Northwest Herald Dr. Gizmo Column Dated Friday September 21, 2012

09/21/2012

"Dr. Gizmo"

By Phil Arendt

 

Gas Gauge Indicates Fuel But Engine Starves For Gas 

Question 1
Recently, I ran out of gas in my 2000 Dodge Grand Caravan with 130,000 miles.  The low fuel symbol on the dash had just come on, the needle showed about one eight full and the overhead display showed 40 miles to empty.  

Recently, the level sensor and pump in the tank were replaced due to a similar problem.  I have asked the technician that did the replacement to see if it can be re-calibrated.  Previous to the original equipment sensor's failure, it was dead-on accurate.

Aside from bending the float rod, do you know if my level sensor or gauge instruments can be accurately calibrated so I don't run out of gas again?          D.P., email

Answer 1

Beside circuit tests of the wiring, the system has three parts that need testing.  The signals from the fuel module in the fuel tank and the body control module communicate with each other.  The results of communication register on the dash fuel level indicator.  Tests of all three should determine if they are accurate within specifications.  Also, it is necessary to make sure the body control module program is up-to-date.

Bending the float rod on the tank module is not an option as this is guess-work.  It’s possible the body control module needs an update calibration, the dash indicator has a fault or perhaps the newly installed part is an aftermarket unit that does not meet all original equipment standards.  If the fuel module is an aftermarket unit it may need replacement with an original equipment part from a dealership.

Noise Appears After A/C Repair

Question 2
The air conditioner compressor went out in my 2002 Ford Econoline work truck.  My van has a 4.2-liter engine and 92,000 miles.  I had my local shop repair it.  They installed a new compressor, condenser, orifice tube, belt, belt tensioner and idler pulley.

After the repair the air conditioner makes a rattling noise.  My shop has tried to determine what is causing the problem.  They installed another compressor but this did not cure the trouble. 

The rattling is driving me nuts.  This repair is costing a small fortune.  Other than the rattling the a/c cools fine.  Do you have any suggestions?  S.L., email

Answer 2
Dynamite should cure the trouble.  All kidding aside, the technician has replaced almost all the major components in the system.  At this juncture, ask the shop to flush the entire system especially the evaporator core.  This procedure may cure the condition once and for all.

Don’t Attempt A/C Repair

Question 3
The air conditioner in my 2006 Toyota Tacoma quit working.  I found that the compressor was not turning on.  When I installed a jumper wire on the compressor plug it turned on but it made an awful sound.

If I install a new compressor and fill the system with Freon from an auto supply store will this fix the trouble?  G.L., email

Answer 3
First of all it is likely you don’t have the tools and expertise to do the repair.  You could be injured.  The system is pressurized.  A shot of pressurized refrigerant in your eyes or on skin could cause serious injury.  We do not want harm to befall you.

There appears to be an internal failure in the compressor.  When this occurs, metal fragments contaminate the entire system.  To fix it requires replacement of critical parts such as the compressor.  It also requires specialized equipment to flush contamination from all of the lines hoses and components.  When the system is sparkling clean and free of debris, specialized equipment must be utilized to test for leaks prior to charging the system with refrigerant and oil.

Faulty Circuit Causes Misfire
Question 4
The check engine light turned on in my 2001 Oldsmobile Silhouette with a 3.4-liter engine and 199,000 miles.  I went to an auto supply store to have computer codes checked.  The parts person found a misfire code for cylinder six and another code for voltage issues for the fuel injector on cylinder six. 

I replaced the spark plug and wire on six.  I also added fuel injector cleaner to the gas tank.  The check engine light turned back on after the work.  The code indicates voltage problems for the injector.  Do you think I should replace the fuel injector?  B.M., email

Answer 4
Voltage problems could be the result of an internal problem in the fuel injector but sometimes the trouble is caused by an external problem.  Check the plug connection on the fuel injector.  It may be contaminated with oil, dirt or corrosion.  It’s also possible a ground connection in the circuit is loose or corroded.  Correct these conditions as needed.  If the injector returns to normal operation after addressing wiring issues, obviously it does not need replacement.

Makes Sense To Dr. Gizmo

Question 5
My 2001 Cadillac DeVille overheated.  The car was towed to my local shop that has been servicing it for many years.  The manager says that depending upon the length of time the engine ran while overheated that it might be ruined. 

When I realized the car was overheating I pulled over and shut off the engine.  Once the car arrived at the repair shop it started and ran fine.  My shop manager said that his technician needs to do some tests but at the very least it is likely the cylinder gaskets need replacing.  He won’t know the extent of damage until the engine is apart.  He has to remove the engine to do the work.  Does this make sense to you?  M.W., email

Answer 5

Yes.  Overheating conditions can ruin an engine in a matter of minutes.  Recently, I examined an engine that overheated.  The vehicle owner said she drove with the hot light on for about one mile.  Two pistons melted from the heat.  The engine needed replacement.

Fortunately, it appears your engine was running normally when it arrived at the repair shop.  More than likely personnel at your shop will find that it does not need replacement.  It’s more likely than not the head gaskets need replacement as this is a common failure.  If so, once the new gaskets are in place the engine will run great for years to come.

Oil Pump Failure Is Coincidence
Question 6
I have a 2006 Honda Civic that I took to a repair shop because the air conditioner quit working.  The shop replaced the compressor.  I picked up the car and the air conditioner was working great.  I drove home without any problems.  The next morning, I started the engine and the oil light turned on.  Immediately, I shut it off.  I called the repair shop and they sent a tow truck.

That afternoon, the shop manager called to inform me that the oil level was proper but the oil pump had failed and needed replacement. 

My car is in great condition.  It has 106,000 miles on it.  I change the oil every 2,500 to 3,500 miles along with a new filter.  Did the shop damage the oil pump when they fixed the air conditioner?  R.T., email

Answer 6

No.  The air conditioner compressor is secured to the outside of the engine.  It is not necessary for a technician to remove anything to do with the oil pump to gain access it.  The oil pump is within the engine.

Fortunately for you the oil pump failed when you were not driving.  If you did not shut off the engine as quickly as you did, engine bearings may have been damaged.  Often when a pump fails, a motorist does not have a safe opportunity to pull to the side of the road to shut off the engine.  They may drive a mile or more to a safe place.  This results in a failed engine due insufficient lubrication of bearings.  You were very lucky.

Now that the oil pump is replaced, your car’s engine may run another 100 or 200,000 miles with the oil change regime and care you provide.  Keep up the good work!     

Thanks for all of your great questions.  Dr. Gizmo can’t wait to answer more.

Phil Arendt is a columnist, consultant and A.S.E.-Certified Master Technician.  Readers may send questions to Dr. Gizmo at P.O. Box 548, Cary, IL. 60013 or e-mail address drgizmo@drgizmo.ws. 09/21/2012 ® DR. GIZMO © 1989-2012