Rough starting diesel



I have a 91 F-250 with a 7.3L diesel, about a year ago gas was put into the tank. The truck then ran for about 30 miles and was shut off, it would not re-start after that. Once the problem was discovered tank was pumped out by a “professional” and I was told there should be no further problems. Since that time the truck as been difficult to start and progressively getting worse. It does start and either dies immediately or runs very rough with me pumping the throttle and smoking for about a minute then runs fine. Any thoughts?



How much gasoline was added to the diesel fuel system?



Did the truck not restart because the engine was locked up? Suspecting piston ring and cylinder wall damage.


No truck never locked up, it did not restart due to gasoline needing spark.

As far as how much I am not sure but memeory tells me about 12 gallons.

Remember it ran for about 30 miles then would not start again, and it may have nothing to do with the current problem although I am very suspious.



Naah. That 12 gallons of gasoline in the fuel system took out the injector pump if it was run over thirty miles. And now the fuel pressure is where it’s just sputering fuel into the cylinders where it’s not being atomized and it blows smoke out the exhaust.

Have the fuel pressure tested, and I bet it shows that the injector pump was damaged from running gasoline thru it.



i agree. your injectors may be junk too.


thanks for the suggestions! does this still apply even though the truck runs fine once it gets going?



Yes. When gasoline is added to a diesel fuel system it damages the seals in the injector pump. When cold, the injector pump can’t develope the proper fuel pressure and it makes the diesel engine harder to start, and when it does start it runs rough. Once the injector pump heats up and the components inside expand the damaged seals seal better, and the fuel pressure is restored and the engine runs normally.