00' GMC Sierra 1500 Long start up time?

cjherrman · August 25, 2005

Well I have a 00' GMC Sierra Z71 w/ a 5.3 liter. The problem that I am having is on start up. Basicly I will put the key in the ignition and wait for a few seconds and then I will turn the key and it will take a long time to start. It cranks over at the same rate as usuall just takes forever to start. Most of the time when this happens I will only try cranking it over for not more than 4 sec because I dont' want to fry the starter or anything else. I am not having this problem every time I start it up it is hit and miss. I have done the following to try and fix the problem with no luck. I need help please!! I am not that tech. advanced at fixing these types of problems.

I first put a new battery in it, then a new fuel filter, I bought a pcv valve but can't find it on my truck. I talk to a guy at my work and he said it would most likely be a crankcase positioning sensor I told him that I thought it would be a fuel pump. I took it to a shop and they ran a diagnostic on with some snap on brand computer and didn't find any codes. They then hooked up a fuel presure guage on the passanger side of the engine and they said they didn't think that was the problem either. They were confused on wether it was sequental fuel injected or something else they were different specs all to gether. I can't honestly remember what the pressure was however I think it was around 55 but I am not positive. Could it have problems starting if it was plus or minus a few pounds of what it calls for? They told me to just go and drive it on the highway and to see if it didn't fix the problem. The other thing that I tried was putting heat in the gas tank but this didn't work either I have ran approximately a full tank of gas through the truck and still the same problem.

There are no test engine lights and the mechanic said that his reader didn't throw any codes, he also said that it wouldn't throw a code if it is the fuel pump. I was thinking of putting new spark plugs but that is probably a waste of time also. One thing that I have noticed is that I can almost hear a clattering noise coming from the tank area when I turn the key to the on position before starting. I am at a loss for what to do. I have gotten quotes from a few shops and they are telling me it will run about $700 and I about lost my mind. Is this something that a beginer like me could replace I wouldn't care how long it takes me to fix it because I have another car to drive. Please help I am desperate. One last thing I only have 40,000 miles on this truck I can't belive that there is something this wrong with it already. Thanks ahead of time.

GM-Tech · August 25, 2005

Fuel pressure is critical on these. Yes, just a few pounds short could be a problem. Specs call for 55-62 psi WHEN THE PUMP IS RUNNING (vehicle not running). This only occurs for 2 seconds when you first turn the key on and as soon as the pump stops running, it will drop below the pressure you had with the pump running. That's normal.

However, once the pump has stopped running, you need to monitor the pressure. It should not continue to drop. No more than a 5 psi drop in 10 minutes. If the pressure drops off to nothing in a few minutes, or immediately, you most likely have a bad check valve in the fuel pump. This will not cause any problem once the vehicle is running. It only allows the fuel line to empty back to the tank when the pump is not running, which causes very long crank times. Basically, the pump will have to fill the entire fuel line from the tank to the injectors, then build pressure once it does. This takes a while.

cjherrman · August 25, 2005

I wish that I would have written down the numbers when I took it too this shaddy mechanic. Do you think I should take it there again and see if it drops. I am pretty sure that it wouldn't drop pressure, are you saying once you turn it off? I think the specs said that it shouldn't fall below 27psi after shut off and it wasn't anywere close to being this low.

I am at a loss here as to what I can do. I called our factory dealership and talked to one of their mechanics and they said it would just cost too much to find out what is wrong with it if it isn't doing this all the time. How much and how hard is it to replace a bad check valve? I would also like to know how hard it is to replace the complete fuel pump for a do it yourselfer. I would probably just try and take the bed off however, do you know somewhere I could get directions on how to do all this off the internet and if it will take special tools? Thanks for all the help.

GM-Tech · August 25, 2005

You can't replace just the check valve. It's internal to the fuel pump so you'd have to replace the pump... actually it's an entire module. It's not cheap, so you want to make sure of the diagnosis before replacing an expensive part and not fixing the problem.

No, the specs don't say it shouldn't fall below 27 psi. Dunno where you got that. The specs say it shouldn't fall more than 5 psi in 10 minutes as mentioned. It's eventually going to fall below 27 psi if you wait long enough. It could even eventually go to almost zero, but that doesn't mean the check valve is bad or there's a problem if it takes all day to go that low.

You shouldn't need any special tools to replace the pump.

cjherrman · August 25, 2005

Thanks for all I help I really appreciate it. I guess what I am planning on doing and after talking to a few local people, I think I am going to wait untill the problem gets worse in stead of trying to throw parts at it.

Do you know about how long it should last if the fuel module is going out? I know it will be approximate and probably no way of telling just looking for an estimate.

Also will it eventually throw a check engine light if it really acts up or eventuly quits working?

One last thing when I turn the key to on before start up and really try to listen for the fuel pump to kick on it sounds kind of like a clattering noise, it really isn't that loud so I don't know if this is what they are suppose to sound like or what.

Sorry for all the questions but I have a inquisitive mind. Lets say it is the pump and I order this pump module from a place like gmpartsdirect.com if this is the cheapest place. How hard is it going to be for a amature to install this? You say no special tools which is nice however I don't have an access to a lift I was just going to possibly drop the tank with it on jack stands or if easier just take the bed off. I guess what I am asking is how difficult is this. I don't mind if it is time consuming just don't want to get half way through and be in over my head. Thanks a lot I really appreciate it.

MR1911 · August 25, 2005

There is a write up in the tech section on how to do it , look up at left in the main section. Oh and look to ebay for you pump module its ALOT cheaper , just be careful who you buy from .

2003Chevyman · September 16, 2005

I have read the info above, and It sounds like I am having the exact same problem. The truck will not start without having to pump the gas to get it going. I get the same clattering noise coming from the Fuel Pump, so I know it is turning on, but just dont know how well it is functioning. I am not that mechanically inclined, so I would like to see if someone can tell me how and where to check the fuel pressue that I am getting. I seem to think it is possibly the fuel pump since it steadily is getting harder to start my vehicle.

I have also had instances where when I am idling at a stop light, the truck will stumble and die for no apparent reason. The truck starts right back up whithout any problems

Any thoughts are suggestion would be greatly appreciated

I have a 2000 Chevy Tahoe with the 5.3L engine.

Thanks in advance

Bubba

GM-Tech · September 16, 2005

I would like to see if someone can tell me how and where to check the fuel pressue that I am getting. I seem to think it is possibly the fuel pump since it steadily is getting harder to start my vehicle.

There's a port on the fuel line towards the left rear of the engine. Just follow the fuel lines in that area. You need a gauge that is designed to screw onto that.

Not sure what pumping the gas has to do with anything. Fuel injection is not like a carburetor.