Detective On Duty

Detective On Duty (A "Sherlock Holmes" effort to find the owner of a vehicle)

Gonzo 2011 It’s pouring down, the tow driver is dropping off a car alongside the shop. Carrying the keys into the office, he’s drenched from head to toe. “Here ya go, have fun with this one.” I knew nothing about the car, and the tow driver only had a last name and nothing more. What to do now? I guess the only thing to do is to see if the tow company had a phone number to go along with the name. I tried the phone number several times, but never got an answer. Since I didn’t have anything else to go on, and I had plenty of other work to do in the shop, I decided to let it sit outside in the rain until I heard from the owner. Several days went by, the rain had stopped and still no phone call. I tried the number again but this time the number was no longer in service. It was an 89 Ford Ranger, looked pretty nice, clean… good tires, no broken glass. Seemed like a nice little truck not to have someone concerned about it. The shop was pretty much caught up that afternoon, so I thought I’d take the keys out to the little truck and see what was going on. Since I hadn’t even bothered to check the truck out beforehand, I figured it can’t hurt to see if there was anything in the glove box for an insurance card or something that might have a name on it. The truck was spotless, there wasn’t anything in the glovebox except for the owner’s manual. No name, no insurance card, not even a scrap of paper anywhere in it. While I’m here I might as well open the hood and check things out. Was I in for a surprise, no wonder the tow driver told me “Have fun with this one.” Under the hood was not a 1989 2.3 liter… more like about a 95 2.3 liter engine. (Pretty much the same engine but entirely different electrical systems.) All the electrical harnesses didn’t match. Now, I need to make another phone call. I called the tow company that dropped it off to ask them where they picked it up from and see if I could track the owner down that way. They knew exactly where it came from. It was from a salvage yard. Ok, time for another phone call. “Oh that truck, yeah I remember that one,” the guy front the salvage yard told me, “The fella who owns it dropped it off for us to put an engine in that he bought from us. We told him we didn’t think it was going to work, even though the original engine was the same size.” However, they didn’t have much more information on the owner than what I already had. But, they said they would keep an eye out for the guy if he showed up again. So here’s this little truck sitting out in my parking lot, with the wrong year motor in it and no owner. Now I need to do some more phone work. This time I decided to use the VIN and the license plate number to find something out. A few more phone calls thru the DMV and I had a name of a guy at an insurance agency. Seems the car was a theft recovery that was picked up by the insurance company. The original motor was blown after a long high speed chase by the police. The owner was arrested on drug charges and the car was confiscated (as is their usual policy). The car then was sold at an insurance auction, after the insurance company obtained it back from the police department. Another phone call led me to the auction house where (after a lot of searching) they came up with the used car lot that purchased the truck. Now I’ve got to call these guys… geez… this is getting to be a long affair. After talking to them and more research they finally had a first name to go with the last name that I already had and a different phone number. I gave the number a try. It rang and rang I was getting worried that all this phone work was going to end up as another dead end. Then a voice came on the phone. “Hey, a, yea … Hello?” “Hi ya doin’ is your name Jake? Do you own a Ford Ranger that had a motor put into it over at a salvage yard?” “Ah… yeah, Ah, wow, like dude… that’s my truck, who’s this?” I gave him all my information and explained to him how I tracked him down. He didn’t seem too impressed, (I thought I did an OUTSTANDING job of tracking this guy down!), but said he was on his way down to see what I’ve done to his truck. The sad part about it… I haven’t done a thing other than poking my head under the hood. When “Jake” finally showed up at the shop, I told him what would have to be done to get the truck running. He was under the impression that you just hook up a couple of wires and it would take off and run like new. Not quite the case there Jake, my friend. It’s going to take a little more than a few wires; more like quite a few wires as a matter of fact. I gave him the options on what could be done with what he had to work with. The big issue was now the cost… (Of course $$) and young Jake didn’t have a dime to spend on it. He was out of a job, and didn’t have any way of paying for repairs. Luckily, the tow bill was paid by the salvage yard (I think they just wanted it out of there) Jake had to go home and think about it. Well, I know what “think about it” really means… it means “I can’t afford it, so I’ll have to think of some other way of taking care of it.” A weekend went by and Monday morning the car was still sitting in the lot. By that afternoon a guy came by snooping around the little Ranger. I went out to greet the guy. He said he was going to buy the truck, and asked me what was wrong with it. I wasn’t surprised when he also didn’t understand what it was going to take to get it going. Later that day Jake called and told me he was selling the truck. What could I say, “OK?” or “Hey dude… I just played “Private Eye” to track you down. At least have the courtesy to ask the age old question, “Do I owe you anything?” So I can at least say; “Nay, no problem, that’s OK thanks for asking… hope you get on your feet soon.” But no, all he said was; “I think he’ll pick it up sometime this week.” Click… Another week went by and no one has come by to look at the truck. I’ve done all that I can… I’ve pretty much given up on the truck and the owner. The next Monday morning when I came into the shop the truck was gone. Not that I was surprised, but I did call Jake and this time I got his answering machine. “Ah, like, ah… I ain’t here… leave a message.” BEEP “Hey, Jake, your truck is gone. I guess your buddy came by and picked it up, come down sometime, and I’ll give you the keys.” All the effort I put into finding this guy, all the time I spent writing down phone numbers, contacting people, gathering information and compiling the history on this truck, and all I have to show for it is a set of keys. I guess I’m not the mechanic on duty … I’m the detective on duty. That was nearly a year ago and I still have the keys. I guess Jake’s buddy doesn’t need the keys either. Maybe someday I’ll put an ad in the paper in the lost and found section: “Lost Ford Ranger… used to belong to Jake… If you found it… I’ve got the keys.” Find even more stories at www.gonzostoolbox.com Be sure to pickup a copy of my best selling book, "Hey Look, I Found the Loose Nut" Short stories from the repair shop with a touch of humor... great gift idea.

How To Safely Change A Tire

Does your Gm car need a special engine oil such as Dexos?

Pat Goss describes why you need to know what type of engine oil is required in your General motors car. Listen below to the audio clip.

Fuel System Diagnostics

Fuel system diagnostics



Fuel delivery, fuel condition, and fuel volatility are an important part of today's vehicles. Getting the fuel to the engine is a lot different today than it was back in the days of carburetors. The only thing the fuel had to do then, was make it from the fuel tank to the carburetor by means of a mechanical pump. Today, it's high pressure pumps, multiple volume controlled fuel pumps, and varying fuel pressures to accommodate engine loads. With all of this going on the fuel has to be monitored constantly to insure of it's condition. These days, the fuel delivery system is monitored and the actual condition of

the fuel lines, the fuel tank itself, as well as the gas cap are

all a part of the evaluation conducted by the PCM. Emission

systems have come a long way from the first attempts at

environmental controls. The very first systems merely

pulled vapor out of the tank by way of a vacuum system and

fed the hydrocarbons into an activated charcoal canister

system for release into the atmosphere. Now, we not only

accomplish that task, but we verify the quality of the job the

system is doing and the integrity of the components in the

emission system.



It's almost impossible to talk about fuel systems without getting into EVAP systems as well. EVAP codes are a very common occurrence. P0455 is one of the most common. “Gross” meaning “large” leak can be an indication of a leak or more than likely... operator error... (forgetting to put the gas cap back on correctly.) P0457 is the more direct code for the fuel cap not installed correctly but either code really means the same thing... a large leak.



Using this example; a 2003 Mazda Tribute, if a P0455 is set the EVAP monitoring system will shut down and not run its self test. A secondary code is usually associated with it (DTC P1450 Unable to bleed-up fuel tank vacuum). The EVAP running loss system monitor will abort and not continue with the leak check portion of its test. If the leak is taking care of (IE.. put the gas cap back on) and the target vacuum is obtained the change in the fuel tank vacuum (bleed-up) will be calculated for a calibrated period of time. The calculated change in fuel tank vacuum is compared to a calibrated value preset in the PCM for a leak as small as .016 mm (.040 inch) in the EVAP system. If it is less than that the EVAP will pass the test. If it fails the PCM will attempt to run the monitor at least three times before setting the code again. DTC P0442 (small leak) These small leaks can be hard to find. A smoke machine works well in these cases. I prefer a smoke that uses a UV dye, but a good smoke machine with just plain smoke will do the trick too.



Here is a list of some of the common EVAP codes

P0440 - general EVAP failure

P0441 – incorrect or un-commanded purge flow (leaking purge valve)

P0442 - small to medium leak detected

P0443 – Purge solenoid electrical fault

P0446 – Blocked canister vent (high system vacuum)

P0449 – canister vent solenoid electrical fault

P0452 – tank pressure sensor voltage low

P0453 - tank pressure sensor voltage high

P0454 - tank pressure sensor voltage erratic

P0455 – large leak detected

P0456 – small leak detected

P0457 - gas cap is not sealing



Most vehicles today will have some sort of fuel tank pressure sensor, or in some cases it will be called an EVAP pressure/vacuum sensor. The FTP (fuel tank pressure) sensor is used to measure the pressure during the EVAP monitor test. When the PCM receives a signal from the FTP that there is excessive tank pressure or vacuum the PCM will then send a signal to the EVAP purge solenoid to correct the fuel tank pressure level.



On Toyota's the FTP sensor should read around 3.3 volts with no vacuum or pressure applied to the sensor. The sensor is a three wire sensor with one wire as a ground, one as the incoming reference voltage (5 volts) and the sensor wire to the PCM. Codes for tank pressure are generated by the results from the FTP sensor voltage which the PCM then interprets into the corresponding code. (service code). When the PCM requests the EVAP solenoid to run it's monitor of the tank pressure it uses the FTP sensor as the determining factor of the actual tank pressure.



Running these EVAP monitors are accomplished two different ways. Ford, GM, and some Asian imports use vacuum to run the monitor, while Chrysler, most European and a few Asian products use pressure to run the monitors. There are a lot of factors that have to be correct in order for the PCM to carry out the EVAP monitor. The ambient air temperature needs to be between 40 and 100 degrees (for most vehicles) and the fuel level needs to be near a half of a tank full. (The air temperature in the tank will effect the fuel vapors.) The barometric pressure must fall between 22 in. Hg on Fords and 19 in. Hg on most GM vehicles. (8,000 to 10,000 feet above see level). Most of the systems are set up to only run the test with the vehicle under 35 mph so that tank slosh is to a minimum. The last but most important thing is there cannot be any other fault codes stored in the PCM. Since the job of the EVAP system is to reduce emissions it stands to reason if there are any emission related codes stored in the PCM the eventual outcome of the EVAP test would be inaccurate.



On vehicles such as Chrysler that use pressure to perform the EVAP monitor test a small vacuum operated air pressure pump is used. The LDP (leak detection pump) pump uses vacuum to pull a small diaphragm up and down, then releases the vacuum to make its opposing chamber draw in ambient air and then force that air into the fuel tank system. A small reed valve allows the air only to go in one direction which allows the internal pressure to rise in the fuel tank system. These systems are called “return-less systems” (no fuel travels back to the tank) and are widely used on most of today's modern cars. Generally it's a small amount of pressure that is applied (.25 psi or more) but it's enough to run the EVAP monitor. The PCM has a preset calculation for the amount of bleed down time it will look for to determine the actual fuel tank pressure.



One other important part of the EVAP system is the

charcoal canister. This is where the fuel vapors are stored.

Charcoal is made by heating wood to around a 1000 degrees

in a sealed container. With no oxygen present during the

burning of the wood, it really doesn't burn but all the

organic compounds are driven off leaving nothing but the

carbon itself. To make it into “activated charcoal”

(the kind used in a charcoal canister) the “carbon” is put

under pressure with oxygen present. This expands the

pores of the carbon molecules creating “activated charcoal”.

Gasoline vapors adhere to the charcoal granules like static

electricity clings to a balloon. A light breeze across the charcoal

pulls the fuel vapors (hydrocarbons) off and cleans the activated charcoal for the next volume of fuel vapors.



Fuel temperature sensors are quite popular now too. A fuel temperature sensor does as the name implies . This is another reading the PCM will use to determine if and when it is appropriate to run the EVAP monitor. On some models you'll even find a FRP sensor (fuel rail pressure sensor) (found on some newer Ford models) this sensor is actually reading fuel rail pressure just as it would be with an external gauge. You can read the fuel pressure without having to hook up a fuel pressure gauge to the line. Installing a fuel pressure gauge to the line and comparing it to the reading on the scanner is a good way of insuring the FRP sensor is reading correctly.





A lot of times the fuel system is blamed for no start, hard to start, and even rough running when in fact it can actually be related to other components in regards to engine operation. One very common problem tends to be the MAF sensor. I've had several vehicles where the car seemed to run just fine when you first started it up but soon after would cough, lose idle, and stall. Fuel pressure is good, spark is good, and the fuel filter is clean. My favorite test for this problem is to use the tools I've got handy. A multimeter with a “min/max” recordable feature is my choice. (There are other ways to accomplish the same task but this is the one I prefer because it works on every type of MAF sensor ever made.) Out of the 4 wires that run to the MAF, one is ground, one is battery voltage, one is 5 volt reference, and the last wire is the sensing wire. Hook the meter onto sensing wire and ground the other lead. Record the voltage spike signal as you take the car from a standing idle to full throttle with a quick snap of the throttle. Once from idle straight to full throttle is all it takes. The record feature on the meter will record the voltage increase as a graph on the screen showing you the actual voltage. Some Toyota's (V6 and 4 cyls.) will only make it up to 3.8 volts... this is considered a good MAF sensor but only on these engine types. If the sense voltage doesn't reach 4 volts the MAF sensor is bad. Simple, but effective test. If you run across a MAF that has 5 wires, the extra wire is usually the air intake temp sensor. If your unsure which one it is try the snap test anyway, obviously if you snap the throttle open and the voltage didn't increase it's probably the wrong wire to be checking. (air temp sensor voltage won't change from idle to full throttle.)







One other part of the fuel system that can be a little tricky to understand is how some of the manufacturers have used the dual fuel tank systems that are found on full size trucks. Instead of two separate tanks these tanks have now become combined together. On a 98 GMC for example, – A short to ground in the sender or wiring will provide a fully empty reading. An open in the circuit will produce a full reading on the dash gauge.



These dual tank vehicles use a fuel pump balance module that measures the resistance of both fuel tank sending units. The module will average the resistances and produce an equivalent resistance reflecting the average of both tanks. Which is what you will see as a gauge reading on the instrument cluster.



The balance module effectively equalizes the level in the two tanks by way of a pump balance relay. At any time the rear tank has about 2 more gallons than the front tank the module will turn on the relay and send fuel to the front tank until the front tank is within a 2 gallon range. (If there is around 2 gallons in the rear tank and the front is empty (or near empty) this process effectively will empty the rear tank first. (I've had customer tell me they filled the rear tank but the gauge still shows ½ tank. Because their front tank was completely empty.) You get a lot of puzzled looks from the customer when you tell them, “That's OK, it's actually correct.”





More and more you'll find the fuel tank readings, fuel line pressure, and the EVAP sensor values on a scanner making the whole process of evaluating fuel delivery problems easier to understand. Diagnosing the systems takes a bit of background in understanding the way each individual system actually operates per manufacturer. Before attempting any repair on a fuel system always make sure to follow the guide lines from the manufacturer. In parts of the country where high levels of salt are used for snow removal be aware that a lot of vehicles mount the charcoal canister, EVAP purge valves and other components under the vehicle and can become susceptible to failure due to corrosion from the salt or even damage from impacted snow under the vehicle.

It's all about having the right information. Learning the way these systems work will greatly enhance your understanding of how to repair them. In the business of automotive repair... you can never know too much, and there's always something new to learn.


Don't forget, check out my website www.gonzostoolbox.com see my latest stories and events coming up. Pick up a copy of my best selling book at the website too.

Are they trying to sell you an alignment?

Pat Goss talks about Alignments. What you need to know,
so that you don't buy an alignment you don't need! Listen below.

Diagnostic Tech: 97 Jeep Grand Cherokee

97 Jeep Grand Cherokee 4.0

Intermittently cutout and stall, lights flickering during cutout

My own mindset goes to crankshaft position sensor problems when I see an engine cutout and stall on these jeeps. Here though we have the lights flickering as well. That could happen just because the rpms are so erratic during the event that the voltage is surging but the lights could be indicating an electrical power problem that is causing the cutout. The initial approach will be the typical, *verify the complaint* method.

The customer had said the truck hasn't failed to restart after stalling but this morning it would not start at all after some lengthy cranking attempts. I decided it was a good time to check for the problem but before I could test for no-start, it fired right up on the next try. After a short drive with no problems I tried a couple hot restarts. The engine did begin to have an intermittent cutout that could be related to crankshaft position signal. It was time to do some testing.

I wanted to start by testing the ASD (automatic shutdown relay), or more specifically to monitor the ASD power output. If the engine computer sees a good crank position signal it will ground the ASD relay, applying power to the ignition coil.

An easy way to test is to use a relay test jumper. You can put these in between the relay and the power box to create easily accessed test points.

If I lose ASD output then I can continue on my theory of crankshaft position signal problems, if the output is good then I can move on to something else and not have wasted any time. Monitoring the ASD showed steady output voltage, even during the engine cutout so there was no problem with that part of the system. I had to this point ignored the check engine light but since my suspicions of a bad crank sensor were proven wrong I needed another point to consider for further testing. The stored engine code was P0351 which indicates a problem with the primary circuit of the ignition coil. Now I had just finished testing that circuit feed at the ASD and it was fine but was the circuit actually fine all the way to the coil? I decided to see. I clamped the meter to the coil primary circuit but this time near the coil connector. The power was good to that point so if this was a circuit problem it was on the negative side of the coil since the code indicated the coil not firing. I kept the engine running and clamped a current probe on the coil trigger wire. The computer provides the coil trigger and is monitoring that circuit so I removed the coolant recovery tank to get clear access to the engine computer connectors. I was suspecting a bad wire or connection so began pulling slightly on the harness. It was immediately apparent that moving any computer connector would cause the cutout and/or stalling symptom.
At this point I would expect that I need a computer but an inspection of the connectors was necessary. I noticed that the two metal screws in the faceplate of the computer were loose. I tightened those. There was a lot of what I assume was dielectric grease on the connectors and the terminals seemed good. I sprayed contact cleaner on the pins and terminals and reattached the connectors. Guess what? I couldn't make it stall or cutout now no matter how hard I worked those connectors. A test drive looked good as well.








Kenneth Hayes
AKA Deranger

Goss on Fuel Grade: Premium vs Regular

Diagnostic Tech: 03 Trailblazer

2003 Chevy Trailblazer 4.2L

The complaint was a noisy cooling fan and an MIL (malfunction indicator light). There are times when the cooling fan is noisy and it is just a normal condition. The fan is electrically controlled by the engine computer and there are times the fan just needs to be on "high". But, when the fan seems to be noisier than usual and the MIL is on it indicates a problem that needs a closer look.

I pulled engine trouble codes with the scan tool and got P0172, P0128, P1481 and P0493. Sometimes you can get more codes than you want. The trick is to try and hone in on what will be most productive to test. P0172 is a rich code. The fuel mixture was too rich at some point and set a code. Under most conditions a rich condition diagnosis can be difficult and many variables to test. Lets go for an overview before trying to get too involved with a single code. A P0128 is an indication that the engine temperature took too long to get warm from a cold start. P1481 sets if the engine computer cannot see an rpm signal from the cooling fan. P0493 indicates the computer was trying to slow the fan rpm but sees rpms that indicate it is turning faster than commanded.

The last two codes are interesting. If the computer sees no rpm signal from the fan it will command the fan to 100% duty cycle. The code P0493 could come from a fan that is stuck on.

A fan running at full duty cycle on a warm up would set a P0128 and an engine that runs too long cold could possibly set a P0172. On the other hand, a P0172 or a P0128 could not set the fan codes so lets concentrate on the fan codes. Now which one? The P01481 or the P0493? We'll let the car decide that by determining which problem is present at this time.

Starting the car and looking at the scan tool pid for fan rpm I saw that at times 0 rpm were indicated, at times there were high rpms indicated but the desired rpm, or the rpm commanded by the engine computer was never being met. The fan itself was operating steadily, nothing erratic at all.

Lets take a look at the wiring diagram. In the graphing capture above, most of the time the computer is seeing a fan rpm greater than desired. The computer "sees" rpm based on the signal

from the cooling fan hall effect sensor on the dark blue wire at pin D of the fan harness connector. From the spikes in the graph you can see a big jump in rpm and five dropouts to zero so it wouldn't be hard to imagine that there are conditions present at times for both fan codes.

If a scope was connected during the event above you would expect to see the fan speed signal as a 5 volt square wave with frequency indicating the rpm. Because the fan rpm is faster than the computer wants you would expect to see no voltage on the white wire on pin B.

What we know so far is that there is an intermittent problem with the fan speed signal (spikes and dropouts) and that the fan clutch is not reacting as it should to the computer commands. Nothing yet condemns a particular part beyond any doubt but it does have the fan clutch becoming a prime suspect. Since we have a P1481, then at times the fan speed signal must drop out for much longer than we've seen so far. At least 11 seconds of no signal on two consecutive trips. The customer says the noise is worse cold. Since the fan would be loudest at 100% duty cycle and since 100% duty cycle is commanded when there is no fan speed signal it sounds like we might see the conditions for the P1481 on a cold start. Normally you wouldn't expect the fan clutch to engage cold. After letting the car cool down I tried retesting from scratch. The scan data on the restart was not the same at all and the fan, it was very loud.

The scan shows no fan speed rpm even though the fan is turning at a very high rpm. If I put a scope on the fan speed signal at pin D I would expect the square wave signal is missing. If the signal is missing then the computer sees no fan rpm and should have full system voltage on pin B, trying to command the fan to turn faster.

A test of voltage between pin E and C showed that I had a solid ground and reference voltage. The testing confirms a bad cooling fan.

Kenneth Hayes

AKA Deranger