GM Truck Club Forum banner

1 - 9 of 9 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter · #1 ·
Hello all, new to the forum 1st post...

I have a 1998 sub 152k miles with a 5.7L vortec.

Over the past 10 months i have replaced the cap, rotor, plugs, wires, coil, battery and due to an intake leak the lower intake manifold gaskets.

I also had sludge in the coolant system that looked like sawdust. i flushed the system 3 times and replaced the coolant and the upper and lower hoses.

The problem with the starting is strange, it will start and runs great but it takes some time. First turn of the key it will crank strong but wont start at all sounds like no fuel. Try again slight turn over. Third try almost starts. On the forth try if I release the key at the right moment it reluctantly turns over like it wants to stall but then runs and runs fine. No hesitation or anything. If i turn it off and restart it its fine. only does it when its cold till the 1st start.

I read the other post like this one from qpe05 called 1997 Silerado ....5.7 vortec . Wont start when cold
. I am going to check the coolant temp sensor and the IAC. I just dont want to have to change $600 worth of parts to find out it was a $30 sensor that was to blame.

Any help will be greatly appreciated...
 

·
Premium Member
Joined
·
1,625 Posts
With sludge still accumulating in the cooling system I would say you should have done the head gasket when you did the intake, because that is what is allowing more oil in the coolant.

Or you messed up when you did the intake gasket.

Have the radiator pressure tested and that should tell you if you have a bad head gasket.

For the starting problem check the fuel pressure before going any further. A low pressure at the pump or a clogged filter can do what you are saying.

Also low oil can also be a problem, the system doesn’t want to let it start if it doesn’t have enough oil pressure.

But my money is on a bad fuel pump.
 

·
Registered
Joined
·
5 Posts
Discussion Starter · #3 · (Edited)
I am hoping that the fuel pump that i replaced less than a year ago is still working normally. but you mentioned oil, do you think i should change the type of oil in the truck. It calls for 5W-30 would a heavier oil provide more pressure and be a better choice @ startup? like a 10w-40.
The sludge is gone now after i flushed the system that was 2 months ago. I have owned the truck for 4 years. i changed the fuel filter 3 months ago. it was a fleet vehicle somewhere in Upstate NY. It had 103k miles when i got it. when i did the wires i noticed they were the origional oem ones the truck came with.
well im gonna check out your suggestions and post again later.
thanks
 

·
Registered
Joined
·
5 Posts
Discussion Starter · #4 ·
Hey,

I checked the fuel pressure @ the fuel rail and it is 61psi with ignition on and 50 psi after the truck is running. The oil is full and reads 40psi @ cranking on the dash gauge.

Yesterday the truck wouldnt start at all.
This morning I hit it with some starting fluid (a 3 second burst on the air cleaner) while cranking it and it started right up. I have great spark @ all cylinders. The spark will jump a 1/2 inch to the exaust manifold. Again once it starts it runs and will restart with no problems.

Is it possible for something to have gotten past the fuel filter and be screwing up the fuel pressure regulator?
Today i am going to replace the coolant temp sensor and clean the IAC and even take a look @ the EGR valve.
Any other thoughts?
 

·
Registered
Joined
·
34 Posts
I would try replacing the fuel filter before any other expensive parts. my 1995 suburban had similar problems and it would bog under heavy accelerating along with hard starts and fuel filter was all it was. so i would start there.
 

·
Super Moderator
Joined
·
1,558 Posts
How thorough was your fuel pressure test? Your test with the starting fluid really suggests to me that the problem is in fuel delivery. Did you do a bleed down test (let the fuel pump shut off and monitor the pressure for several minutes to see how quickly the fuel system loses pressure)? How long did it take for the pressure to come up to 61 psi? At the next cold start, try cycling the key on and off a few times before starting to see if the additional pump cycles will pressurize the system and get to start like it should. My own experience with this particular complaint is that it is often caused by the fuel system not being able to hold pressure (due to a bad check valve in the pump or similar), which means that the system needs more time to build that pressure back up.
 

·
Premium Member
Joined
·
6,542 Posts
I agree with shorty, you have a fuel delivery issue. In addition to the system tests he recommended I'd look at the injectors also. How many miles are on the inlectors? Have they ever been cleaned?
 

·
Registered
Joined
·
2,428 Posts
Just my opinion

Out of left field, I'd check the timing too. GM has had known troubles with abnormal distributor gear wear. Also you had to remove the distributor when working on the top end, so you might have not re-installed it correctly. Check for a loose distributor hold down.
 

·
Registered
Joined
·
5 Posts
Discussion Starter · #9 ·
Hello again,

The fuel pump was 2 months ago i checked the repair records.

The fuel pressure took less then 1 second to hit 61psi and after the truck ran I left the gauge on for 10 mins and it didnt drop at all. There was pressure in the line when i hooked up the gauge. Tonight ill leave the gauge on it and see what the reading is in the morning.

The injectors are 153k miles old and i would say have never been cleaned or changed or even looked at. LOL.

I did notice tho last night when i started it to go home it took a long time cranking for the oil pressure to come up. about 5 to 7 seconds of cranking. do you guys think it is possible that the lifters are to blame with the high mileage on the motor?

I also did see some signs of wear on the distributor gear but was unable to get a replacement one. I decided it was good enough for now but i think i will change it. The distributor gear couldnt have changed the timing more then 1 or 2 degrees with the ammount of wear on it.

well guys keep the ideas comming,

thanks again....
 
1 - 9 of 9 Posts
Top