STRANDED- fuel delivery issue 8.2 DD

[silvermachine]

Hello all, my bus (1988 GMC 8.2L DD) is stuck where I parked it last in Chattanooga TN, and I live in Asheville NC so I’m trying to get back home. I am near a friends house so I am okay for the time being but I need to get this thing started ASAP.

It cranks over fine but won’t start. I sprayed a small amount of ether into the air box and it started up but quickly died so I know I have a fuel delivery issue. My original thought was that the fuel filters were gelled so I replaced those (they turned out fine) and put the correct mix of diesel 911 and antigel in the full fuel tank.

There is no primer bulb anywhere along the fuel lines so next I added a Holley auxiliary fuel pump near the gas tank. When I open the drain valve on the fuel filter housing, pressurized diesel comes out so I know it’s working. Batteries have been fully recharged, but it still won’t crank over.

I have a 1500w coolant heater & an oil pan heater so the engine being cold is not the issue here.

I think there may be air trapped in the lines somewhere but I’ve never bled fuel lines and there are no good tutorials on how to do that on this type of engine. Can anyone tell me how to bleed air from a fuel line on an 8.2 Detroit Diesel?

I’ve attached photos of where the fuel lines connect to the engine and the fuel filters. Is that little screw between the lines the bleed screw?

Any and all help is much appreciated!!

[joeblack5]

Google...

diesel engine trader 8.2 dd cranks, no start.. march11, 2011

Goes pretty deep..from air in line, bleeding procedure and stuck solenoid upto stuck injector that prohibit other injectors from firing, so I hope you are ready for that.

Good luck,

Johan

[Booyah45828]

How long has it sat? If it's sat for a while, the injector racks might be stuck. They typically stick wide open, but I imagine the could stick closed as well.

Detroits use a unit injector, so there aren't your typical injector lines between the injection pump and injector for you to have air in, only a cavity in the head that is fed by the gear pump. The air in that would have bled when you fired it off of either, so long as fuel was present to the gear pump.

I'd be looking at the governor housing and checking that the shut off solenoid is operating, apart from that, they're typically pretty reliable starters.

[cadillackid]

Originally Posted by Booyah45828

How long has it sat? If it's sat for a while, the injector racks might be stuck. They typically stick wide open, but I imagine the could stick closed as well.

Detroits use a unit injector, so there aren't your typical injector lines between the injection pump and injector for you to have air in, only a cavity in the head that is fed by the gear pump. The air in that would have bled when you fired it off of either, so long as fuel was present to the gear pump.

I'd be looking at the governor housing and checking that the shut off solenoid is operating, apart from that, they're typically pretty reliable starters.

does the 8.2 use the same injection system the old 2 strokes did?

ive had to free those racks before

[Booyah45828]

Yup, mechanical unit injector actuated off the camshaft. Not a bad system, just throws people for a loop as it's not as common as a pump-line-nozzle system, especially on medium duty engines.

[silvermachine]

Originally Posted by Booyah45828

How long has it sat? If it's sat for a while, the injector racks might be stuck. They typically stick wide open, but I imagine the could stick closed as well.

It hasn’t sat for more than a week without starting it up. I suppose I’m prepared for it to be an injector issue. After all, with this auxiliary fuel pump now installed, if it was a fuel pump issue or just air trapped in the lines, wouldn’t that be taken care of by this? I’ve seen people say it could be a shutoff solenoid or injector pump. But I’m prepared for the worst.

I’ll be looking at it more thoroughly later today. I’ve got a diesel mechanic coming over. If anyone has suggestions for a streamlined order of operations here/ any more suggestions for things to look at I’d sure appreciate it.

[silvermachine]

So it turns out it was a vapor lock in the fuel lines. Not an injector issue thankfully. We used the auxiliary pump and cranked the bus while cracking open the fuel send lines and all the air slowly bubbled out. It started after about 10 minutes of this. Relatively easy fix and I’m back on the road!

Also, it turns out the fuel pump isn’t electronic, it’s some type of hydraulic system.

[bus-bro]

Maybe the 8.2, but an old 6-71?

[joeblack5]

Why would you say that, ??

Unit Injectors are as good as it gets.
Pressures can be higher and that gives a cleaner more efficient burn... You need to carry only one spare and is relative easy to replace and a lot cheaper then a whole inline pump.


You need to read up and study more. It is sad and expensive that you need a mechanic to solve an air bubble.

Good luck
Johan

[Booyah45828]

No such thing as vapor lock with a diesel. You've likely got air intrusion from a leak in one of the supply lines or in the seals on the lift pump itself.

Put the fuel return into a 5 gallon bucket, start the engine and look for bubbles. If you have them present, you've got air intrusion and you'll need to find the source.

[cadillackid]

I had an issue with my DT360.. sicne the Lift pump on mine is at the injection pump, thwe whole fuel system.. lines, water separator, filters, are all on negative pressure.. so a leak is never a visible leak.. I never saw fuel burt when it was hot outside and the bus would sit a couple hours.. . . the bus would run 10 seconds then stall.. id have to prime and prime then it would start and run...



hot diesel expands.. a lot.. then contracts when it cools.. at that slow rate.. instead of sucking fresh fuel from my tank it sucked air.. so next time I drove it, the fuel in the oinjection pump body would run out before fresh made it from the tank...



since it was never visible it didnt show up as a fuel leak being all negative.. I eventually found a banjo fitting that looked suspect.. so I took the line off where it came from the tank into the beginning of the near engine piping.. used a hand pump and pressurized with some fuel in a jug.. sure enough the banjo fitting got wet.. I replaced the bad short-line and bam! no issues since...

[Booyah45828]

Also make sure your holley pump has a high enough flow rating, as it could become a restriction if it doesn't. You didn't list any specifics on it so it's worth mentioning.

[Johnthebusboy]

How is the shut down solenoid? Had mine fail once, in the drive way.