truck shakes when i crank it.....

[GREASE FIRE]

my fuel filter got clogged today - i didn't even know there was a dash light that said "fuel filter" until it came on, and shortly after i started losing power and even stalled out once on the way home. I finally did get home though, going real slow and then put a new filter in. I filled it up with fuel first then gave it several good cranks before using the glow plugs to prime it. Then after using the glow plugs it started for just a second then stalled, now it won't start at all. When i turn it over it seems to crank faster and faster like it is about to start, but instead the whole truck starts to rattle and shake heavily. It has done this before but usually it will start after a while.

does anyone know what this shaking condition is all about? i have never had it happen on other trucks, just this one.

the last time this happened was last summer when i ran out of fuel (sending unit did not work) and after filling the tank and priming the system it did the same thing, just cranked and shaked until finally one quick shot of starter fluid got it going. But this time that did not work either. Although i cranked a lot, it was never for more than 15 seconds plus the engine was warm and i gave it a couple minutes between - but my starter, which was already having problems, finally gave out and now it seems to be shot. But i found out it has a lifetime warranty so i may be able to get another one. IN the meantime, however, i would like to figure out what is going on so when i get the new starter it will run again.
Any help appreciated!


thanks,
Paul

 

[towcat]

air in the system. rev the *** out of the motor and it'll clear up.

 

[LCAM-01XA]

You got some air man, mine used to do the same for a few days - fire up, then try to die on me - it was the fuel content of the IP that got it going, but it was the air in the return lines that was trying to stall it - Calvin is right, pedal to the floor clears 'em up real nice, I keept mine right around 2500 rpms for a few seconds and she was good.

 

[Diesel JD]

You may have to crack those injector lines and crank to get the air out. Unfortunately I have a lot of experience with these issues, having run the thing out of fuel too many times to count.

 

[GREASE FIRE]

You got some air man, mine used to do the same for a few days - fire up, then try to die on me - it was the fuel content of the IP that got it going, but it was the air in the return lines that was trying to stall it - Calvin is right, pedal to the floor clears 'em up real nice, I keept mine right around 2500 rpms for a few seconds and she was good.

i still don't understand how air in the injector return lines could be the problem. The injectors have to pop first in order to allow the extra fuel to go into the return lines, right? they are not just open all the time, othewise they would have to withstand the high pressure of the IP. OR do i have this all wrong? How could air in those lines travel "upstream" into the injectors or injector lines?

All my injector return lines were replaced in recent years (prev owner) with the braided kind with clips. If someone thinks they could be leaking can you tell me how to find the leaks and fix them?

thanks again,
Paul

 

[Diesel JD]

It really doesn't take much to get air in the system, in fact you got probably 99.999% of it out when you primed your new fuel filter and tried for a start...but that remaining tiny amount was enough to stall you out and now, you have a small amount of air trapped on the pressure side. The return lines may not even leak a bit and you could still get air from the high pressure side. You just have to crack those lines and bleed until you have fuel, then cycle your glow plugs and crank the thing in 15 second on 2 minute cooldown bursts until it starts then keep up your rpms till it smoothes out. Should fix it. By the way those return lines can leak pretty easily if you're not careful...even just bumping them can do it at times.

 

[subway]

It really doesn't take much to get air in the system, in fact you got probably 99.999% of it out when you primed your new fuel filter and tried for a start...but that remaining tiny amount was enough to stall you out and now, you have a small amount of air trapped on the pressure side. The return lines may not even leak a bit and you could still get air from the high pressure side. You just have to crack those lines and bleed until you have fuel, then cycle your glow plugs and crank the thing in 15 second on 2 minute cooldown bursts until it starts then keep up your rpms till it smoothes out. Should fix it. By the way those return lines can leak pretty easily if you're not careful...even just bumping them can do it at times.

i second JD on this one. hold the accelorator to the floor for max flow to the injectors to help purge the air. when it catches keep the rpms up and it will smooth out. run out myself more times than i care to admit with an air leek i am tracking.

 

[jperecko]

Watch out for weak batteries too. I ran mine dry and had this problem... Would not start... bled the lines... still would not start. I trickle charged the batteries overnight and same thing. Finally I just bought 2 new batteries and it started just fine. It seemed that the starter was just barely not getting enough power to crank it fast enough... almost like it was enough speed for a couple cylinders to fire... but not all. The truck would keep stuttering and shakiung as you describe.

 

[LCAM-01XA]

i still don't understand how air in the injector return lines could be the problem. The injectors have to pop first in order to allow the extra fuel to go into the return lines, right? they are not just open all the time, othewise they would have to withstand the high pressure of the IP. OR do i have this all wrong? How could air in those lines travel "upstream" into the injectors or injector lines?

Air travels uphill man, it gets in the filter head and allows fuel to gravity-drain back in the tank. There are 1-way valves in the system to prevent that, but I'm yet to see one that actually works like it should.

 

[GREASE FIRE]

Air travels uphill man, it gets in the filter head and allows fuel to gravity-drain back in the tank. There are 1-way valves in the system to prevent that, but I'm yet to see one that actually works like it should.

as far as the check valves go - i was thinking to add one but i thought the mechanical lift pump had one so i never bothered. Was i wrong about the lift pump - or are you saying it has one but just does not work?
either way i guess i will add one now - can't hurt.
thanks,
Paul

 

[Mr_Roboto]

The fuel doesn't drain back through the pump, it drains back through the return lines. Air in, fuel out.

 

[LCAM-01XA]

Yeps, lift pump does have a 1-way valve and it does seem to work, the one that's acting up is the one in the filter head where the return line connects - tis supposed to only open when there's pressure from the lift pump, which in theory should isolate air intrusions from draining the filter head, but it's my understanding that it rarely works good.

 

[DeepRoots]

i've got two, one way check valves on my truck.
Mcmaster carr has them, 3/8inch. Cost like $15 and nearly no pressure loss.

 

[GREASE FIRE]

Yeps, lift pump does have a 1-way valve and it does seem to work, the one that's acting up is the one in the filter head where the return line connects - tis supposed to only open when there's pressure from the lift pump, which in theory should isolate air intrusions from draining the filter head, but it's my understanding that it rarely works good.

I actually thought that was the problem a couple months ago so i removed it and put a plug there in the filter head and also plugged the return hose that came out of it. Unfortunately, it made no difference at all so i am still confused. thanks for the suggestion though.

Paul

 

[joe_diesel]

It does sound like air. I've only had it happen on the front end loader. Problem is finding the source of the air leak, if that's the problem.

Could you tell if the fuel filter was plugged. I changed mine with every oil change (gets a little exspensive) and it never looked clean but, did you find that the filter looked to be in poor condition? In other words were you able to verify that the filter light came on because the filter was only dirty?