84-6.2 chev farm truck

I use this truck for snowplowing on my farm. It has been hard to start lately. Will start then quit and have to crank forever before it goes again. I checked the fuel lines and have replaced the glow plugs. Today I removed and tested the mechanical transfer pump and it works fine. I started it and it ran for 2-3 minutes and quit. Can't get it to go now. How do I bleed the fuel system and also how long should the glowplugs stay on before starting?
Thanks, Don from Canada

I'm not sure I fully understand. Once it's running and warmed up is it OK?

The most common problem with any CK 80s diesel truck is getting a rust hole in the fuel somewhere between the fuel pump and the fuel tank. Since the fuel pump sucks fuel from the tank, once you get a hole somewhere, you don't get a fuel leak. It just sucks air, and won't start or run right.

Best way to diagnose IF you think you're sucking air is to hook up a gravity feed fuel source directly to the filter-housing. An outboard motor fuel tanks works great. Hook up the gravity tank, get it bled and started. If it runs fine then shut if of and retry later. If still find - then you can assume you've got a rust pinhole somewhere in the rear fuel line or fuel pickup. It's happened to every 80s GM diesel truck I own.

No, if you are sure you do NOT have a rust-hole problem, how about your pump? All the pump used on 6.2s were doomed to failure until they got updated in 1985. Since your's is an 84, I'm going to assume it already failed and was updated - but who knows? If it was NOT updated, it has the same plastic ring inside the pump that fails on many Deere AC, IH, Case, and Ford farm tractors. If it has failed, it will keep starting and then dying, over and over.

If you've ruled out all that, GM and the US Military also came out with another update kit to prevent the pump from getting air-bound and losing its prime - especially after being parked over night. The fix is a new regulator check/valve on top of the injection pump (cost $7), and a new stype fuel pump with better one-way check valves.

As far as the glow plugs and how long? What plugs did you install? Hopefull the German Beru plugs that Delco reboxes and sells as AC60Gs. They take longer to heat then the old ones, and need a good 12 seconds minimum to heat up. The older plugs took 9 seconds - and if you went longer they burnt up and blew up (junk).

sounds to me like u have a leak or sucking air on the inlet side of fuel pump. bleed it after filter, and at injectors.those glow plugs are 6volt i believe, so thats why they cycle on and off. should only be on for maybe 6 or 7 seconds at a time.those old ones were they burnt out or did you even check them?once its started you dont need the glow plugs anymore. inform what you find.

In addition to the "air" theory,

Fuel filter, glow plug controller, or gelled fuel.

If it does it when warm also, you've probably got a pump problem.

Allan

You have a very small leak in the orings at the fuel filter on the firewall. Is not cheap to rebuild the unit. One way is to by pass it and use a inline fuel filter. Back when I had a 6.2 in a 84 it done the same thing. I ran it for 3 yrs with the inline. They will tend to start and run for about 15 seconds then die. I ended up giving it a sniff of either to pop it off and get her running again. Much easier on the starter and batteries. It takes very little air to shut down a rotory injection pump.
Bob

I had a similar problem with my GMC 6.2. Finally traced it down to a pin hole in the intake line above the fuel filter sock IN THE FUEL TANK. About drove me crazy trying to find that. Check all duel lines, transfer valve, all connections, filter housing, etc. Mine has a Racor filter, and I could see the air build up in the plastic filter bowl. Stock filters are metal encased, and can"t see the air.

Owned a 86 and still own a 83 6.2. the inj pump will draw air at the throttle shaft after a number of years and may not show any external fuel leakage. Had it happen to both mine at least once. Had to crank like crazy in the morning. the end result was a rebulit inj pump. Yes you can just put a new seal in, but if you're that close youo might as well do it all the way.

I should have mentioned that my old 83 is a rust bucket now and last summer it developed a stall. After doing all the fundemental steps mentioned here by one by one bypassing the mech pump, the primary then secondary filter, I found a rusted out line right under the floor of cab.

Firewall-mounted single filter setup is after the fuel pump, not before. It's on the pressure side, not the suction side. If it leaks, it doesn't draw air, it just leaks fuel. Only the 1982-83 6.2 trucks have a filter on the suction side of the fuel pump. If an 84 is drawing air from the filter, it can only happen if the filter is completely plugged, or the fuel pump isn't working.

I am going by what the diesel shop told me. They sold for the manufature that GM bought the filter base from. I even replaced the filter to elimanate a plugged filter. I by passed the filter block and the problem was solved. Its something to do with the block itself allowing it to get air in some how. A $4 inline filter did the trick on that truck.
Bob

All the GM USA designed diesels used Stanadyne fuel and water filtering systems. GM Japanese designed (Chevettes, LUVs, S10s) used Diesel Kiki or CAV systems. Regardless of year, the filter has to stop particles bigger then 10 microns or the injection pump can sieze.

As I said previously, the 1984 system has one filter and it's on the pressure side of the filter, not the suction side. If the fuel pump is working, and the filter is not plugged or frozen, it cannot cause the injection pump to suck air. Leak fuel, yes. 1982 and 1983 is different since it uses dual filters, and one IS on the suction side of the fuel pump.

Probably any injection pump shop is going to be Stanadyne authorized, so that's probably the connection. Stanadyne/Roosamaster is the pump that all the later rotary Bosch, Lucas, and Diesel Kiki pumps are modeled on. They all had to buy rights from Stanadyne to build their own "copy" pumps.

1981-1983 C,K,G,P 6.2 diesels use an optional inline fuel heater. Stanadyne Model 75 two filter system. One filter on the suction side of the fuel pump and the other on the pressure side.
Most also have a water-purge valve at the fuel tank along with a water drain on one of the filters. Also has a filter restriction indicator that goes off with 14 inches of vacuum.

1984 All 6.2 C/K diesels starting in 1984 use the Stanadyne Secondary Sentry two-stage Model 80 filter system. One filter, but two-stage. The filter housing has a built-in fuel heater. 110 watts and comes on at 20 degrees F and shuts off at 46 degrees F. Also has a built-in water trap, drain, and water-in-fuel sensor.

1978-1984 5.7 diesels use Stanadyne Model 50 fuel filter system.

1985 5.7 diesels use Stanadyne Model NB9 fuel filter system.

1993 and up 6.5 diesels use Stanadyne FM100 fuel filter system.

Glow plugs - all civilian 1982 - 1985 6.2s came with Delco 9G glow-plugs. Now get replaced with Delco AC60G (made by German Beru). These plugs take longer to heat but have built-in current limiters to prevent burnout.

1982 - 1984 6.2s use a separate controller, relay, and inhibit switch. With original glow plugs, they stay on 8 to 10 seconds when first used. If replaced with the newer Delco AC60Gs, they have to stay on 14 seconds. Note that a bad diode in the alternator can trick the controller into not working.

1985-1993 6.2s and 6.5s have the relay and controller all in one unit. At cold start, it turns on the glow plugs for 6 seconds. If plugs get replaced with the new Delco AC60Gs, the controller needs to be modified to run 12 seconds.