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1995 firebird not starting after engine swap


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#1 Narfbrain

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Posted 05 May 2020 - 05:58 PM

So I have a 1995 firebird that I bought with 151,000 kms and a siezed engine I found 1996 Lt1 to replace it with 36,000kms on it I have swapped it out and have a no start now, it seems to be fuel related as it will start off ether and can be run off ether.....I drained the tank and put in fresh premium, changed the fuel filter, it primes just fine the fuel pump kicks in as it should and it will start momentarily....but only momentarily it flashes and instantly dies, it will run off ether but that is all any idea of maybe a ground wire or something I may have forgotten somewhere for the injectors? it is also not vats as I have bypassed the vats already I would appreciate any help

#2 Injuneer

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  • Year: 1994
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  • Model: Firebird Formula
  • Engine: 381ci LT1 stroker
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Posted 05 May 2020 - 07:59 PM

Have you checked the two injector fuses - #9 and #10 in the under hood box?
 

Have you verified the pink wire in each injector harness connector has 12 volts (key on, engine off, connector off the injector)?

 

The ground for each individual injector is provided by the PCM to the black/other color wire on the connector, to fire the injector.  Each injector can be checked with a ‘noid light, while cranking the engine.

http://shbox.com/1/1995_pcm3.jpg

 

I'm assuming you kept the 1995 PCM and wiring harness.  

 

Different subject, but did you swap your 1995 knock sensor (4,000 ohms) in place of the 1996 knock sensor (100,000 ohms)?  Won't prevent the engine from starting, but can cause a knock sensor code, and result in almost constant spark timing retard.


1994 FIREBIRD FORMULA
FRED

 
381ci all-forged stroker (Callies Stealth, Oliver billet rods, BME 2618-T61 nitrous pistons) - 10.8:1 - CNC LT4 heads/intake - Comp Cams solid roller - MoTeC M48 Pro engine management - 8 LS1 coils - 58mm TB - 74#/HR injectors - 300-shot dry nitrous - TH400 - Gear Vendors 0.78:1 O/D - Strange 12-bolt - 4.11 Pro-Street gears - AS&M headers - true duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP / 800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117 MPH straight motor
 
https://www.firebird...9_698_32777.jpg

 


#3 sea dog

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Posted 06 May 2020 - 04:12 AM

Have you put car on an obd 1 scanner and checked for codes? There are codes that don't light the check engine light, but can disable fuel injectors from opening. Dtc 41 & 42, both icm related codes are examples.

 

When you turn key on, does security light come on. Then go off after a few seconds? This is normal, it means vats security is in good working order. If security light stays on injectors & starter are disabled. But do to car being 25 years old, a previous owner might have bypassed the theft deterrent relay which would let starter work even if security light is on.

 

If security light doesn't turn on at all, this indicates a burned out bulb, or previous owner might have removed bulb to mask a vats problem.

 

Download the 95 service manual at following link. It will have code explanations, troubleshooting, wiring diagrams, etc. http://www.mediafire.../?40mfgeoe4ctti

 

Manuals provied by our member GaryDoug.



#4 Narfbrain

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Posted 06 May 2020 - 05:26 AM

I have not got around to fuses as of yet I will do that today I do not have an obd1 scanner with the obd2 port and cannot find one in town yes my security light goes out I bypassed the vats already the car should be fine as it worked until the car threw a rod through the pan haha just looking for ideas is there any way I can use the paperclip trick to get my codes on this?

#5 Narfbrain

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Posted 06 May 2020 - 05:34 AM

And yes I swapped the knock sensor

#6 Injuneer

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Posted 06 May 2020 - 06:00 AM

If you have access to an OBD-1 scanner, you can use jumper wires to connect to your 16-pin port:

 

Courtesy of Shoebox

 

http://shbox.com/1/xraycable.jpg



#7 Narfbrain

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Posted 06 May 2020 - 06:07 AM

I'm not having any luck even finding an obd1 to jump over, can't find Noida lights either.....but basically I should have a 12v injector pulse while turning it over correct? So I could technically jump a meter to the injector harness crank it over and look for pulse if there is a pulse it would probably be a fuel issue?

#8 Injuneer

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Posted 06 May 2020 - 06:11 AM

You can also download (free) a copy of Scan9495, written specifically for the OBD-1 PCM.  Buy or build a cable and you can read PCM, ABS, and SRS codes, clear them, test actuators, etc.  The software was written by GaryDoug, who is an active member here.  It can also record a data log of ~50 sensors and PCM parameters, which I have found extremely useful in diagnosing engine problems for members.

 

https://www.firebird...9495-lt1-obd-1/

 

 

My guide to LT1 scanning:

 

https://www.firebird...scanning-guide/
 

 



#9 Narfbrain

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Posted 06 May 2020 - 06:11 AM

Is it possible that it is an opti issue? It appears as though the cam position sensor is in the opti which I am assuming controls injector pulse

#10 Injuneer

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Posted 06 May 2020 - 06:13 AM

The cam position data is required to time BOTH the ignition and the sequential fuel injection.  If you have spark you most likely have cam position signals.  And here's a way to test:

 

Courtesy of Shoebox

 

http://shbox.com/1/4....html#opti_test


1994 FIREBIRD FORMULA
FRED

 
381ci all-forged stroker (Callies Stealth, Oliver billet rods, BME 2618-T61 nitrous pistons) - 10.8:1 - CNC LT4 heads/intake - Comp Cams solid roller - MoTeC M48 Pro engine management - 8 LS1 coils - 58mm TB - 74#/HR injectors - 300-shot dry nitrous - TH400 - Gear Vendors 0.78:1 O/D - Strange 12-bolt - 4.11 Pro-Street gears - AS&M headers - true duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP / 800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117 MPH straight motor
 
https://www.firebird...9_698_32777.jpg

 


#11 Narfbrain

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Posted 06 May 2020 - 06:40 AM

I may have found someone with a scanner here I was thinking it was odd it would spark and not fire injectors

#12 sea dog

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Posted 06 May 2020 - 07:00 AM

Here's a link to a 16 pin obd1 aldl to usb port on pc cable. http://www.obd2allinone.com/aldl.asp

Use it with the scan9495 program.

 

Also, since you own an opti equipped car, you should invest in a PC based oscilloscope. They are about $70 on Ebay, Amazon, etc. With it you can check the low & high resolution pulses from opti. They are square waves that can only be 100% tested with a scope.

 

But, why I'm saying you should get the PC based scope is; there is a fuel enable signal that has to be sent by theft deterrent module (TDM) before PCM will open up fuel injectors. Signal is another square wave.

 

You could have no codes, no problem with security light going off and still not have injectors open. This is because system self check doesn't check to see if TDM fuel enable signal is the correct square wave.

 

I had a no start problem with my 90 dd. Even though I checked the fuel enable signal with a multimeter set to frequency, it passed that test. It wasn't until I scoped the signal that I found out TDM was sending a crazy skewed signal to pcm. Even though I had the proper frequency, the ecm in my car wouldn't accept it and open injectors.

 

My solution was a good used TDM. But, they make a fuel enable signal bypass module that sends out the correct 50 hertz squarewave signal pcm needs to open injectors. It's easy to hook up and doesn't cost a fortune.



#13 Narfbrain

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Posted 06 May 2020 - 07:44 AM

Sounds like you are referring to the vats module bypass at 50hz which I have already done

#14 sea dog

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Posted 06 May 2020 - 10:25 AM

In that case, you might still want to buy a pc based oscilloscope. You need to see if it's sending the correct 50 hertz square wave to pcm. Without that signal injectors won't open.



#15 Narfbrain

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Posted 06 May 2020 - 10:55 AM

Have confirmed fuel pressure I have 44lbs on the prime port 50lbs when cranking

#16 Narfbrain

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Posted 06 May 2020 - 01:09 PM

Have ordered in the only code reader I can find so I can scan the car tommorrow morning when it arrives at the part store to find out about codes.....figures I get that year haha couldn't be a 94 I can check with a wire or a 96 I have a Mac diagnostic for.....but should know what's happening tommorrow
I have a spare opti off the original engine I can try as well but don't want to drain coolant and such unless I really have to I ordered the gaskets and they are sitting in the car right now waiting to swap but want to read codes to see if maybe I am looking in the wrong spots.....maybe I just missed an important ground somewhere could be over reading the entire thing maybe I just missed something

#17 Injuneer

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Posted 06 May 2020 - 02:13 PM

Only 93 can flash the codes by shorting the DLC pins.  Won't work on a 94.  94 and 95 use the exact same PCM.


1994 FIREBIRD FORMULA
FRED

 
381ci all-forged stroker (Callies Stealth, Oliver billet rods, BME 2618-T61 nitrous pistons) - 10.8:1 - CNC LT4 heads/intake - Comp Cams solid roller - MoTeC M48 Pro engine management - 8 LS1 coils - 58mm TB - 74#/HR injectors - 300-shot dry nitrous - TH400 - Gear Vendors 0.78:1 O/D - Strange 12-bolt - 4.11 Pro-Street gears - AS&M headers - true duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP / 800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117 MPH straight motor
 
https://www.firebird...9_698_32777.jpg

 


#18 ZumpTA

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Posted 06 May 2020 - 03:05 PM

You don't have to remove an OptiSpark to test it.  Procedure is in the Factory Service Manual, or at the link Injuneer gave you in post #10 along with the statement "If you have spark you most likely have cam position signals."

 

did you use your injectors or keep the ones that came with the replacement engine?   How about the ICM and coil?  Your known good parts or the ones that you received?  How long can you keep it going on ether?


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#19 Narfbrain

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Posted 07 May 2020 - 07:11 AM

ICM and coil are off my engine used injectors and fuel rail from the engine I picked up......my reader should be in within a few hours here just waiting on the call

#20 Injuneer

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Posted 07 May 2020 - 08:28 AM

When doing the scan, look for DTC 46.   That is the code that sets if the PCM does not receive "the proper signal" from the theft deterrent module after 1.7 seconds.  The tolerance on the 50 Hz signal is a range of 40-60Hz.  That code does not turn on the SES light.






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