7.4L Hard Starting

elkfool · 12-08-2006, 11:32 AM

I have a 99 Silverado with a 7.4L Vortec that was overhauled 3500 miles ago.

Ever since I have reinstalled the engine it has had a hard starting issue where when it is warmed up it turns over for 3-4 seconds before it fires right up.

When it is cold it ALWAYS fires right up but when it is warm it has this issue. Once it fires it fires right up and idles smooth. I have no fault codes or other noticable issues with the truck.

What should I look for to alleviate this issue? Have any of you had this issue with your trucks?

2verpsters · 12-08-2006, 02:03 PM

I owned a 99 3/4 ton crew cab with the same motor and had the same problem. I never did figure it out and since I knew the boys at the local Chevy garage, we tried all kinds of stuff. Cold starts were awesome, hot starts were a 30 second ordeal where the motor turned and turned and then finally caught, but then coughed and sputtered for a few seconds before it returned to a smooth idle. Acted like a carbed motor, 1st like it was flooded, and then once it started, like the choke was stuck on. Tune ups, from air filter to plugs didn't help. Resetting the comp didn't help. New air flow sensor didn't help. After market parts made it worse. Only good thing I can say is that it always started eventually. I put 124000 miles on it and it never let me down, so I just put up with it.

Chevy808 · 12-09-2006, 12:40 PM

Sounds like a fuel pressure regulator problem. $60 -$70.00 replacement fix. A leaking injector can cause fuel pressure drop too so you might want to check that also.

bradrhale · 12-11-2006, 07:51 AM

an injector leak is going to have tell-tale signs when you crank it up and it hits on that cylinder.

2verpsters · 12-11-2006, 10:01 AM

We did the pressure regulator route, didn't change anything on mine. It is a cheap fix, but a pain in the butt to do. It's hidden underneath the funky intake plenum that Chevy put on those motors. You need to split the plenum to get to it and a set of new gaskets for the plenum, luckily you don't need to get into the intake at all. Injectors are a good point, I don't think we ever did anything with that on mine, but it doesn't seem like that motor had individual injectors on a rail, I think it was one big one that fed all 8 cylinders. I could be wrong on that though, it's been a while since I had that truck.

nnunez · 12-12-2006, 01:05 PM

Maybe a vacuum leak?
I had a (not so) similar encounter with my old truck and the breather element was not on tightly at the intake.
I sprayed starting fluid at vacuum connections (while the truck was running) and that is how I found the problem.

elkfool · 12-31-2006, 10:02 AM

I installed a GM fuel pressure regulator and so far that seems to have fixed the issue.

12-08-2006, 11:32 AM	#1
elkfool Junior Member Join Date: Dec 2006 Posts: 8	7.4L Hard Starting I have a 99 Silverado with a 7.4L Vortec that was overhauled 3500 miles ago. Ever since I have reinstalled the engine it has had a hard starting issue where when it is warmed up it turns over for 3-4 seconds before it fires right up. When it is cold it ALWAYS fires right up but when it is warm it has this issue. Once it fires it fires right up and idles smooth. I have no fault codes or other noticable issues with the truck. What should I look for to alleviate this issue? Have any of you had this issue with your trucks?

12-09-2006, 12:40 PM	#3
Chevy808 Senior Member Join Date: Nov 2006 Location: Born & raised in Hawaii had to move to Salt Lake City...bummer Posts: 275	Sounds like a fuel pressure regulator problem. $60 -$70.00 replacement fix. A leaking injector can cause fuel pressure drop too so you might want to check that also. __________________ '85 Oldsmobile 442 '93 Chevy 2WD C1500 350 Silverado Extended Cab Shortbed '95 Chevy 4WD K2500 454 Silverado Extended Cab Long Bed

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12-08-2006, 02:03 PM	#2
2verpsters Full Member Join Date: Oct 2006 Location: Baldwinsville, NY (Upstate) Posts: 23	I owned a 99 3/4 ton crew cab with the same motor and had the same problem. I never did figure it out and since I knew the boys at the local Chevy garage, we tried all kinds of stuff. Cold starts were awesome, hot starts were a 30 second ordeal where the motor turned and turned and then finally caught, but then coughed and sputtered for a few seconds before it returned to a smooth idle. Acted like a carbed motor, 1st like it was flooded, and then once it started, like the choke was stuck on. Tune ups, from air filter to plugs didn't help. Resetting the comp didn't help. New air flow sensor didn't help. After market parts made it worse. Only good thing I can say is that it always started eventually. I put 124000 miles on it and it never let me down, so I just put up with it.

12-11-2006, 07:51 AM	#4
bradrhale Moderator Join Date: Apr 2006 Location: Texas Posts: 2,990	an injector leak is going to have tell-tale signs when you crank it up and it hits on that cylinder.

12-11-2006, 10:01 AM	#5
2verpsters Full Member Join Date: Oct 2006 Location: Baldwinsville, NY (Upstate) Posts: 23	We did the pressure regulator route, didn't change anything on mine. It is a cheap fix, but a pain in the butt to do. It's hidden underneath the funky intake plenum that Chevy put on those motors. You need to split the plenum to get to it and a set of new gaskets for the plenum, luckily you don't need to get into the intake at all. Injectors are a good point, I don't think we ever did anything with that on mine, but it doesn't seem like that motor had individual injectors on a rail, I think it was one big one that fed all 8 cylinders. I could be wrong on that though, it's been a while since I had that truck.

12-12-2006, 01:05 PM	#6
nnunez Senior Member Join Date: Dec 2005 Posts: 307	Maybe a vacuum leak? I had a (not so) similar encounter with my old truck and the breather element was not on tightly at the intake. I sprayed starting fluid at vacuum connections (while the truck was running) and that is how I found the problem.

12-31-2006, 10:02 AM	#7
elkfool Junior Member Join Date: Dec 2006 Posts: 8	I installed a GM fuel pressure regulator and so far that seems to have fixed the issue.