Archived truck dies on highway: help!!

[thaddad]

4 times in the last year my truck has died. It is a 93 Dodge W-350 with Cummins Diesel. The first time it happened I checked the filter and it was full of fuel. After towing it back to my shop I cracked all the injector lines and it had fuel spraying as far as the bottom of the hood. After much head scratching I went home for the night and didn't sleep well thinking about it. The next morning I checked the shutoff solenoid it clicked and had power. I cracked one injector line and turned the key and the truck started. I drove the truck with the same half tank off fuel and could not get it to die again. I changed the lift pump and the filter as routine maintenance. (The pump was weeping oil). The truck ran fine for 10 months. One month ago it died again while pulling a hill in 4th gear. It acts as though it runs out of fuel. The filter is full when this happens and the hand pump has no affect as the system is pumped up to pressure already. I cracked 4 lines and cranked until all the air and froth was gone. Tighten the lines and the truck starts. It clears up after 30 seconds or a minute just like when you change a filter and have to work out the air. This also happened twice 2 days ago and bleeding makes it start. I have also pulled the lines 3 times and cranked it to see if any injectors blow bubbles. All have been fine everytime. My theory is that a nozzle hangs open and the cylinder pumps air back to the injector pump killing the engine. Has anyone seen an injector do this??? How do I isolate the bad one or do I change all of them? Any help would be appreciated as this is my tow truck for my business. Thank you Tim

 

[Nordby]

I doubt the injector is hanging and pumping air back to the injection pump, then getting circulated all over the other cylinders. When my injection pump came apart, I had many incidents where a piece of the pump would get to an injector and not allow it to seat - symptom was when the truck ran, lots of white smoke, and trying to high pressure bleed while the truck ran it never bled out - constant white foam.



The simplest answer could be unreliable power to your shutdown selenoid, or the selenoid itself going on the fritz.



However, sounds like you are getting air in, and sounds similar to one I had on a 1992 early on when I got it. Air is going to come from the line between the lift pump and tank, or in the return line from injectors back to the lift pump, or between the lift pump and the injection pump. Folks told me that you won't seep fuel on any of these lines and still have an air leak. Some mechanics suggested to use ether, spray the lines, wait, and see if the motor revs (like a vacuum leak in a gasser). Problem is, you have an intermittent problem that shows up only under at least some load.



A vacuum with your gas cap will cause a borderline air leak to be intermittent, next time your truck dies, loosen the gas cap immediately and check for a vacuum. The place where I found my leak was between the water/fuel separator and the injection pump. There is a line that runs underneath the grid heater/intake housing that has a coupling in it - you cannot see this coupling without a mirror, or standing on your head. Mine had come loose and the rubber seal deteriorated - when the truck created a vacuum on the fuel tank, it was easier for the injection pump to suck air I guess, then get it from the lift pump which must have gone less efficient due to the vacuum.



Hope this helps, I'll respond with other ideas I might have forgotten, it's been over a year without the problem now...

jon

 

[BV]

Air in the fuel

A good way to check for air in the fuel lines is to put one of those clear glass filter housings in the fuel line (Note: leave the filter out of it).



I have read many issues with the return lines on the 94-97 range but it could be common on the 1st gens as well. Most of the symptoms from this was hard starting.

 

[wcjp]

Someone posted on the 2nd Gen forum a few weeks ago with a rough idle problem. His fuel hoses had dry rot. They would suck air in but still prevent the diesel from leaking.

 

[thaddad]

still no answers

Yesterday I checked and replaced my shutoff solenoid. It looked ok no metal or gunk on or near it. but I put the new one in anyway. I also changed the filter. (it was perfectly clean,only 4k on it) I also vacuum tested the line from the lift pump to the tank with my mightyvac. I am able to get to the fuel sender easily because of the wrecker body. I also checked all I could see around the pump and the filter ect. No leaks or bad lines that I could see. Of course the truck ran great for the 10 m. I drove it. I know it will die again after a while. HELP!!! Tim

 

[illflem]

Sometimes a failing shutdown solenoid will close when it gets hot, usually during long drives, hills or hot weather. They usually recover pretty fast on their own. Guess you won't know unless it does it again. If you have an air leak I doubt if it will fix itself as you indicated. How does it die, does it run poorly or just shut down?

 

[thaddad]

The truck shuts off gradually it does not shut off

as if you turned the key off,it gets kind of hollow feeling and within seconds it just quits firing. No skipping or smoking just dies.





TH

 

[illflem]

My feeling is that short of an injection pump problem you may have already fixed it. I guess it's just a matter of time to see if it does it again. Let us know what happens.

 

[Nordby]

thaddad,



everything you have described in how your truck dies. Not like you turned the key off, not smoking, just power loss, then it would just quit. And then it starts up again in a while, etc. , is exactly what my truck was doing.



I'd be fine, no air, until the fuel tank made a vacuum, then air got in through that fitting hidden under the grid-heater/intake housing. Tighten or replace that fitting, and make sure your gas cap is vented.



Your air may be coming from somewhere else, but I'd bet vacuum, heat and fuel use are causing the problem.



If your injection pump was going, there would be pieces of it in your shutdown selenoid, it would plug up, and your truck would not turn off when you turned the key off. Also, you'd get a piece or two that would get in the way of your injectors and not let them reseat - causing smoke and power loss like you wouldn't believe.

 

[thaddad]

Fitting

Nordby o1, Correct me if I'm wrong,but, isn't the fitting you are talking about on the pressure side of the lift pump. after the filter and before the injector pump? Wouldn't that leak fuel while the engine was running and possibly suck in air at rest and cause a no or hard start. or maybe rough idle or start stall condition at cold start up? Or, does the injector pump have the ability to suck air in if no fuel pressure or volume of fuel is present in the feed line?





Thanks for the concern. Tim H

 

[Nordby]

Sorry for the slow reply, I am in here a bit, but get the notifications on yahoo mail, which I monitor once a week or so. WHoops.



Yes, you are correct, pressure side of the lift pump, and your logic seems right to me too.





The injection pump gurus will have to answer for sure, but If I had to bet the injection pump sucks (sometimes in more ways than one, like when it fails!).



So, add a vacuum to your tank, stressing out your lift pump, and if weak (new or not, I dunno, but I swapped new ones on there too with no luck on this problem) it could begin to starve the injection pump for fuel. If the injection pump sucks, it could certainly grab air from that fitting. Also, positive pressure might just self-seal it, while neutral or negative pressure might open it up. If the injection pump cannot pull fuel, then my theory is all bogus, and then I have no clue what I did to fix my problem, and since it has been a year or so, I have no prayer of remembering what else it could have been!



I tell ya, I had the thing apart, fuel tank on the ground, empty, blowing air through hoses, checking return lines, swapping lift pumps, swapping fuel/water separators, the whole drill. Back together, die at idel occaisionaly, but die on the highway while towing, for instance.



When I found that fitting hand-tight, I jumped for joy, tightened it, and never saw the issue again. It wouldn't necessarily be that fitting, but I'd bet a combination of several things is getting air in and starving you for fuel.



jon

 

[Joseph Donnelly]

I've been told that bad o-rings in the fuel prefilter/heater assembly will cause the engine to seem to miss on one cylinder. The bad cylinder seems to move around so one time bleeding #1 helps, then some other # seems to have the miss.