89 vette prom help
Thread Starter
Instructor
Joined: Aug 1999
Posts: 172
Likes: 0
From: Virginia
89 vette prom help
Working on a 1989 6 speed corvette.
Car starts and runs. Stalls after 10 minutes and won't restart. All parameters read except pulse width. I ran a scratch test from the signal wire and the pump primes but no injectors. I've replaced the ECU twice with the same prom. I tried the dealer and this prom is discontinued and none left in the country.
I tried used and can only find A/T. I tried to remove the prom from the memcal to see if the limp chips were at fault but the chips are soldered. I need a complete replacement memcal. It is stock but I'll step it up if it is available.
My Prom # is "APYP 3499" I don't know if there is another that would work. It will restart after a few hours and run a few minutes. It is not setting any codes at this time but came in with a few related to prom & ECU. I reset them and they didn't return.
I checked all powers & grounds good spark and fuel pressure. No injectors.
Car starts and runs. Stalls after 10 minutes and won't restart. All parameters read except pulse width. I ran a scratch test from the signal wire and the pump primes but no injectors. I've replaced the ECU twice with the same prom. I tried the dealer and this prom is discontinued and none left in the country.
I tried used and can only find A/T. I tried to remove the prom from the memcal to see if the limp chips were at fault but the chips are soldered. I need a complete replacement memcal. It is stock but I'll step it up if it is available.
My Prom # is "APYP 3499" I don't know if there is another that would work. It will restart after a few hours and run a few minutes. It is not setting any codes at this time but came in with a few related to prom & ECU. I reset them and they didn't return.
I checked all powers & grounds good spark and fuel pressure. No injectors.
Team Owner
Joined: Jan 2003
Posts: 20,333
Likes: 263
From: Summerland B.C. Canada
You might want to check/replace the ignition control module. When they are going bad, they fail after heating up. The ICM also sends a reference signal to ECM, without the reference signal, the ECM will not fire the injectors.
Melting Slicks
Joined: Jan 2008
Posts: 2,065
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From: Jasper Texas
Melting Slicks
Joined: Aug 2003
Posts: 3,409
Likes: 400
From: Lakeville MI
While cranking (and scanning) can you see the DRP (Distributor Reference Pulse) period?
This would indicate if the ecm is seeing the reference pulse.
No reference pulse, no fuel and also no rpm.
An 89 needs to see 8 pulses or 2 revolutions before any cranking fuel is supplied.
This would indicate if the ecm is seeing the reference pulse.
No reference pulse, no fuel and also no rpm.
An 89 needs to see 8 pulses or 2 revolutions before any cranking fuel is supplied.
Last edited by tequilaboy; Aug 21, 2008 at 04:49 PM.
Thread Starter
Instructor
Joined: Aug 1999
Posts: 172
Likes: 0
From: Virginia
Forgot to mention I'm ASE certified and have checked the basics. I have good spark and fuel pressure and it flunked an injector scratch test where you probe the purple and white wire and scratch it to power to fire the injectors and simulate the ign module. I need a memcal or someone who can make one.
Melting Slicks
Joined: Aug 2003
Posts: 3,409
Likes: 400
From: Lakeville MI
Did you do it more than 8 times to simulate more than 8 reference pulses?
Could the throttle position sensor be shorted to 5 volts? This would also zero the injectors.
I do have the apyp bin file on hand that could be programmed onto any memcal, or you could use your existing memcal with an adaptor and new eprom.
Could the throttle position sensor be shorted to 5 volts? This would also zero the injectors.
I do have the apyp bin file on hand that could be programmed onto any memcal, or you could use your existing memcal with an adaptor and new eprom.
Thread Starter
Instructor
Joined: Aug 1999
Posts: 172
Likes: 0
From: Virginia
I did try more than 8 times and this one isn't SFI it fires 4 at a time. I have a RPM signal and no pulse width, using a Snap-On scanner. I'm pretty sure it is in the memcal. Can you get one and do it for me. Give me a price. Mine might be in the limp chips not the prom so the apyp code may not be enough. Another memcal with the apyp code will do fine and replace it all.
Thread Starter
Instructor
Joined: Aug 1999
Posts: 172
Likes: 0
From: Virginia
All other parameters are fine including TPS volts at .54
The car will run for 10 minutes and go into closed loop everything looks normal and then with no reason it starts to stumble and run out of fuel. The fuel pressure is at 45 when it occurs then it dies and won't restart for a few hours. While cranking I have all my inputs and no injector pulse width. I've replaced the ecm twice but never the prom.
The car will run for 10 minutes and go into closed loop everything looks normal and then with no reason it starts to stumble and run out of fuel. The fuel pressure is at 45 when it occurs then it dies and won't restart for a few hours. While cranking I have all my inputs and no injector pulse width. I've replaced the ecm twice but never the prom.
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Melting Slicks
Joined: Aug 2003
Posts: 3,409
Likes: 400
From: Lakeville MI
Another possibility that will prevent fuel output is VATS.
The VATS system is intended to prevent cranking and also prevent fuel output. It could be partially malfunctioning in a manner that still permits cranking, but does not supply fuel.
I'm no VATS expert, but one way to eliminate the possiblity is to turn off the VATS enable switch in the chip's bin file, and reprogram the chip with VATS disabled, or you could try an F-body non-VATS memcal if you have one available.
I don't have any spare memcals to offer. If you want to buy a moates style adaptor or similar device, I could send a programmed eprom with apyp and/or apyp with vats disabled for testing.
I would be surprised if the memcal itself is the source of the problem.
http://www.moates.net/product_info.p...products_id=32
The VATS system is intended to prevent cranking and also prevent fuel output. It could be partially malfunctioning in a manner that still permits cranking, but does not supply fuel.
I'm no VATS expert, but one way to eliminate the possiblity is to turn off the VATS enable switch in the chip's bin file, and reprogram the chip with VATS disabled, or you could try an F-body non-VATS memcal if you have one available.
I don't have any spare memcals to offer. If you want to buy a moates style adaptor or similar device, I could send a programmed eprom with apyp and/or apyp with vats disabled for testing.
I would be surprised if the memcal itself is the source of the problem.
http://www.moates.net/product_info.p...products_id=32
Pro
Joined: Jun 2008
Posts: 531
Likes: 0
From: Calgary Alberta
Sounds exactly like my '89 a few years back... start it enough times and eventually wouldn't go at all...
I would suggest changing the e-prom before searching othet components.
Someone out there's gota have one that they've upgraded from...?
Just to be sure - check with a friend or someone in your local club with the similar car and borrow their e-prom for a few hours. Then you'll know if you're chasing a ghost
I would suggest changing the e-prom before searching othet components.
Someone out there's gota have one that they've upgraded from...?
Just to be sure - check with a friend or someone in your local club with the similar car and borrow their e-prom for a few hours. Then you'll know if you're chasing a ghost
Thread Starter
Instructor
Joined: Aug 1999
Posts: 172
Likes: 0
From: Virginia
I found my problem with the help of a vette tech at the carlisle show this weekend. It turns out that I have multiple injectors with low resistance that are causing the drivers to shut down in ten minutes. I checked them all and it was an easy test to ohm them. 16 ohms is good and I had 3 below 10. I changed them and my prom problem is solved. I'm glad it's over. Thanks for all the input.
