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Discussion Starter #1
2000 chevy silverado, 4.3L V-6, 2WD

My truck died on me friday night...

INFO:

i was at the beach and i really dont think this is a culprit but i hit a pretty bad bump in the sand with my left front wheel(likely where someone had built a firepit or something, nice sized hole) friends knee hit the truck into neutral while he was in the center seat (no big deal, i shifted right back into drive calmly and was on my merry way back down the beach), drove another 2 miles to meet a friend and parked facing the water. I left my truck on because i was playing some tunes for about 30-40 minutes (I do that all the time no problems) and finally we decided to leave. So i got back into my truck turned the music down and shifted my truck into reverse.

PROBLEM:

  • After reversing about 5 feet my truck died...
  • tried starting it back up, no start
  • engine is cranking
  • sounds like backfire
  • checked all fuses
  • has fuel
  • replaced fuel filter
  • fuel pump works
  • no loose wires(that i have found)
  • wires, plugs, boots good
Had a friend tow me off the beach to a gas station, where we continued to try and start it, finally i saw on my airraid intake that a vacuum hose was disconnected and plugged it back in, started my truck instantly!!!!!
let it run for 5 minutes, reversed about 20 feet, then shifted into drive and died again. i checked that hose but no matter how its connected doesnt affect anything(and as a friend told me, he said my truck should start even if that hose wasnt connected, that it could still run off atmospheric pressure, its just something with emissions)
spent about 5 hours that night checking stuff, has not started once since...

  • engine does spark
  • fuel runs to engine
  • looked inside throttle body, and you do see a flame inside the throttle body when you crank it, every so many cranks
  • couple thousand miles ago replaced crankshaft position sensor
  • about 5000 miles ago replaced cap, rotor, plugs, wires
  • ran my programmer through my truck and NO DTC's
had much help from friends and family mechanics and nothing yet, however only spoke to family mechanics through the phone

very irritating, if you know anything please let me know...
thank you!
 

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You need to do a fuel pressure test. that way you can be sure it is enough fuel getting to the motor.
 

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Discussion Starter #3
yes i have heard a few people say that and it needs to be somewhere between 50-60psi i believe, but i dont have the tool for that, and fuel smell is evident when cranking and in throttle body... have you any say on flames inside the throttle body? as one friend noted, that seemed odd...
 

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you need at least 58PSI for the motor to start,and there is a chance that the Fuel Pressure Regulator has gone out and is just dumping the raw fuel into the intake.
 

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Discussion Starter #5
what would i need to check that?
 

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You will need a fuel pressure tester. and when you turn the key to on, you will get your fuel pump reading, and if it is low and falls very fast after you turn the key off then you know that the FPR is shot, and changing that takes about 1-2hours. If you have less than 55PSI and the pressure holds steady after the key is turned off then your fuel pump is shot.
 

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Discussion Starter #7
easy pick up at an autozone?
and do you have much faith in that?
if it turns out both are good, what would you then suggest?
sounds like you know your shiz, thank you :)
 

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Yeah Autozone will have a Fuel Pressure tester. If both of those are good then you will want to take a close look at the Mass Air Flow sensor, and Also on a thought swap around the Fuel Pump Relay with one that isnt in use in the relay panel. But ive got a fairly large feeling it is one of those two.
There is a chance it is the ignition module as well. But start with Fuel since you have spark, and Fuel. I would lean that you just arent getting enough.
 

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Discussion Starter #9
alright, and i have swapped a few relays already including ignition relay, but ill make sure i swap the fuel relay
and ive checked the m.a.s.(visually) but dont really know what to physically look or in that...
ill try to pick up a kit for the pressure tomorrow, will any generic schrader valve pressure tester work, autozones is $60.00!
 

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They do loaner tools. Dont buy one just rent it.. Alot less money and if you dont work on cars regularly then you wont need it enough to justify the money spent.
 

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Discussion Starter #11
thank you, i will post results asap
 

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while your at you might as well buy some electrical parts cleaner and T/B cleaner give the MAF and T/B a good cleaning
 

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Discussion Starter #13
where is this valve i connect to for the fuel pressure? is it the one right behind the throttle body before the fuel line goes in?
 

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Discussion Starter #14
UPDATE:

so i tested my fuel pressure and when i turn the key to the on position i get 60 psi then over 10 seconds it drops to between 57-58. when i turn the key off it remains there and doesnt lose psi at all (well for the 5-10 minutes i watched it)

so i am all outta ideas...
 

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I keep coming back to the backfiring you hear & what you say about seeing flames in the TB. These flames are coming from the cylinders when they are lighting off & are traveling back up through the intake manifold in order for you to be able to see them in the TB. This indicates to me that either the ignition timing is off (too advanced & is fireing before the intake valves are closed), or the cam timing is off. Either one will get these results. I don't think hitting the big hole in the sand would have caused this, but hard to say. If your cam timing is off a compression check will show this & is easy to do.
When your friend knocked it out of gear did your engine see some high PRMs?
 

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Discussion Starter #16
from what i heard as i usually pay attention to that, my engine only went up to about 3000 when i looked, in previous encounters with friends and knees i have jumped to 4500 and still been fine, so i am almost 100 percent confident i didnt rev up too much at all because i caught it pretty quick.

what about this compression check???

and yes i have heard some commentary about timing being off but im not too knowledgable on that subject, but i know the labor is time consuming

thanks for insight guys
 

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A compression check will tell you the basic health of your engines cylinders. In your case it would show if your valve timing has changed (if it's off & is allowing compression to dump into intake manifold)
Since this all started does it seem like your engine cranks over easier? Spins over freer than it did before while cranking?
 

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Discussion Starter #18
sorry, i meant like where could that be performed? and from what ive seen the engine has to be hot, how could they check it if my engine wont start?

and i dont think it has changed to be honest...
 

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Yes it's best to do the compression check when the engine's up to operating temp for accuracy, but you're stuck with this one.
You could actually buy a good guage & do the comp check yourself. It's something that you can use on every engine you will ever have, (car, truck, motorcycle, lawn mower, etc) or you could borrow/rent one at AutoZone, but if it's cranking at the same speed as before, then I'm leaning more towards ignition timing. If the valve timing was far enough off to be backfiring through the intake manifold, it should crank over a lot easier because of the low compression & you haven't noticed any difference in cranking speed.
Just for drill, grab the distributor & see if it's loose, or the cap got knocked loose when you hit the hole, or if the cap is askew.
 

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Discussion Starter #20
exactly how tight should the cap be, should it not move at all or can it have some play in it?

---------- Post added at 07:53 PM ---------- Previous post was at 07:33 PM ----------

if this helps at all i have no idea if you can understand, but its worth a shot.....

this is what my truck sounds like in a sense....

craank-cra-cra-cra-craank-cra-cra-cra-craank-cra-cra-cra-craank-cra-cra-cra-craank-cra-cra-cra-craank-cra-cra-cra-craank


its not a steady crank like normal... (or as a truck not starting would normally sound to me)

which i believe sounds like this...

craank-cra-cra-cra-cra-cra-cra-cra-cra-cra-cra-cra-cra-cra-cra-cra-cra-cra-cra-cra-cra-cra-cra-cra-cra.....until it starts
 
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