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I am having a starting problem with a 1998 chev 1500 with a

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5.7 vortec. the only codes...
I am having a starting problem with a 1998 chev 1500 with a 5.7 vortec. the only codes present are p0420 and p0430. it starts 100% when it is cold but has to crank a long time when it is at operating temp. do you have any ideas as to what could cause this?
Submitted: 2 years ago.Category: Chevy
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Answered in 22 minutes by:
5/24/2015
Chevy Mechanic: Tim's Auto Repair, mechanic replied 2 years ago
Tim's Auto Repair
Category: Chevy
Satisfied Customers: 16,167
Experience: Have owned a repair shop for 25 yrs.
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Hi,My name is Tim,
I will do my best to assist you
from the way you explain,,the first thing to do here is to check the fuel pressure when the engine is warm and while turning the starter,,these must have no less than 60psi at all times,,the fuel pump may be weak when it gets hot and needs replaced,,if the pressure is good,and from the codes you get,the problem may be a clogged catalyst converter,this would cause back pressure and make the engine hard to start
thanks
PLEASE COPY AND PASTE the link below to your browser, I have uploaded more info on this there please copy and paste the link below to your main browser[INTERNET EXPLORER or FIREFOX]
.
https://www.dropbox.com/s/m111uyg1eqeb4cx/0523-98-chevy-truck-DTC%20P0420%20Catalyst%20System%20Low%20Efficiency%20Bank%201.doc?dl=0
.
if the link doesn’t work that way, try it this way
thanks
.
www.dropbox.com/s/m111uyg1eqeb4cx/0523-98-chevy-truck-DTC%20P0420%20Catalyst%20System%20Low%20Efficiency%20Bank%201.doc?dl=0
.
If you are satisfied with my answer, Please Rate my answer by clicking the rating button so I can get credit for my work. I’m not always going to be giving you good news, so please don't let this stand in the way of you accepting my answer. .it does not cost you more money and we will still be able to communicate, ,.please understand, i can not see, hear or touch the vehicle and only know what you tell me. Bonuses and positive feedback are appreciated.. if you are not satisfied with my answer, please do not leave bad feed back ,i will gladly opt out and let another expert handle the question. .if i have sent any diagrams, please print them. .sometimes you may need to right click the image [,then save picture as]to save it to your computer so you can open it with your picture program...Please ask if you need more help
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Customer reply replied 2 years ago

I have already checked the fuel pressure and it is as you say. 60psi. when the engine is warm and acts up. the right side cat is cut out and replaced with a piece of pipe but the other side is still in there. that's why I took out the o2 sensors to make sure it wasn't a plugged muffler or the other catalyst converter. the wiring looks fine and no o2 codes present. sometimes it will work fine for a day but normally tends to act up quite often. any other ideas greatly appreciated. thanks.

Chevy Mechanic: Tim's Auto Repair, mechanic replied 2 years ago
the other thing that may cause the long crank time would be a bad crank sensor,,these can break down with heat sometimes when they go bad..
i wouldnt think the o2 sensors would cause this,though,not having the convertor may be why you get the codes
thanks
If you are satisfied with my answer, Please Rate my answer by clicking the rating button so I can get credit for my work. I’m not always going to be giving you good news, so please don't let this stand in the way of you accepting my answer. .it does not cost you more money and we will still be able to communicate, ,.please understand, i can not see, hear or touch the vehicle and only know what you tell me. Bonuses and positive feedback are appreciated.. if you are not satisfied with my answer, please do not leave bad feed back ,i will gladly opt out and let another expert handle the question. .if i have sent any diagrams, please print them. .sometimes you may need to right click the image [,then save picture as]to save it to your computer so you can open it with your picture program...Please ask if you need more help.
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Customer reply replied 2 years ago

I have changed the crank sensor already but sometimes a used one is also faulty. if it drives for a long time it starts fine if you start it immediately but if you let it stand for about 10 minutes to an hour it will be acting up. the timing was out some when it started doing this and resetting it did make a difference. do you think this could have something to do with the cam sensor maybe?

Chevy Mechanic: Tim's Auto Repair, mechanic replied 2 years ago
no
the cam sensor wouldnt do this..
i would think the crank sensor or the distributer cap
thanks
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