Trinidad Diesel Troubleshooting
Here is an easy way to zero in on a stalling problem.
If it feels like someone reached over and turned off the key and it fires back up right away it's the injection pump.
If the same thing happens but it has to cool down before restarting it's the PMD / FSD(pump mounted driver).
If it stumbles and than stalls then it is air in the fuel lines. If it is this one try switching fuel tanks and just turn the key to run but don't start the engine. Listen to the fuel pump for a change of noise pitch. The pump is really loud when the pump is out of fuel and will have a muffled sound when pulling fuel. Sometimes the baffle in the main tank will brake away from the tank and the pump will suck air when the tank is just off full.
Also check for vacuum lock. If the fuel tank vent is plugged air can't get into the tank to replace the fuel that's drawn out. Remove your fuel cap and see if the truck runs.
Turbo Charger Problems
Vacuum Pump. Should be 8-12 HG. Boost switch. On top of passenger intake. Remove the big black air tube and check the two vacuum lines.
One goes to the vacuum pump the other goes to wastegate actuator. It's common for boost switches to go bad. Air lines can have leaks also.
Check actuator with truck off. It should move back and forth easily. Next pull actuator rod out all the way and start truck. If the vacuum is good the actuator rod will pull all the way in.
Check blades on turbo fan. they should spin freely with no noise. If turbo is really cooked it probably wont spin easy and will have to be rebuilt.
Glow Plugs & Diesel Starting Problems
If 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.
Diesel Injector Problems
Diesel injectors can suffer from the same kinds of ailments as gasoline injectors, including varnish deposits, clogging, wear and leakage. Today's low sulfur diesel fuels are more likely to leave varnish and gum deposits on injectors, and also provide less lubrication so you might recommend an additive to keep things flowing smoothly.
Diesel injectors operate at much higher pressures than gasoline injectors. Over time, their opening pressure can drop. Up to 300 psi is considered acceptable but more than 300 psi means the injectors should be replaced or reset back to their original operating specs. You'll need some type of pop tester to check the opening pressure of the injectors if you suspect this kind of problem.
Dirty injectors will lean out the air/fuel mixture, causing a loss of power, rough idle and sometimes white smoke in the exhaust. Leaky injectors will richen the air/fuel mixture and cause black smoke.
There are a couple of ways to find a bad injector on a diesel engine. One is to use a digital pyrometer to check the operating temperature of each cylinder. A temperature reading that's lower than the rest would indicate a weak cylinder. If compression is okay, the problem is restricted fuel delivery. Another quick check is to use an ohmmeter that reads tenths of ohms to measure the resistance of the glow plugs while the engine is running. The resistance of the plug goes up with temperature, so if one or two cylinders read low, you've found the problem. For example, if a glow plug normally reads 1.8 to 3.4 ohms on a hot, running engine, a reading of 1.2 to 1.3 ohms on a glow plug would tell you that cylinder isn't producing any heat.