I have a 2000 M-Class Mercedes SUV and have had to repair it very often. The latest mystery is that it sometimes won't start. Sounds like the fuel pump is not working but if I wait a few minutes, it starts. Any suggestions?

check cables at battery and starter - have charging system checked at parts store - free

When it "won't start" does the engine spin over or does it not spin over?

Check fuel pressure to determine whether or not the problem is related to fuel delivery.

Is the security light illuminated?

What do you mead "the standard six times"
May be security relates if it limits your attempts to start it.

Can you hear the fuel pump running when you try to start it? (may have to remove gas cap and listen as someone tries to start it).

Kinda sound like a loose connection--check the fuel pump and ignition fuses and relays, make sure that they are making good connections in their sockets.

Lots of helThe “Hands On” Vehicle Testing Reference
A guide for the professional vehicle technician as well as the interested DIY. Over 800 photos and illustrations show "How To" test: batteries, computer/modules and sensors, continuity, current paths, connections, switch contacts, fuses, fusible links, circuit breakers, generators (alternators), relays, starters, shared current paths (the vehicle base system), engine compression, cylinder leak, fuel, fuel pumps, fuel injectors, as well as miscellaneous tests from "How To" use a mechanic’s stethoscope to six different ways to check for a blown head gasket. Detailed information about the DVOM - digital-volt-ohmmeter and where and "How To" place the meter probes to do effective troubleshooting is included as well as amp draw testing with a DVOM and "How To" correctly read and use the inductive pick-up.
This book was designed as an illustrated “hands on ready reference”. Its purpose is to save you time by giving you illustrated clear examples of the tests, while informing and helping you understand each test as you do them; and above all, to help you improve your electrical, electronic, as well as some mechanical troubleshooting skills. Each test can be quickly located and used at the vehicle with the “Quick Index” that begins on page 4.
The book clearly explains voltage drop and how to find its root cause. Whether you work on gasoline or diesel autos or trucks, motorcycles, snowmobiles, or all terrain engines, you will find this book helpful in honing and improving your troubleshooting skills.
I encourage you to look over this index. I know you will be glad you added this ready reference to your tool box.
Index to “The “Hands On” Vehicle Testing Reference
Page
16 How to Set 2 different Meters to Read All of the Following: Open Circuit Voltage, Charging Voltage, or Source Voltage.
18 How to Place the Meter Probes to Find Open Circuit, Charging, or Source Voltage.
20 How to Set the Meter to Read Source Voltage Available to Any Load on the Vehicle.
22 How to Place The Probes to Find The Amount of Source Voltage Available to Any Load on the Vehicle.
24 How to Set the Meter for Reading Voltage Drop Between the Battery Positive (+) Terminal and the Input Pin to Any Load.
26 How to Place Probes Voltage Dropping Between the Battery Positive (+) Terminal and the Input Pin to Any Load.
28 How to Extend Meter Leads When Testing a Long Distance From the Battery.
32 How to Get the Most Out of the MIN/MAX Setting on Your Meter.
33 How to Test The Resistance of Your Voltmeter Tests Leads.
36 How to Test the Accuracy of a Digital Voltmeter.
44 How to Use a Temperature Probe That Plugs Into a Voltmeter.
190 Understanding the “Diode Test Mode” of a Digital Volt/Ohm/Amp Meter.
30 About Meter Selection.
31 Understanding a Meter’s MIN MAX Mode.
34 How Accurate is Your Test Meter?
35 A Word About the .5% Accurate Meter.
37 Does Your Meter Need to be “Calibrated”?
38 About Checking One Meter’s Reading Against Another.
39 When and Why You Should Change Your Meter’s Battery.
40 When To Push the “Hold” Button on a Digital Voltmeter.
40 When to Push the “HZ” (frequency) Button on a Digital Voltmeter.
41 What Can a Meter’s “Bar Graph” Tell You?
42 What You Need to be Aware of When Using an “Auto Range” Meter.
45 How Accurate Should Test Results Be?
45 About meter input impedance.
46 Understanding What a Voltmeter is Reading.
66 How to Do Voltage Drop Testing With the EZ 3 Step.
91 How to do “Base System Testing”.
49 What is Voltage?
50 What is Voltage Drop?
51 What Should You Check First Before Doing Voltage Drop Testing?
52 What Can Cause a Voltage Drop?
53 Don’t Overlook a Detailed Visual Inspection.
54 How Connections Affect Voltage Drop.
56 About the Blade to Female Terminal Connection “Drag Test”57 About Terminal Connection “Fretting”.
60 How Heat Can Cause a Voltage Drop.
61 How DC “Motor Drag” Can Affect Voltage Drop.
62 Understanding “In-Rush” Current.
64 How DC Motor In-Rush Current Can Affect Voltage Drop .
65 About Wire Insulation Porosity and Voltage Drop.
70 Understanding the Difference: "Voltage Available to the Input Pin/s of Any Load", and "Voltage Drop in the Current Path“.
75 About Ignoring Polarity When Looking For Voltage Drop.
76 About Voltage Drop Testing Polarity.
77 About Probe Placement When Voltage Drop Testing on the Voltage Feed Side.
79 The Importance of Correct Probe Placement When Looking for Voltage Drop.
82 About Using a Grounding Source Other Than The Battery Negative (-) Terminal.
84 If You Think any Grounding Point Will Do, Read This.
90 “Ball Park” Voltage Drop Standards.
95 When the Testing Voltage is Exactly the Same as the Source Voltage.
96 When the Voltage Drop is Still Excessive After Repair, Then What?
97 How to Set a Meter to Read Amps.
98 How to Set a Meter to Read mA (milliamps) and ?A (micro amps).
100 How and Where To Use an Inductive Pick-up.
101 How to Get an Accurate Reading with an Inductive Pick-up.
102 How to Calibrate a “Rotating Knob” Inductive Pick-up Plugged Into a Voltmeter.
103 How to Calibrate a “Zero Button” Inductive Pick-up Plugged into a Voltmeter.
108 How to Read a 1 mV-per-amp Inductive Pick-up When a Voltmeter is Set to mV.
109 How to Read a 1 mV-per-amp Inductive Pick-up when a Voltmeter is set to Volts.
110 How to Read a 10mV/Amp Inductive Pick-up when a Voltmeter is set to mV.
111 How to Read a 10mV/Amp Inductive Pick-up When a Voltmeter is Set to Volts.
112 How to Read a 100mV/Amp Inductive Pick-up with a Voltmeter set to mV.
113 How to Read a 100mV/Amp Inductive Pick-up with a Voltmeter set to Volts.
116 How to Adapt a Current Clamp (Amp Clamp, Current Probe) to an Oscilloscope.
117 How to Make and Use a 10X Inductive Multiplier.
104 About The Sensitivity of a Calibrated Meter.
99 About Amp Draw Testing Probe Polarity.
106 How Accurate is the Current Clamp?
114 About Inductive Pick-ups (Amp Clamps, Current Clamps, Current Probe).
115 About “Current Ramping”.
118 How to Test the Open Circuit Voltage of the Battery. 120 How to Test the Voltage Drop Between the Battery (+) or (-) Post and the Clamp.
122 How To Find The Voltage Drop Between: The Battery (+) Terminal and a Positive (+) Pigtail Attached to a Fuse Box or BEC.
124 How to Test the Voltage Drop of a Battery (+) Pigtail Wire Between the Battery (+) Terminal and a BEC.
125 How to Test the Voltage Drop of a Battery Positive (+) Pigtail Wire Between the Battery Positive (+) Terminal and a Fuse Box.
127 How to Test the Voltage Drop Between the Wire and the Clamp Material in a Battery (+) Cable or (+) Pigtail Wire.
129 How to Test the Voltage Drop Between: The Battery Negative (-) Terminal and Where the Negative (-) Cable Attaches,
131 How to Test the Voltage Drop Between the Battery Negative (-) Cable Conductor and its End Connectors.
133 How to Test the Voltage Drop Between the Battery (-) Terminal and Where a Battery (-) Pigtail Attaches.
135 How to Test the Voltage Drop Between the Battery Negative (-) Terminal and the Bulkhead Ground Strap.
137 How to Test the Voltage Drop Between the Bulkhead Ground Strap and the Block.
138 How to Test the Voltage Drop Between the Battery (-) Terminal and Ground Straps not Directly Attached to the Negative Cable.
140 How to Use Two More Ways to Test a Ground Strap Not Attached to the Battery Negative Cable.
144 How to do a Voltage Drop Test Between Truck Bed and Cab Sheet Metal.
146 How to Set the Meter to Read the Voltage Drop Between the Battery (-) Terminal and the Output Pin or Case Ground.
148 How To Place The Probes To Find Voltage Drop Between: The Battery (-) Terminal and The Output Pin or Case Ground.
150 How to Test the Voltage Drop on the Ground Side of a Case Grounded Module or Component.
151 How to Do a Battery Load Test Using a VAT 40 or 45.
153 How to Do a Battery Load Test Without a Load Tester.
154 How to Do a 3-Minute Charge Test on a Battery.
156 How and Where To Hook Up An Auxiliary Battery to Avoid Losing Computer Memory.
158 How to Test For a Shorted Battery in a 2 Battery System.
161 How to Find The Battery’s Parasitic Drain on a Battery Using a Meter Set to Read mA.
163 How To Find The Battery’s Parasitic Drain Using a 1? /10watt Resistor In Series With Battery Post and Cable.
165 How to use the Kent-Moore J-38758 Parasitic Draw Test Switch.
172 How to See if The Battery Has Low Resistance That Could Cause Generator/Alternator Diodes to Burn Out.
174 How To Hook Up Battery “Jumper Cables”.
176 How to Neutralize Battery Acid.
177 How to Charge the Battery.
159 About “Parasitic Drain”.
160 Drain Times Until Battery Goes Dead.
167 How to Find the Battery’s Parasitic Drain by Reading the Voltage Drop Across a Fuse.
170 Can You Use an Inductive Pick-up to Find Parasitic Load?
178 How a Battery Cable to Terminal Connection Can Cause a Voltage Drop That Can Cause Ring Gear Damage.
179 About the “Side Mount” Battery Cable Connections.
182 How to Test the Voltage Drop of Computer Voltage Feed Wires That Can Be Back-probed.
184 How to Test the Voltage Drop of Computer Ground Wires that Can Be Back-probed.
186 How to Load Test Computer Voltage Feed Wires That Cannot Be Back-probed.
188 How to Load Test Computer Ground Wires That Cannot Be Back-Probed.
191 How to Test a Diode Removed From a Fuse Box or BEC (bussed electrical connector).
192 How to Test a Diode.
193 How to Test an LED (Light Emitting Diode) Using a Test Light.
194 How to Test an LED (Light Emitting Diode) with the Diode Test Mode of a Meter.
195 How to Test a NPN Transistor.
196 How to Test a PNP Transistor.
198 How to Test for a PCM (Power Train Control Module) Reset.
201 How to do a Quick Test to See if the MAF (Mass Air Flow) Sensor is Your Problem.
202 How to Test for a Bad MAF (Mass Air Flow) Sensor with a Scan Tool.
203 How to Narrow Down Which Computer is Drawing an Excessive Amount of Current.
204 How to Use a “NOID” (Neon Organic Iodine Diode) Light.
205 How to Test the Resistance of a PM (Permanent Magnet) Generator.
206 How to Test a Knock Sensor.
210 How to Test a Thermistor Temperature Sensor.
214 How to Test the Computer Sensor Reference Voltage.
216 How to Test for an Open Throttle Position Sensor With a Voltmeter.
217 How to Test a TPS (Throttle Position Sensor) with the Bar Graph on a Voltmeter.
218 How to Test a Throttle Position Sensor With an Oscilloscope.
219 How to Test a MAP (Manifold Absolute Pressure) Sensor With a Voltmeter and Vacuum Pump.
220 How to Measure Frequency of a MAP or Mass Air Flow Sensor.
221 How To Test a Carburetor MC (Mixture Control) Solenoid.
222 How to Convert Frequency and Duty Cycle Measurements to Pulse Width.
226 How to Check for a Shorted Computer Controlled Solenoid or Relay.
223 How to Find a Dead Oxygen Sensor With a Voltmeter.
225 How to Test the Voltage Drop on the Ground side of an Oxygen Sensor Signal.
231 How to Test the Oxygen Sensor With an Analog Lab Scope.
227 Quick Test for Oxygen Sensor Response Time to Lean and Rich Air/Fuel Ratio.
228 How to Bench Test an Oxygen Sensor with a Propane Torch
207 Quick Test to See if a Hall Effect Switch is Working.
180 About Touching Removed Battery Cables Together to Clear Computer Memory.
181 About Scan Tool and Battery Charger Hooked Up at the Same Time.
181 About Scan Tools.
199 Things to Consider Before Re-flashing a Module.
230 No Meter Test for an Oxygen Sensor Heater Problem.
231 How to Test the Oxygen Sensor With an Analog Lab Scope.
232 The Case for Load Testing All Wires.
234 Before You Jump Into Any Type of Diagnosis on a Computer Controlled Vehicle, Revisit The Fundamentals.
235 What to Do Before You Replace a Computer or an Electronic Control Module.
236 About Welding on a Computer Controlled Vehicle.
237 About Diodes.
241 About Light Emitting Diodes (LED). 242 About Transistors.
243 About Basic Logic Gates.
246 About Computer/Module Logic Control.
251 How to do a Basic IC Chip Test on a Discrete Component Board.
252 About Resistors.
254 About (PM) Permanent Magnet Generators.
213 About Thermistor Temperature Sensors.
255 About the TPS (Throttle Position Sensor).
208 About Hall Effect Switches.
256 About “Pulse-Width Modulation”.
258 Understanding a “Signature Waveform”.
259 About “Sensors”.
261 About Oxygen Sensors.
264 About Oxygen Sensor Heater Control.
265 About Oxygen Sensor “Cross Counts”.
266 Ohm Meter Testing of Resistance Variable Sensors.
267 About Voltage Referenced, Resistance Variable Sensors.
268 About Voltage Referenced, Frequency Variable Sensors.
269 About Linear and Non-Linear Sensor Response.
271 About Temperature Coefficient Relative to Resistance.
272 How to Use a Digital Logic Probe.
274 How to Measure the Resistance of a Component (Circuit Load or Sensor).
275 How to Test the Resistance of a Resistor.
276 How To Do Continuity Testing With A DVOM (Digital Volt Ohm Meter) Set as an Ohmmeter.
277 How to Test for Continuity with a Test Light.
278 How to Read Accurate Resistance Values With or Without a Zero Button.
279 How to Test For Continuity in a Single Length of Wire With An Ohmmeter.
280 How To Tell if Solid State Components are Affecting Ohmmeter Resistance Readings.
296 How to Test for Available Voltage to a “Hot at All Times” or “Hot in Run & Start” Current Path.
299 How to Load Test a “Hot At All Times” and a “Hot In Start Or Run” Current Path.
300 How to find Both Ends of the Same Wire Buried in a Wire Loom with an Ohmmeter.
301 How to find Both Ends of the Same Wire Buried in a Wire Loom with a Voltmeter.
302 How to find Both Ends of the Same Wire Buried in a Wire Loom with a Self-Powered Test Light.
303 How to Test The Voltage Drop of any Length of Wire.
305 How to Test the Voltage Drop of a “Suspect Wire Connector”.
281 How Your Body’s Resistance Can Interfere With an Ohmmeter’s Reading.
282 Why Continuity Testing is NOT Reliable.
283 Cautions When Using an Ohmmeter.
285 How Battery Cable Position, Key ON/OFF, and Engine Running Affect Ohmmeter Readings.
287 Understanding Static and Dynamic Resistance.
289 What Does Series and Parallel Resistance Have to do With Troubleshooting?
290 Floating Voltage Values (Ghost Voltage) and What They Mean.
304 Quick Test For a “Suspect Connector”.
306 Importance of T-Pin or Acupuncture Probe Placement when Testing for a Bad Connection.
307 How to Test Any Mechanical Switch Contacts Using an Ohmmeter.
308 How to Find a Switch with Excessive Resistance Using a Voltage Drop Test.
316 How to Find an Intermittent Voltage Spike or Voltage Drop Out.
317 How to Test a Condenser/Capacitor With a Digital Ohmmeter.
318 How to Test a Condenser/Capacitor With an analog meter.
319 How to Troubleshoot a Ground “Splice Pack”.
321 How to Test a Rear Window Defogger Using a Test Light.
322 How to Test a Rear Window Defogger using a Voltmeter.
323 How to Test For a Good Voltage Feed With a Test Light.
324 How to Test For a Good Ground With a Test Light.
312 Obvious and Not So Obvious Causes of Intermittent Circuit Problems.
313 How to Deal With an Electrical/Electronic Intermittent.
315 Suggestion for Looking for That Electrical/Electronic Intermittent.
325 Understanding the Difference Between a “Switched to Voltage” and a “Switched to Ground” Current Path.
326 Types of Faults That Can Develop in Any “Switched to Voltage” or “Switched to Ground” Current Path.
327 Understanding Shared Current Paths.
328 Importance of Shared Current Path Testing.
329 Examples of Shared Current Paths on the Voltage Feed Side.
330 Examples of Shared Current Paths on the Ground Side.
331 How Voltage Drops in Shared Current Paths can Affect Drive-ability.
332 What a Difference 300mV (.300V) Can Make In a “Shared Ground”!
333 About Switch Contacts Used in Current Paths.
335 About Coefficient of Expansion Related to Metal.
336 Inside a BEC-Bussed Electrical Center.
337 How to Test the Voltage Drop Between the Battery Positive (+) Terminal and the Bussed Electrical Center – BEC.
339 Where and How to Add New Circuits to a Vehicle.
340 How to Stop Electrical Switch Pop “Noise” in a Radio.
341 How to Avoid a “Cold Solder Joint”.
342 How to Use Heat Shrink to Seal a Soldered Wire Connection.
343 How to Make a Soldered Connection Without an Electric Soldering Iron.
344 How to Use a Jumper Wire.
345 Precautions to Observe Whenever a Vehicle Component is Unplugged.
346 Observed Amperage Draw Range of Loads on Various Vehicles.
347 About Wire.
348 About Brush Bounce, Spring Tension, Arcing and Radio Frequency Interference (RFI).
349 About “Twisted Pair Shielded Wire”.
350 How Components Fail.
351 About Piercing, Splicing, and Repair of Wire.
353 About the T-pins & Acupuncture Piercing Tools.
354 About Corroded Connectors Caused by Water Intrusion.
356 About Weather Pack Connectors.
357 How to Troubleshoot a Short to Ground.
360 How to use an Inductive Pick-up to Locate a “Short to Ground” Wire.
361 How to Find a Short to Ground that Results in a Blown Fuse Using an Ohmmeter.
362 Understanding the Terms “Short to Copper”, “Turn to Turn”, and “Internal Short”.
363 Understanding “short to voltage”, “short to power”, “short to ground”, and “dead short”.
366 What might happen when two different current paths make electrical contact?
378 How to Troubleshoot a “Short to Voltage” / “Short to Power”.
388 How to Locate a Bad Fuel Injector Without Disassembly.
389 How to Do a Bench Load Test on a Fuel Injector.
390 How to Find a Dead Fuel Injector in a Port Fuel Injected System.
391 How To Find a Dead Fuel Injector With a Mechanic’s Stethoscope.
392 About the Digital Logic Pulser.
393 How to do an Injector Flow Test with a Logic Pulser.
394 How To Check the Resistance of Any Fuel Injector.
396 How to Test for a “Shorted” Fuel Injector.
397 How to Test for a Fuel Injector’s Waveform.
400 About the “Signature Waveform”.
401 About Fuel Injectors.
402 How to Test the Fuel Pump on an EFI Vehicle with a Fuel Return System.
405 How to Test Fuel Pump Pressure Through All Ranges of Engine Operation With a Scan Tool.
406 How to Test the Amperage Draw of an Electric Fuel Pump.
408 How to Tell the Difference Between a Fuel Pump Pressure or Volume Problem.
409 Quick Test For Good Fuel Volume With a Scan Tool or Digital Volt Meter.
410 How To Find the Percent of Alcohol in Gasoline.
412 How to Find Out if There is Gasoline in a Diesel Fuel Tank.
415 How to Use a Blown Fuse to Direct Your Troubleshooting.
416 How Air Space in a Current Path Causes Heat.
417 How To Test Fusible Link Wire.
418 How To Test a Fuse “In The Fuse Box” With a Voltmeter.
419 How To Test a Fuse “In The Fuse Box” With a 12Volt Test Light.
420 How to Test a Fuse “Removed From the Fuse Box” Using an Ohmmeter.
421 How to Test a Fuse “Removed from the Fuse Box” Using a Self Powered Test Light.
422 How to Test the Voltage Drop Across a AGC® , OES® Fuse Connection.
423 How to Test the Voltage Drop Across an ATC®/ATO®, Maxi®, or Mini® Fuse Connection.
425 How to Test a Suspect Circuit Breaker.
413 About fuses.
414 Never Assume any Fuse is “Good” by Just Looking At It.
426 About the Type 1 Auto Reset Circuit Breaker.
427 About the Type 2 Modified Reset Circuit Breaker.
428 About the Type 3 Manual Reset Thermal Non-cycling Circuit Breakers.
429 About the Positive Temperature Coefficient (PTC) Circuit Breaker.
430 How to Quickly Find Out if the Alternator is Charging.
431 How to Test the Voltage Drop Between: the Generator Output and the Battery Positive (+) Terminal.
433 How to Test Connectors and Connections of the Generator/Alternator Positive (+) Pigtail Wire.
434 How To Test The Voltage Drop of The Generator Ground.
436 How to Test the Voltage Drop Between the Generator Housing and the Block.
438 How to Test the Generator/Alternator Charging Voltage.
441 How to Test an Alternator /Generator for Undercharge and Overcharge.
442 How to Test a 3 Phase Generator (Alternator) for AC Riding on DC.
444 How to Check for Bad Diodes in a Non-Computer-Controlled Generator (Alternator) Using the “Diode Test Mode”.
446 How to Test for Shorted Diodes in the Generator (Alternator) Using The “Micro amp (?A) Range” of the Meter.
448 How to Use a Compass to Help You Troubleshoot Generator Charging Problems.
449 How to Use a Lab Scope to Measure Ripple Voltage.
452 How to Test the Generator Rotor for Current Draw.
454 How to Polarize a Generator.
451 About Generator/Alternator Testing.
455 How to Find a “False Air” Leak Using Propane
456 How to Verify That the Crankcase Can Hold a Vacuum on a Carbureted or Throttle Body Fuel Injected Vehicle.
457 How to Verify That a Rough Idle on a Carbureted or Throttle Body Vehicle is Not Caused by “Blow By”.
458 How To Deal With Engine “Knock”, “Ping”, “Detonation.
457 How to Test for a Bad Power Brake Booster.
473 How to Use a Timing Light.
473 How to Use a Timing Light to Find a Misfire.
474 How to Test for a Bad Throw-Out Bearing.
475 How to Check the Engine’s Intake Manifold Vacuum Looking for a Vacuum Leak.
477 How to Do a “Dry and Wet” Compression Test.
479 How to Do a “Running Compression” Test.
483 How to do a Cylinder Power Balance Test.
484 How to Do a “Cylinder Leak Down” Test.
488 How to do a Quick Test to See if a Water Pump is Working as Designed. on Fluid in the Combustion Chamber.
489 How to Check For a “Blown Head Gasket” with a Radiator Pressure Tester.
490 How to Check For a “Blown Head Gasket” Using a Battery Powered CO Tester.
491 How to Check For a “Blown Head Gasket” With an Air Compressor.
492 How to Check For a “Blown Head Gasket” Looking for False Boiling.
493 How to Check For a “Blown Head Gasket” With a Gas Analyzer.
493 How to Check For a “Blown Head Gasket” With a Combustion Leak Tester.
494 How to Test for Coolant (water & antifreeze) in a Vehicle’s Oil.
481 About the “Relative Compression Test”.
460 Quick Test for Checking Excessive Timing Chain Slack on a Distributor Equipped Engine.
461 About the Manometer (Slack Tube).
462 About Troubleshooting Trailer Wiring.
465 Help Backing a Trailer onto a Hitch.
466 Open Circuit Voltage Testing Caution!
467 About the Teslite® - Open Circuit Voltage Tester.
468 Open Circuit Voltage Feed Side Testing with a Teslite®.
469 Open Circuit Voltage Ground Side Testing with a Teslite®.
470 Consider a Pyrometer/Thermometer.
471 About the Infrared Thermometer.
495 How to Find a Leak in an Exhaust System Using Transmission.
496 How to Find a Leak in an Exhaust System Using a Shop Vacuum Blower.
496 How to Check for a Plugged Exhaust System Using a Removed O2 Sensor Hole.
497 How to Check Exhaust Back Pressure to See if the Catalytic Converter is Plugged.
498 How to Find the Source of Radio Frequency Interference (RFI) Noise in a Vehicle.
499 How to Tell if an Engine Hesitation is Loss of Spark or Loss of Fuel.
503 How to use the ST125 Spark Tester.
504 How to do a Cranking Coil Stress Test Without a ST-125 Spark Tester.
505 How to Test for Spark Plug Wire Carbon Tracking and a Leaking Spark Plug Boot.
506 How to Test For a Shorted Secondary Coil Winding.
508 How to Test the Primary Resistance Values of DIS Coils.
509 How to Test the Primary & Secondary Resistance Values of Oil Filled Coils.
510 How To Find a Misfiring Coil on a Coil-On-Plug “COP” System.
511 How to do a Comparative Resistance Test on a Distributor-less Ignition System.
512 How To Check For Radiator Overheat.
513 How and Where to Use a Mechanic’s Stethoscope.
514 How to Use a Compass to Help You Troubleshoot.
515 How to Diagnose Bad Ball Joints.
516 How to Diagnose a Bad Wheel Bearing.
517 How to Check for Acid Content In Coolant With a Voltage Drop Test.
518 How to Check for Water in Brake Fluid Using a Voltage Drop Test.
519 How to Find Volts, Amps, Ohms, and Watts.
520 Understanding the term “Bar”.
521 How to Deal With that “Chirping Belt”.
522 How to Inspect an Engine Belt Using a Timing Light.
507 About the Resistance of Spark Plug Wires.
523 Observed Wire Sizes Used In Vehicles.
524 Temperature Conversion Chart – Centigrade to Fahrenheit / Fahrenheit to Centigrade.
525 Where to Start When Dealing with a No Start due to a “No Crank”.
525 Where to Start When Dealing with a No Start but Engine does Crank.
527 How to Test the Voltage Drop of a Relay Contact.
528 How to Troubleshoot a Relay Controlled Circuit.
529 How To Test a Relay Coil Winding For Engineered Resistance Value.
530 How to Bench Test for a Relay’s Contact Resistance.
532 How to “Hot Wire” a Relay Coil For the “Click”.
533 How to Test a Relay With a Diode Across The Coil Winding.
539 How to Troubleshoot a Non-Computer Controlled Relay Circuit.
537 How to Test a Relay With a Resistor Across The Coil Winding.
543 How to Load Test a Relay Coil Winding.
535 About Relays with a Surge Suppression Diode.
538 About Relays With a Resistor Across the Coil Windings.
526 Understanding the Relay Coil Winding “Control” Circuit and the “Load” Circuit.
544 More About Relays.
545 About “Starter Solenoids” and “Continuous Duty Solenoids”.
546 How to Test the Cranking Voltage Available to the Starter Motor.
548 How to Find the Actual Voltage Drop Between: the Battery (+) Terminal and the Starter Motor Armature Lead.
550 How to Test the Voltage Drop of the Starter Motor Ground.
552 How to Test the Voltage Drop Between the Starter Housing and the Block.
554 How to Test the Voltage Drop of a Starter Mounted or Remote Mounted Solenoid.
558 How to do a Starter Motor Amperage Draw Test With an Inductive Pick-up Plugged Into a Digital Voltmeter.
560 How to do a Starter Motor Amp Draw Test with a VAT 40 or 45.
562 How to do a Starter Motor Amp Draw Test With a Load Tester That has a Voltmeter and Amp Meter, but No Inductive Pick-up.
556 Quick Test for Cranking, Charging Voltage Looking for Excessive Starter Amp Draw With No Inductive Pick-up Using MIN/MAX.
563 Understanding “Starter Motor Heat Soak” Starts Cold, Once Hot - No Start.
564 A Suggestion for the Color Blind Using Wiring Diagrams.
564 Smokes Bad Only When First Started Cold, Once Running, No More Smoke?
565 Working Alone? Some Suggestions.
566 How to Deal with a Rusted or Seized, Brake Bleeder, Tapered Plug, Nut, etc.
567 How to Remove a Rusted Disc Brake Drum or Rotor.
568 In The Event Your Cell Phone Goes in The Hot Tub, or Your Scan Tool or Voltmeter Get Soaked
569 About Parts Removal and Replacement.
570 To Use a Torque Stick or Not
571 General Rules for Allowable Voltage Drop in Vehicle Circuits.
573. Sources for Useful Information on Vehicle Understanding and Testing.
574. The author, Joe Glassford’s experience.
Available at: WWW.Vestest.com
www.Vestest.com
Joe Glassford
4 Grizzly Lane
P.O. Box 3401
Sunriver, Oregon 97707
541-788-0338p here:

when it is running is the engin light on?

The dealer or a shop which specializes in Mercedes will have to check the security system, if you suspect that to be the problem. (Even the specialty shop may not have the equipment to check it)