Long Crank Time, 1999 4.8l

MyYamR7 · April 10, 2007

Hello, I have a 1999 GMC SLE 2wd with the 4.8L engine, it has 103k miles on it.

Lately it has been hard starting and it cranks over for 5 or 6 seconds before it starts..mostly when the engine is warm? It always starts up when it's cold and it'll usually start up within 5 or 10 minutes from tha last time it ran, anything after that, I get the long crank time.

The dealer says it "could" be the fuel pump and they want 800 beans to change it and can't say for sure if it will fix it or not. They did say the fuel pressure is normal..

Someone else told me it could be a shrader valve (sp? ), that little thing on the fuel rail to test the fuel pressure?

Any ideas?

Thanks

RCH · April 10, 2007

When you turn the key to the run position without starting the engine, do you hear the fuel pump pressurize the line? You should hear it for two or three seconds. If you don't hear it, you may want to check your oil pressure switch as it is in the circuit. good luck.

MyYamR7 · April 10, 2007

When you turn the key to the run position without starting the engine, do you hear the fuel pump pressurize the line? You should hear it for two or three seconds. If you don't hear it, you may want to check your oil pressure switch as it is in the circuit. good luck.

Yes, I can hear the pump come on.

RCH · April 11, 2007

Have you check line pressure? If it is too low it could be your fuel pressure regulator. Also, if you remove your air cleaner you can see if the injectors are spraying fuel. Have you replaced your fuel filter lately? If you disconnect the fuel line from the throttle body you can attach a guage to check fuel pump pressure. I was having the same problem on my 1991 Sierra, fuel pump pressure was in spec. after attaching a guage, so I reconnected everything installing the guage in line permenently, started the truck and the pressure was low, so I replaced the fuel pressure regulator and it was back to spec. hope it helps.

Z71Rider · April 12, 2007

Have you check line pressure? If it is too low it could be your fuel pressure regulator. Also, if you remove your air cleaner you can see if the injectors are spraying fuel. Have you replaced your fuel filter lately? If you disconnect the fuel line from the throttle body you can attach a guage to check fuel pump pressure. I was having the same problem on my 1991 Sierra, fuel pump pressure was in spec. after attaching a guage, so I reconnected everything installing the guage in line permenently, started the truck and the pressure was low, so I replaced the fuel pressure regulator and it was back to spec. hope it helps.

It's not TBI (throttle body injection), so you won't be seeing gas spray. It's a direct injection system. Definitely change out the fuel filter...cheap and easy...but, I'd bet on the fuel pressure regulator. Google something like "Silverado/Tahoe Hard Start Issue", and I think you'll see something come up that is indicating that the fuel pressure reg is a common cause of your symptoms. Also, it's alot cheaper than the fuel pump.

GatorFan · April 12, 2007

My 2000 4.8L was giving me some issues and it ended up being the Fuel Pressure Regulator. I read on one of the forums (don't remember which one) that the easiest way to check your regulator is to pull the vacuum line from it. If gas comes out of the line, it is your regulator. I tried that and I had gas come out of it, naming this as my problem. I think I paid about $85 for it at the dealer but it comes as a complete kit, everything you need. I read somewhere that aftermarket regulators do not fit so I opted to buy the GM part. Everything went together in about 10 minutes and the truck runs great now.

Hope this helps.

RCH · April 12, 2007

Thanks for the correction Z71rider , my 1991 Sierra was the old style, but checking to make sure the injectors are not restricted might be a direction. Have you run some injector cleaner through it? maybe a couple tanks of premium gas.

Rick Dorion · April 12, 2007

I too had that problem on my 5.7 at 100,000. In my case, the MAF had a film of dust on the wires/screen. After cleaning, my rough idle, excessive cranking went away. Hopefully it's simple but this is worth checking in any event and easy.

RCH · April 12, 2007

I found this on another forum, same problem you described.LOL

"I have a '99 with the 4.8 liter. I replaced the Fuel Pressure Regulator and it seems to run great now. Starts everytime. About two months ago it starting occurring and kept getting worse. If it wouldn't start I could floor the excelerator pedal and it would fire up but sputter for a while. My truck also seemed to drag when I let off the excelerator pedal when driving and would also stall sporatically. "

"Check your fuel pressure regulator. It should be located on one of the fuel rails to the injectors on top of the engine. Pull off the vacuum line and see if there is any gas that pours out. If so it has gone bad. I paid $62 for mine from the GMC dealer. Advance Auto had it for about $59 but was out of stock. Took me about 15 minutes to replace."