Mechanics

STARTING PROBLEM

1999 GMC Safari

Engine Performance problem
1999 GMC Safari 6 cyl Two Wheel Drive Automatic 160000 miles

Sputters and seems like it's barely getting enough fuel when starting. Can't drive off right away. After about 10 seconds running, rpm smooths out and is fine and runs with no problems. Can be made to start much better, but not perfect by turning key on and off a few times without starting to cycle the fuel pump. If engine has been running and you turn it off and start shortly after it is also fine. Needs to be off an hour or two to have the problem. Fuel pressure is 53 lbs running, pops up to 60 when fuel pump is on and engine is not running, or when the engine is shut off. Showing codes P0118 Engine Coolant Temperature Sensor Circuit High Voltage and P0452 Fuel Tank Pressure Sensor Circuit Low Voltage.
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Sfjim
June 7, 2008.



The fuel pressure should be 60-66psi when you turn the key On. Also test the CTS resistances hot and cold could be the trouble not running smooth before the 10secs.

Rasmataz
Jun 7, 2008.
The pressure is exactly 60 with the key on. Drops to 50-53 while running but will go back to 60 psi temporarily if you step on the gas. Is that normal?

I'm replacing the temp sensor and the fuel filter to see if there are any changes. If no change, I guess the fuel pressure regulator is next.

Tiny
Sfjim
Jun 7, 2008.
But will go back to 60 psi temporarily if you step on the gas. Is that normal? Yes

Is this the CPI Vortec -the regulator is under the intake manifold tuning valve-

The Spider is the little CPI injector with 6 little injector lines and poppets at the end of those lines. Looks like a spider if you imagine hard enough.
There are 2 larger lines that connect to it also, they're the fuel supply and fuel return to the fuel tank lines.
If you take the top off the manifold, you'll find a puddle of gasoline. A puddle on the driver side is cracked fuel supply & return lines. The CPI is OK, buy a nut kit(which is what they call the fuel lines?)!
A puddle on the passenger side means the CPI regulator is bad but another regulator is available.

Rasmataz
Jun 8, 2008.
Turns out the fuel system was fine. After understanding how to do that part I decided to replace the ECT sensor first since it was so much easier. When I dug it out, I found the plastic connector base broken off and no electrical connection at all. The ECM didn't know the engine temp. Replaced that, and so far so good - perfect starting and no codes. Got lucky on this one maybe. Thanks for all the help.
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Tiny
Sfjim
Jun 9, 2008.

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