need help badly with 00 gmc jimmy
 

I'm back again I'm sure this has been asked before but I couldn't find it so I'm gonna ask I'm having a startin problem 2000 gmc jimmy 4.3 vortech with over 200,000 miles on it 4x4 now with the issues aside from the 4x4 acting up like they commonly do it won't start it will turn over all day long but will not fire I've put in new battery ans spark plugs in it cleaned rotor button to get better spark but nothing now the odd thing is if I hook up the battery booster it will start faster than you can let off the switch but the moment I turn it off and try to start it with the battery it won't start but will turn over all day long once again but once its hooked up on the booster it starts again. I have never seen a car do this and I'm pretty mechanically inclined and I'm totally lost with it if anyone can help please let me know as this is my wifes daily driver and its getting pretty annoying having to boost it everytime you start it. Thanks in advance to anyone who can help.

Battery
 

Did you just put in any battery or did you get one with the correct cranking amps?

the battery i bought has 700 cca on it which is 150 more than tha battery i took out of it

since ur fairly mechanically inclined, do you have a fuel pressure gauge? if so go check the pressure for starting (turn key to on but not starting position), leave it for 5 min and recheck pressure, put booster cables on blazer - check pressure, boost blazer and get it running - check pressure, hold throttle cable for WOT and check pressure again.... REPORT pressures here for us :)

It should be around 60lbs for starting, leak down should be minimal over 5 min but not uncommon to drop some, running should be around low to mid 50's and WOT i dunno but we need the number. Pressure issues could easily be causing your problem and the extra powerz avail could be making the pump work properly.

Ok it has sufficient fuel pressure has sufficient voltage on the battery I did get it hooked up on a comp today and it came back with the code of p1351 ignition circuit high voltage from wat I found on here with the obdII trouble codes looks like to me the ignition module could possibly be goin out on the vehicle but I'm not 100 percent on this if anyone has had this issue before and got it resolved please let me know asap cause I'm goin to try to replace the imc tomorrow 2/9/11 thanks in advance

I had the same problem only mine would come and go...left my wife stranded, I would go and pick it up ...start no problem. This went on for a while. I found the coil wire on the coil itself had corosion in it. When I put new delco wires in it I had put a lot of the die electrical compound on the ends, in time that stuff would dry up letting moisture in. I cleaned up the end, put more compound in it and it fired right up. Now I check that end 3,4 times a year. Hope this might help

I would change your ignition module too.

Diagnose the issue. Taking the shotgun approach to auto repair might work for some, but diagnosis is the only sure way to fix the problem correctly the first time.

Trouble Code Listing:
P1351 - Ignition Control [IC] Circuit High Voltage
If you have any questions pertaining to diagnostic steps, please ask them and we will try to get you through it.

ok i have checked everything i can think of icm ground wire and hot wires even added and extra ground strap from the motor to the body and still nothing still haas the same problem but it has developed a new issue now if you give it alot of gas at once it falls flat on its face rpm will rise rapidly but it will barely move out of its tracks but if you ease into it it does juss fine any suggestions besides a bullet lol

Last time I had that code, it was my spark plug wires.
I went thru all the stuff listed, except for wires: Module, coil, cam pos sensor, etc.
New set of wires cured it.

plug wires are the only thing i havent done yet ive done everything else to it ive even went as far as to clean out fuel lines and tank juss by the way its acting plug wires were the next thing i was goin to try on it