Z71 K1500 Starting Problems

bigdaddyviking67 · #1 08-11-2004, 11:08 AM

I am having problems with my truck not starting. It will start then cut off real fast. It will continue to do this for a few minutes. I have to pump the gas pedal hard to keep it running, then when it get warmed up it seems to run fine. The fuel pump is six monthes old, fuel filter new. Whats the deal????

95silverado · #2 08-11-2004, 01:11 PM

Is the new fuel pump an OEM or an aftermarket? If its an aftermarket pump, check your fuel pressure when the truck is acting up. The after market pumps don't hold up. If the fuel pressure is ok, check the temp sensor. Hope this helps.

bigdaddyviking67 · #3 08-12-2004, 10:27 AM

Quote:

Originally Posted by 95silverado

Is the new fuel pump an OEM or an aftermarket? If its an aftermarket pump, check your fuel pressure when the truck is acting up. The after market pumps don't hold up. If the fuel pressure is ok, check the temp sensor. Hope this helps.

It's a NAPA fuel pump. It's still under warranty so if the fuel pressure sucks I'll go with an OEM pump.

SpitAndDirt · #4 08-12-2004, 02:58 PM

Hey, check out my post that I wrote down for another member.
http://www.automotiveforums.com/vbul...d.php?t=267196

It's long, but I think it's got some really good info. The only thing is that my post is geared towards the Multi Squirt (MFI) system used on GM trucks 96' and up. 95' and below have Throttle body injection with only 2 injectors. Do you have any codes, have you tried the paper clip between "A" and "B" pins on your ALDL to read them? I might look at vacuum lines very closely for leaks. I can't tell you for sure, but you may have a Throttle Position Sensor going out, which takes a reading from the position of the butterfly in the throttle body. They wear out over time. I don't believe you have a problem with the pump, personally. But I need more specific information about how the truck runs to help you better. Hope this helps -Chris

bigdaddyviking67 · #5 08-13-2004, 10:57 AM

Quote:

Originally Posted by SpitAndDirt

Hey, check out my post that I wrote down for another member.
http://www.automotiveforums.com/vbul...d.php?t=267196

It's long, but I think it's got some really good info. The only thing is that my post is geared towards the Multi Squirt (MFI) system used on GM trucks 96' and up. 95' and below have Throttle body injection with only 2 injectors. Do you have any codes, have you tried the paper clip between "A" and "B" pins on your ALDL to read them? I might look at vacuum lines very closely for leaks. I can't tell you for sure, but you may have a Throttle Position Sensor going out, which takes a reading from the position of the butterfly in the throttle body. They wear out over time. I don't believe you have a problem with the pump, personally. But I need more specific information about how the truck runs to help you better. Hope this helps -Chris

I don't think its the pump either, it runs fine when it gets warmed up, I dont think it is the TPS either, That went out on me when the truck was under warranty and the symptoms are not the same. When I turn the key it starts then will die real fast. When I keep restarting it and pumping the gas it trys to rev up but dies quickly. After a while of doing this it will stay running by pumping the pedal fast but it is sputtering while pumping the pedal. Once able to rev the engine to 3500 rpm without it dying it stays running but idles at 1000 rpm when normally it idles at 200-300 rpm's

95silverado · #6 08-13-2004, 03:41 PM

With a fast idle like you have, it sounds like a vaccum leak. Check all your vaccum hoses, The throttle body gasket, and power brake booster for a leak.

SpitAndDirt · #7 08-13-2004, 07:41 PM

I thought about something that may cause it to do this. Have you checked your Manifold Absolute Pressure sensor? All your vacuum lines may be fine, but if the computer is getting false vacuum readings from this sensor it could also be causing the sputtering. One other thing, your truck idles around 200-300 RPM? That sounds a bit low to me, but if thats normal for your truck I guess it's alright. I'm really surprised you don't have any codes to tell us about. -Chris

slacker_53 · #8 08-15-2004, 12:10 PM

'99 and up (new body style) with the 4.8L, 5.3L, or 6.0L have a fuel pressure regulator mounted on the driver's side, midway above the valve cover.

It has a vacuum line attached to the top side of it, pull the vacuum line and if you get raw fuel out of it, then the regulator is bad.

Easy fix (you can do it yourself) regulator? about $70.00.

This sound like it may fix your problem.

-slacker

bigdaddyviking67 · #9 08-16-2004, 10:31 AM

If the MAP sensor was bad wouldn't I get a code, I checked the codes and the result was no codes stored. It seems to be getting harder to get it started. I don't see any bad hoses, so it might be the NAPA fuel pump. My neighbor works at a GM dealership as a mechanic, so he is going to check the pressure from the pump for me, and if its good, I will have to go from there and start checking other things. Maybe its the oil pressure sensor?

SpitAndDirt · #10 08-16-2004, 11:37 AM

Your starting to run out of options if the pump is good, but if your neighbor is a GM certified Tech, he should be able to pinpoint more items that you might be leaving out, not to say that you are on purpose, but maybe your overlooking something obvious. Hell, you could even have a programming issue with your computer, a clogged EGR valve, corroded terminal connections, water in the fuel, the list could go on for awhile. I'm sorry that I couldn't have been of more help, but not being there to hear, see, and touch makes diagnosis real hit and miss sometimes. -Chris

bigdaddyviking67 · #11 08-16-2004, 12:24 PM

Well when I get it figured out, I will post the problem so you know what it was. Thanks for everybodys help....

bigdaddyviking67 · #12 08-23-2004, 10:59 AM

I have not done anything to the truck but add some fuel additives when putting in gas and the truck seems to be running better. Yesterday it started and stayed running on the second try and after I added gas it stalled and I had to turn the key 10 times and pump the gas pedal to get it to stay running, then it ran fine. During the ride home from the gas station it started to stall out but I kept it going by pumping the gas and after 20 seconds of doing that it ran fine again. This morning it started and stayed running on the second try and ran fine all the way to work (32 miles). I am thinking it is not the fuel pump????

93silverado · #13 09-16-2004, 02:48 AM

big daddy did you ever get it figured out my 93 is doing the same thing its at the shop getting scanned now let me know if yours is fixed, I'll
post a fix if the mech finds anything that works.

bigdaddyviking67 · #14 09-16-2004, 10:12 AM

Quote:

Originally Posted by 93silverado

big daddy did you ever get it figured out my 93 is doing the same thing its at the shop getting scanned now let me know if yours is fixed, I'll
post a fix if the mech finds anything that works.

No, my wife went out of town for 2 weeks and I have been running it every day. It seemed to get better, but still stalled a few times while initially starting it during the two weeks. Now that she is back I let it sit for a day or two and it has a hell of a time starting. Once it gets warmed up enough to stay running it's fine. When its cold it takes 5 minutes to get it started and keep it running. When its cold it turns over starts then kills quickly. It will restart and when I step on the gas it sputters like it isn't getting fuel. It will do this untill I can get the rpm's over 3500. Once I can get the rps to 3500 it will stay running, anything lower than 3500 will kill the engine when I let off of pumping the gas pedal.

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