96 GMC 454 Hard start
_gforce57
03-15-2005, 08:41 PM
Hi guys. This is my first time on the forum. Hope one of you smart guys can give me a hand on this problem. I have a 1996 GMC Sierra 3500 with a 454 cu. engine. I bought it back in October and have noticed since that it starts very hard. By that I mean I have to crank it four to six seconds almost every time I start it.
Sometimes on morning starts it starts right off like a good gm should. The big problem is after I have run it for a while then shut it down for about twenty minutes. Then crank, crank, crank. If I start it within that first twenty minutes it starts right up.
I have taken it to the local gm shop and they replaced the fuel pressure regulator. That didn't do the trick. Brought it back and they thought they noticed a knock sensor code so they changed that. Still no good. The poor truck has been back to the shop six times and they still haven't figured it out.
Head scratcher eh?
The fuel pressure during cranking is at 55 pounds then drops off to about 50 pounds while idling. After several minutes to an hour I noticed the fuel pressure is between 20-30 pounds.
Could the fuel pump be the problem? It is my understanding that the fuel pressure should be 55-61 pounds during idle. Or do I need to look at a different cause.
Appreciate your time,
Gerald
Sometimes on morning starts it starts right off like a good gm should. The big problem is after I have run it for a while then shut it down for about twenty minutes. Then crank, crank, crank. If I start it within that first twenty minutes it starts right up.
I have taken it to the local gm shop and they replaced the fuel pressure regulator. That didn't do the trick. Brought it back and they thought they noticed a knock sensor code so they changed that. Still no good. The poor truck has been back to the shop six times and they still haven't figured it out.
Head scratcher eh?
The fuel pressure during cranking is at 55 pounds then drops off to about 50 pounds while idling. After several minutes to an hour I noticed the fuel pressure is between 20-30 pounds.
Could the fuel pump be the problem? It is my understanding that the fuel pressure should be 55-61 pounds during idle. Or do I need to look at a different cause.
Appreciate your time,
Gerald
2000CAYukon
03-16-2005, 02:11 PM
Hi guys. This is my first time on the forum. Hope one of you smart guys can give me a hand on this problem. I have a 1996 GMC Sierra 3500 with a 454 cu. engine. I bought it back in October and have noticed since that it starts very hard. By that I mean I have to crank it four to six seconds almost every time I start it.
Sometimes on morning starts it starts right off like a good gm should. The big problem is after I have run it for a while then shut it down for about twenty minutes. Then crank, crank, crank. If I start it within that first twenty minutes it starts right up.
I have taken it to the local gm shop and they replaced the fuel pressure regulator. That didn't do the trick. Brought it back and they thought they noticed a knock sensor code so they changed that. Still no good. The poor truck has been back to the shop six times and they still haven't figured it out.
Head scratcher eh?
The fuel pressure during cranking is at 55 pounds then drops off to about 50 pounds while idling. After several minutes to an hour I noticed the fuel pressure is between 20-30 pounds.
Could the fuel pump be the problem? It is my understanding that the fuel pressure should be 55-61 pounds during idle. Or do I need to look at a different cause.
Appreciate your time,
Gerald
When you turn off the key, it is the fuel pressure regulator's job to maintain the correct pressure in the fuel rail. Typically, hard starts after being shut off for 20 minutes, can be a bad fuel pressure regulator or an injector or two that is leaking. Fuel leaks into the cylinders and floods the engine causing the hard starts.
Either the new fuel pressure regulator is bad or you have one or more injectors leaking. The pressure should not drop to 20-30 lbs after a few minutes.
//2000CAYukon
Sometimes on morning starts it starts right off like a good gm should. The big problem is after I have run it for a while then shut it down for about twenty minutes. Then crank, crank, crank. If I start it within that first twenty minutes it starts right up.
I have taken it to the local gm shop and they replaced the fuel pressure regulator. That didn't do the trick. Brought it back and they thought they noticed a knock sensor code so they changed that. Still no good. The poor truck has been back to the shop six times and they still haven't figured it out.
Head scratcher eh?
The fuel pressure during cranking is at 55 pounds then drops off to about 50 pounds while idling. After several minutes to an hour I noticed the fuel pressure is between 20-30 pounds.
Could the fuel pump be the problem? It is my understanding that the fuel pressure should be 55-61 pounds during idle. Or do I need to look at a different cause.
Appreciate your time,
Gerald
When you turn off the key, it is the fuel pressure regulator's job to maintain the correct pressure in the fuel rail. Typically, hard starts after being shut off for 20 minutes, can be a bad fuel pressure regulator or an injector or two that is leaking. Fuel leaks into the cylinders and floods the engine causing the hard starts.
Either the new fuel pressure regulator is bad or you have one or more injectors leaking. The pressure should not drop to 20-30 lbs after a few minutes.
//2000CAYukon
Kevcules
03-17-2005, 10:17 PM
I have a 91 Sierra half ton and it has cranked over longer than normal ever since I had it. (9 years) I have it tuned well, all the time , doesn't help. It starts better cold than if I leave it for 30 minutes after being hot and try again.
Are you turning the key half way then waiting for a second or two for fuel pressure to build up before starting?
Something I do when it's really cold and I can't rely on the battery to turn the engine for so long is to press on the gas peddle about one inch then turn the key. This does start it sooner by putting more fuel in, I think.
This constant cranking is some what normal for GM as I'm told. At least you build some oil pressure before the engine starts to save some dry start life.
Kevin
Are you turning the key half way then waiting for a second or two for fuel pressure to build up before starting?
Something I do when it's really cold and I can't rely on the battery to turn the engine for so long is to press on the gas peddle about one inch then turn the key. This does start it sooner by putting more fuel in, I think.
This constant cranking is some what normal for GM as I'm told. At least you build some oil pressure before the engine starts to save some dry start life.
Kevin
michaelmeck
03-21-2005, 01:26 PM
There is a sensor on your oil pressure that will not allow your truck to start until a certain pressure is achieved. this very well could be why it is cranking so long before it starts.
MrBillPro
03-21-2005, 07:51 PM
There is a sensor on your oil pressure that will not allow your truck to start until a certain pressure is achieved. this very well could be why it is cranking so long before it starts.
And were would that sensor be located at? I have never heard of that heck as long as it starts your doing good, I would also think if it were an injector leaking you would smell the gas bad upon start up and why would it start good in the morning or cold if it were an injector gas leaking into a cylinder would probably be worse at that point, my truck has been starting like this for over 100,000 miles and still runs good I just have never worried about it, I will tell you what my "honest" mechanic buddy tells me it's a vortec it's bullet proof drive it don't worring about every little thing and don't call me until it won't start so I took his advice. :grinno:
And were would that sensor be located at? I have never heard of that heck as long as it starts your doing good, I would also think if it were an injector leaking you would smell the gas bad upon start up and why would it start good in the morning or cold if it were an injector gas leaking into a cylinder would probably be worse at that point, my truck has been starting like this for over 100,000 miles and still runs good I just have never worried about it, I will tell you what my "honest" mechanic buddy tells me it's a vortec it's bullet proof drive it don't worring about every little thing and don't call me until it won't start so I took his advice. :grinno:
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