bleeding the fuel system

[TStClair]

I just replaced the intake manifold gasket to try to find the 5-6 pounds of boost I have lost. I loosened the high pressure lines and now it won't start. Before it would start almost instantly.



I bled the low pressure side, the pump, and tried to bleed the high pressure lines. When I use the lift pump, I can't see any effect at each injector like I can when I bleed the low pressure side and the pump. I have a 1991 motorhome with the rotary pump. I energize the fuel solenoid with the key and pump over 200 strokes with the lift pump. With just #1 cracked, no fuel or air comes out. I also get the same result at the other injectors.



When I crank it with the starter, and one injector line loose, it leaks all over the place. I do each injector the same way and get fuel every time. But, it still won't start.



Two questions:

1. How do I check whether it is sucking air?



2. Is it possible to hook in an electric fuel pump between the lift pump and injection pump, and bleed the entire system that way? What is the thread size for the connections of the lift pump?



Any thoughts on the subject would be appreciated.



Tom

 

[DieselBuzz]

Bleeding out, so to speak

My system was dry, I cranked w/ the key so I had fuel leaking at each injector separately. It wanted to start even before I had them all bled. My only ideas would be to check the lines for leaks. Then make sure you have all of your electrical connections right and tight. Especially to the KSB and the fuel solenoid.

Art

 

[DieselBuzz]

911

I don't know if you have had any luck getting it going. You could try the 911 forum to get more help.

Art

 

[TStClair]

Thank you Art. What I will try is to crack each line at the injector as I crank it with a remote starter button. As the fuel comes out, I will tighten it up. I will then go to the next injector and do the same. It should start at some point (sound like wishful thinking?).



I spoke with someone at Cummins and he told me that every time I cranked the engine over, I let air into the system when I stopped cranking, and there was a loose line at an injector. So... if I tighten the fitting while it is leaking fuel and the engine is still cranking, it should not allow any air in.



We'll see. I won't be able to get to it until Saturday, so will let you know when I get it started.



Tom

 

[lcalder]

Originally posted by TStClair

Thank you Art. What I will try is to crack each line at the injector as I crank it with a remote starter button. As the fuel comes out, I will tighten it up. I will then go to the next injector and do the same. It should start at some point (sound like wishful thinking?).



I spoke with someone at Cummins and he told me that every time I cranked the engine over, I let air into the system when I stopped cranking, and there was a loose line at an injector. So... if I tighten the fitting while it is leaking fuel and the engine is still cranking, it should not allow any air in.



We'll see. I won't be able to get to it until Saturday, so will let you know when I get it started.



Tom

If you tried to start it with out any fuel coming out of the injectors at all you could have damaged them to a point where they are not spraying but squirting fuel and this will prevent the engine from firing up

 

[TStClair]

What I did today was to bleed each line at the injector as I was cranking it. I then used WD-40 in the intake manifold, and it almost started. I ran out of it, and got more. The new WD-40 didn't make it kick at all (they must have changed the formula since I bought the original can). I then got a can of starting fluid (eyther). It started right up, and I was able to keep it going for about 30 seconds, controlling it by the amount that I sprayed into the intake manifold. It sounded terrible, and I hated doing it because I suspect it is hard on it. When I stopped spraying, it died. If there was air in the lines, that should have cleared it out I think. It doesn't appear to be getting fuel, but when I crack the line at each injector, there is fuel present.



The suggestion that the injectors could have been hurt cranking it without fuel is new to me, but could explain what has happened. It just doesn't seem likely. It has always had fuel when I cracked the line at each injector. I suppose I can remove the injectors and have them tested, but it doesn't seem likely that that would be the problem, but at this point I am running out of options.



One thing I might check are the electrical connections. They have electricity to them, but I don't know if the cold start is suppose to all the time. If I am getting fuel at the injectors, doesn't it mean the fuel solenoid is working? Does the fuel solenoid either work or not at all? Is it possible to work a little? Should there be a click when I apply power to it?



It was starting fine before I replaced the intake manifold gasket, so I think it is likely to be air in the fuel system, or a bad electrical connection. This is discouraging.

 

[Matt S]

Are you sure you didn't knock off a wire to the shut-off solenoid? Using ether isn't the best thing for the truck. I'd look there first. You aren't getting the fuel/fuel pressure to run the truck. It would only run when you had starter fluid in it. When that was gone, it quite. Seems like it isn't getting fuel.

 

[illflem]

The way that has always worked for me when bleeding is to crack the nut at three or four injectors start cranking till fuel appears then tighten the nuts, will start then run rough for awhile. This is assuming you have fuel to the injection pump.

 

[DieselBuzz]

What the????.......

From what you have discribed it sounds like there is no fuel getting through the injectors. Why this would change with a gasket change on the manifold??? Got me. Injector damage, change in fuel pressure from the pump??? Hang in there and I hope you figure it out soon.

Art

 

[TStClair]

I just pulled the return line off and it has fuel flowing back when I crank it.



There is electricity at the fuel solenoid, and there is a 'click' when I disconnect/reconnect it.



All I can think of at this point is that the injectors were somehow damaged, although I don't understand how that might have happened.



I get a steady stream of fuel when I disconnect the return line and crank it, and I even get fuel out of it when I use the pump lift lever. There doesn't seem to be air in it either. The fact that I am getting fuel there implies to me that the fuel solenoid is working, and fuel is getting to the injectors.



I suppose the last step, before I call in professional help is to remove the injectors and have them tested. I have never heard of injectors being damaged so easily, but maybe...



I will let you folks know what the results are. Thanks for your comments on this head scratcher.



Tom

 

[BushWakr - RIP]

Just as an addition to all the other suggestions... . DANGER!! do NOT use ether especially if it is cold and the 'heaters' kick in. If you do you may discover what happens when extreme heat meets raw ether in the manifold !!!



Thats a piece of advice I got from a 2000 year old line haul driver in the interior of BC.

Ps: Good luck with the starting problem. I'm curious to know what happens/happened.



Regards, Bob

 

[TStClair]

OK, I got it to run. I started again from scratch and bled the low pressure side (no air evident). Then I opened all of the lines at each injector. I then cranked it until fuel was pulsing out of each injector, and tightened it. It started kicking when I tightened the 3rd one. It actually started (roughly) when I tightened the 4th line, and got messy as I tried to tighten the last two lines. It ran rough for a few seconds, then smoothed out. It starts easily now and runs smoothly (for a diesel).



The difference was that I opened all the lines at once, and cranked it longer than the recommended 30 seconds (necessary since I couldn't work that fast).



Thanks for all the suggestions.



Tom