yeah that makes me think its the fuel pump. with the key on, engine off, you should hear the pump running for about 3 seconds. also you should have about 55psi fuel pressure. if you can get your hands on a fuel pressure tester that would be a great way to verifiy if the pump went kaputs.

 

Thanks. I'll try to figure the pump out.

Bernie

 

I bought a fuel pressure gauge for $40 and found I had enough pressure. I had heard a mechanic on the radio talking about a fuel pressure regulator and figured that was my next best bet. It was and cost me another $40 to buy one. Unfortunately, in this motor, its located under the fuel/manifold plenum which had to come off. It was a 3 hour job for me but the truck is back running. it sputters a little when cold, so if anyone has an idea about that, let me know. I'm going to go back and check my connections and bolt tightening. Thanks for your interest.

 

Could be the poppets acting up, I know they are prone to failure, which is why in 2002? GM got rid of them and moved the fuel injectors at the intake versus up high. Although it may not be the cause, just something to look into, so don't buy a new spider setup just yet.

 

OK-thanks. Interesting to know they were changed the next year. Mine seems to be working OK now.

 

I didn't see if you had a SES light. Are you able to check for codes? I'm curious about the MAF sensor, but don't run out and buy one, they ain't cheap.

K&N filters are good, but people tend to over oil them which causes problems, too.

Just random thoughts running through my head.

 

Thanks. I had 4 codes for bad O2 sensors! That hardly made sense as the thing wouldn't run even cold. I changed 2 but from what I could figure, none were bad. After I changed the fuel pressure regulator, located under the intake plenum in this V6, the truck sputtered a little at first but now, 400 miles later is working as it should. I'm now not liking the fuel delivery system of this motor. As a previous writer noted, its different now.

 

Glad you solved it. Did you get those codes from a hand scanner or the dealer?

 

The codes were on a friends hand scanner. Guess I don't have much faith in those now. Do you work on these things professionally? Familiar w/ pressure sensor problems? The mechanic who had a radio show nailed it but failed to mention I'd have to remove the intake plenum.

 

The spider setups are very touchy to fuel pressures, a bad FPR or Fuel Pump will cause awful running conditions. From 92-95, they had CPI, which was a great setup for power, but the spider was prone to failing. It utilized 1 injector and 6 poppet valves to distribute fuel. TBI was still used as well until 95 and the Silverado's never had the CPI setup even though it made quite a bit more power. In 96, the engine received new heads and a new intake with a new setup for Fuel Injection called SFI. Basically it how had 6 injectors mounted up high in the plenum and 6 poppets at the intake runners. Sometime in 2002-03 the change was made.

Glad you got it fixed though!

 

I'm the used car mechanic at a Nissan dealership so I work on everything. I've seen fuel pressure regulators crap out on just about everything. I've also seen hand scanners give false codes, there's another thread on here about a truck having a diesel turbo code... and it's not diesel OR turbo.

Hand scanners are good 99% of the time.

Just thinking, did you get P0171 or P0174? Those are lean codes reported by the O2 sensors. It doesn't mean they're bad. Almost universally the only codes that tell you the actual part that's broke are P0420/P0430, catalytic converter efficiency below threshold bank1/bank2. These come up when the PCM measures no difference between the before and after O2 sensors. Dodge has a PCM update that MAY fix it, but not always. Everybody else, you just need cats.

Every other code needs to be diag'd. What were the codes?

 

Yeah - I didn't write them down so I can't tell you. It did say bank 1 & 2 sensors. Nothing in the manual about the codes meaning converter problems. I believe the FPR's on the V8 trucks are out in the open which would be a lot better. Under this manifold and spiders and poppets sure seems screwy.

 

I was only using the cat codes as an example. The O2 sensors will tell you bank1/bank2 sensor1/sensor2, but I was looking for the word "lean". A stuck open fpr will cause a lean condition and throw codes P0171 and/or P0174 calling out "O2 sensor (11/12/21/22) system lean".

 

I was only using the cat codes as an example. The O2 sensors will tell you bank1/bank2 sensor1/sensor2, but I was looking for the word "lean". A stuck open fpr will cause a lean condition and throw codes P0171 and/or P0174 calling out "O2 sensor (11/12/21/22) system lean".

My '02 Silverado with the 4.3 also quit in the last couple of weeks. Just wouldn't start one morning. Cranked but no go. It was raining so I checked the distributor and wiring. They were dry and in good condition but no start. Next day when I went to work on it, it started fine. 2 days later, no go again. Checked spark, looked good on several plugs, figured it was fuel related. Got the O2 codes on both banks. Did the simplest thing first: changed the fuel filter. When I broke the filter loose and gas started dribbling out, I tried to start it and it fired up but wouldn't keep running. Put the new filter in and it ran fine for 2 days. Then 2 days later wouldn't start again. Last Sunday, unbolted the bed, slid it back a foot or so and put a new fuel pump in. Again, it ran fine Sunday. This AM, tried to start it and it just cranks. Argggh! So now with a new filter and pump, does this sound like the pressure regulator? I'm considering getting a pressure gage but the connection on the fuel line (at the back of the engine facing TOWARD the firewall) is pretty hard to get to in order to attach one and since the same problem occurred with the old pump, I'm guessing the pressure at the test point will be ok. Just wanted to add my 2 cents to this thread. Looks like an FPR replacement this weekend.

 

On mine, I thought fuel pump the whole time - til I bought a pressure gauge. Now you got a new pump so thats not it. It definitely sounds like mine was acting before the I changed the regulator.

 

I was only using the cat codes as an example. The O2 sensors will tell you bank1/bank2 sensor1/sensor2, but I was looking for the word "lean". A stuck open fpr will cause a lean condition and throw codes P0171 and/or P0174 calling out "O2 sensor (11/12/21/22) system lean".

My '02 Silverado with the 4.3 also quit in the last couple of weeks. Just wouldn't start one morning. Cranked but no go. It was raining so I checked the distributor and wiring. They were dry and in good condition but no start. Next day when I went to work on it, it started fine. 2 days later, no go again. Checked spark, looked good on several plugs, figured it was fuel related. Got the O2 codes on both banks. Did the simplest thing first: changed the fuel filter. When I broke the filter loose and gas started dribbling out, I tried to start it and it fired up but wouldn't keep running. Put the new filter in and it ran fine for 2 days. Then 2 days later wouldn't start again. Last Sunday, unbolted the bed, slid it back a foot or so and put a new fuel pump in. Again, it ran fine Sunday. This AM, tried to start it and it just cranks. Argggh! So now with a new filter and pump, does this sound like the pressure regulator? I'm considering getting a pressure gage but the connection on the fuel line (at the back of the engine facing TOWARD the firewall) is pretty hard to get to in order to attach one and since the same problem occurred with the old pump, I'm guessing the pressure at the test point will be ok. Just wanted to add my 2 cents to this thread. Looks like an FPR replacement this weekend.

Am I seeing a pattern? Is it not starting when it rains? If so, you need to check connectors. Also, if water's getting into a harness and the insulation's breaking down, the water could be causing an electrical short that goes away when it dries out.

 

Yeah, that's kind of what I thought at first, but it also didn't start when it hadn't rained for a few days.

As an update, a while back I had started getting MAF codes but the truck still seemed to run ok most of the time with an occasional sluggishness. When that happened, I sprayed it with MAF cleaner and it would take care of it. When I got the fuel pump this last weekend, I decided to take care of the MAF problem for good as well so I also ordered a MAF sensor, which came yesterday. Truck would not start immediately before installing the new MAF. Replaced the MAF sensor and it fired right up. Ran fine today. I won't call the problem solved until it starts day after day for a week or two. From everything I've heard, a MAF sensor issue will cause "driveability" problems but wouldn't prevent a truck from running. I was even told by a mechanic that if you disconnect the MAF connector completely, it will go into a "default" mode of sorts but the truck would still start and run. Now, I don't know what to believe. If it happens again, will definitely replace the fuel pressure regulator.

 

What is MAF and wheres the sensor?
Thanks!

 

Mass Air-Flow sensor, it's the sensor that's located in the intake tube after the air filter and before the butterfly. Normally it's pretty obvious where it's located as it has a rectangular shaped portion outside of the cylindrical tube. Also, when disconnected, it has a honeycomb looking media.

 

There's also an electrical connector attached to it.

The stock unit has it in the same place.

 

Thanks much - I'm learning more about these new fangeled motors.

 

What is MAF and wheres the sensor?
Thanks!

As others said, it's pretty easy to get to, probably one of the easiest things to change on the truck. There's 2 hose clamps on it and the electrical connector as silversurfer said. It has a few thin heated wires that sit in the air stream , it detects the mass of the air via change in these wires. If the sensor gets fouled with dust, etc. you can get a can of MAF cleaner at any auto parts store and spray it on the wires and the honeycomb intake side. One of the symptoms I had was I'd be driving along at freeway speeds and the truck would try and stall and throw MAF codes. I was getting suspicious that the sensor was failing because I was having to do this more often (not driving in any dirtier environments either) and the codes were happening more often. Never thought it would cause a complete "no-start" condition. Jury is still out on it being the culprit, but it DID start right up again this AM.

 

What is MAF and wheres the sensor?
Thanks!

Here is some (hopefully) useful info for you: How to Inspect and Clean a Mass Air Flow Sensor (MAF)

 

Yeah, that's kind of what I thought at first, but it also didn't start when it hadn't rained for a few days.

As an update, a while back I had started getting MAF codes but the truck still seemed to run ok most of the time with an occasional sluggishness. When that happened, I sprayed it with MAF cleaner and it would take care of it. When I got the fuel pump this last weekend, I decided to take care of the MAF problem for good as well so I also ordered a MAF sensor, which came yesterday. Truck would not start immediately before installing the new MAF. Replaced the MAF sensor and it fired right up. Ran fine today. I won't call the problem solved until it starts day after day for a week or two. From everything I've heard, a MAF sensor issue will cause "driveability" problems but wouldn't prevent a truck from running. I was even told by a mechanic that if you disconnect the MAF connector completely, it will go into a "default" mode of sorts but the truck would still start and run. Now, I don't know what to believe. If it happens again, will definitely replace the fuel pressure regulator.

A faulty MAF can cause a starting issue i have a 96 s10 blazer with the 4.3L and the MAF failed on me and my blazer would not start most of the time with it connected so i disconnected the MAF and drove my blazer around for a day until i could replace it.

A bad maf sensor can indeed cause a vehicle not to start. But in the case of the 4.3 it uses the maf and MAP sensors for fuel management and can be run with no MAF connected because it will use the MAP and stay in closed loop to keep the motor running so that you can get home or to a part house and replace it but it will not run as good as it should and burn more gas running it like that.

 

Truck ran fine the last few days, started right up. This AM, it wouldn't start. Tried for over an hour, testing connections, etc. Figured my next step was to replace the Fuel Pressure Regulator but I wanted to get a Fuel Pressure Gauge to do some diagnostics per the manual first since replacing the FPR is a PITA on the 4.3L (why did they bury it in the intake manifold???) Couldn't find a fuel pressure gauge to "rent" at an auto parts store locally so figured I'd buy one later and let the truck sit (I've got another vehicle to drive). Noticed a "Prime" contact position on the fuse block and checked the manual schematics and it bypasses the fuel pump relay. So I jumpered it to 12v, heard some noises around the throttle body like the system was working. Let it run for a couple of seconds. Then I hit it again and let it run for about 3 more seconds. Truck fired right up. Aha! (Of course, I've been down this path before.) In previous failures, I had replaced the fuel pump relay with another one from the fuse block and even shorted the output point of the relay to 12v. It made no difference at the time.

So, I'm thinking that it probably IS the FPR as running the pump manualy (using PRIME) for longer than the 2 secs that the pump runs on startup may have put more than the usual pressure/fuel into the regulator thus allowing it to start. Does this make sense? Also, any idea if this will damage the pump or other parts in the fuel system? Haven't found anything in the Manual about the PRIME function yet.

I won't be able to do an FPR replacement for a week or so, so I'm going to keep that jumper wire in the cab and see if I can repeatably get it to start by using the PRIME point if it won't on its own.