2004 Chevy Blazer RWD 4 door, odometer at approximately 170,000 mi

PROBLEM: crank no start

PROBLEM DESCRIPTION: On the morning of Dec 23, the vehicle struggled to start a little bit but did start. After driving a few hundred feet and going up a slight incline (maybe 5 degrees), there was a single loud clank and it felt like someone took a metal hammer and struck the bottom of the vehicle somewhere beneath the front seats. The vehicle had difficulty moving forward upon pressing the accelerator but was able to move forward. It was driven back a few hundred feet to its parking space and after that it was crank no start. Couldn't hear the fuel pump but that doesn't mean it wasn't working, and slapping the fuel tank didn't get it to start.

Took it to the dealer and they are saying it's the fuel pump but that they can't explain the clank and the fact that the vehicle could move. There is 12V at the fuel pump.

I don't see how the vehicle could have moved forward if it was the fuel pump. The dealer says there are no codes, although there were historical codes for the instrument panel and a headlight which disconnected during their testing.

MAINTENANCE HISTORY: The vehicle has been kept current on maintenance with regular oil changes. Oil is brown in color and at midlevel between MIN and MAX on the dipstick. Fluids (transmission etc) were performed at a chevy dealership at 150,000 mi.

REPAIR HISTORY: The fuel pump and fuel filter was replaced by an independent mechanic in 2023, and AC Delco parts were requested. An idler arm was replaced with an AC Delco idler arm a few months ago. Brake calipers were replaced with rebuilt calipers several years ago. No accidents, orignal owner.

Since the fuel pump was replaced in 2023, the gas has never been below a quarter tank.

Never towed with this vehicle, always drove it very gently. Overwhelming majority of driving use was for transporting one or two passengers. Occasionally there was some cargo but nothing heavy.

Any rapid thoughts folks can provide would be appreciated since the vehicle is in the shop and the clock is ticking. Thanks!

 

Non AC Delco/Delphi fuel pumps have high failure rate. Did they do a fuel pressure test? If no pressure and 12v/ground at the pump then the fuel pump is likely the problem.

George

 

The fuel pump on these have been discontinued I am told. The mechanic who did the first fuel pump replacement says he can (and did) source directly from the two suppliers of AC Delco (I'm not sure what those companies are...).

I am viewing this video:

-- shows the AC Delco part but the mechanic doing the work says that the wiring harness is slightly different with regards to the connector

-- here we can see he is crimping

The original mechanic says he simply used a plug and that there was no crimping but I am thinking that this may be incorrect. If there is crimping I am now suspecting either mechanical disruption of the crimp or perhaps corrosion of the connection.

The dealer wants to replace with an OReilly fuel pump.

Is there some way that the clank and the loss of most but not all power at the wheels can be explained by fuel pump failure? This is what really bothers me. If it truly was the fuel pump, I am thinking that there would be a complete loss of power and the vehicle would be stopped in the street after a small amount of coasting. In my case, the vehicle was still able to slowly move foward (not coasting).

 

Soldering and shrink wrapping is always better than crimping on critical electrical connections so I agree with you there. That does not guarantee that that’s what happened but that would be sound electrical work. Verifying 12 V right at the pump lead would be the very best way to determine if it’s the pump but not just the positive lead but the negative lead as well to verify that there is not a ground connection issue which is just as bad as a power lead issue. The problem is there’s no port access to the top of the fuel pump so getting to the leads without dropping the tank is difficult at least and maybe impossible. If they did fuel pressure testing, and it failed that’s your indication that you have a fuel system problem. It does not immediately condemn the pump because you have to troubleshoot the power connections as I outline, but it really doesn’t matter how it failed, if there’s not adequate fuel pressure and it doesn’t hold during a leak down test that’s gotta get fixed, no matter what. Now if they get to proper functioning, fuel pressure and the truck still doesn’t run right then we can talk about where to go next. Any electrical component can fail intermittently, or marginally, that’s why wrapping the fuel tank will sometimes get you home


George

 

The dealer mechanic has confirmed that they have 12V and a good ground at the pump and that there is no fuel pressure, so this strongly suggests that the fuel pump is the issue.

I have asked them to drop the tank and send photographs. I have a hunch that I am going to see crimped wires on the pump. The vehicle had been driven in the rain a couple of days prior so water ingress and/or corrosion/oxidation seems likely. I am going to ask them to measure the impedance on the pump itself--if I see zero or infinity, that means that the pump itself has died right? And if they see any number other than zero or infinity then this is corrosion/oxidation or a mechanical displacement of the crimp.

The dealer has confirmed that they would not be crimping and would solder and use a proper water-resistant shrinkable tubing to insulate the wiring if we move forward with a fuel pump replacement.

My question then becomes this: the dealer wants to replace the fuel pump with an O'Reilly fuel pump.

Is there any magic I can do to source an OEM fuel pump or OE equivalent for this 2004 Chevy Blazer 4.3L Vortec? The original lasted 165,000 miles and many cycles of running until the. If this current pump is dead (rather than merely connector issue), it lasted barely more than a year! How long will the replacement pump last, and what is the best pump I can source?

 

My oem fuel pump lasted 110K miles and the tank ran dry a few times. The replacement FP was a Delphi and it is at 105K miles and still running

eBay shows new Delphi pumps available for your truck.

George

 

The mechanic who did the first replacement crimped the cables. I don't understand--does that represent substandard workmanship? The instructions from Delphi say to crimp, use a heat gun to shrink the shrinkable tubing insulation, and then wrap with electrical tape. I am trying to understand whether this failure has occurred due to any mis-installation of the fuel pump. Some sources say that you are supposed to solder, while others say that solder is brittle and not suited to the vibrations in this automotive environment.

 

Crimping with the correct crimp, crimp tool/setting, and heat shrink seal is acceptable. Soldering is best with mechanical linking of the wires like proper twisting, high quality solder joints (flux/proper heat/good flow/shiny) and heat shring seal/strain relief. Some people say not to solder in an automotive application but I have not had any problems after 50 years, not with suspended loose wires.

If the original mechanic crimped properly as above its not bad workmanship. That said, either option can be done poorly and any good subsequent mechanic can tell the difference. The biggest issue after this is the quality of the fuel pump. I recall a member here years ago that went through 3 off brand pumps in rapid succession.

George

 

The dealer replaced the fuel pump with a Delphi at my request (they were going to use a cheap O'Reilly part) and also the fuel filter. They used soldering and waterproof shrinkable tubing.

After replacement of the fuel pump and fuel filter, the vehicle now starts and runs normally.

Lesson learned: for folks who come across this article, apparently if your fuel pump dies (or mostly dies?) while driving (at low speed), you may be able to continue to move the vehicle forwards (not coasting) for a little while, and you may hear a rather loud clank from under the vehicle and feel a rather strong thud from beneath the seats. I am rather sure I did not drive over debris when the clank was heard.

The dealer did a multi-point inspection and marked "red" for the transmission, engine oil, and power steering, and "yellow" for engine cooling system. Verbally I was told by the mechanic that the engine oil was leaking just a little bit (and that the vehicle had been rather well cared for). As mentioned, the fluids have been changed fairly recently so are these marks meaningful or are they just trying to sell me some service items I don't need? Aside from looking into the engine oil, nothing has been suggested or recommended with respect to the aforementioned red and yellow stuff.

 

Thanks for the update. These are so valuable to those who might come across it as you mentioned.

I would be suspicious of those scores on the condition of your fluids. I'd go by if they have been replaced at the proper interval which it sounds like they have. The only reason to ignore that is there is some contamination in the fluids, but that would mean you have a much larger problem on your hands than just old fluid. Sadly there is a reason dealer service departments have a bad rep when it comes to trying to stick it to their customers.