fuel pump isn't out--whats wrong?--Magnus and other fuel system gurus

[Josh]

the pump works when i keyed the ignition and when i gave it power to that little red wire by the pcm. , gas comes out, we disconnected the line before the fuel filter (this was changed recently less than 3k miles). I have heard the map sensor, my friends moms tahoe had the same problem and this was it.

So the car cranks and doesn't wanna turn over
i need to check
-fuel filter
-MAP sensor??
What else??
-ignition
-could there be a clog in one of the lines?

Thanks a lot guys
Josh

[DEE97GTP]

It could be the crankshaft position sensor. When it goes bad, you don't get any fire to the plugs. No SES light either. It happened to my GTP a couple of years ago.
I had the same symptoms, but it started off as an intermittent problem, then got worse.
DEE

[Magnus]

Are you getting spark? You need to check for that.

[Mike Mayron]

<blockquote>quote:</font><hr>Originally posted by DEE97GTP:
It could be the crankshaft position sensor. When it goes bad, you don't get any fire to the plugs. No SES light either. It happened to my GTP a couple of years ago.
I had the same symptoms, but it started off as an intermittent problem, then got worse.
DEE<hr></blockquote>

I second that one. It left me stranded 2 hours away from home (at a friends luckly) and pissed when it happened to me. If I left it alone for an hour or two it'd startup fine, and could drive about half a mile (or rather so many rpms) w/ no problem before it'd shut down again. I figured it was just a small amount of fuel that would get it siphoned up and get me that far. I was all ready to replace the fuel pump aswell, but no parts stores carried them so it went to the dealer instead. Turned out to be the cam sensor :rolleyes:

Don't do this w/o a good supply of vasoline ;)
I didn't walk the same after that $500 raping :eek:

Get the codes pulled and change it yourself if it's the culperate.

Isn't that lame how the computer shuts it down when I can't figure out where the cam is instead of relying on other sensors to determine if things are still running smooth? Isn't that what o2's and knock sensors are for? GM could have atleast given us a limp home mode [img]graemlins/bs.gif[/img]

[Josh]

The dealership tech said he thinks its either a clogged line or filter, or the map sensor, this is assuming I have spark will I'll check when I get outta school in a few hours. He also said if the new map sensor ($50 part) doesn't fix it, it could be the pcm. This sucks.

[ March 19, 2002: Message edited by: Josh ]</p>

[Josh]

Now this one will really screw with your heads, just as it did to us.

Fuel filter looked good, drained it and bolted it back up.
Checked the map sensor, on the middle wire with the ignition on, i should have read over 2 volts with my voltmeter. I got nothing. But i did get 5 volts on the other terminal, thats labeled as a 5 volt reference.
So with the map sith unplugged i removed a plug wire, stuck a plug in it and told my friend to ground it, while i crank my car.
THE CAR STARTED!?!
So we were like WTF? I turned it off, put the plug wire on, and reconnected the map.
-again it started. Let it run, had an ses.
-and again, we let it idle for a few, also had ses light.
-lower the car, turned it off so i could get my truck key off the keyring, and went to start it
It WON'T START! My car is possessed. I guess that means the map sensor is faulty because its working intermidently.

[TurboProject]

If you wanted to check the MAP sensor you could do the following:
You have to check the voltages with the sensor still plugged in, use pins or something to get at the wires while it's plugged in.
To check the reference voltage connect to the black and grey terminals with a volt meter and it should be about 5 volts. Then to check the signal voltage, connect the volt meter to the green wire and the black wire and with the ignition on but engine not running it should be 4.5 to 5 volts. Then if you can get it started it should go down to about 1.5 to 2 volts at idle and will increase with throttle advancement. At wide open throttle it will be around 4.5 volts. Hope this helps.

[Josh]

Thanks I'll have to try that out, i was just checking the voltage with the plug disconnected because I didn't know I had to do while its hooked up., duh.