86 with APYP only starts once
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86 with APYP only starts once
I'm having a strange problem with my 86 4+3. I'm running the 89 APYP bin with CSI disconnected. The engine will start after the first crank and run fine. If I shut down the engine and try to restart, it will only crank. No amount of throttle input will get it to start and no codes are thrown. I have the chip in a Moates adapter. If I remove the chip and reinstall it, it will start immediately with a large RPM flare. It does not seem to be temperature dependent, it will occur on a dead cold engine, or a hot engine. However, If I let the car sit for several hours it will fire. Also, if I remove the adapter and put the stock chip in place, it will start reliably. Any ideas?
#2
Melting Slicks
Could be that the ecm is not seeing enough distributor reference pulses on subsequent restart attempts.
89 ($6E) bins wait to see 8 distributor reference pulses before activating the injectors, so they behave differently during cranking than earlier $32 and $32B bins.
No idea why it works the first time however, but fails to start afterward. Is the fuel pump priming?
Why would you want to run APYP on a 4+3 car??? I would choose an 87-88 $32B bin for this application.
I understand that 86 4+3's in particular are problematic due to the lack of a 1st gear switch and different shifter switch wiring compared to the later cars.
The 86 O/D on/off switch is connected to pin C8. The same pin is used for the first gear switch in 87-88 cars.
That being said, I would still use an 87-88 $32B bin with the O/D on/off switch repinned at the ecm to the 87-88 pin C7. I think I could live without the 1st gear switch and call it a 4+4....
Now there is another alternative....I did hack in the 86 first gear detection logic into an 88 4+3 bin years ago for use in 86 cars. The switch input was also changed in the programming to avoid the repin operation mentioned above. A few users on this forum have used my hybrid 86/88 bin with good results, but I've received very limited feedback on it over the years, so ymmv.
https://www.corvetteforum.com/forums...-86-4-3-a.html
89 ($6E) bins wait to see 8 distributor reference pulses before activating the injectors, so they behave differently during cranking than earlier $32 and $32B bins.
No idea why it works the first time however, but fails to start afterward. Is the fuel pump priming?
Why would you want to run APYP on a 4+3 car??? I would choose an 87-88 $32B bin for this application.
I understand that 86 4+3's in particular are problematic due to the lack of a 1st gear switch and different shifter switch wiring compared to the later cars.
The 86 O/D on/off switch is connected to pin C8. The same pin is used for the first gear switch in 87-88 cars.
That being said, I would still use an 87-88 $32B bin with the O/D on/off switch repinned at the ecm to the 87-88 pin C7. I think I could live without the 1st gear switch and call it a 4+4....
Now there is another alternative....I did hack in the 86 first gear detection logic into an 88 4+3 bin years ago for use in 86 cars. The switch input was also changed in the programming to avoid the repin operation mentioned above. A few users on this forum have used my hybrid 86/88 bin with good results, but I've received very limited feedback on it over the years, so ymmv.
https://www.corvetteforum.com/forums...-86-4-3-a.html
Last edited by tequilaboy; 11-12-2015 at 08:13 PM.
#3
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Could be that the ecm is not seeing enough distributor reference pulses on subsequent restart attempts.
89 ($6E) bins wait to see 8 distributor reference pulses before activating the injectors, so they behave differently during cranking than earlier $32 and $32B bins.
No idea why it works the first time however, but fails to start afterward. Is the fuel pump priming?
Why would you want to run APYP on a 4+3 car??? I would choose an 87-88 $32B bin for this application.
I understand that 86 4+3's in particular are problematic due to the lack of a 1st gear switch and different shifter switch wiring compared to the later cars.
The 86 O/D on/off switch is connected to pin C8. The same pin is used for the first gear switch in 87-88 cars.
That being said, I would still use an 87-88 $32B bin with the O/D on/off switch repinned at the ecm to the 87-88 pin C7. I think I could live without the 1st gear switch and call it a 4+4....
Now there is another alternative....I did hack in the 86 first gear detection logic into an 88 4+3 bin years ago for use in 86 cars. The switch input was also changed in the programming to avoid the repin operation mentioned above. A few users on this forum have used my hybrid 86/88 bin with good results, but I've received very limited feedback on it over the years, so ymmv.
https://www.corvetteforum.com/forums...-86-4-3-a.html
89 ($6E) bins wait to see 8 distributor reference pulses before activating the injectors, so they behave differently during cranking than earlier $32 and $32B bins.
No idea why it works the first time however, but fails to start afterward. Is the fuel pump priming?
Why would you want to run APYP on a 4+3 car??? I would choose an 87-88 $32B bin for this application.
I understand that 86 4+3's in particular are problematic due to the lack of a 1st gear switch and different shifter switch wiring compared to the later cars.
The 86 O/D on/off switch is connected to pin C8. The same pin is used for the first gear switch in 87-88 cars.
That being said, I would still use an 87-88 $32B bin with the O/D on/off switch repinned at the ecm to the 87-88 pin C7. I think I could live without the 1st gear switch and call it a 4+4....
Now there is another alternative....I did hack in the 86 first gear detection logic into an 88 4+3 bin years ago for use in 86 cars. The switch input was also changed in the programming to avoid the repin operation mentioned above. A few users on this forum have used my hybrid 86/88 bin with good results, but I've received very limited feedback on it over the years, so ymmv.
https://www.corvetteforum.com/forums...-86-4-3-a.html
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You were spot on about the 8 reference pulses tequilaboy. I forgot to put into my tuning notes that I modified the crank fuel multiplier table (months ago). I added more fuel in the first few reference pulses to light the engine off faster. I think I was adding too much fuel before the engine could get up to speed. I also had zeroes at the end which I think means it would never give any fuel after 24 pulses....not sure what I was thinking there. Engine would start in this condition if it sat long enough. Here's a copy of the table. I went back to stock multipliers and the engine starts reliably now.
Reference Pulse Multiplier (stock) Multiplier (mod)
1 0 0
2 0 0.5
3 0 0.5
4 0 0.5
5 0 0.5
6 0 0.5
7 0 0.25
8 0 0.25
9 0.5 0.25
10 0.5 0.25
11 0.25 0.25
12 0.25 0.25
13 0.25 0.25
14 0.25 0.25
15 0.25 0.25
16 0.25 0.2
17 0.2 0.2
18 0.2 0.2
19 0.2 0.2
20 0.2 0
21 0.2 0
22 0.2 0
23 0.2 0
24 0.2 0
Reference Pulse Multiplier (stock) Multiplier (mod)
1 0 0
2 0 0.5
3 0 0.5
4 0 0.5
5 0 0.5
6 0 0.5
7 0 0.25
8 0 0.25
9 0.5 0.25
10 0.5 0.25
11 0.25 0.25
12 0.25 0.25
13 0.25 0.25
14 0.25 0.25
15 0.25 0.25
16 0.25 0.2
17 0.2 0.2
18 0.2 0.2
19 0.2 0.2
20 0.2 0
21 0.2 0
22 0.2 0
23 0.2 0
24 0.2 0