New to the forum so thanks in advance for any advice/help. I have 1983 GMC with a 6.2. Had been running fine. Was in driveway idling for about 10 minutes and died unexpectedly. Now it won't crank. I am definitely a rookie when it comes to diesels so apologies in advance for any dumb questions or answers. Here is what I have checked so far (note this truck has two spin-on style filters, one between tank and lift pump and one between lift pump and IP):

- Did not check glow plugs or anything related to glow plugs because engine was very warm when it died, and immediately would not start again where previously it would if engine was warm, but maybe I should?
- I did notice on the primary filter (between tank and lift pump) that the peacock was cracked open a little, but I don't know how long it may have been in this position.
- That led me to remove primary filter and did notice it was not full of diesel (about 1/2 full).
- I topped it off with diesel and re-installed.
- I disconnected pink wire from injection pump, opened peacock valve and cranked engine. Nothing coming out of peacock valve.
- Closed peacock valve and disconnected inlet line to secondary fuel filter (after fuel lift pump). Disconnected pink wire to from the injection pump and cranked. Fuel shot everywhere.
- Reconnected that line and disconnected the "out" line from the secondary filter (one that goes to IP). Cranked and fuel shot out from filter everywhere.
- Also turned on ignition, disconnected pink wire to IP and touched it to the terminal on the IP solenoid. I can hear it clicking so assuming it is working?

In summary it appears that fuel pump is working and so is solenoid on IP. Any thoughts on what may be wrong or what else to check?

Any help is greatly appreciated.

 

First, just to clarify: In the subject and first paragraph you say it won't crank, but you mention cranking it at least a couple times during your diagnostics. If it's stopped cranking, clearly that's the first thing you need to fix, but I'll address the fuel system.

That's most likely the source of the problem. If the petcock is open, it's sucking air through the petcock instead of fuel from the tank. If it died while running, the air got into the injection lines and will have to bleed out through the fuel return lines on the injectors before it'll fire again. The only way to do that is to crank it for a while; it'll go faster if you hold the pedal to the floor. Don't run the starter longer than about 15-20 seconds at a time, and let it cool down for at least as long as you ran it before trying again.

You can crack one or a few injection lines at the injectors and crank briefly to check for fuel there. But it's possible to have fuel there and air higher up in the line, and it won't pop the injectors because the air just compresses, and all that fuel & air has to leave before it'll pop the injectors and fire.

You're supposed to open the bottom petcock to check for/drain water, and open the top one to let air in so any water can drain. Other than that, they need to be closed.

All that did was suck in more air.

I like to have an electric pump before the primary filter/water separator, ideally at a low point like mounted on the frame. It's a big help in getting air out of the fuel system up to the injection pump.

 

Thank you very much for the response. First my apologies as you are correct: It cranks, but no start. I will go with your advice and give it a shot. A couple of side questions: Is it normal for the primary filter to be half full of diesel when you remove it? When you install the electric pump, do you wire it such that it is running while the truck is running or is it just used to prime? If used to just prime is the fuel able to flow freely via the mechanical lift pump when the truck is running?

 

No; any air in the fuel system means there's a problem. In this case, I didn't think of it before, but did you happen to find the bottom petcock not tightly closed? There's nowhere else fuel in the filter could go, even if the top petcock is open. Other than that, if air gets into the filter it'll leave before any but a tiny bit of the fuel, because the outlet is at the top.

I run it all the time, powered through the ignition switch; on my '83 Suburban it's connected to the 12v wire to the injection pump. But I suppose you could use it just to prime. I use solenoid pumps, like Facet cube, which have 2 flapper valves, so would add only minimal restriction when not running.

 

Success! I do think the valve was partially open on the top pulling in air, but I also think I had filter that needed to be replaced (can't confirm though). I will be putting in an electric pump close to the tank this weekend, and will use your idea of splicing into the IP solenoid "pink" wire. I do have a slight concern that the mechanical pump may not be pulling enough vacuum from the tank, but I have decided to tackle that one later.

Thank you very much for your responses and advice. I am grateful.