Thermo-time switch bypass L-jet
07-10-2006, 03:57 PM
#1
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Thread Starter
Thermo-time switch bypass L-jet
Hello,
A while back I was noticing a longer cranking time while I was starting my car. After some trouble shooting, I concluded that everything in my starting system was working fine. However, it was taking me sometimes 6-8 seconds for the engine to fire up.
Research revealed that the L-jet does not really use the cold-start injector to start the car in warm-cold start conditions or even cold-cold start in warm weather. This is controlled by the thermo-time switch located on the front of the water manifold. It is a temp-sensitive timer which switches the ground to the CS injector. The 12V to the CS injector arrives through the starter relay only when the ignition switch is in the START position.
I have concluded that in hot weather I don't have any starting enrichment at all, and probably most L-jets are about the same. I decided to disconnect the TT switch and ground the connector which the TT switch was refusing to ground in warm conditions.
Voila! Instant starts! I can't count "one-one-thousand" before it is started.
Now I understand that if the car doesn't fire up, the CS injector will continue to spray while the starter is turning, and this may flood the engine. So far the only time the car has cranked for any length of time was before, when the CS injector probably wasn't even firing.
I wil have to see how this works in different weather conditions, since I drive my car in winter. For warm climate cars this may be a useful improvement if you car is starting with difficulty.
Good luck, YMMV
A while back I was noticing a longer cranking time while I was starting my car. After some trouble shooting, I concluded that everything in my starting system was working fine. However, it was taking me sometimes 6-8 seconds for the engine to fire up.
Research revealed that the L-jet does not really use the cold-start injector to start the car in warm-cold start conditions or even cold-cold start in warm weather. This is controlled by the thermo-time switch located on the front of the water manifold. It is a temp-sensitive timer which switches the ground to the CS injector. The 12V to the CS injector arrives through the starter relay only when the ignition switch is in the START position.
I have concluded that in hot weather I don't have any starting enrichment at all, and probably most L-jets are about the same. I decided to disconnect the TT switch and ground the connector which the TT switch was refusing to ground in warm conditions.
Voila! Instant starts! I can't count "one-one-thousand" before it is started.
Now I understand that if the car doesn't fire up, the CS injector will continue to spray while the starter is turning, and this may flood the engine. So far the only time the car has cranked for any length of time was before, when the CS injector probably wasn't even firing.
I wil have to see how this works in different weather conditions, since I drive my car in winter. For warm climate cars this may be a useful improvement if you car is starting with difficulty.
Good luck, YMMV
07-10-2006, 04:02 PM
#2
Administrator - "Tyson"
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Rod Underwood is having a cold start / stumble issue I think is very much related to this. I told him about a "fix" my mechanic tried many years ago when the L-Jets were still in production. He installed a resistor to the thermo switch to fool the system into running richer. I do not have any specifics about the resistor, what size - I have not been able to talk to him about this since I remembered the story.
07-10-2006, 04:23 PM
#3
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Thread Starter
Hacker,
I think you may referring to a mod involving the Temp 2 sensor. I believe Porken has worked on a variable resistor to fool the engine into running richer. The engine thinks it is cold and gives more fuel.
The TT switch and CS injector system only operate for 1-10 seconds during startup. My mod is active only when the starter is cranking.
I think you may referring to a mod involving the Temp 2 sensor. I believe Porken has worked on a variable resistor to fool the engine into running richer. The engine thinks it is cold and gives more fuel.
The TT switch and CS injector system only operate for 1-10 seconds during startup. My mod is active only when the starter is cranking.
07-10-2006, 04:24 PM
#4
Inventor
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Maybe if you removed the thermo-time sensor from the coolant bridge? Retain the sensor, but have it be sensitive to air temp, instead of coolant temp?
I had a variable resistance connection to the TempII for a while, but it didn't do much, so I removed it.
I still have my cold start delete/TempII faker circuit, which works great.
clic pic for thread
I had a variable resistance connection to the TempII for a while, but it didn't do much, so I removed it.
I still have my cold start delete/TempII faker circuit, which works great.
clic pic for thread
07-10-2006, 04:49 PM
#5
Administrator - "Tyson"
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Originally Posted by j.kenzie@sbcglobal.net
Hacker,
I think you may referring to a mod involving the Temp 2 sensor. I believe Porken has worked on a variable resistor to fool the engine into running richer. The engine thinks it is cold and gives more fuel.
The TT switch and CS injector system only operate for 1-10 seconds during startup. My mod is active only when the starter is cranking.
I think you may referring to a mod involving the Temp 2 sensor. I believe Porken has worked on a variable resistor to fool the engine into running richer. The engine thinks it is cold and gives more fuel.
The TT switch and CS injector system only operate for 1-10 seconds during startup. My mod is active only when the starter is cranking.
07-10-2006, 06:31 PM
#6
Rennlist Member
Originally Posted by Hacker-Pschorr
Rod Underwood is having a cold start / stumble issue I think is very much related to this. I told him about a "fix" my mechanic tried many years ago when the L-Jets were still in production. He installed a resistor to the thermo switch to fool the system into running richer. I do not have any specifics about the resistor, what size - I have not been able to talk to him about this since I remembered the story.
I have a replacement (rebuilt) L-jet coming tomorrow and will see if that's the problem, but the resistor did help a lot.
Thanks, Hacker!!More to come.
Rod
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07-10-2006, 07:46 PM
#9
Three Wheelin'
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i think you should post that. I would take 15 min to put in (not hard wired) and it would give you a REALLY good idea what is going on! see if its dropping lean or rich when it stumbles and see what AF you are actually idling at
05-17-2015, 06:02 PM
#10
Intermediate
I was having a difficult/no start problem with my 84 auto, and was advised that I might need to replace the tt switch. I agreed that it did seem to be temp related, so I started shopping. Damned things are pricey!
(when you can find them!) I found this thread and your bypass. MUCH better!
Thank you!
(when you can find them!) I found this thread and your bypass. MUCH better!
Thank you!
05-17-2015, 07:03 PM
#11
Timely thread as Roger tossed me one of the new ones he's carrying. Didn't ask the price but they are new manufacture.
05-17-2015, 08:48 PM
#13
