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OT - 98 GMC Pickup

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Joe in MI

04-12-2008 18:17:53




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I have a 1998 GMC Sierra half ton w/ the 305 with about 110000 miles. Today I went to start it and it was turning over a lot faster than normal, but wouldn't catch. Every once in a while while turning over it would strain like it was under load, then go back to turning really fast. It never fired.

This is the first time I used it (or tried to) since bringing it home after having some work done on one of the rear brake lines. When we loaded the truck on the flat bed (after the brake line let go as I was driving down the road) we noticed a little coolant leaking from the engine compartment somewhere. They couldn't find the source at the shop, and it didn't leak anymore. It ran fine all the way home.

I dunno if this is related - the fuel pump has been running a little longer than usual after I shut the truck off. It used to run a second or two at the most - lately its been running 3 or 4 seconds.

I was thinking maybe clogged fuel filter. A buddy suggested broken timing chain. (I like my idea better- $$$ :oops: )

Since it's rainy and cold and dark, I haven't looked any deeper. Any ideas or suggestions for tomorrow?

Thanks

Joe

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Joe in MI

04-14-2008 13:40:44




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 Re: OT - 98 GMC Pickup in reply to Joe in MI, 04-12-2008 18:17:53  
I replaced the cap and rotor today. It fired up almost instantly!
I am REALLY glad it wasn't the timing chain.

Thanks everybody for your responses.

Typical Michigan weather - two days ago when this happened it was 32 degrees and raining / snowing. Now it's 55 degrees and SUNNY! Good outside wrenchin' weather!

Joe



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Joe in MI

04-13-2008 09:50:32




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 Re: OT - 98 GMC Pickup in reply to Joe in MI, 04-12-2008 18:17:53  
I pulled the distributor cap this morning. The rotor is turning, so its not the timing chain.

The points and rotor bug are covered in black, sooty carbon. Everything under the cap is either covered in carbon or a fine white powder. I'm guessing this has something to do with it.
I'm going to pick up a new cap/rotor tomorrow - I'm betting it will run a lot better.

I'm also going to change the fuel filter - It's due anyway.

I'll post back with my final results or more questions - thanks to everyone who responded so far!

Joe

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Bob

04-13-2008 09:50:17




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 Re: OT - 98 GMC Pickup in reply to Joe in MI, 04-12-2008 18:17:53  
As far as the fuel pump running longer than normal after cranking or running, there is an oil pressure switch that serves as the backup to the fuel pump relay operated by the 'puter.

If the oil is cold or thicker than normal, OR the OP switch is failing, that is what causes the longer operation of the electric fuel pump.



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Ron-MO

04-13-2008 09:41:28




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 Re: OT - 98 GMC Pickup in reply to Joe in MI, 04-12-2008 18:17:53  
Symptom that rings a bell to me is the fuel pump rinning longer than usual. Squirt some fuel down the throttle body and give it a try. If it fires you likely have a bad fuel pump, which is not uncommon with GM about those models, and mileage. I have replaced about every one I had with around 100,000 on them. Some say running them low on fuel heats the pump and shortens their life, but I don't know that to be fact.

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teddy52food

04-13-2008 07:29:27




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 Re: OT - 98 GMC Pickup in reply to Joe in MI, 04-12-2008 18:17:53  
Typical timing chain symptoms. Please let us know what you find.



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hndymann22

04-13-2008 06:41:40




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 Re: OT - 98 GMC Pickup in reply to Joe in MI, 04-12-2008 18:17:53  
If you want to check it without taking too much time, grab a timeing light and put on #1 plug wire and have someone turn it over while shooting at crank pulley. If the light blinks u have fire, and if the timeing mark is showing up at number one on crank pulley then it is not in your valve system. That is where I would start checking if it was me...
Hope everything works out for u...



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Hobo,NC

04-12-2008 19:10:02




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 Re: OT - 98 GMC Pickup in reply to Joe in MI, 04-12-2008 18:17:53  
Sounds like the distributor cap is wet from that coolant leak they could not find



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Ken(Ark)

04-12-2008 18:55:32




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 Re: OT - 98 GMC Pickup in reply to Joe in MI, 04-12-2008 18:17:53  
Check to see if your getting any spark .

The plugs fire a hair short of top dead center and cause a little resistance . That"s why its hard to start a hot rod with the timing really advanced. When the motor is running there is a lot of momentum by the rotating mass that easily overcomes the advanced spark .

If your not getting any spark you will only have compression without added resistance and the motor will spin a little faster when trying to start.

Might not have anything to do with your problem , but its a free test , just get your brother in law to hold the plug wire and crank it over .

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Ken(Ark)

04-12-2008 19:01:01




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 Re: OT - 98 GMC Pickup in reply to Ken(Ark), 04-12-2008 18:55:32  
P.S. if your not getting spark it doesn't mean its in the electrical / distributor system . Like Brian pointed out , it might be a broken timing chain keeping the distributor from turning .

If you aren't getting spark and cant see if a rocker arm is moving (1st choice), pull the distributor cap and see if the rotors turning (2nd option).



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Brian Bell

04-12-2008 18:23:38




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 Re: OT - 98 GMC Pickup in reply to Joe in MI, 04-12-2008 18:17:53  
Take the oil filler cap off and see if the rocker arms are moving...if so, not broken timing chain. Also try pouring a very small amount of fuel down the throttle body or give it a snort of starting fluid and see if it busts off. Could be that you have a bad fuel pump. I replaced the one on my 94 GMC Z71 at about 140000 miles...drove into work fine...never would start that afternoon. As far as the coolant, that could be a freeze plug leaking, the radiator, water pump, rad hoses, heater hoses, etc...need more info on the general area of the leak...could also be the intake gaskets..mine leaked at the front of the intake on the drivers side and appeared to be a bad water pump until I cleaned up the front of the engine and watched it. If it ends up being the fuel pump...it's usually easier to lift up the bed than to drop the tank...good luck and post back with your results.

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