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Monday, December 31, 2018

Dr. Gizmo Column


01/01/2018 

“Dr. Gizmo”
By Phil Arendt

Question 1
I have 2000 Chevrolet Silverado 1500 with a 5.3-liter V-8 engine that sometimes starts hard.  Normally, the engine starts within the first two revolutions.  When it does not start right away it cranks for about six or seven seconds before I shut off the key.  If it cranks longer the cranking slows down and I have to shut off the key.  When I try to start again it starts right up. 
I have been to two different shops for this trouble.  They have done several tests on the spark plugs and fuel injectors but did not find anything wrong.
One shop suggested replacing the fuel pump even though it passed tests.  I told them to go ahead so they replaced the fuel pump, fuel filter and regulator.  This made no difference.
My truck has 197,000 miles.  I’ve owned it since it was new.  This is the only trouble I have ever had with it.  Have you ever heard something like this?  M.T., email

Answer 1
Every day in this business brings on new challenges.  Your truck is no exception.  The one clue that stands out the most is your description of the engine revolutions slowing down while cranking.  Sometimes a technician will overlook a clue such as this because he or she is looking for another issue that might be complex in nature.  The condition you experience might be due to low voltage.  A battery cable might be loose.  Maybe the battery no longer holds a full charge and needs replacement.  Just maybe a battery cable connection is suffering from corrosion.
It’s time for a technician too look for a basic cause for the condition.

Question 2
The parking and dash lights quit in my 1999 Toyota Celica GT.  I checked the all the fuses.  All of them are good.  I also checked if power is at the fuses for the dash and parking lights.  There is power.  I then used a jumper wire to apply power to both sets of lights.  They work. 
Is this caused by a broken wire or is there something else I should look for?  R.K., email

Answer 2
It would be helpful if you utilized a wiring schematic.  Be this as it may the trouble might be caused by a faulty relay or perhaps a broken or corroded ground connection.  You will find relays for the lights in the fuse panels.  Since it appears you have equipment to test circuits, you should be able to test the relays and ground connections. 
What needs repair all depends upon what you find.  The cure might be as simple as a thorough cleaning of a ground connection.

Question 3
I have a 2010 Chevrolet Equinox LS with a 2.4-liter engine that quit while driving a steady speed on the highway.  It has 162,000 miles.  No warning lights came on when it shut off.  It shut off as if I turned off the ignition.  It was towed to a reliable shop.
After tests and some disassembly my shop said the timing chain jumped.  They said that this is an interference engine and it might be shot.  They said that the valves and pistons smashed together.  They say this causes broken pistons and valves.  They won’t know for sure how much damage there is until they disassemble it.  They suggested installing a rebuilt engine instead of tearing this one apart to inspect the damage.
I did not hear any metallic sounds when the engine stopped.  Is what they are saying right?  Can this engine be saved?  Is it better just to replace it?  D.V., email

Answer 3
What happened might have caused severe damage to the pistons but maybe not.  Sometimes when this happens the only damage is to the cylinder head.  Consider asking a technician just to remove the cylinder head for inspection.  He might find bent valves and certainly debris from the timing chain.  The pistons might have gone through this incident without damage.  If so the engine does not need replacing.  A technician can install a new cylinder head and timing chain and all should be well.

Question 4
When I start the 7.3-liter engine in my 2001 Ford Excursion Limited with 288,000 miles it smokes like crazy and runs rough.  This began shortly after a vacuum pump was replaced. 
Once the engine warms up it runs fine.  Does this have anything to do with the vacuum repair?  If not what do you think is wrong?  R.P. email

Answer 4
It’s not likely your diesel is suffering from this condition due to previous repairs for the vacuum pump.  More than likely the issue is caused by a fuel system problem such as contaminated fuel or perhaps failed glow plugs.  It appears the engine is spewing unburned fuel.
It’s time to visit a repair shop that specializes in diesel engine repairs.  Tests will find the cause.  Consider leaving the vehicle overnight so a technician can experience the trouble when the engine is stone cold in the morning.

Question 5
The battery in my 2004 Volkswagen Touareg with a 4.2-liter motor dies overnight.  My car has 151,000 miles.  The battery is only six months old so I doubt it is the problem.  I have checked all the fuses.  They look fine.  I also have checked removed the battery cables to clean them.  They are now clean and tight.  Over the weekend I charged the battery all day but the next day it was dead.  Everything is turned off.  Do you think the alternator generator is the cause of the trouble?  D.N., email

Answer 5
While the battery is only six months old it might be defective.  It should be tested.  It might need replacement.  It’s also possible it is suffering from excessive parasitic discharge.  Although all switches are turned off there might be an issue such as a stuck relay, failed computer module or another issue draws power from the battery.  While it is possible a fault in the alternator causes the condition it would not be wise to replace it until tests show it has a fault. 
Consider a trip to an experienced technician who will perform tests and determine the cause.  Repair might be as simple as replacing a relay.

Question 6
 My 1993 Cadillac DeVille failed to start. It did absolutely nothing when I turned the key.  The dash lights came on and that was it.  I had it towed to a shop that has been servicing it for many years.  Of course after the tow truck arrived at the shop the car started without any problem and was driven off the flatbed truck.
My shop restarted it without any trouble several times during the day.  The only thing they found is that the security light flashes after it starts.  They say there must be something wrong with the security system but tests have not found any problems.  Do you have any suggestions?  H.L., email

Answer 6
This is an interesting problem.  Tests did not find any issues but it appears your technician is on the right path.  There does indeed seem to be an issue with the antitheft system. 
It’s likely your technician performed diagnostic test that checked modules.  No problems were found.  It’s time for him or her to look for other possible causes.  One place to look is at the steering column.  There is a key resistor and related conductors.  It’s possible a conductor has a small break that intermittently opens the circuit.  This will prevent starts. 
If indeed a technician finds this is the trouble it’s likely he will suggest a couple different repair options for you to consider.
         
Thank you for all the 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 his e-mail address drgizmo@drgizmo.ws. 01/01/2018 ® DR. GIZMO © 1989 – Present  

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