well everything i've learned say's 9.6 v is acceptable for the battery to be good after fifteen seconds of cranking .

 

I also agree. Having seen many LT1s crank in real time with a scanner I can testify to first hand knowledge that the ECU will work perfectly even with a voltage drop down to 7 volts. I have the logs to prove it too.

Regardless, I agree with speedy's recommendation of inspecting the cables/wiring harness.

 

the other thing i was thinking is what if you have the wrong starter . you said you repalced it but did you maybe put a revese rotation starter in . it would cause it to run backwards

 

well, yes, that is good for a battery, but too low for proper function of the electronics

 

I beg to differ on that most electronics in a car are designed to operate in a wide range of voltage . this is why sensor refrence voltages are at 5 volts to account for this and not 12 volts .

 

everything that uses 5 volt(sensors only) is designed with that in mind, however, the main power feed for ECUs are 12 volt for a reason, most may stay running as low as 9 volt, but the other electronics in the vehicle will shut down everything non needed to run the engine(gauges, heater , ect.), wipers and lights are the only things that will keep running, safety issue

 

Was there ever any solution to this problem?

 

TTT

Same problem here...any solution??

 

Hahaha... I've just got to laugh. I'm having the same problems and I go to site after site based on google/camaross searches, read a hundred posts only to find that the last posts never post a resolvement. It's like the guy dies or something. Just my luck...

 

yeah, i know, sometimes it may happen that they sell the car, or wreck it, but others just don't care about these threads, once they fix it

 

To my knowlage, more than 10 volts at the battery while cranking indicates a good battery. 11 is great, you might get that on an optima red top starting a d15 honda. 9 or less is too low and will burn up a gm starter in short order. Seems like everything has been covered... at least 3 times! My first thoughts would be a weak optical sensor that intermittanly sends signal to the pooter at cranking rpm's. Does the rpm reading on the scantool seem accurite? Does the scantool indicate crazy readings from the coolant temp sensor? The coolant temp sensor has much more control over fuel and timing than most would think (esp when starting)... thats a general thought and not lt1/gm specific (what other input does can it use?). Just throwing out ideas, ive seen conquest/starions and sentras litterally pour fuel out the tail pipe due to bad coolant temp sensors. The pcm uses the sensor in the water pump as its imput, the one in the head is for the gauge. I wish you luck... you deserve you car back after all this hard work.

 

Hum...I to was wondering about a resolution to this. My 94 5.7 is about to tick me off to no end. First we had probs with it not starting after it had run for a while and then we replaced the fuel pump because they told me pressure was to low and it ran great for 1 week and stranded me doing the same stupid not starting crap and backfiring if it was running. Now it won't start at all but will when you spray some starting fluid up in there. I don't think its opti crap but something else we can't figure out.

Any ideas? We have been working on this for 3 years! We had the auto shop put it on the computer but the only thing they told me was fuel pump...which is crap because there is something more wrong then that.

Thanks for any help.

 

Mine is all figured out. I had a brand new LTCC that had issues(Sent it to TurboBob and he didn't find a single problem with the unit. He suspects it may have been my connector) and went back to a stock ignition and mine fired right up. You wouldn't believe what all I changed and bought (that didn't fix squat I might add) before I went back to stock ignition. Have you gone thru the diagnostics on the Opti and the Optispark harness? Look at shoebox's site to get those if you aren't familiar with the process. Tell us what you've tried and found so far so we don't refer to things you've already examined.

 

To eliminate fuel pump, put a cheap fuel pressure gauge (I bought a Harbor Freight version) on your schrader valve and make sure:
1. Vacuum line off Fuel Pressure Regulator, Key on = 43'ish PSI
2. With Vacuum line on and engine started, idling = 38'ish PSI

Also, there is a 'test port' (Also depicted on Shoebox's site, I believe) that allows you to apply 12v and you can hear the pump run. It is over next to the PCM in the visible wiring harness split loom. You can run a jumper wire from the battery to this port to verify the pump works.

Also, there has been numerous posts about peoples Fuel Pressure Regulator rupturing the inner diaphram and that lets raw gas dump into the intake. Pull off the vacuum line and see if there's any gas in that vac line running from the passenger side intake to the FPR.

You might see if the FP relay is bad. Take it off and jumper it to see if it stays on. Or just replace it. They're only about $27 at O'Reillys, Autozone, etc.

 

Ok been out working on the beast. We got a noid light and the computer set on the kitchen table all night. We put the light on and it worked. It was the closest my car has come to starting since Friday. It just choked out tho. After we put it all back together it just turned over no fire. We put the light back on there and nothing. We cycled the key off/on several times and it would try to start...there was fire. It was choking out like someone slammed a carb shut tho.

Ok now it was running so i went back out to see what he did. He had the noid light hooked back up and only had 6 of the 8 injectors hooked up. It was backfiring something terrible but hey it was running. So he put it all back together and nothing. NO FIRE.

So we are thinking that it is the computer and when we do something different to it it changes its mind. LOL I know lame but when you have it all together right it say OH HELL NO this ain't gonna work.

Any thoughts before I have spend another 200 bucks on it?

I think we have ruled out fuel pressure being the problem.