M1028 shakes with full tank.

[lolercaust]

I haven't found any thing that discusses this. Keep in mind i NEVER "top off" my vehicles, but i do fill to F and i some times miss judge the amount i need and i might go a little over F. My truck runs great and idles like a top until i refuel then she wants to shake. When i say shake i mean body panels shuttering, fuel door vibrating and it does it very loudly. It only does it when the fuel tank is 3/4 or above while in gear idling. The higher the gauge reads the harder the shutter and as i burn fuel it slowly subsides and the stops once i go below 3/4 of a tank. It only does this in gear at idle with a full tank and as soon is i touch the gas to go it stops. Any one ever seen this before?

 

[Coal Cracker]

Gas cap vent, water in fuel tank, fuel pump weak or fuel return blocked.

 

[lolercaust]

Thats the thing the IP isn't leaking and the check ball and fuel behind it are crystal clear and the lift pump is new less the 4000 miles. Though admittedly checking the vent and returns would be a good idea which is some thing i haven't done yet, but i haven't felt the need to she runs and drives great. If it was plugged up the truck would run like its starving for fuel and when i remove the fill cap the tank would gasp for air and it doesn't. Still it only does it when its 3/4 or more full which is the odd part to me. As for water in the fuel eeeeeh i doubt it, Me my father and every one else in the neighborhood with a diesel go to the same gas station and none of them have had water problems. As well as with so many people refueling there the diesel isn't siting in the tanks for very long. Though i will say, is there water in my tank? after thirty years im sure there is but the WIF light sees im OK and the injectors haven't had their tips blown off yet. Iv spent all day flushing and re flushing the cooling system but tomorrow ill give the fuel system a full shack down. I drive the truck every day and its more embarrassing then any thing for the truck to shiver like it does on a full tank.

 

[nyoffroad]

WOW this is an odd one. I wonder if it's something to do with the fuel return? (Gotta go with Coal cracker here) Maybe when the tanks full it somehow it blocks the fuel return line and increases the back pressure on the IP? I'm just guessing but I think it's worth a shot. I'd remove the return line (with a full tank) and run it to a container and start her up. good luck, I'm going to watch this!

 

[antennaclimber]

My M1008 does the same thing. The fuel door rattles like crazy at idle, I have not noticed a correlation between the rattle and the fuel level. I keep the truck full of fuel at all times. The truck always starts and runs great.

When I start driving it again (after the road salt goes away) I will see if the fuel level affects the amount of vibration at idle.
Karl

 

[lolercaust]

There is one thing that i forgot to mention, like i said it only does it at a stop in gear idling. The shacking coincides with the fuel sloshing in the tank. When the fuel moves forward during the initial stop the shacking slightly increases and when it flows to the rear the shake lessens. so i can sit in the truck and KNOW when and how the fuel flows back and forth in the tank just by the shacking increasing (fuel to front) and decreasing (fuel to the rear).

HOLLY COW I GOT IT!!!! Theres trash in the tank! the sening unite or "liquid transmiter" is in the front half of the tank right! the fuel flows forward at stops pulling the trash with it clogging the mesh screen of the sending unite thouslly chocking the engine of fuel. But why it only does it only full is beyond me, one would think just driving it around would stir all the crap up any ways. It cant be water related because there is a gap between the pick up and bottom of the tank that gives you some breathing room from water build up. The fuel floats on top of the water (that might be in the tank) meaning the crap in the tank has to be fuel saturated so i floats atop the water as well. But even then why only with a full tank. i think tomorrow ill feed my mighty-vac down the fill tube and see what i can suck out. If it was a return line (at least at the tank) nothing could block it from with in the tank due to the constant positive flow pressure. Maybe the trash is fuel saturated but heavy enough to sink any way over time and driving around doesn't "shake things up" like adding gallons of fuel. Which might re-suspend every thing for a while and i don't know any one else wana add to my hack job theory of fluid dynamics.

 

[lolercaust]

I don't let her go bellow a half tank ever...half full is totally empty at least that's what the army taught me, info for what its worth.

 

[Gripy]

Keep us updated, this is an interesting problem. I've had my truck rattle horribly at slow idle. First the fuel door, I just added a piece of weather stripping. Then I had rattling from the rear wheel well, I used canned expanding foam to fill up the gaps in the metal to stop the rattle.

 

[lolercaust]

OK so iv been playing with the truck, i took the tank vent line off the upper fill neck. Then plugged the neck and turned around the vent hose over the tank and added a breather element. I did this after the tank gasped for air at the pump, so i figured a venting problem was the culprit after all. It did help with the shaking a bit. One day my dad told me about a 22R yota he had when i was little that had a vapor lock problem from ****. No one could figure out what was causing it but leaving the gas cap loss solved the problem...how? no one knows? So after that i returned the vent system to factory and just gently snug on the gas cap so it stays. Also iv learned that the old style fuel gauges in these trucks really are hit and miss. So if the truck has a 20G capacity at least one or two gallons arnt accounted for on the gauge so when you do hit "E" you can still go a little farther if need be. So if im at a quarter tank it should take about thirteen gallons to hit full, NOPE takes ten....don't know why i guess the truck just has character. Probably just an old miss adjusted arm or rheostat or what ever is in there.

Also I found a few injectors going out. Used a stethoscope to listen for the pops and a couple barely puffed. So thats what i did all week end, injectors came with no rings and had to order those. A few return lines died during surgery and no one sells that diameter line by the foot in my area. So i wasted a day waiting for auto zone BS kit to arrive. I'm glad i did it though i pushed the truck a few days with a rough uneven idle but she is running like a top and a very even clatter. Even got rid of some of the vibrating and i got a few horses back. But I do have to ask does any one know why i hear a long swish as i accelerate all most like listening to the spray of the injectors. Im not that familiar with the sound of indirect injectors. I looked through the TM's but theirs no mention of it. Next week when i refuel ill see if the truck still shudders or not. I'm off to ask Google about the swishing sound.

 

[CUCVEightyFive]

My M1008 does the same thing. The fuel door rattles like crazy at idle, I have not noticed a correlation between the rattle and the fuel level. I keep the truck full of fuel at all times. The truck always starts and runs great.
Karl

My M1008 is doing this as well. I was curious if you ever got to the bottom of it and came up with an answer? The rubber bumpers are in place and are still soft and pliable.

My M1008 is doing this also. Nothing I've tried has helped. I was curious if you have ever found a solution?

 

[rodent]

Mine also vibrates at idle in gear. Doesn't matter where the tank is. Looking to do injectors next.