Unplugging Cold Start Injector
#1
Junior Member
Thread Starter
Unplugging Cold Start Injector
Hello, I have been having trouble with my car stalling after cold starts. I unplugged the cold start injector this morning and it took longer to start, but ran fine with it unplugged. I am wondering if I can get away with just leaving the injector in there and unplugged. A tidy engine isn't all that important to me. I am also wondering if getting the computer reprogrammed or getting a prom from a 3.1 engine will help with the extended starting times. I have an 86 firebird with a 2.8 and automatic transmission.
Thanks
Thanks
#2
Supreme Member
Join Date: Feb 2005
Location: Hawaii
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Car: 89' Firebird
Engine: 3.4L V-6
Transmission: 700-R4
Axle/Gears: Whatever came stock!
Re: Unplugging Cold Start Injector
I dunno if a 3.1 PROM will work since it has a digital EGR etc...
But the TPI guys just leave it unplugged and let it crank longer / give it a little gas to help it get going.
But the TPI guys just leave it unplugged and let it crank longer / give it a little gas to help it get going.
#3
Re: Unplugging Cold Start Injector
The cold start injector gets its power (+12v) from the ignition switch side of the starter solenoid.
On the front of the engine close to the thermostat housing and next to the Coolant Temperature Sensor there is a cold start switch or coolant temperature switch that sends the ground to complete power the cold start injector. Below is from another post on how the cold switch works. It only works when engine is cranking.
This from an older post on the forum V8 section. The cold start injector on the V6 works the same way.
This is how the cold start injector works:
The ground side of the cold start injector runs through its own coolant temperature switch that's located in the intake manifold below the thermostat. The temperature switch also contains a heating element that limits the time the injector is "on", inversely proportional to coolant temperature - it's on more when cold, on less when the coolant is kinda cold (within its operation range).
The cold start injector turns on only when the ignition switch is in the start position and the coolant is "cold"; the temperature switch is closed and grounded which completes the electrical circuit.
When the coolant is "hot", the coolant temperature switch is opened. In this case the electrical circuit is opened so the cold start injector will not turn on when the ignition switch is in the start position.
On the front of the engine close to the thermostat housing and next to the Coolant Temperature Sensor there is a cold start switch or coolant temperature switch that sends the ground to complete power the cold start injector. Below is from another post on how the cold switch works. It only works when engine is cranking.
This from an older post on the forum V8 section. The cold start injector on the V6 works the same way.
This is how the cold start injector works:
The ground side of the cold start injector runs through its own coolant temperature switch that's located in the intake manifold below the thermostat. The temperature switch also contains a heating element that limits the time the injector is "on", inversely proportional to coolant temperature - it's on more when cold, on less when the coolant is kinda cold (within its operation range).
The cold start injector turns on only when the ignition switch is in the start position and the coolant is "cold"; the temperature switch is closed and grounded which completes the electrical circuit.
When the coolant is "hot", the coolant temperature switch is opened. In this case the electrical circuit is opened so the cold start injector will not turn on when the ignition switch is in the start position.
#4
Junior Member
Thread Starter
Re: Unplugging Cold Start Injector
So from what I understand I should try getting a new coolant temperature switch? It seems like the cold start injector is staying on too long and is causing the engine to stall. Is this the right sensor?
https://www.napaonline.com/en/p/MPET...pressionRank=7
https://www.napaonline.com/en/p/MPET...pressionRank=7
#5
Re: Unplugging Cold Start Injector
Ricks Camaros shows it is out of stock with a price close to $300. If a new one is available it would be expensive. List of GM vehicles that used the same switch at the bottom of post. Someone in the forum said it has a timer built in to the switch so it only operates for 9 seconds.
Check your existing CSS with a meter for proper operation. The switch is closed supplying ground. Below is from Factory Service Manual for V8 but V6 operates the same way.
when the engine is cold but opens around 100 degrees.
+12 Volts DC supplied only when cranking engine
List of vehicles with Cold Start Switch from a member who found a replacement in junkyard on a corvette
I should be picking up the Cold Start Switch here shortly. In case anyone was having this issue as well here are the vehicles that the part is on. Same part for the V6, V8 (305 and 350) and the L4
1985 Buick Skylark L4-151ci 2.5L TBI,V6-173ci 2.8L 2BBL,V6-173ci 2.8L MFI
1986-1985 Cadillac Cimarron L4-122ci 2.0L TBI,V6-173ci 2.8L MFI
1989-1985 Chevrolet Camaro V6-173ci 2.8L MFI,V8-305ci 5.0L MFI
1989-1987 Chevrolet Camaro V8-350ci 5.7L MFI
1989-1988,1986-1985 Chevrolet Camaro V6-173ci 2.8L MFI,V8-305ci 5.0L MFI
1989-1988 Chevrolet Camaro V8-305ci 5.0L TBI
1989-1988 Chevrolet Camaro V8-305ci 5.0L TBI,V8-350ci 5.7L MFI
1987-1985 Chevrolet Camaro V8-305ci 5.0L 4BBL
1986-1985 Chevrolet Camaro L4-151ci 2.5L TBI,V8-305ci 5.0L 4BBL
1986-1985 Chevrolet Camaro,Celebrity L4-151ci 2.5L TBI
1986-1985 Chevrolet Cavalier L4-122ci 2.0L TBI
1986-1985 Chevrolet Cavalier,Celebrity V6-173ci 2.8L MFI
1986-1985 Chevrolet Celebrity V6-173ci 2.8L 2BBL
1985 Chevrolet Celebrity V6-260ci 4.3L MFI
1985 Chevrolet Citation II L4-151ci 2.5L TBI,V6-173ci 2.8L 2BBL,V6-173ci 2.8L MFI
1988-1985 Chevrolet Corvette V8-350ci 5.7L MFI
1986 Oldsmobile Cutlass Ciera L4-151ci 2.5L TBI,V6-173ci 2.8L 2BBL,V6-173ci 2.8L MFI,V6-231ci 3.8L MFI
1986-1985 Oldsmobile Firenza L4-112ci 1.8L TBI,L4-122ci 2.0L TBI,V6-173ci 2.8L MFI
1985 Oldsmobile Firenza L4-112ci 1.8L TBI,L4-122ci 2.0L TBI,V6-173ci 2.8L MFI
1986-1985 Pontiac 6000 V6-173ci 2.8L 2BBL,V6-173ci 2.8L MFI
1985 Pontiac 6000 V6-260ci 4.3L MFI
1986-1985 Pontiac 6000,Firebird L4-151ci 2.5L TBI
1988-1985 Pontiac Fiero L4-151ci 2.5L TBI,V6-173ci 2.8L MFI
1989-1985 Pontiac Firebird V6-173ci 2.8L MFI,V8-305ci 5.0L MFI
1989-1987 Pontiac Firebird V8-350ci 5.7L MFI
1989-1988,1986-1985 Pontiac Firebird V6-173ci 2.8L MFI,V8-305ci 5.0L MFI
1989-1988 Pontiac Firebird V8-305ci 5.0L TBI
1989-1988 Pontiac Firebird V8-305ci 5.0L TBI,V8-350ci 5.7L MFI
1989 Pontiac Firebird V6-231ci 3.8L MFI
1987-1985 Pontiac Firebird V8-305ci 5.0L 4BBL
1986-1985 Pontiac Firebird L4-151ci 2.5L TBI,V8-305ci 5.0L 4BBL
Check your existing CSS with a meter for proper operation. The switch is closed supplying ground. Below is from Factory Service Manual for V8 but V6 operates the same way.
when the engine is cold but opens around 100 degrees.
+12 Volts DC supplied only when cranking engine
List of vehicles with Cold Start Switch from a member who found a replacement in junkyard on a corvette
I should be picking up the Cold Start Switch here shortly. In case anyone was having this issue as well here are the vehicles that the part is on. Same part for the V6, V8 (305 and 350) and the L4
1985 Buick Skylark L4-151ci 2.5L TBI,V6-173ci 2.8L 2BBL,V6-173ci 2.8L MFI
1986-1985 Cadillac Cimarron L4-122ci 2.0L TBI,V6-173ci 2.8L MFI
1989-1985 Chevrolet Camaro V6-173ci 2.8L MFI,V8-305ci 5.0L MFI
1989-1987 Chevrolet Camaro V8-350ci 5.7L MFI
1989-1988,1986-1985 Chevrolet Camaro V6-173ci 2.8L MFI,V8-305ci 5.0L MFI
1989-1988 Chevrolet Camaro V8-305ci 5.0L TBI
1989-1988 Chevrolet Camaro V8-305ci 5.0L TBI,V8-350ci 5.7L MFI
1987-1985 Chevrolet Camaro V8-305ci 5.0L 4BBL
1986-1985 Chevrolet Camaro L4-151ci 2.5L TBI,V8-305ci 5.0L 4BBL
1986-1985 Chevrolet Camaro,Celebrity L4-151ci 2.5L TBI
1986-1985 Chevrolet Cavalier L4-122ci 2.0L TBI
1986-1985 Chevrolet Cavalier,Celebrity V6-173ci 2.8L MFI
1986-1985 Chevrolet Celebrity V6-173ci 2.8L 2BBL
1985 Chevrolet Celebrity V6-260ci 4.3L MFI
1985 Chevrolet Citation II L4-151ci 2.5L TBI,V6-173ci 2.8L 2BBL,V6-173ci 2.8L MFI
1988-1985 Chevrolet Corvette V8-350ci 5.7L MFI
1986 Oldsmobile Cutlass Ciera L4-151ci 2.5L TBI,V6-173ci 2.8L 2BBL,V6-173ci 2.8L MFI,V6-231ci 3.8L MFI
1986-1985 Oldsmobile Firenza L4-112ci 1.8L TBI,L4-122ci 2.0L TBI,V6-173ci 2.8L MFI
1985 Oldsmobile Firenza L4-112ci 1.8L TBI,L4-122ci 2.0L TBI,V6-173ci 2.8L MFI
1986-1985 Pontiac 6000 V6-173ci 2.8L 2BBL,V6-173ci 2.8L MFI
1985 Pontiac 6000 V6-260ci 4.3L MFI
1986-1985 Pontiac 6000,Firebird L4-151ci 2.5L TBI
1988-1985 Pontiac Fiero L4-151ci 2.5L TBI,V6-173ci 2.8L MFI
1989-1985 Pontiac Firebird V6-173ci 2.8L MFI,V8-305ci 5.0L MFI
1989-1987 Pontiac Firebird V8-350ci 5.7L MFI
1989-1988,1986-1985 Pontiac Firebird V6-173ci 2.8L MFI,V8-305ci 5.0L MFI
1989-1988 Pontiac Firebird V8-305ci 5.0L TBI
1989-1988 Pontiac Firebird V8-305ci 5.0L TBI,V8-350ci 5.7L MFI
1989 Pontiac Firebird V6-231ci 3.8L MFI
1987-1985 Pontiac Firebird V8-305ci 5.0L 4BBL
1986-1985 Pontiac Firebird L4-151ci 2.5L TBI,V8-305ci 5.0L 4BBL
#6
Junior Member
Thread Starter
Re: Unplugging Cold Start Injector
What exactly am I looking for with the multimeter? Am I just seeing if the voltage changes when cranking and then stops when the engine starts?
#7
Re: Unplugging Cold Start Injector
On a cold engine below 100 degrees 12vdc should present on the connector for the cold start injector when cranking the engine. On a warm engine over 100 degrees no voltage should be present when cranking the engine.
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#8
Junior Member
Thread Starter
Re: Unplugging Cold Start Injector
On a cold engine it is only getting 10 volts and on a warm one there are zero
#9
Re: Unplugging Cold Start Injector
Since your car starts it is likely the cold start injector is working even with the voltage a bit low. There are videos of people using a 9 volt battery on a bench to pulse clean injectors. The cold start injector supplies extra fuel only while cranking. Since the voltage is 0 when the temperature is over 100 the cold start switch is doing what it is supposed to do.
You could remove the cold start injector and see if it is supplying fuel but since your car starts it is probably working. Some members have advised against removing the cold start injector because it is hard to get out and back in. The oring on the cold start injector is easily damaged and it is hard to find a replacement.
Have you tested your fuel pressure?.
You could remove the cold start injector and see if it is supplying fuel but since your car starts it is probably working. Some members have advised against removing the cold start injector because it is hard to get out and back in. The oring on the cold start injector is easily damaged and it is hard to find a replacement.
Have you tested your fuel pressure?.
#10
Junior Member
Thread Starter
Re: Unplugging Cold Start Injector
I personally haven't but i took it to a mechanic and had the fuel pump replaced and that brought the pressure from 30 to 44.
#11
Member
Re: Unplugging Cold Start Injector
Would the cold start injector stay stuck on for a warm engine because of a bad coolant sensor or thermal switch? (Cold start switch)
Mine seems to run the cold start scenario every time when the engine is fully warm. It takes about the same rev up time which is really annoying as wouldn’t expect every time you turnover a warm engine.
Appreciate any help as studying this thread and the shop manual. What page number was this from?
Mine seems to run the cold start scenario every time when the engine is fully warm. It takes about the same rev up time which is really annoying as wouldn’t expect every time you turnover a warm engine.
Appreciate any help as studying this thread and the shop manual. What page number was this from?
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calidude (06-07-2022)
#13
Member
Re: Unplugging Cold Start Injector
I’ll test for this and see if I have voltage on the injector when warm for starters then, thanks 🙏
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