2000 GMC Jimmy Start Problems

Kess

New member
I have a 2000 GMC Jimmy with 129K on it, 4.3 Vortec engine. Start fine if sitting for a few days, even on cold mornings, but after driving it for a few miles and letting it sit for a while, it seems to not want to start, cranks, but like no fire or maybe a fuel problem. Pretty sure the fuel pump as benn replaced recently as I just bought it recently. It runs fine on the road, idles fine, no missing or rough idle, shifts great. Looks as if the dist. has been replaced, not sure when or if the plugs and wires have been replaced, but seems to run good.
Just a starting problem, which is pretty common on these 4.3 Vortec engines from what I read. Most point to the Spider fuel injections system, meaning the fuel regulator common problem, but don't know if it has been replaced or not, probably not. Had " check engine soon" come on, I replaced the EVC Selonoid on top fo engine and cleaned the MAS and new air cleaner (old one was not that bad), Just that crazy start problem, but starts fine after sitting all night or all week-end, just has problem after it runs a few miles and you get back in to start it and it just cranks. All lights seem fine, not codes...

Thanks
 

Kess

New member
2000 GMC Jimmy 4.3 Vortec, 129K miles

Yes, have good fuel pressure, tested around 61 psi, holds for over an hour.
Fuel pump replaced, selonoid valve back at tank replaced,new wires, plugs, dist. checked and button all OK. MAS cleaned, only won't start after warm,,starts in milliseconds when first try when cold..
Can cool down PCM (Computer), and it starts right up, or in heating the Computer, it won't start. Have sent Computer off to A-1 for rebuld, rec'vd back and same problem. Am wondering if they did a thermal test on it or just checked it cold? Think will send back to then for another test with mention to heat it up first.
It runs just fine once running,,no problems at all..just starting problem when you run it a little and try to restart. Am thinking Spider is Ok since did fuel pressure test and it held pressure for an hour or more. Anybody out there that thinks it may be the PCM computer?
Have asked mechanic to test the cold start sensor,,he seems to think it is Ok,,also, have read where a bad ignition switch can cause hard starting? but only does this when warm up a bit.
Fustrated!
 

Kess

New member
When my 4.3 Vortech engine is cold, it starts in milliseconds, but after warm, hard starting prevails...I can apply some heat to the PCM computer module when motor is cold, and I experience hard starting issue. Makes me think PCM, might be going bad...It runs fine after it starts, no missing or missfireing,
I have checked fuel pressure, and am getting around 61 and it holds that for A little over an hour, so am assuming spider is OK,,BUT NOT REAL SURE, and do not know if it has been replaced, but don't believe so..SUv ONLY HAS 129k MILES ON IT. Think I NEED TO REPLACE SPIDER?

Anyone else out there have this same problem? My Jimmy is a 2000 model with 4.3 Vortec engine.
At wits end...
 

Kess

New member
2000 GMC Jimmy 4.3 Vortec, 129K miles, start problem

Start Problem after engine warms up, start fine when cold or sitting overnight.
Mechanic said, it is a fire problem, not fuel.
Have had plugs replaced, wires, distributor, rotor, think it may be something to do with "no fire" problem. Maybe PCM, but have sent it off twice to A1 for them to check and it came back with same problem. I don't think they thermal tested it, I mean heating it up a bit to check it, cause if I heat mine up some with a hair dryer when engine is cold,,it gives me the no start problem, meaning you have to crank it 4 or 5 times b4 it will start.
Could it be the stator in the distributor acting up? Like I said, when cold, it starts right up like it should, but if you drive it a little and cut it off and try to restart it, it may take 4 times or more to get it started...I have heard that the ignition switch gave problems in this vehicle also, have not replaced it yet.
Mechanic said it was a not firing problem, not fuel related.
Runs fine after starting and driving down the road, not miss, no codes,,
Oh well....
 

Kess

New member
Believe now it is fuel related,,,or looking into the Temp. sensor and or the fuel filter.
Starts super good first thing in the mornings after sitting overnight,,after you run it for around 4/5 minutes and try to restart,,it won't start,,,it just cranks,,,if you wait around a minute and keep trying, don't mean cranking all the time,,just hitting the key every now and then..it will start...but in checking fuel pressure, when in no start condition,,fuel pressure drops to around 36,,,otherwise it runs around 55/60 when running, fuel pump was replace around 6K miles ago. have good ignition.
going to try and get fuel filter replace, although it was replaced around 5K miles ago. After that, will change Temp. Sensor,,have already replaced the oil pressure sensor and
Crank sensor. runs fine when running,,no miss or anything. I don't smell gas..
has new plugs, wires, etc. only has around 138K miles on it.

thanks in advance
-kess in VA.
 

Kess

New member
Question: Should I see a code if I disconnect the cooler Tempeture Sendor?, if , I am not seeing one when plug is disconnect from the sensor,,,seems to make no difference weather it is connected or not,,don't see any difference in the start problem. Anyone out there that may know the answer to this? I am about ready to change out the Temp sensor, then if that don't fix it, then will try the fuel filter although it was replaced about 14 months ago and the Jimmy runs fine when running, no problems,,just start up
Thought it strange it does not shoot a code when wire is disconnected from Temp. sensor.
thanks
 

Kess

New member
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...
 

Kess

New member
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.
 

Kess

New member
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.
 

Kess

New member
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...
 

Kess

New member
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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