1990 chevy 350 keeps stalling

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  #1  
Old 03-18-07, 01:21 PM
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1990 chevy 350 keeps stalling

I have a 1990 Chevy with a 350 cu. in. (5.7), fuel injected throttle body and my engine has been stalling out. Sometimes it will run fine for a few weeks then all of a sudden, it stalls all the time. It will mostly start fine the first time, but now just going 1/2 mile it will stall 4-6 times and I have to come to a complete stop and put it in park, in order to start it back up. It will start up again just fine after waiting 5 seconds, run another 30-60 seconds than stall out again.
I changed the fuel-filter, spark plugs, M.A.P sensor and neutral safety switch but it still stalls out. I checked the fuel pump pressure with a gauge and it is above 9 p.s.i, but then it starts to drop and the engine stumbles untill the pressure drops to almost nothing then the engine stalls. I can keep the engine running if I jump the Diagnostic terminal and put 12 volts straight to the fuel pump terminal but I dont want to drive around like that.
I must also note...that no codes are being set and if I go through all the testing procedures in the books I bought for my vehicle at HELM, it says the ECM might be bad or the green wire with white stripe coming from the ECM to the fuel-pump relay. First of all I cannot find anything small enough to stick into the back of the wiring harness at the ECM to even check if I have voltage at that wire, any ideas on something small to insert there?
Also, isn't a vehicle still supposed to start in neutral? It seems dangerous to me to have to pull over with no power steering when ever I stall out.
I probably replaced a good neutral safety switch just because of this.
Actually if I remember this stalling never existed untill I had off-idle sluggishness and emptied a bottle of fuel-injector cleaner into the fuel tank. Soon after that the stalling began. Also, I notice while watching the volt-meter everytime just before the fuel-pressure drops and right before the engine stalls the voltmeter will gain about 1-2 volts which I can see on the gauge just before it stalls.
I would hate to just go on replacing parts like a shade-tree mechanic and I have been an auto-mechanic for 25 years, but I have never considered myself a technician.
I would hate to shell out $100 for a new ECM and only wind up with 2 of them...not to mention the M.A.P sensor, the fuel-pressure gauge, the spark plugs, the neutral safety switch and the constant wear and tear on my starter motor.
Thanks for any H.E.L.P.
Almost forgot...I did hook up my timing light and watched the fuel-injectors and light with the engine running and when it stalled and I tryed to restart, I could see the timing light flashing but no fuel from injectors.

...There is no replacement for cubic inch displacement...
 

Last edited by NewHomeowner396; 03-18-07 at 01:57 PM. Reason: mispelled
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  #2  
Old 03-18-07, 02:32 PM
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Thumbs up

Well there is a few things that might cause this.
#1 the fuel filter on the fuel pump in the tank can be cloged.
#2 the crank senser is defective.
Check ou these things first. It is also a lot cheeper.
 

Last edited by the_tow_guy; 03-19-07 at 08:25 AM. Reason: Not necessary to quote entire post.
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Old 03-18-07, 02:48 PM
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Smile Stalling

#1 the fuel filter on the fuel pump in the tank can be cloged.
#2 the crank senser is defective.

Would I still be able to hotwire the fuel-pump at the diagnostic terminal if the filter was clogged?

Would a defective crank sensor effect a running engine?
 
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Old 03-19-07, 08:22 AM
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Unhappy Crank sensor

Autozone says my vehicle doesnt have a crank sensor...
 
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Old 03-19-07, 08:27 AM
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I think you have a bad pump or, as Goldwing suggests, a clogged pickup screen ON the pump. I don't know for sure, but I suspect 9 psi is below factory specs. I know the 350 Chevy in my wrecker won't run on 9 psi and the symptoms you have are exactly what I get when the pump is going belly up which happens about every year and a half to two years for me. Not sure why fiddling with jumping power to the pump makes any difference.

Added note: Checked the specs and the fuel pressure is supposed to be 9-13 psi, so even before it stumbles you are at minimum pressure spec.
 
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Old 04-12-07, 06:11 AM
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Smile Ecm

Well, I found a ECM on ebay for $79.99 and installed it and fixed my problem. I guess my books from HELM were correct.
 
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Old 04-12-07, 05:53 PM
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I would have bet money on the pump. Glad it turned out well.
 
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