I was handed down a 1986 6.2L K5 Blazer that’s been sitting in storage for a long time, but started regularly. My son has been using it for about three weeks, and a few nights ago it stopped running and would not restart. My first thought was clogged fuel filter.

I had it towed home. The next morning it struggled to start, but did start eventually, but only with me holding my foot to the floor. It idled for about 30 seconds and stalled. I did not try to restart it. This again seemed like the fuel filter to me, and enough fuel worked its way past the clog over night to get it to start, but it is still clogged.

I have never owned a diesel before but do have experience with gasoline engines. My understanding is that because there is no ignition system, the only thing that could stop a running diesel from running is lack of fuel.

Yesterday I got a new fuel filter. I noticed the four holes were labeled inlet, outlet, sensor, and drain. I blew some air into the inlet, and it easily came out the other three holes. I put my fingers over the sensor and drain holes, and air still easily came out of the outlet hole. I wanted make sure it worked like any other inline fuel filter, so when I removed the other filter, I could test it in the same manner to confirm it was clogged.

Before I replaced the filter, I opened the drain on the fuel filter housing and caught the fuel that came out. Absolutely no water. I removed the filter, drained out the fuel, and tried to blow through it. It seemed completely clogged, as I was hoping.

I installed the new filter. I hooked jumper cables from my car to the blazer to try to keep the batteries fresh. I turned on the ignition and waited for the glow plug light to go off. I cranked the engine over for about 10 seconds. I opened the bleeder valve on the top of the fuel filter housing to bleed out some air. I got nothing but air. I repeated this procedure four more times. I started getting fuel from the bleeder screw. I cranked the engine over again, and it sputtered. The next time I held my foot to the floor, and it started, but stalled as soon as I let of the gas pedal. I started it again, with my foot to the floor, and this time kept on partial throttle to keep it running. After a few seconds I let it idle, and was very happy it was running and only had a clogged fuel filter. I removed the jumper cables, and a few seconds later the alternator starting squealing. My son told me it had also done that to him the other day. I went back inside to look at the voltmeter. It was clearly not charging. It was sitting at 8-9 volts. A few seconds later it stalled. I hooked the jumper cables back up, and was able to get it to sputter a few times, but never able to get it to start and stay running. At first there was clearly fuel coming from the tail pipes, but after a while it didn’t seem like fuel was coming through again. The batteries were not holding up well, even with the jumper cables, so I decided to call it a night.

I am a big believer in fixing what you know is broken, so the next thing I will do is replace the alternator, but I was looking for peoples input as to what they think might be going on.

Could there simply still be air in the system, and I just need to run it a little more before it starts to go back to normal?

Could the bad alternator and having only 8-9 volts cause the injector pump or something else to not work properly, and that is why it stalled out after I removed the jumper cables? It did exactly the same thing the day before, BEFORE I replaced the fuel filter. Maybe the fuel filter was never the problem? I couldn’t blow any air through the filter I removed. Could I have had two problems at the same time? Seems unlikely.

Any ideas or thought would be greatly appreciated. Thanks.

 

Low voltage might be the cause of the stall if the electric fuel shut off solenoid (if equipped)could not remain open?