New 350 Engine - Problems - HELP

Fusion85 · 09-20-2006, 04:44 PM

Hi, first post.

I'm here to get some help. My dad put a new 350 short block and new transmission into his 1991 GMC 1500. It ran for about 2 weeks or so. Then it died and now it wont stay running. When you start it, it will automaticly die. He took it to the GMC place and 2 mechanics and they cannot figure it out. It will stay running as long as you give it alot of gas.

I need to get it fixed, it's been sitting in my yard since 2004. I changed the spark plugs on it today, the old ones were pitch black on the ends. It did'nt help at all.

My friend thinks its jumping time or spark plug/wires.

Also the oil pressure gauge goes all the way up when you give it gas.

Please help.

Thanks

**bruiser** · 09-20-2006, 06:09 PM

The truck has been sitting for two years without running?

Fusion85 · 09-20-2006, 06:47 PM

I started it every few months. But basiclly it hasnt moved. I drove it down the road today.

Volt-Schwibe · 09-20-2006, 07:28 PM

i can think of a few things that would possibly cause this.

to start with, it almost sounds like there is a severe vaccuum leak, as if a hose broke from being old, or just flat out slipped off. also, the carb gasket may have blown a leak, it's not common but it happens.

it could also be an issue with timing, but a short block comes with the timing chain and gears already on it, so those parts are extremely new, and shouldn't have worn enough to skip teeth after two weeks.

the fact that it only ran for two weeks and just suddely failed to stay running, that makes me wonder if the distributor has rotated on it's own a little.

might also be rust clogging the idle jets in the carb. that would also make it not want to run unless you hold the pedal down a bit.

crazijoe · 09-20-2006, 07:56 PM

1991.... Wouldn't that be TBI?

Volt-Schwibe · 09-20-2006, 09:51 PM

Quote:

Originally Posted by crazijoe

1991.... Wouldn't that be TBI?

if it is TBI, then this points to a couple other things.

possibly the idle control solonoid (ics), or the o2 sensor, or even the thottle position sensor (tps).

might even be the fuel pressure regulator.

**hwm54112** · 09-21-2006, 09:30 PM

or fuel filter gummed up-old gas

i6power · 10-05-2006, 11:09 AM

So your saying if you rev the motor it will run correct? If so try putting the pedal down to where its almost about to die, and give it just enough so that it wont die. You may find a sweet spot where although your just holding on the gas, not pumping it the motor will rev up, drop down, rev up, drop down etc. If that is the case then it sounds to me like you have bad gas.

lhuser · 10-05-2006, 08:15 PM

Quote:

Also the oil pressure gauge goes all the way up when you give it gas.

that comes from hose leaks. I should recommend to change oil, hoses and clear the gas tank. To me, it seems that hoses are the entire problem.

**JamesO** · 10-09-2006, 05:33 PM

I would question the gasoline, possibly bad, possibly water, possibly Diesel in it?

Check the charging system, if for some reason the regulator is messed up and the charging Voltage is going too high, the ECM will probably start to shut down. If the charging Voltage goes over about 16 Volts, this is a problem.

Also if the motor is TBI, there is a gasket under the TBI that goes bad that can cause rough and erratic idle. Easy and cheap fix.

Also be careful with the oil. I have seen situations where the oil gets saturated with gasoline and this can cause all kinds of problems.

JamesO

**bruiser** · 10-09-2006, 06:05 PM

What happened to the OP?

09-20-2006, 04:44 PM	#1 (permalink)
Fusion85 Registered User Join Date: Sep 2006 Posts: 2 OS: XP	New 350 Engine - Problems - HELP Hi, first post. I'm here to get some help. My dad put a new 350 short block and new transmission into his 1991 GMC 1500. It ran for about 2 weeks or so. Then it died and now it wont stay running. When you start it, it will automaticly die. He took it to the GMC place and 2 mechanics and they cannot figure it out. It will stay running as long as you give it alot of gas. I need to get it fixed, it's been sitting in my yard since 2004. I changed the spark plugs on it today, the old ones were pitch black on the ends. It did'nt help at all. My friend thinks its jumping time or spark plug/wires. Also the oil pressure gauge goes all the way up when you give it gas. Please help. Thanks

09-20-2006, 07:28 PM	#4 (permalink)
Volt-Schwibe Asst. Manager, Automotive Forums; HJT Trainee Join Date: Jan 2003 Location: Behind you, watching you as you type. Posts: 7,372 OS: Click "My System" to view details My System	i can think of a few things that would possibly cause this. to start with, it almost sounds like there is a severe vaccuum leak, as if a hose broke from being old, or just flat out slipped off. also, the carb gasket may have blown a leak, it's not common but it happens. it could also be an issue with timing, but a short block comes with the timing chain and gears already on it, so those parts are extremely new, and shouldn't have worn enough to skip teeth after two weeks. the fact that it only ran for two weeks and just suddely failed to stay running, that makes me wonder if the distributor has rotated on it's own a little. might also be rust clogging the idle jets in the carb. that would also make it not want to run unless you hold the pedal down a bit. __________________ <signature> TSF is funded by our Admin's pocket, care to help? Power Tip: Subscribe to your thread (Thread Tools) to receive an instant email notification when you get a reply. New Members: Creating a single new thread in the correct section is the best way to assure your thread will receive a reply. </signature>

09-20-2006, 07:56 PM	#5 (permalink)
crazijoe Registered User Join Date: Oct 2004 Location: Omaha, The Center of the Universe Posts: 7,632 OS: WinXP, Win2K3 My System	1991.... Wouldn't that be TBI? __________________ Microsoft MCSA + Messaging, MVP, A+, Network+ http://i16.photobucket.com/albums/b3...other/Help.jpg Do you want a real Republican? HDD diagnostic tools / HDD data recovery software

09-20-2006, 06:09 PM	#2 (permalink)
bruiser TSF Enthusiast Join Date: Jul 2005 Posts: 1,977 OS: xp	The truck has been sitting for two years without running?

09-20-2006, 06:47 PM	#3 (permalink)
Fusion85 Registered User Join Date: Sep 2006 Posts: 2 OS: XP	I started it every few months. But basiclly it hasnt moved. I drove it down the road today.

09-21-2006, 09:30 PM	#7 (permalink)
hwm54112 TSF Enthusiast Join Date: Oct 2005 Posts: 2,233 OS: WINXP	or fuel filter gummed up-old gas

10-05-2006, 11:09 AM	#8 (permalink)
i6power Registered User Join Date: Oct 2006 Posts: 9 OS: xp	So your saying if you rev the motor it will run correct? If so try putting the pedal down to where its almost about to die, and give it just enough so that it wont die. You may find a sweet spot where although your just holding on the gas, not pumping it the motor will rev up, drop down, rev up, drop down etc. If that is the case then it sounds to me like you have bad gas.

10-09-2006, 05:33 PM	#10 (permalink)
JamesO Join Date: Mar 2005 Location: Fairfax, VA USA Posts: 2,289 OS: 98SE, W2k Pro, XP Pro	I would question the gasoline, possibly bad, possibly water, possibly Diesel in it? Check the charging system, if for some reason the regulator is messed up and the charging Voltage is going too high, the ECM will probably start to shut down. If the charging Voltage goes over about 16 Volts, this is a problem. Also if the motor is TBI, there is a gasket under the TBI that goes bad that can cause rough and erratic idle. Easy and cheap fix. Also be careful with the oil. I have seen situations where the oil gets saturated with gasoline and this can cause all kinds of problems. JamesO

10-09-2006, 06:05 PM	#11 (permalink)
bruiser TSF Enthusiast Join Date: Jul 2005 Posts: 1,977 OS: xp	What happened to the OP?