X won't start - yes, another one....

[BetchaCantRide]

Okay, been searching all afternoon for a solution on here, and have narrowed things down to what seems to be a very strange problem....

after lunch today, went to start the X, and turned over very strong, but no start. I've narrowed the problem down to the OBD/fuel injectors:

-getting fuel and pressure to fuel rail; pump/relay/FPR are all good

-getting a good spark

-voltage is good

For the fuel injectors to operate properly, they need to receive a 'pulsing' voltage from the computer that cycles w/ the firing order of the engine. Well using a voltmeter on the injector connectors, it seems that they are getting a steady voltage rather than the pulsing one, which keeps them from injecting fuel into the combustion chamber properly.

I need to know if there is a sensor or something else that might 'cause the injectors not to work properly. I've tried reseting the computer, but have had no success. I need this vehicle for work, so good suggestions ASAP would be greatly appreciated!

THANKS

 

[GenerationX]

You can't use a voltmeter on those or even a digital one. its too fast of a pulse for it to pick up(why it reads as a constant voltage). If your injectors were fed a constant voltage your injectors would dump fuel and hydrolock your motor.

 

[BetchaCantRide]

Actually that isn't true about injectors...keep in mind that they are solenoids, not motors. A selonoid only works at the moment that voltage is introduced to it, then it remains in the open or closed position untill the voltage is removed - that's why the injectors need to receive voltage in pulses from the computer.

Thanks for the input about the voltmeter, i'll keep that in mind.

 

[410Fortune]

Whats the fuel pressure at the rail?

Have you tried listening to the fuel pump in the tank to make sure it's on.

You have tested for spark right?

I know these questions are basic but we gotta know...

Have you tried running the KOEO test?

 

[TPLYNCH]

Bad coil pack or Crank Position sensor could be causing your problem....

There was a loooong thread several months ago re non-starting, and unfortunately I can't remember what the fix was... but is was a strange one. Try searching for ex won't start or ex still won't start and see if it pops up....

 

[410Fortune]

If you have access to a friends or spare EEC you can try swapping them out, sometimes only part of the EEC will go bad, making it VERY hard to diagnose.

What are the circumstances of this problem? I mean yesterday it ran perfect and now it doesnt? Or did the truck sit for 3 months? or did you weld on it yesterday? Anything like this can help.........

 

[BetchaCantRide]

Okay, let me try to cover all your responses...

The truck sat for about a week while I was on the AT in west va, came back truck started fine in the evening. Next morning went to work and the to lunch with no problems. After lunch, wouldn't start at all. The problem happened all of the sudden, and I haven't been able to get it started since.

I don't know the fuel pressure at the rail (due to my lack of a pressure gauge), but I did turn it 'on' while the shrader valve was depressed, and it shot on hell of a line of fuel - the pump and relay are both fine. I am getting a spark. The fault seems to be something with the injectors. I think today I'm going to pick up a code scanner and see what codes the computer is throwing. It really seems like there is a sensor or something telling the computer to shut off the injector system. A while back, I read a post about a guy who had a similar problem, and turned out that the chip in his key was bad. I'm wondering that if the chip was bad, would I still get spark and fuel pressure but no fuel injection?

Thanks for the help guys (gals too)

 

[GenerationX]

I do know they're solenoids. which is why they get pulses instead of a constant voltage.

If I remember correctly, the injectors are provided +12v ALL the time. Only when its their time to open do they get ground from the computer. So if you checked the voltage using a common ground such as the negative battery terminal, you would get 12v all the time.

 

[410Fortune]

thats correct. Infact almost all of the sensor and solenoid signals sent from the brainbox are - signals, so the injectors get constant power, then the pulse comes from the EEC on the - side. The canister purge works the same way.........

 

[Lemondrop]

I think you can get a "Noid" light from ost auto parts stores . This will tell you if the injectors are firing , or what they are doing .

 

[BetchaCantRide]

Well dang, I guess you do learn something new everyday - thanks guys.

I've pretty much given up and decided to take the X to the shop tomorrow. I'll be sure to let you guys know what the problem was as soon as I get it back.

LATER,

ROB

 

[BetchaCantRide]

okay, so I had the truck towed to the shop today, and apparently I have a bad fuel pump. I guess checking the fuel rail for gas to squirt out isn't good enough.....I guess my fuel pressure at the rail was less than 5psi. Anyway, looks like I'm gonna be busy part of this weekend. Just to let you guys know....be sure to check the amount of pressure in the system, not just that it's getting pressure - I thought that when I fuel pump died, I didn't work at all, I guess that's not the case.

peace

 

[Jason_25]

Just for future reference: the correct way to test the fuel pump is to get the truck idling with the guage attached, and "pinch" the return line coming out of the FPR. Pressure should spike to atleast 45 PSI or so, if not, you have a bad fuel pump.

 

[Lemondrop]

I was gonna say I had a Nissan sentra I worked on once that fuel would squirt out of the schrader vavle but the pump was bad . I just thought it was a once in a lifetime deal

I could actually smack the bottom of the fuel tank and the pump would start running . Drove me nuts finding the problem . My mother owned the car and would call me up and say it wouldnt start . When I arrived where she wa it would fire right up . I messed with it at home for about 2 hours one day before the pump seized again . Talk about a butt kickin .