Posted on November 11, 2011 - by Richard

2004 Chevrolet Silverado HD Poor Mileage

Symptoms for 2004 Chevrolet Silverado HD Poor Mileage:

This 2004 Chevrolet Silverado HD poor mileage problem happened to my ATS customer after buying this truck from an auction lot. When he first saw the truck, the exteriors were in great shape and had a diesel engine on it. The selling price was a little bit low but it had over 100k miles on it. He bought it on the spot but while driving it home, the truck started missing and cannot ran over 25 mph.

Since the auction lot gave him a good deal, he felt there was a hidden reason for the low price. He had it towed to the dealer and after paying $300 and 24 hours later, they could not figure the problem and wanted more money. Since he was a retired diesel mechanic, he took upon himself to fix it in his backyard. A week later and after spending lots of aggravations and $450 on parts, he joined ATS and asked for help.

Initial Tests of 2004 Chevrolet Silverado HD poor mileage:

1.) Won’t run higher than 25 mpg and has lots of white smoke in the tail pipe.
2.) Checked for codes but none found
3.) Replaced fuel filter and fuel pump

Diagnosis of 2004 Chevrolet Silverado HD poor mileage:

When I read this 2004 Chevrolet Silverado HD poor mileage problem, the first thing that I asked was: Did you check the diesel basics? This means checking the following:

1.) What is the engine compression? This is important because his symptoms showed incomplete combustion as shown by white smoke. A good diesel engine compression tester should have at least 400 psi cylinder pressure with the compression gage hooked up at the glow plug holes (see the diesel compression tester picture shown above).

2.) Are all fuel injectors working? The spray pattern can be checked at glow plug holes while cranking. Injectors should spray a little then quit should be normal. A constant spray while cranking means the injectors are leaking.

Notes when testing diesel injectors:

The ignition relay must be disconnected when doing this test to prevent the engine from starting. An ATS diagram should be used in order to locate the ignition relay.

3.) The fuel pressure should be monitored and compared for each cylinder. All pressure reading should be similar otherwise, check the fuel pressure regulator and fuel relief valve. When testing for fuel pressure, it should be done with engine idling. If you have a live data scanner, each injector can be killed to compare each cylinder performance.

4.) There are other basic tests and they include verifying the vacuum pressure at idle, cylinder leak down test (see previous blog or ask ATS), fuel hold down pressure, etc.

Final Fix for 2004 Chevrolet Silverado HD poor mileage:

After giving him all these repair suggestions, he found that half of the engine cylinders did not have any compression reading at all. When he opened up the valve cover, he found the push rods were bent. This usually happens when trying to start this engine during cold weather and using lots of ether starting spray.

More Tips for 2004 Chevrolet Silverado HD poor mileage:

1.) Never buy any vehicle no matter how cheap unless inspected by a certified shop or mechanic.

2.) Most auction car lots are also victimized by some scrupulous owners who deliberately sell a vehicle with big problems. This is why when going to auction lots, always go there a day ahead so you can check the vehicle you are bidding for. If you are not a mechanic, take one with you when you visit the auction lot.

Thanks,

Richard

Note:

ATS has lot of files for 2004 Chevrolet Silverado HD poor mileage FIXES so you can do it yourself. Just because it is a diesel engine, it is hard to fix. Troubleshooting basics are the same. Find out more from ATS now!