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Help!..Problem Starting!


tommyg79
09-24-2007, 07:53 PM
I have a 96 Blazer, with about 160,000 kms. The fuel pump went about a month and a half ago, I got a new one and changed it, the new one lasted a week and crapped out, I took it back and exchanged it. So now it was running good for a few weeks and then it started giving me problems starting. It will just crank and crank untill finally it catches, and then other times it starts perfect. My starter is starting to go due to this. Now I can hear the fuel pump work when i turn the key to on, and i know its got fuel pressure because i tested it. So what else could it be?? Any advice would be much appreciated! Thanks

old_master
09-25-2007, 08:44 PM
What is the fuel pressure and does it hold after the pump stops running?

wulfsbane
09-26-2007, 03:56 PM
I had the same problem but without the fuel pump it wouldnt start so i changed the cam position sensor under the rotor now it says my timing is out but its starts just fine lol

tommyg79
09-26-2007, 07:32 PM
Runs in high 50's, drops some when stops running!

old_master
09-26-2007, 07:39 PM
Anything less than 60psi will cause driveability issues. Here is a guideline for checking:

Fuel pump operation:
The fuel pump circuits are designed to activate the fuel pump relay continuously any time the key is in the START position. When the key is in the RUN position, the fuel pump relay remains activated provided the Powertrain Control Module (PCM) is receiving a signal from the crankshaft position sensor. If the engine stalls, or is not running for any reason, the PCM will deactivate the fuel pump relay after approximately 2 to 3 seconds. The 2-3 second ON time is commonly referred to as “fuel pump prime”.

Fuel pressure test:
This test checks the pumps ability to build sufficient pressure, and the systems ability to hold it. Install the fuel pressure gauge to the test port near the distributor. Turn the key to the RUN position but do not start the engine. While the fuel pump is running, fuel pressure must be 60-66psi. After approximately 2 to 3 seconds, the fuel pump will shut off. Fuel pressure must remain between 55-60psi for several minutes. A drop in pressure below 55psi indicates excessive leak down.

Post your results.

tommyg79
09-27-2007, 06:19 PM
Ok so i tried it out, while pump is running fuel pressure is about 63 after pump stops drops just under 60. Tried it out a couple of times with same results!

old_master
09-27-2007, 06:23 PM
Is the SES light on? If so, what codes are in memory?

tommyg79
09-28-2007, 05:42 PM
No codes in memory, I have a code reader, but whatever is causing the problem does not set off the light, so it's not much use. I have the GM service manuals 1&2 for the truck, but their difficult and vauge!

old_master
09-28-2007, 08:11 PM
You need to determine if the problem is fuel or electrical. When it cranks and does not start, connect the fuel pressure gauge and make sure pressure is 60psi minimum. If pressure is good, check for spark at more than one spark plug. (Needs to be a blue, not orange, spark.)

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