The smell of fuel

[smac]

I have a '91 6.2L Sub. with over 200K miles on it. Lately, I see white smoke out of the exhaust, the engine feels like it is stumbling, and I smell fuel when I try to go into OD. It seems like the engine has too much fuel, or the fuel isn't being combusted fully. I would have thought that that would happen all the time though. Does anyone think it is a timing problem or have any ideas?

[john8662]

Seen this before, if it's just occasional, maybe its been sitting awhile? This is signs that the injection pump is on its way out and is weak, I notice that they run much better after a good hard acceleration. The white smoke is a sign of running too lean, or the firing temp is too low.

[smac]

I follow what you are saying, the engine really struggles when I am going uphill or an incline. That is when I see the white smoke and smell raw fuel. The engine also surges when I go around a sharp bend. I have some basic mechanical skills, is switching out an injector pump possible for a basic machanic? Is an injector pump the same as a fuel pump? Do you have any idea on what a garage would charge to do this?
I really do appreciate your help on this.

[john8662]

First and foremost, change the simple things before changing the injection pump, from your second description it sounds like its re-ocurring. First thing, go purchase a new fuel filter, this should be around no more than $20. Replace the filter, and follow the procedure of purging the air out of the new filter before your initial start. This includes removing the old fuel filter from the filter holder on the firewall, the installing your new filter. The next thing you will do is open the valve found on the fuel filter housing that is on the upper left hand corner of the holder. Then locate the ignition wire on the injection pump itself (under the cruise control servo and behind the thermostat crossover). Unplug the large red wire, then go inside and crank the engine over, the engine won't start, you will crank the engine in 10 sec intervals letting the starter cool for 2 minutes between cranks until you get diesel fuel coming out the petcock near the valve you opened. It helps to have a hose connected to this petcock to avoid making a mess (have that hose go into a jar, etc.).

If changing the fuel filter doesn't do the trick (after drive), then change your fuel lift pump on the side of the engine, with that kind of mileage, its suspect as well as the final injection pump.

Keep us posted.

[smac]

Tonight I replaced the fuel filter with a Purolator brand filter, I primed it as instructed, and took her for a run. She is back to running well when I step on it or try to go up a hill. I want to thank you for your assistance with this. That fuel filter probably hadn't been changed in over a year so I know that it was due. I think that I will take the advice of the members of this page and replace the fuel filter a lot more often than I was.

Thank you again for your help. Diesel's rock. Everyone on this page has been very helpful and friendly. I won't hesitate to ask other questions when the situation arises.

I did have one question. I unplugged the large red wire as instructed, turned the engine over for 10 seconds and then let it cool for 2 minutes. At the end of the third go of that, I thought that the engine was starting. But I stopped turning the key and didn't let that happen. Did I unplug the wrong wire, or was the engine getting enough fuel at that point to start? Just wondering for future reference.

SmacDiesel

[john8662]

If it didn't start while you were cranking it the first two times, I suspect you have the right wire. There are three wires that go to the injection pump, that are single wires. The large wire is the ignition and will be a 10ga wire. I don't know why it would sound like it was starting unless the wire still still close enough to touch the terminal. Glad that you have the engine running well again! Its a great feeling when things work!