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Car Diesel Questions and Answers - This category contains featured questions as examples. They relate to most vehicles.

Question: 1983 Mercedes 300SD  Diesel mileage: 105,000. Engine will not shut off when key is turned to off position. Also, braking very weak and right electric window will not go down. All happened the same day at the same time. Vacuum system? I tested the vacuum pressure with a gauge but what is a good reading? Also, checked vacuum lines for damage or leaking. Am I on the right track or is it something else?

Answer: Yes, you are on the right track. You probably have a vacuum leak somewhere. The vacuum pump should have approximately 20 to 25 inches of vacuum.

Question: Ford F250 Diesel 6.9 pick up. Recently, the glow plug light continues to flash after the truck is started and warmed up. We were questioning what part would cause this malfunction and moreover, is this a warning that there is future problem coming.

Answer: Your problem is caused by a faulty glow plug control relay.

Question: 1989 Mercedes Benz 300 turbo diesel mileage: 120,000. Before and after the overhaul, when I step on the accelerator (for example to overtake a car) the performance is very poor. On the other hand, when I push the kit down (from 3rd to 2nd) it is like pushing the brake. Do you know why this occurs?

Answer: Two things to check that would cause your poor performance, incorrect injector timing and no boost pressure from the turbo.

Question: 1999 Chevrolet 3500 turbo diesel mileage: 92,000. I would rather not admit this, but I'm not sure what to do. My truck is sitting in the drive with a full tank of Kerosene. I drove about 20 minutes home, shut it off and when I tried to start it again, it wouldn't start. Imagine that... I then figured out that I had filled the tank with kerosene. What should I do? Will I have problems from here on out? I am sick just thinking about it.

Answer: Whoops! Drain the tank and refill it with diesel fuel. Then loosen one of the fuel lines by the fuel pump and replace fuel filters to remove as much of the kerosene as possible. It will take a while to get all the kerosene out before it will start.

Answer: You may have a bad main injector pump.

Question: 1989 Chevy 3500 Turbo Diesel mileage: 133,000. After the truck is hot, it will not start. The batteries are good and it will crank. When it is cold, it starts without a problem. After it starts, it runs without a problem, but if I have to shut it off, it has to cool down to restart.

Answer: What we have found is that when the starter solenoid gets hot it will not engage the starter. If you don't have one already, check to see if there is a heat shield that can be put on. Also, check with your local supplier to see if there is a high temperature starter available.

Question:   1985 Ford E350 Diesel Van mileage: 72,000.  Having trouble with cold starts on this work vehicle.  When cranking to start, sounds as if engine is not getting fuel, but it usually starts after prolonged cranking and pumping of accelerator.  We have had fuel pump changed, injectors, fuel filter, cold start solenoid, and there has been little improvement.  As a result, starter and battery are taking a beating from all the extra starting work.  This problem seems to be directly related to the temperature in our shop.  We have heat in the garage, but it only keeps the place about 50 or so.   When we get cold weather (10 - 15 today) the problem gets worse.  Would a crankcase heater help this problem?  I know larger diesel trucks have plug-in warmers for winter use.  Is this something we should look into?  How difficult is it to install?  Appreciate any ideas you can offer.

Answer:   Your hard start problems may be caused by a faulty fuel pump that supplies fuel to the main injector pump.  As for the warmers, check out the fuel pump first since you have apparently gotten by for a long time without them in the past.

Question:   1989 Chevy 2500 Silverado turbo diesel mileage: 155,000.  Engine stalls when traveling.  This happens occasionally.  When engine stalls, pull over and turn ignition off.  I then turn ignition on and start the vehicle and proceed to drive away.  Occasionally I will only put transmission in neutral when stall occurs, restart engine, and continue.  There has been no problem-starting engine at any time.  The trouble codes come out as 35, 36, 39, 68, 78; there is no code 12.  Hope you can be of assistance.

Answer:  Code 35 is injector pulse with error (short).   Code 36 is injector pulse with error (long).   Code 39 is TCC stuck off (transmission).   Code 68 is overdrive ratio error.  Code 78 is waste gate solenoid fault.

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Repair Topics / Diesel