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2001 Gmc Sierra C3


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Thanks for all the info, I will check it out and see what it looks like. I also noticed then the fuel pump kicks on it doesnt sound like it is building up pressure. You cant here it drag down so to speak.

Edited by Carls LQ9 SS (see edit history)
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Well I know on mine you can't really hear it pulling down, but if you sit there and turn the key a couple times you can hear the regulator kick in and start returning some of the fuel to the tank. Sounds like a swishing type noise when it starts bypassing. Your pressure regulator may be not allowing any pressure to build up, that's why the only real to check is with a fuel pressure gauge. Since the nipple is after the regulator on these trucks.

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there is a reason why flooded vehicles get salvaged....

 

 

However, if you want to get this started you will have to check all of the electrical plugs for corrosion. Next you will have to check your ignition wires from the column and ignition switch to the BCM. A change in resistance will cause VATS to kick in and prevent the truck from running. So, to check VATS, you will need to have someone disable it from the tune... If it then starts it will be an issue with corrosion in the wiring.

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The reason I bought this vehicle is because it was supposed to be on an incline backing down a boat ramp when the water damage occoured and wasnt supposed to have any water in the wiring under the dash. But when I got it home and I got to inspecting everything it had infact been submurged level and the engine and everything to some water in. So I guess I kinda got in a mess with it. I will take the dash apart and inspect all the connections to see what they look like. Thanks for the info chpspecial. I will get a pressure tester tomorrow 2001silveado364 and check the pressure. Thanks for all the help guys.

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Huh, well did the bcm or pcm go under water? More importantly, was it salt water? Do like CHP said and check and CLEAN every connector to make sure there's no contaminants interfering with function some how. Good luck with it, push come to shove, you'll have to replace the bcm and pcm. And if it got water in the engine like you sayurgent.gif get ready to replace the knock sensors in the NEAR future, they hate water.

Edited by 2001silverado364 (see edit history)
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It was salt water I think because it is a Texas truck. I checked the bcm and the water line stopped about half way up on the outside of the box. I checked and cleaned the connections and still nothing. If I let the truck sit for a while and try and start it, it will hit and try to start but thats about it. I think I would be better off just changing the complete cab harness...Oh and one other thing, will the bcm out of the parts truck work with the computer in the c3?

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I don't see why not, I don't think anything is really bcm specific. I kinda doubt the bcm is causing it not to start but who knows. Probably a good idea to take the bcm apart and clean it with fresh water to get all the contaminants off the circuit boards inside it.

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  • 2 weeks later...

Wow, where do you start. If I read this correctly, the truck initially ran for a while (at idle anyway) but would run rough or misfire at higher rpms......Is that correct? Also, taking into account your other comments about the heat under the vehicle, etc.

 

If I was to guess, I would say that the vehicle either still has some contaminated fuel; did you siphon fuel out or completely empty it out by turning tank upside down and also flushing residue out of tank----also what about fuel in lines? There could also be damage causing engine to misfire. The term "Damage" being used very broadly; i.e. anything from water in any electrical connectors (coils, pcm, etc) or plug wires or mechanical damage to engine. If the engine ingested water, it could/probably would bend connecting rods, etc. I've seen engines that had a bent connecting rod that didn't sound like a diesel----just didn't run right (were basically down on compression in that cylinder----depends on the motor/circumstances). Either way, this vehicle was missing which will cause raw unburned/partially burned fuel to get in the exhaust. The O2 sensor/s picks up the higher oxygen content (unburned/partially burned air/fuel charge) and think the engine is lean. It will add more fuel to compensate causing a rich condition. The catalytic converters are forced to try and burn this excess fuel and depending on how severe this can and probably did overheat the converter/s. Severe enough it can melt the converter down and cause an exhaust restriction. Many times severe enough to not allow the engine to run.

 

Need to determine if engine is dying because of VATS inteference or exhaust restriction. If exhaust, this would have been due to misfire condition. In that situation we would want to find out why it is misfiring. I would start with basic tests. I would look at spark, fuel pressure (mechanical engine condition; i.e. compression) and fuel quality. Spark testers, compression testers and fuel injector noid lights are cheap and available at any local auto parts store. IIRC, the VATS systems will basically shut down the injectors if there is a security event. In other words it will stop pulsing the injectors if someone is attempting to steal the vehicle. Usually, a few seconds after start up IIRC. That would be easy to monitor----have the noid light plugged into one cylinder and monitor when engine is started and when it dies. A scan tool (Tech 2 or similar) can be used to monitor for a VATS system event as well.

 

Also, can watch fuel pressure during event. Need to see if something is dropping out. Fuel source is very suspect and could be very likely as engine runs for a few seconds then dies. In the dealer, if bad fuel was suspect we could try using an alternative fuel source (fuel injector cleaner machine or tool) --- basically bypassing fuel system and using known good fuel source. Compression could easily be checked too. Exhaust backpressure is also checked easily (remove O2 sensor and install tool) if tool is available. Most people don't have tool, so a vacuum gauge can be used as a rough indicator of potential restriction. Install vacuum gauge and monitor vacuum at idle. Let's say you have 17" of vacuum at idle. Now raise rpm to 2000 rpm----your vacuum should increase a minimum of 2". If you have a restriction (exhaust, intake, etc) the vacuum will be lower then 19" (in this example) at 2000 rpm. Usually in cases like this (where vehicle won't hardly run) the vacuum will drop off well below 10" at 2000 rpm.

 

Too many questions at this point so I'm all over the page----need more info to try and pinpoint problem. Good luck and hope it works out for you.

 

P.S. I would take the time (after you get this running) to go through all of the electrical connectors below the water line and make sure they didn't ingest any water. If they did, I would empty it out and flush with electrical cleaner spray. Flood cars are scary as you can get some really weird electrical problems months after the event in many cases (due to corrosion). Also, if you suspect a problem with a connector don't assume it is good just because you don't see any water/corrosion in a connector. The water could come past the wire/weather pack seal on the backside of the connector and cause corrosion at the wire to terminal area (backside of connector basically). Hope that made sense.

Edited by slowfive0 (see edit history)
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