Fuel issues

[mattgunguy]

I have a 79 m35a2 with the LDT-465-1C motor. She started up fine yesterday morning. Yesterday afternoon she started real sluggish like. I let her idle for half an hour, & started heading home. 4-5 miles later she died in middle of the road. So today after getting her towed home this is what I have tried. I think it's a fuel problem. She will fire up with ether and then die. I've drained the tank, & added fresh fuel. Changed all the fuel filter & double checked for air in the lines. Checked to make sure the fuel shut off isn't stuck in the off position. Made sure the fuse for the fuel pump is good. When she fires up with the ether we aren't seeing any smoke either.

Any advice on what to do next would be appreciated. My Google fu doesn't seem to be up to the task at hand, the TM hasn't been forthcoming either. Unless I'm missing something,which is entirely possible. Is there a way to check the fdc and injectors?

 

[gimpyrobb]

You get fuel out of the bleeder on the secondary filters with the power switch on?

 

[mattgunguy]

Yes sir. I didn't last night when F'ing with it, but did after changing the filters today.

 

[gimpyrobb]

You said you checked the lever under the shut off plate is free? After that, it gets complicated

 

[mattgunguy]

If I let it sit for 10 minutes or so, & then try to start up she will for a second or so. Yes I checked the lever.

 

[gimpyrobb]

Sounds like an air leak if it "hits" at all. I would verify the fuel gaskets are in right. I was going to say check the plunger, but if it catches, its plunging.

 

[doghead]

You changed 3 fuel filters, right?

 

[mattgunguy]

Yes. 3 filters. Replaced the gaskets on each. The was a lot of gunk in the bottom of the can on the primary & some oily sludge in the bottom of the secondary. Where would one start checking for a air leak? I'm good with gas motors, but still working the learning curve on these diesels.

 

[mattgunguy]

I'm not getting fuel to the injectors. Is my fdc toast, or clogged up? Injector pump bad maybe?

 

[gimpyrobb]

Sorry, I had to attend to some other things. So the filters are new and the fuel shut off lever moves free. If it sits for 10-15mins, it will try to start, but not. Have you pulled the filter cans off and verified the gaskets are on right? That is what it sounds like to me.

 

[mattgunguy]

yes, I went back and double checked the gaskets. I'm at the double guessing everything I've done stage.

 

[Floridianson]

Just to be clear there are three filters. Primary, Secondary and finial. You FDC does not control a no fuel problem. Your FDC should be bypassed later after you get things figured out. Did you take off the shutdown cover and feel that the fuel control rod is not binding?
If you have fuel at the fuel bleed between the filters and fuel rod is free and when you push it towards the firewall it will snap back to the forward 7 oclock pisition then your probley looking at a new Hydrolic Head.

 

[welldigger]

Judging by the symptoms he is describing I'm leaning towards the button on the bottom of the hh plunger falling off.

 

[mattgunguy]

Spoke to gimpyrobb on the phone, & followed his advice. Pulled all the injector lines to see if anything is flowing. And it's a no go. The head is not a pumping. Gonna eat something and then pull the head. Hoping it's fixable, but prepared for the worst. I'll read up on the plunger in the meantime.

 

[gimpyrobb]

Call if you have any more questions. Sorry to hear this.

 

[Floridianson]

Judging by the symptoms he is describing I'm leaning towards the button on the bottom of the hh plunger falling off.

Yea wonder why this seems to be happing so much. Could it be the plunger sticking and the button is getting hit hard?
Agreed pull the head.

 

[welldigger]

Yea wonder why this seems to be happing so much. Could it be the plunger sticking and the button is getting hit hard?
Agreed pull the head.

40 or 50 year old parts wearing out.

 

[welldigger]

Now that I have thought about it you may be onto something with that plunger sticking idea. That clip that holds the button on is pretty flimsy so I have often wondered why it would all of the sudden break off. It does seem to be remarkably common. I don't know if it's a design flaw or as I stated, just old and worn out.

 

[gimpyrobb]

What I have found is that the 3-finger clip that holds the "button" on breaks and that lets the button float around in the chamber. It then pushes the plunger higher up than it normally travels and sticks in the "up" position. Thats what I have found anyway.

 

[mattgunguy]

Well, we got the head pulled. Stupid little clip had come off. Put the clip back on & got everything put back together. Got her to fire up. Made it about 100 yards down the road, & she died again. I'm going to assume the clip fell off again. What's the likely hood that it's the plunger that's worn out versus the clip being worn out. Should I get a new head or just some clips. I don't mind getting a new hydraulic head. Just costs a bit more than new clips.