85 6.2 no start

[Detroit Dan]

Was asked what I knew, so I told him I'd look online and see what Icould find out. All I know is 85 6.2 Chevy, something wrong with the glow plugs but if you mess around with the controller it will fire, but only with the throttle to the floor. It will run and sound fine for a matter of seconds, then die off every time. My guess was that the glow plugs are not vital to the scenario, because once it starts it shouldn't matter. I'm thinking fuel delivery problem. I think the filter was either checked or changed, reportedly the injector pump was replaced by the owner or previous owner recently. Not know if it ran since the pump was installed or not.
Is there a simple answer to what would cause it to start and run for seconds? A priming issue? I know when I had the 6.5s the filter holds a great deal of fuel, so it would run longer on what it carried, but I know nothing about 6.2s. Does kind of sound like it's running out of prime. He told me he thinks it has fuel pressure and isn't out of prime because if you crack the top of the filter it spews fuel. I'd like to be able to tell him it's something simple.
Thanks for any imput.

 

[just a number]

I'd first be looking for an air leak. it'll cause a whole lot of starting issues. make sure the gas cap is a diesel version too,see that one before, different pressure setting. also confirm is the water has been drained at the filter.

make sure he fixes the glow plug setup, unless you like extra work:rolleyes5:

 

[ak diesel driver]

the mech fuel pumps are known to suck air but still pump fuel,all without a drop of fuel leaking

 

[WarWagon]

1985 is a mech pump and the fuel filter boxes are known to leak air around the restriction sensor or something or other on them. The throttle shafts/advance piston also leak air on the IP. Possible the fuel pump has failed. How does the oil smell - Like Fuel?

The Glow plug controllers on those years... Just replace it with a 1993 model and rewire as necessary.

Starting and stalling is an air problem. Otherwise check the pink wire on the IP for constant 12V - that is all you need after it starts other than fuel.

How many miles on the injectors?

 

[just a number]

how to check for air/fuel leaks

These trucks were equipped with a combination fuel filter/water separator/fuel heater ("square" filter). If your truck is equipped with a "round" filter, see the procedure for early model trucks.

Hook an air compressor hose into the return line at the injection pump (IP). The line you want is the rubber one that goes into the front of the IP. Alternatively, you can stick the air hose into the filler neck, but that is not as effective.

You can also modify a fuel cap with a valve stem off of a tubeless tire and use an air chuck to supply the air, which works good.

Whatever way you choose, the next step is to open the air bleed valve. It is located on the top of the fuel filter mounting block. There is a hose fitting right next to it. Hook a hose onto that, and run the hose into a pop bottle (this will collect whatever fuel you bleed out). With the fuel cap on tight, turn on the air to about 4 psi. Give it some time to fill the fuel tank. Fuel will start to flow out of the bleed valve and into the pop bottle.

When the pop bottle is about full, close the bleed valve. Then turn off the air. Disconnect the air line, wait for any remaining pressure to bleed out of the tank, and then reconnect the return line to the IP.

If you used the modified fuel cap or the hose in the filler neck, you can ignore these last few steps.

Once you have bled the air out of the system to that point, you may need to crank for a while to get it to start. It is not necessary to loosen injector lines to bleed the system to the injectors on the 6.2. Simply crank until it starts. You will need to do this in several cranking sessions of about 15-25 seconds in length so that you do not burn out the starter.

Utilize air pressure to test your fuel supply system for leaks. The procedure for connecting the air is the same as the one used to bleed the system, however you don’t loosen the fitting at the fuel filter (on 1982-1984 models) or open the bleed valve (on newer models).

Once you have the system under pressure, crawl under the truck and look for fuel leaks (it might be a good idea to wear safety goggles when you do this). Work slowly from the fuel tank to the injection pump. You need to look very closely, because any leaks are likely to be very slow leaks. Check every connection, every hose, the fuel pump, the fuel filter(s), and the tank switch (if the truck has dual tanks). In short, check everything.

When you think you’ve checked everything, go back to the fuel tank and start over. A good thorough inspection should take about fifteen or twenty minutes. Anything that is just barely seeping fuel needs to be repaired. Fix any leaks, test it again, and when you get to the point where it no longer leaks, bleed the air out of the system.

Replace the rubber hose on the return line with a clear hose before you start the engine. Start the engine and let it run for a while. If it runs good, take it out on the road for a short distance. Then look at the clear hose and look for any bubbles. If there aren’t any, you are probably in good shape.

If everything looks good, but the engine won’t start the next morning, you probably need to replace the fuel pump. Replace the pump, bleed the air out of the system, and you should be in good shape.

this write-up is thanks to HIGHSIERRA2500 on the dieselplace.

 

[Detroit Dan]

thanks guys. so essentially Im looking for it to be sucking air someplace, which would not necessarily result with big fuel leaks?

 

[just a number]

something as simple as a weeping line will add up to a leak. check real close around the front crossmember. lots of crap gets piled in there(snow/salt,mud). the hangers(where it bolted to the frame is another bad spot.

 

[iamdave0887]

1985 is a mech pump and the fuel filter boxes are known to leak air around the restriction sensor or something or other on them. The throttle shafts/advance piston also leak air on the IP. Possible the fuel pump has failed. How does the oil smell - Like Fuel?

The Glow plug controllers on those years... Just replace it with a 1993 model and rewire as necessary.

Starting and stalling is an air problem. Otherwise check the pink wire on the IP for constant 12V - that is all you need after it starts other than fuel.

How many miles on the injectors?

85 and up was the exact same GP controller as the 93. 82-84 was the crappy one with the "controller" and the fender mounted relay. My 85 has the gray all in one setup from the factory.

To the OP, as far as your problem. Sounds like a bad seal on the restriction switch. May not leak much fuel save for a few drips, but lets a ton of air into the system when the engine is off.

Had this issue with '85 K-5. Took tons of cranking and "foot to the floor" to get it started, then sometimes it'd stall sometimes it wouldn't, but it would run like crap and cough/sputter until the air was bled out.

Also had the issue with fuel in oil due to a bad mech LP. Ditch the mech LP and put a blockoff plate and an electric pump in instead. You'll thank yourself the first time you've got to change and re-prime the system when you change the fuel filter.

 

[WarWagon]

My 1988 1/2t burb had a grey GP controller, but, the controller used a switch in the head to turn it off when the engine is hot vs. the internal sensor of the 1993. The 1988 also had a large cap in it that was prone to breaking loose and bouncing the contacts. (Chattered with the glow plug light flashing while overheating the plugs.) Both the sensor and the cap failed on mine at one time or another causing the glow plugs to break in the engine and impact in pistons.

The older round units are the horrible one I refer to. Thx for the year update on that.

The 1993 being an all in one unit is why I recommend it esp after the head sensor cut out switch nearly cost me an engine on the 1988.

 

[Detroit Dan]

well, to clarify, its not mine. it belongs to a customer who brought it into the shop of the company I drive for. Tech asked me because he knows I've had some GM diesels (6.5tds). All I know is owner had someone remove the injector pump, send it to Phoenix for rebuild, got it back and installed and it's still doing the same thing. Which tells me, the IP isn't the problem, but what do I know I'm just a truck driver. They have ruled out the solenoid. All the fuel lines and the lift pump were replaced a year ago (its sat since then). Tried telling them to test for air leaks, no one wants to listen.
Now a diesel guy has looked at it and thinks there's something wrong inside the IP. I'm questioning if the fuel in it is even any good, it's sat for a year plus. They refuse to put the line into a can of fuel to try it, which should prove the pump works. Fuel filter is full, but I bet they dont know if its full of water. I heard it run today for about 10-20 seconds, motor sounds great, runs too good to have a timing problem or bad injectors.
Oh well, we tried. Thanks for the help. I'll let you know if they ever do figure it out.

 

[just a number]

well atleast nobody can say you didn't try, and you might even get to say "I told ya so".:agreed: we'd all like to know the solution if you do find out.

 

[Detroit Dan]

a diesel guy (heavy truck) says he thinks its the governor. The IP has been pulled and sent back for rebuild.