To start and run properly, injector timing has to be accurate. A quick visual inspection will tell you if the timing marks are lined up. Refer to the vehicle manufacturer’s timing procedure if you suspect timing is off or the pump has been replaced recently. On newer diesels with electronic injection pumps or direct injection, you’ll need a scan tool to make any changes.
Air in the fuel can also be a cause of hard starting or a no start condition. Air can make the engine die after it starts, and make restarting difficult. Air can enter the system through any break in the fuel line or via a bleedback condition.
To determine if air is the problem, install a clear return hose on the return side of the injection pump. Crank the engine and observe the line. Air bubbles in the fuel would tell you air is entering the inlet side of the pump. The injection pump itself is usually not the source of the air leak, so check the fuel lines and pump.
A worn or clogged pump can also make an engine hard to start. If the condition has been getting steadily worse accompanied by a loss of power, and the engine has a lot of miles on it (more than 75,000), the underlying cause may be a pump that needs to be replaced.
Before condemning the pump, though, check the fuel filters. Clogged filters can cause fuel restrictions that prevent the pump from doing its job properly. The primary water separator/fuel filter usually needs to be changed about every 30,000 to 40,000 miles, and the secondary filter about every 20,000 to 30,000 miles. Newer fuel systems with a single filter usually require service about once a year. If the filter has been neglected, chances are it may be restricted or plugged.
More features and functions, please visit our site and welcome to contact our customer-service for any help.http://www.kfzdiagnosegeraet.de/
2012年8月12日星期日
GLOW PLUGS
IIf slow cranking isn’t the problem, perhaps there’s something wrong with the glow plug system. Most passenger car and light truck diesels have glow plugs to assist cold starts. The glow plugs are powered by a relay and timer that routes voltage to the plugs for the prescribed number of seconds. When the timer runs out, the relay is supposed to turn off the voltage. But relays sometime stick and continue to feed voltage to the glow plugs causing them to burn out. One or two bad glow plugs on a V8 engine might not cause a noticeable starting problem during warm weather, but it can when temperatures drop.
Glow plugs can be checked by measuring their resistance or continuity. Excessive resistance or a lack of continuity would tell you the plug is bad.
If one or more glow plugs have burned out, are heavily coated with carbon or are not receiving their usual dose of start-up voltage, the engine will become progressively harder to start as temperatures drop, and will idle roughly and produce white smoke in the exhaust for several minutes once it finally starts. If all the glow plugs are burned on the end, you’d better check the injection timing because it is probably overadvanced.
To see if the glow plug module is providing power to the glow plugs, use a voltmeter to check each plug for the specified voltage when the ignition key is turned on. No voltage? Check the glow plug control module connections, ground and wiring harness. The glow plugs themselves can be checked by measuring their resistance. Replace any plugs that read out of specifications.
Hard starting can sometimes be caused by a glow plug module that fails to turn the glow plugs on or doesn’t keep the plugs on long enough when the weather is cold. On GM 6.2/6.5L diesels, there have been reports of heat from a still-warm engine causing the 125-degree inhibit switch inside the controller to shut off making the engine hard to restart. The cure here is to relocate the control module away from the engine. On Ford 7.3L diesels, the control module can cut off early if there are two or more bad glow plugs. We have also heard of control modules that do not keep the glow plugs on long enough for easy cold weather starting. The on-time is sufficient for warm weather, but not cold weather.
More features and functions, please visit our site and welcome to contact our customer-service for any help.http://www.kfzdiagnosegeraet.de/
Glow plugs can be checked by measuring their resistance or continuity. Excessive resistance or a lack of continuity would tell you the plug is bad.
If one or more glow plugs have burned out, are heavily coated with carbon or are not receiving their usual dose of start-up voltage, the engine will become progressively harder to start as temperatures drop, and will idle roughly and produce white smoke in the exhaust for several minutes once it finally starts. If all the glow plugs are burned on the end, you’d better check the injection timing because it is probably overadvanced.
To see if the glow plug module is providing power to the glow plugs, use a voltmeter to check each plug for the specified voltage when the ignition key is turned on. No voltage? Check the glow plug control module connections, ground and wiring harness. The glow plugs themselves can be checked by measuring their resistance. Replace any plugs that read out of specifications.
Hard starting can sometimes be caused by a glow plug module that fails to turn the glow plugs on or doesn’t keep the plugs on long enough when the weather is cold. On GM 6.2/6.5L diesels, there have been reports of heat from a still-warm engine causing the 125-degree inhibit switch inside the controller to shut off making the engine hard to restart. The cure here is to relocate the control module away from the engine. On Ford 7.3L diesels, the control module can cut off early if there are two or more bad glow plugs. We have also heard of control modules that do not keep the glow plugs on long enough for easy cold weather starting. The on-time is sufficient for warm weather, but not cold weather.
More features and functions, please visit our site and welcome to contact our customer-service for any help.http://www.kfzdiagnosegeraet.de/
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