multiple 98s and never had a problem. Regarding the BCM, I have only seen an issue in factory applications (typically LT1 Impalas/Caprices) where a customer has an issue with the key. So they want the VATs turned off. What they fail to realize is that the key is creating a voltage drop which is read by the BCM, the BCM 'OKAYS' the voltage drop and sends a 50-Hz signal to the PCM to pulse the injectors. Additonally the BCM in those applicaitions will also trigger a starter/ignition relay.

That said, if you arent running a BCM I dont think you have to worry about any of that. If VATs is off, it is off. I still think you should get a scanner on the car and take a look at what the PCM is seeing when you crank the car to start it. It will at least get in you in a positive direction.

Jon
PSI