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dwrick33
Novice
Aug 23, 2010, 6:48 PM
Post #1 of 10
(2465 views)
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98 gmc 4.3l
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wont start in am. use either will start up run great..after it runs few mins it will start..and if pluged in it will start to help me out thanks
(edited as entire post was in subject line - intact as was - just moved content to body of post)
(This post was edited by Tom Greenleaf on Aug 23, 2010, 6:56 PM)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 23, 2010, 7:00 PM
Post #2 of 10
(2453 views)
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dwrick33: Welcome to the site but can you clarify what exactly is going on with this please?
Saying it wont start then after it runs it will start is a bit confusing
T
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dwrick33
Novice
Aug 23, 2010, 7:07 PM
Post #3 of 10
(2446 views)
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if you try to start it in the morning it wont start ..but if you use either it will start right up.and run great..and after you let it run a few mins .shut it off it will start right back up..and also if you plug it in and the engine stays warm .it will start up nice..if the engine is cold .it wont start in any temprature,?why and how can i fix this?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 24, 2010, 2:29 AM
Post #4 of 10
(2440 views)
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? Are you plugging it into a block heater to be able to run it? Sounds like it just doesn't like colder to start and is fine when warm - right?
If so there's a sensor for what temperature the engine is called a CTS (coolant temp sensor) that tells the computer to deliver more fuel when cold and back off as it warms up to normal that could be the problem.
It's right near the thermostat with two wires. The plug can even be a problem to those. They can be tested also but not very expensive.
Try some starting fluid in throttle body and if it starts right up and behaves we have a cold start problem here. Could even be fuel pressure is low or other problems but start with simple things and do more testing than parts tossing,
T
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dwrick33
Novice
Aug 24, 2010, 4:35 AM
Post #5 of 10
(2434 views)
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yes if its 78 80 out side first thing trying to start it it wont start .will just crank over..BUT if i give it a shot of either it will start right up..also if i plug it in no matter the temp out side warm or cold it will start up..but just wont start after a few hours? help
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 24, 2010, 5:56 AM
Post #6 of 10
(2422 views)
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When you say "plug it in" -- what do you mean? Is that a block heater or a battery charger or what?
If ether (starting fluid) always works it's clearly lacking proper fuel when cold. Yes - even 80 degrees Fahrenheit is cold to an engine.
Running, the general temp goes up close to 200F and takes an iron engine quite a while to cool down fully.
This could be a few things. A fuel pressure problem as this engine is known to be very fussy or the wrong signal sent saying it's always warm to computer of the couple likely problems,
T
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dwrick33
Novice
Aug 24, 2010, 5:59 AM
Post #7 of 10
(2418 views)
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yes its a block heater/. also iv checked the fuel pressure too and it 64 psi could it be the iac sensor?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 24, 2010, 7:19 AM
Post #8 of 10
(2410 views)
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Fuel pressure is ok for starting.
This is temp sensitive so not likely IAC.
Since this can run normally when warm it still leads to coolant temp sensor or it's connection. If no connection it will always think it's warm and not deliver enough fuel for a proper start when cooler as computer tells it how much to deliver like a choke on a carb engine would.
It looks like this by the plug view with it unplugged........
Black and a Yellow wire should go to this so you find it.
You could test that with an ohm meter. Higher resistance with it colder and lower when warmer in gradients but it probably either works or not - I don't have the exact chart.
In other words if it was unplugged or plug to it didn't make good contact OR it didn't work it would send the signal the engine was always warm and inadequate fuel would be delivered. You can test it or toss is @ $15 bucks not a big expense but that's not the best way to go. Better to test it and if this thing is fine we look for some other temp sensitive reason or wiring from this to computer is broken!
If you have a check engine light on it should show this in a code reading as "something wrong" -"no signal" or something. OBDII code readings might lead you even if CEL (Service Engine Soon) light isn't on.
This is a temp sensitive no start problem. Since it's about 80F where you are right now and it will stay running with starting fluid it COULD be this. If tons colder and this system has failed it wouldn't stay running or would take several tries.
There are a zillion other sensors but by description so far this is just cool sensitive. 80F isn't like being below zero.
Not sure how warm block heater heat to but my guess is not much more than the 80F but possibly up to 100F or so.
At least unplug the thing and see if it's all corroded at the plug to it if you can't test it out/rule it out,
T
(This post was edited by Tom Greenleaf on Aug 24, 2010, 7:25 AM)
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dwrick33
Novice
Aug 24, 2010, 7:23 AM
Post #9 of 10
(2407 views)
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ok thank you ill try this and let you know how i make out thanks again for you help
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Aug 24, 2010, 7:28 AM
Post #10 of 10
(2404 views)
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I had just edited that to say black and yellow wires (just two) go to that thing - near thermostat. I hope it's just that easy as you can just replace that or the plug end if bad,
T
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