Bleed fuel system

[Toddnj]

Thanks in advance. I know there are many threads on this topic but none seemed to give me what I needed. I changed the fuel filter on my 1982 k5 chevy blazer, 6.2L diesel. Air got introduced to the system and now it won't start. Realize I need to bleed it but can't figure out what this actually means. Attached are some pics. On another thread I saw the statement, "you gotta bleed the lines at the injectors.... with the starter. crack'em all loose a turn or 2 then crank until at least a few or all start weeping fuel then retighten." I'm new to diesel so I'm not really sure what, in the pictures, needs to be loosened... or where they are. Please help!

[DmaxMaverick]

Welcome aboard!

What you are looking for is not pictured. The "injector lines", where they need to be loosened for bleeding the injector lines, are at the heads, about where a spark plug will be on a gasser, except they will have fuel pipes/nuts instead of wire boots.

However, you may not need to do any of that. If it's air-locked due to opening the high pressure side or installing a new pump, it may be necessary, but you aren't doing that. If only after a filter change, the first thing you need to do is bleed the filter. Normally it's simple, so take notes for future changes......

Charge batteries, if necessary (this time, it shouldn't be necessary next time).

Disconnect the pink wire from the injection pump (forward-most on top, to the left of the return hose outlet on the pump in your #2 pic). This will prevent any (further) air from moving to and through the IP.

Open the bleed valve at the top of the fuel filter assy. Route a hose from the bleeder to a container, if possible (not required, but a lot less messy). If you have a helper, have them watch for fuel coming out of the bleeder, then signal you.

Crank the engine starter. Stop cranking when fuel comes out of the bleeder. Don't worry about how much, just a stream.

Close the bleed valve. Replace the pink wire at the injection pump.

Attempt to start as normal. You may have to crank the starter more than usual, so be careful to not overheat it. It may take several attempts, but crank no more than about 20 seconds at a time, with 5 minutes between attempts to allow the starter to cool. When it "tries" to start, apply a little throttle to help it. When it starts, throttle it enough to keep it just off idle. It may surge up/down until all the air is purged. Once it will maintain an idle, drive it. The higher engine load will purge the remaining air more quickly.

Do this after future filter changes, and it should be a simple task, with very little effort and time. Often, you won't even notice a starting difference once complete. Many folks recommend "pre-filling" the filter. I do not. Introducing the chance of getting unfiltered fuel into the clean side of the filter, defeats the purpose of the filter. The lift pump will fill it very quickly (10-15 seconds) if the above steps are followed.

[Toddnj]

Thank you. I created more of a problem that I needed to. I realize this after all the research I've done, which is also supported by your answer. I changed the filter and did not bleed it. Rather I started the engine. It ran fine until all the fuel that was in the lines went through, then it stalled. duh!

I have since bled the filter and am confident there is no air in the line up through the filter output. From there, there is air in the lines. Some posts I have read state that I merely need to crank the starter and eventually it will start. Do 15-20 second bursts and wait, repeat. I have a trickle charger on so I go out every 20 minutes and do it. Will this eventually work, or do I need to loosen the lines? Here is a picture down lower under the air filter. Are these the lines that need to be loosened (that is if then need to be...)?

Previous owner put glow plugs on a buzzer button. So can I just keep cranking the engine and then periodically heat up the glow plugs before trying to start?

Thanks again!

[DmaxMaverick]

Thank you. I created more of a problem that I needed to. I realize this after all the research I've done, which is also supported by your answer. I changed the filter and did not bleed it. Rather I started the engine. It ran fine until all the fuel that was in the lines went through, then it stalled. duh!

I have since bled the filter and am confident there is no air in the line up through the filter output. From there, there is air in the lines. Some posts I have read state that I merely need to crank the starter and eventually it will start. Do 15-20 second bursts and wait, repeat. I have a trickle charger on so I go out every 20 minutes and do it. Will this eventually work, or do I need to loosen the lines?

It will eventually start, if it's in a running condition (except for the air). At this point, you shouldn't be too far away from that. You can speed it up by loosening some of the injector line nuts. Only loosen the ones you can easily reach. The engine will start with only a few, then the others will catch up as it begins to clear. After 3-4 of your priming cycles, try it with some glow and it should start, or at least try to start. Note: it may be quite smoky until most/all the air is purged, and it's warmed up.

If you continue what you've been doing, you'll probably have it started before reading this reply.

Here is a picture down lower under the air filter. Are these the lines that need to be loosened (that is if then need to be...)?

NO!!
Right lines, wrong ends. The injector line bleeding is at the other end of those lines at the back of the pump. You should be able to easily see some of them at the (out)side of the heads, with small rubber/braided hoses (return lines) leap-frogging from one injector to another. Use a wrench on the injector body (upper) and one on the line nut. You ONLY want the line nut to turn, not the injector, or upper half of the injector. They should be very tight, before and after. Only crank the starter until fuel weeps slightly. Any more is just more mess, with no more gain.

Previous owner put glow plugs on a buzzer button. So can I just keep cranking the engine and then periodically heat up the glow plugs before trying to start?

Nothing wrong with that. All of mine are like that (older Diesels), which I prefer. Depending on the type of glow plugs you have (may be VERY important), glow cycle methods can vary. If you have AC-9G plugs (original type), plan on replacing them at your soonest convenience. They swell when they fail, and get stuck in the head. Not critical, but a real PITA, and never at the right time. 8 second glow periods maximum, period. 11G plugs don't fail, but don't last long when glowed long periods. 8-10 seconds at a time. 60G plugs last a long time and don't swell, but may require double the glow time, especially during winter. No worries, with your setup, but not a "fast" plug. If you have Quick-Heat plugs, follow the suppliers recommendations. Usually 8-10 seconds is all that's needed to get them to full heat in the coldest winter. Less is required during warmer times. After-glow as needed to smooth the cold idle and clear up smoke. Not required, though. The engine will warm up quickly beyond that need.

Thanks again!

You're welcome!

[Toddnj]

I continued to crank the engine but it has not worked yet. On the way to work this morning I wondered if maybe cranking the engine was not moving any fuel. So after work I just disconnected the fuel filter outlet hose and cranked the engine. There was no fuel coming out. Should I have expected to see fuel come out of the filter output hose while cranking the engine? If so, what does this tell me?

I did not crack the FI lines because I wanted to figure out if maybe I have another issue?

[DmaxMaverick]

Your fuel lift pump may have gone south. In a closed, previously running system, the fuel lift pump can quit pushing fuel, but the injection pump is able to pull fuel. This usually causes power loss and delayed response, but a healthy IP can be barely noticeable. The IP's do well to pull fuel, but don't prime themselves well after you've allowed air in, such as you did.

Disconnect the filter inlet line and check for fuel flow. After verifying flow, install a fuel gage on that hose and crank. It should produce 4-7 PSI quickly. If you get good flow and pressure, check the operation of the filter assembly and element. A defective or incorrect filter may not allow fuel flow.

If you get very little or no flow/pressure, suspect the lift pump. It's located at the lower/right/front of the engine (looks exactly like a gasser mechanical pump). It has a weep hole at the bottom of the pod, and if it's wet with fuel, the pump diaphragm has ruptured. They can also fail in other ways and not leak, such as failed check valves. If you have to replace the pump, it isn't difficult, but there are some tricks and shortcuts, so come back before you start. Use ONLY a GM, Delco, or Delphi pump. The others are junk.