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trees 10-16-2005 05:39 PM

Chasing TPI Gremlins
Some of you may know I converted my Bud's 72 Chevy PU to TPI. I used the hardware from an 88 Camaro, blocked off the "9th" injector, used a MAP controller and 92 5.7 computer and Painless Wiring harness. It ran like a champ with power and torque gains as well as increased fuel milage until my Bud did the unforgivable. The battery went down so he decided to recharge the battery. He has the old timers disease of CRS and did not disconnect the battery (I was not there to hold his hand) and on top of this, he cross wired the charger leads. Well, he finally got the battery charged and cranked it up to take it for a spin. During this trip it started running like crap and he limped home and gave me a call. After some trouble shooting, I determined the battery was low because the alternator was bad. He picked up a rebuilt alternator and decided he wanted to go with the internal regulator. I left him to this task. Later, another distress call: want rev past 2000 RPM. My first inclination was he fried the chip or computor when he cross wired the charger so I started trouble shooting by taking the computor and chip to the guy that burned it. After he had it for a couple of weeks, he determined it was fine and even ran it in his Monte Carlo to make sure. I then checked all the sensors and the distributor, ignition module, coil and rechecked all the values of the TPS, MAP, IAC, oil pressure and coolant temp sensors, and the operation of the knock sensor. Everthing checked good. We then took it to a guy that was very knowledgable and had the state of the art test equipment and he also was pulling his hair out. He spent a lot of time on the phone with the Painless tech support. On his own, he discovered the problem that will sound simple to a lot of you, but maybe some one will learn something. We had converted the truck to HEI about 3 years before doing the TPI and it ran great. It ran great after the conversion until the low battery/cross wiring charger/internal regulator conversion. Well, it seems that my bud put in a new wire to the ignition switch when he deleted the external regulator and the wire he put in was a resistance wire!!! The ECM was only getting 9 Volts!!! AAAAARRRRRGGGGGGG!


Siggy_Freud 10-17-2005 12:12 AM

So I take it all is well and good now? I was having some TPI gremlins of my own recently that for the life of me I couldn't figure it. I think I finally chased it down to the remote starter unit in the truck. One day while working on it, the starter magically started engaging by itself. Talk about ghosts and gremlins :).

trees 10-17-2005 07:49 AM

Yep, all is well now except I am going to play with the base timing a bit today. We set it at 10 degrees when first installed, but reset to 6 after digging into the books for the base timing for the 92 5.7 smog hog. Since there is no smog junk on the motor, 30 over on the bore, big valves and mild cam, I think we can handle a bit more timing advance. We will begin with 8 degrees and use the old stop watch for some 1/8 mile accelerations to see where the best setting is located.


Siggy_Freud 10-17-2005 11:05 AM

Just keep in mind that the computer will assume the base timing is set at whatever the chip sees and wont limit the extra advance through the RPM range (as well as max advance limit). So by giving it another 2 or 4 initial, your actually giving it 2 or 4 more throughout its entire RPM band. I imagine you already know this but I thought I'd mention it just incase . . .

Glad to hear all is well.

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