Help bleeding diesel injection

[cobbkevin]

First time poster, long time listener!
I hope this isn't too long-winded, but I'm trying to give some background information. The tractor is an older Ford 3500 Industrial which is my first diesel engine. It was originally my wife's grandfather's machine. My FIL drove it to our house a couple of weeks ago (it had a lot of smoke and seemed running a little rough). The next day he started it and demonstrated the FEL and the back hydraulics to me (but he used starting fluid). Apparently SF has been used for recent memory.
The next day I tried to start it and nothing. It cranks but doesn't start. He came over and confirmed that it was in neutral, kill switch position, etc but he couldn't get it to start either. A shop mechanic came out and went through a quick trouble-shooting. He opened a bleed screw at the fuel filters and got nothing. He indicated that the filters must be dirty. I ordered new ones (and a shop manual). One filter was actually a sight glass / sediment bowl and was pack full of mud! These haven't been opened for 15+ years. I've totally cleaned up the bowl and installed a new filter element in the other side.
I've went through the process in the manual for bleeding (I think)! I've opened the top bleeder screws on the filter cover and they both flow freely. When I open the bleed screw on the side of the CAV injection pump and crank the engine it squirts about a foot stream. However, when I opened an injector line it only drips when I crank the engine. I then opened the hard lines (only 2 - I can't reach the back one) at the back of the pump up to the injectors. They only drip when the engine is cranked. I don't see any other bleed locations in the manual. Could the pump have gone bad from dirty fuel?
I don't think I've missed anything.
How does the kill switch circuit work? Does it stop fuel inside the pump from reaching the injector lines? If so, could it be stuck? I've manipulated it manually at the pump and it 'feels' like it twists but I don't have anything to compare it to.
Any thoughts would be greatly appreciated!

A diesel newbie,
Kevin

 

[john_bud]

Kevin,

Well, you sound like you have done all the right generic things. (always good to hear). I can't give any specific CAV pump input, just more generic stuff.

Yes, the pump can go bad from dirt. Easily.

As you may know, SF is bad stuff. It works in the short term, but can blow the ring lands right off the pistons. I just rebuilt a SF queen with 2/4 pistons with blown lands.

You may have a tired engine in the tractor. Do you have access to a diesel compression tester? Your shop mech may have the stuff. It would be good to know if the smoke and rough running was from a bad engine or just clogged fuel filter.

When you cracked the lines, did you have the "throttle" -- really the fuel control lever or some such technical name -- put in the middle. So it would run at about 1/2 of rated RPM? How full is the tank? A full tank will help the system bleed faster. How long did you crank the engine over? It may need 4 - 10 sessions of 15 seconds of cranking followed by 2-4 min of starter cool off time to get fully rid of air. Don't be afraid to have a charger on while doing this, your battery will like that.

good luck!

jb

 

[XANDROS_user]

JB, In response to your response may I ask a question: Is it feasible to attach a hand held mechanical vaccum pump (as used in bleeding brake systems) to purge /syphon the fuel to the injectors? Are there too many gates/switches/obstructions? Is it feasible to attach open hoses to injector lines? Saving the wear and tear on the battery and starter. I dunno. Just asking.....

 

[RobJ]

No I don't think it's worth all the trouble to put a bleeder system on the injector lines. If the lines are completly drained, it still only takes a half minute of turning to fill them up.

Kevin...didn't you say the tractor will run once started with SF? What color smoke? Was it still running rough at a high idle? Say max throttle? When cranking you should get a nice little spirt from the injector line because the governer has the throttle in max position. After it has run for a few minutes can you shut it off and crank it right back up without SF? Also while running pull one of the injector lines and see what sort of fuel is coming out.

Sounds like the pump will build up enough pressure when the motor is turning fast enough. Cranking is not fast enough. May be time to pulll the pump and have it tested on a bench.

Good Luck,
Rob

 

[higgy]

Depending on the engine and its design SF is not so bad. For example my JD 4020 has a SF distributor built into the system for use under 30 degrees, however, it does not have glow plugs.

on the injectors there are several things that may be incorrect/need tweaking.

When replacing the filters and cleaning the bowl, were you certain that you did not introduce contamination? I would think the answer is yes.

The pump that the individual lines are connected to is the high pressure pump that supplies fuel to the injector/nozzle, there is a difference. On a nozzle system the high pressure pump supplies the pressure to crack off the nozzle and introduce the fuel into the cylinder. With an injector it is supplied to the injector at a pressure less than required for opening the injector tip and a mechanical arm usually driven from the camshaft presses on the injector which is also a small pump and squirts the fuel into the cylinder.

The nozzle type is more prone to air than an injector.

I am assuming that you have injectors. The place to bleed the injectors is where the hard lines meet the injector, not at the pump. I normally loosen half of the injectors on the engine at the joint to the hard line. Do not back the coupling off so far as to be disconnected, just loose.

Roll the engine over, when you start to see fuel dripping from the connectors tighten them up, if you can get someone to continue rolling the engine while you do this. Many times the engine will start while you are tightening the lines up, or before you get them all tight, that’s ok.

When you get ready to fix this long term as stated before you will want to have the fuel pump bench tested, the other thing to do is pull the injectors and have them tested as well. Injectors get old as well and stop providing the proper pressure for the fuel when injected, when this happens the fuel will not atomize correctly. This can lead to black smoke, hard starting and if bad enough engine damage.

 

[patrick_g]

If you do get the engine running again, you still want to bleed each injector one at a time. Only loosen the connection at the far end of the line away from the high pressure (sometimes called the distributor pump) and only loosen it just enough for a small fuel flow. Don't get in too much of a hurry. Let a little fuel run out to ensure little or no air left behind. Tighten that connection and go to the next. Do them all.

Often there is a place to bleed air from the fuel system at the highest point in the fuel system (where air would naturaly accumulate) On my Ford there was a Schrader valve in the fuel system next to the filter before the high pressure pump. I used a Schrader fitting and plastic hose from a can of "Instant Spare" to make bleeding easy.

With the engine running I screwed the hose's fitting onto the Schrader valve and uncrewed it when all the air was gone and when just fuel with no air bubbles was being expelled into my tomato can. The fuel was clean so I poured it back into the tank.

There are other problems possible with worn out diesels. It has happened that a worn out diesel had so much blow by that oil fumes from the crankcase would make it into the combustion chamber and be burned as fuel. No harm no foul??? Well you can't shut the engine off or control its speed with the throttle. Kill switches don't help and turning off a fuel petcock will not help. The engine is getting air and fuel and conitinues to run, sometimes too well as there is no way to govern speed. You can block the air intake to kill it. You may have to give it the shirt off your back, wadded up and shoved into the air inlet.

Pat

 

[cobbkevin]

Thanks for all the help. I'll try again tonight. I might not have cranked it long enough. The only reason I opened the lines down at the pump was to see if the lines were plugged.
One of you asked if I started it on SF. I have not tried the stuff since I've cleaned the filters, I guess it might start and run for a second but I don't like using it unless it's a last resort. I'll keep fiddling and see what I can acomplish and let you know what I find out.
Thanks again!
Kevin

 

[john_bud]

Kevin,

As others have stated, I don't think you would get much gain in a vacuum bleed -- but I have NOT tried it. Might be interesting to try...

Also, I have never had to bleed after an engine was started. The air will purge from a running engine, at least in my exp.

Oh, If you have a helper. You can crack the lines open (yes, do all 3!!) and have the tractor pulled by a truck or other tractor. The "dead" tractor will need to be in high gear. Then close up the lines and pull some more. It will start and you can do that with a flat battery.

Post back with how it goes!

jb

 

[cobbkevin]

Well - no luck! I cranked and cranked but at best I only got one line with a drip up at the injectors. I'll remove the pump and take it to a shop. I think I've read that they can 'bench test' them to determine condition before they open them up. Taking it off seems like a DIY operation, but not cracking one open. That sounds much more like an expert-only operation.
Thanks for the tips! At least I don't feel like I've overlooked something obvious (like many times before)!
Kevin

 

[CATMAN]

Taking a fuel injection pump off may seem to be easy, but I warn you that it MUST be correctly TIMED to the crankshaft and camshaft when it goes back on! Normally, anyone who does remove a fuel injection pump on a diesel engine would first put the engine to TDC-1(Top Dead Center of # 1 cylinder) {#1 piston at the top and ready for the "power" stroke},then they would unbolt the pump and take it in to serviced. If one doesn't do this at the beginning of the repair, then a qualified mechanic would pull the valve cover and hand rotate the engine(going in normal engine rotation) and put the engine on TDC-1 by watching the valvetrain on the #1 cylinder. Remember that camshafts and fuel injection pumps rotate at 1/2 engine rpms, so looking at marks on the flywheel (or pinning the flwheel) doesn't necessarily mean you are on TDC-1. I recommend a knowledgeable mechanic reinstalls that pump. Too much timing(advanced) can and will melt aluminuim pistons on a direct injected diesel. This info is generic, as I am not knowledgeable about your specific tractor.