Injector pump leaking (78 BJ40)

[dieselDaryl]

I've been trying to resolve an intermittent problem with the fuel delivery on my 78 B motor. It's an intermittent problem what rears its head occasionally in two forms:
1) At idle it has almost died completely once or twice. Giving more pedal has resulted in it almost stalling out.
2) When running at faster speeds (4th gear) tilt I can sometimes hear it miss, usually when decelerating or at light throttle. It did it on the downside of along uphill run.

It only ever happens when the truck is warm. Idle is almost always smooth and at the same RPM.. Doesn't go up or down (except once when it gradually decreased and ran rough and stalled out. Once I started it, it idled perfectly again)

Any ideas? I've checked the fuel lines and haven't found any leaks. Fuel filter has been replaced. The fuel system has been primed repeatedly. I don't think that it’s the diaphragm because idle is relatively consistent. I was thinking it could be a vacuum problem until I had a look today and spotted a leak on the injector pump. Since diesel is getting out, I assume that means air can get in. I've looked through the archives but can't find the purpose of this screw. Can anyone tell me? Is this the drain screw at the bottom of the diaphragm?

[canucksafari]

Daryl, I don't know that IP but I am willing to bet there is a o ring behind that screw which is shot. The others seals may not be too far behind it. The cheap fix would be to remove it and replace the o ring (viton type material only). If it is a set screw, then count the rotations and mark it with a dab of white paint. Put on the new O ring and re-install. The better but more expensive route would be to pull the IP and replace all seals (and maybe have it checked for a rebuild). I was in your shoes last year just before Christmas. In my case it was a small O ring from the timing nut. I went the expensive route as my IP is gear driven off the crank and it has an O ring on the IP drive shaft which requires it to be pulled apart. If that little seal went on mine it would dump diesel into the sump. So it made sense to bite the bullet. It sure does suck to have to pay that around Christmas.

[dieselDaryl]

Well I don't want to spend too much time or money on the B in there as I have a 3B sitting here that will get rebuilt and swapped in at some point. The B has been running decently since I've had the truck so I don't want to give up hope on it yet.. I'm just worried that whatever the problem is, it's going to get worse when I'm out in the middle of nowhere..

Does anyone know what that screw is actually for?

[lostmarbles]

I've got the B diesel too and I think the injector pump is exactly the same on both the B and 3B engines (but I could be wrong - as always).
Just had a sqizz under the bonnet of mine and it sure looks that leaking screw/bolt goes into the part of the injector pump where the diaphragm sits. In other words it goes into the "governor housing".
In fact it looks like it would thread into the intake-manifold-venturi-vacuum-side of the diaphragm.
So I wouldn't expect diesel fuel to be behind it.

Anyone with any more clues on this?
Here a drawing from the engine manual:

[canucksafari]

It could be engine oil on the bolt. Inline IPs are crank lubed. If it is engine oil (smell), then Daryl don't assume an air leak is causing your problems. I am assuming you have replaced your fuel filter. Does your IP have a screen filter at the inlet? If so, I recommend you check it. These screens rarely get attention and they do get clogged up. On the rotary pumps it is just under the banjo fitting of the feed line at the pump.

[Moe R]

If the B and 3B are the same that is to drain a small anount of oil that seeps in there.U do this when you preform an engine oil change.There is no fuel behind that screw. There should be a copper washer behind the screw. There is an inline screen ur susposta clean every now and then.I did mine and put pics on here. I'm computer challanged or I would bring it up for u. but u should be able to find it. Good Luck.

[lostmarbles]

Originally Posted by Moe R

If the B and 3B are the same that is to drain a small anount of oil that seeps in there.U do this when you preform an engine oil change.There is no fuel behind that screw. There should be a copper washer behind the screw. There is an inline screen ur susposta clean every now and then.I did mine and put pics on here. I'm computer challanged or I would bring it up for u. but u should be able to find it. Good Luck.

Wow. Thanks Moe.

Always pays to try and help others because you often learn yourself in doing so. As is the case for me here.

Cheers

PS. I'll undo mine when I get a moment and let you know what comes out (after almost 30 years of never being undone)

[lowenbrau]

MO is right.

Sometimes they get so full of oil that it does affect how the fuel rail moves, relative to the throttle. Everybody should drain theirs every decade or so.

[Moe R]

I'm not so sure I'd wait a decade to drain her but every now and then is probably fine. I have a maint. bulletin somewhere I'll post if I can find. Anyway, I think Daryl's air leak is learking in some other area. Time to break out the Columbo, (dective on TV) trench coat and look for more clues. U could hook up the 3B and still have the same problem. I don't think I'd give up on a good motor but I might turbo it

[dieselDaryl]

I suppose I could hook up a clear tube to see if there is air in the fuel supply. But the problem seems to be so intermittent I'm not sure if it would help. The occasional missing doesn't bug me all that much but it almost dying at idle twice does.

The first time it happened it was a slow decline over a few minutes at idle when I was stopped at the side of the highway. This was after doing 9 hours of highway driving without a hitch.

The second time it happened was in town at a red light after driving for maybe 10 minutes or so. I thought about it being due to a bad fuel pickup in the tank, but in both cases the fuel tank was at least half full.

and yes, the fuel filter was one of the first things I changed..Vacuum buildup in the tank maybe? blocked fuel return line?

As far as the turbo goes, I've been thinking about it. I've got the junker turbo and the garret->13BT Manifold Adapter. From what I've read a 3B head will mate up to the B. SO I've thought about using the 3B head and 13BT intake manifold on the B bottom end. That way it gives me a trial run of sorts before putting it all on the 3B bottom end..

Daryl

[lostmarbles]

Originally Posted by dieselDaryl

I suppose I could hook up a clear tube to see if there is air in the fuel supply......

If you get air out of the bleed screws (when you operate the primer pump) then you have an air contimination problem (probably from a tiny leak on the suction side of the fuel pump). In my opinion there's no need for the clear tube to back up that diagnosis.

..... The occasional missing doesn't bug me all that much but it almost dying at idle twice does. ....... in both cases the fuel tank was at least half full.........

Makes me think - Perhaps water contamination?
I regularly remove the plug in the bottom of my fuel tank to ensure I never get a problem from anything lying in the bottom of my tank.

.....Vacuum buildup in the tank maybe?..

I wouldn't go down that road. My tank often has a good vacuum on it and I have no problems

[dieselDaryl]

[quote=lostmarbles;2835179]If you get air out of the bleed screws (when you operate the primer pump) then you have an air contimination problem (probably from a tiny leak on the suction side of the fuel pump). In my opinion there's no need for the clear tube to back up that diagnosis.
[QUOUTE]
Okay, I'll give that a shot..

Originally Posted by lostmarbles

Makes me think - Perhaps water contamination?
I regularly remove the plug in the bottom of my fuel tank to ensure I never get a problem from anything lying in the bottom of my tank.

It could but but I regularly run Howes through the system. Maybe I'll run the tank really empty and then drain the bottom..

The strange thing is I never have noticed a loss of power at high speed/RPM... ever..

[Moe R]

X2 on the vacuum mine has a ton and is fine.I like it cuz I feel that vacuum=less free air=less condensation/water. Seems like it comes down to air or some asshat put a ping pong ball in ur tank and the rig has to be just right to give u problems. Pulling at straws here, still
air can be a tricky problem.

[Moe R]

Have u tried bleeding the injector pump housing?

[brownbear]

Originally Posted by lostmarbles

If you get air out of the bleed screws (when you operate the primer pump) then you have an air contimination problem (probably from a tiny leak on the suction side of the fuel pump). In my opinion there's no need for the clear tube to back up that diagnosis.

the filter is pre IP, once the return from the nozzles re-routes to the IP it never sees the filter again. So bleeding pre filter or at the filter only gets you an air free supply.

If you have a leak(air) at the IP or nozzles it will not be seen at the first bleed point. You need to crack the nozzle lines while running. See if foam comes out. Keep a rag up there and crack 1/2 a turn, one at a time. Otherwise the air just keeps moving about in there.

Drain that plug and tighten it up. See if that helps the idle issues.

If it doesn't just replace the diaphragm. Its 20 bucks and an afternoon. The governor is pretty pneumatic controlled. So it should be the first point of troubleshooting.

[lostmarbles]

Originally Posted by brownbear

.....once the return from the nozzles re-routes to the IP it never sees the filter again. So bleeding pre filter or at the filter only gets you an air free supply........

Hmm. This is something I don't understand Brownbear. On my B engine, the return from the nozzles joins the main fuel line just before the fuel pump (which of course is upstream of the filter). This means that any air bubbles that do get into that return line will indeed pass through the filter again (and so tend to get trapped at the top there - even if it is their "second time through").

PS. But I'm certainly not saying you should only bleed the filter. You MUST always bleed at the IP too. And in my opinion, whether or not you crack the injector nuts depends on just how much air has been allowed to get that far. A couple of tiny bubbles getting that far will usually either pass right through the injectors (as the engine does a little "miss") or end up back at the top of the fuel filter as described (via the return line).But any more than a few tiny bubbles, and you won't be able to start it without cracking those nuts.Well that's what I've found.

[dieselDaryl]

Thanks guys.. I'll try the suggested remedies in the next couple of days. Of course, I won't actually know if it made a difference until some time passes..

[Moe R]

I ran out of fuel once and the course of action is to bleed the IP first. U do this using the primer pump, crack that nut and see if u get any foam. In my case there was much air. Next bleed the filter, then finally the injectors. My rig would not even puff until I blead the IP. I had a friend come to turn the engine over for me while I cracked the injector nuts. He hit the starter and it started on the second try. I got a little foam from each injector and drove home. I'm sure bleeding the IP was the key. It may not be in this case but it is a simple procedure that might help.

[lostmarbles]

Originally Posted by canucksafari

It could be engine oil on the bolt. Inline IPs are crank lubed. If it is engine oil (smell), then Daryl don't assume an air leak is causing your problems. I am assuming you have replaced your fuel filter. Does your IP have a screen filter at the inlet? If so, I recommend you check it. These screens rarely get attention and they do get clogged up. On the rotary pumps it is just under the banjo fitting of the feed line at the pump.

Since I have the same B engine, I can safely say there is another "strainer" (screen filter) at the inlet to the fuel pump too. Since this one is located upstream of the "real fuel filter" (upstream of the changeable-cannister filter), it is much more likely to become clogged than any positioned downstream of it.

(Actually the B engine might not have one of these strainers in the banjo on the IP fuel inlet. I replaced that hose recently and can't recall seeing one there.)