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GMC Forum: 2000 GMC Jimmy Start Problems
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  #11  
Old 12-03-2018, 08:39 PM
Kess Kess is offline
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Drives a 2000 GMC Jimmy 4WD 4.3
 
Join Date: Oct 2017
Location: Virginia
Posts: 14
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Can a bad ignition coil be the root of my problem? Jimmy runs fine when running,,just the start issue after first int initial start, I don't suspect a leak down in fuel pressure as it starts easily first thing in the mornings, but if you try to restart it say a few minutes later, it just cranks, it trys to run but quits like it is out of fuel. and when it gets into this no start situation, it cranks but won't hit a lick, but if you wait long enough, say a couple minutes or so, and keep trying, it will eventually fire right up. Engine does not have to be warm for it to not start, like I said, just after it does start, and a couple minutes later when you crank it, it won't start until it gets ready too. My fuel pressure will go down to around 36 when in no start condition. Have been told my coil is starting to break down, (showing the white on the side), COULD THE COIL BE THE ROOT OF THE PROBLEM? HAVE ALREADY TIRED THE IGNITION MODULE, NO DIFFERENCE IN STARTING PROBLEM. fUEL PRESSURE HOLD FOR AT LEAST 45 MINUTES.
Someone said to use the 12 volt connection right beside the fuel pump relay in fuse box under hood, says it goes directly to the fuel pump to prime it. I am going to try that next, but not sure if the ignition sw. has to be on or off to do this..seems if it shoots 12 V. directly to the fuel pump to prime it, then ignition does not need to be on. am going to monitor the fuel pressure with the 12 V hooked to the terminal right beside the fuel pump relay, and record fuel pressure reading, then unhook it and wait 10 minutes and see if pressure drops of if pressure holds.
Anyone out there ever done this test? Have changed out crank sensor and oil pressure sensor,,no help there...am in process of troubleshooting the temp. sensor, but using a resistor with unplugged connector going to coolent temp. sensor down low in block on driver side. I read where a 1.5K resistor is just about right to provide good starting and correct temp. reading on inside gage. If it cures the no start condition with the resistor, then I would know that the coolent temp. sensor is bad. I can get it running without the temp. sensor plugged in, and I get NO codes at all,,,don't think this is normal,,as I read where I should get the P0128 code if coolent temp. sensor is bad. It doesn't seem to make any difference weather the coolent sensor is plugged in or not..

Hope your able to read all of this crap without getting too bored.

Thanks in advance...
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  #12  
Old 12-04-2018, 05:15 PM
Kess Kess is offline
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Drives a 2000 GMC Jimmy 4WD 4.3
 
Join Date: Oct 2017
Location: Virginia
Posts: 14
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Starting now to think it is the Ignition Switch after doing some serious trouble shooting this afternoon, in checking furl pressure with my gage..seems I have good pressure if use the test terminal on the fuse block going directly to the fuel pump bypassing the fuel pump relay and ignition switch and all else..It goes directly to the fuel pump to prime it.
Have 62 psi in checking it like that, only 55 or less using the key to prime the pump, sometimes, even less than that, in the high 40's..One time,,with no pressure showing on the gage, turn the key on to prime the pump..no pressure at all....Took 5/6 times before I saw any pressure on the gage to be able to start the Jimmy. It went up to around 56 to 58 finally and was able to start...It should read around 60.
Being it took so many times before any pressure showed, using the key to prime the pump..am thinking it is the ignition switch after all. A pretty common problem for the year 96 to 2001 Blazer and Jimmy.
Will let you know more after I have the switch changed out.
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  #13  
Old 12-07-2018, 12:16 AM
Kess Kess is offline
Junior Member
Drives a 2000 GMC Jimmy 4WD 4.3
 
Join Date: Oct 2017
Location: Virginia
Posts: 14
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Have determined that the reason for it not to start after starting first time,,is LOW FUEL PRESSURE. am currently troubleshooting low voltage going to fuel pump,,in no start conditions, I am only showing around 44 psi of fuel pressure,,,when it does start, I am seeing around 55 or above. Using the fuse block prime terminal to energize the fuel pump, I see around 61 psi, every time. I am thinking that the fuel pump is good,,,and I might have a wiring problem somewhere...I think the ground is good back there because of the good pressure I am getting using the fuse block prime terminal,,,tested it 7 times in a row doing that and it always came up instantly to around 61 or 62 pressure. Next will troubleshoot the under hood fuse block,, fuel pump relay is good, will check voltages tomorrow at that fuel pump relay, in and out etc.
Will post if I have any success. 2000 gmc jimmy 4 WD. 139K miles.
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  #14  
Old 12-18-2018, 11:33 AM
Kess Kess is offline
Junior Member
Drives a 2000 GMC Jimmy 4WD 4.3
 
Join Date: Oct 2017
Location: Virginia
Posts: 14
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Latest news on my 2000 Jimmy 4.3..I have a fuel pressure gauge hooked up to test valve under the hood,,I leave it there now all the time to monitor fuel pressure. I still have the no start condition I had before, meaning, it will start just fine when no pressure is showing on the fuel pressure gauge,,if you drive iti a little and try to start it again, with 58 psi showing on gauge, it won't start,,,just cranks...BUT, IF YOU PUSH THE BLEED BUTTON ON THE FUEL PRESSURE GAUAGE TO TAKE PRESSURE TO 0,,THEN IT STARTS RIGHT UP, NO PROBLEM..Go figure...what the heck? Holds pressure good, new fuel pump 26 months ago,,runs fine otherwise when running. New battery, plugs, wires...could it have something to do with the coil? see some signs of coil breaking down..OH, and fuel pressure in no start conditon, reads only around 42 psi,,too low for it to start, but if I relieve pressure (0), then it starts right up...fuel line restriction? has 16 month old fuel filter....Help...please...
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  #15  
Old 12-18-2018, 04:17 PM
Kess Kess is offline
Junior Member
Drives a 2000 GMC Jimmy 4WD 4.3
 
Join Date: Oct 2017
Location: Virginia
Posts: 14
Default

Also, forgot to mention,,,the reason for the no start condition is because of not quite enough fuel pressure,,these engines are supposed to have 55 or higher I understand...When in no start condition,,it is only aroiund 52 or so. I am wondering if low voltage is my problem back at the fuel pump,,probably need to check that, hopefully can remove the driver side rear tire to get to the wiring to fuel pump, I think,,anyone have an opinion on this? I have already tried another fuel pressure relay under the hood, good voltage there.
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