Not getting enough fuel -- idles but will not rev

[Wardcolorado]

So.... having an odd problem with my 1984 D50, 4D55T. It starts fine, and idles (very low rpm, lower than normal), and it'll even drive around -- very very slowly in 1st low range 4wd. But, it will not rev at all. Pushing the accelerator down gives zero results, as does manually revving it directly on the IP. When you very first start it it will rev for the first 2 or 3 seconds if you try, then back to low rpm idling. As if it has a little fuel reserve in the lines or the injection pump, but then can't get enough fuel. But it keeps idling really low and doesn't stall out, usually. Classic symptoms of a clogged fuel filter, so I just put a brand new on on. And NO change at all... what the heck? This started this winter when I ran either ran it out of fuel or gelled it or both -- oops. I parked it till it got warm and now I'm trying to get it running again. Anyway, I purged the system of air, and I am getting fuel at all four injectors when I crack them. But, obviously not enough. For a little while this spring after I purged the air and gave it new fuel it would occasionally rev, but now it will not at all. So... is there another filter somewhere I should check? Back in the tank maybe?

BTW, I do have an inline electric fuel pump as well and having it on or off doesn't make any difference.

I do have a spare IP if I have to, but if it's simply a different filter somewhere, I'd rather not get into swapping the IP.

Thanks

Zeke

[BradMph]

You get the same reaction from an e pump on and when it's off? Sounds like the E pump isn't working at all then. Check your fuel pressure if you have a gauge.

[Wardcolorado]

The electric pump is definitely working -- at least lots of fuel squirts out when you take the hose off of it, though I have not checked the pressure. It never used to have the electric pump till this started happening, but I added that thinking that maybe it would help.

[camoit]

It almost sounds like the governor stuck. When you start a diesel it will start in full throttle. Once it starts the flyweights push on the spring making it go back to idle. When you push on the throttle it pushes on another spring opposite side of the governor. This moves the fuel plunger to open and allow more fuel to the injection pump.

[Wardcolorado]

Hmmmm.... sounds like a possibility. How do I check for this... I assume the governor is fully contained inside the injection pump since I don't see anything external.

[camoit]

yep. it's inside. try sending mike warme an email. his mail is listed in other posts. he might have a trick to fixing a stuck pump.

[Wardcolorado]

So. It's running properly now, or so it seems. Took it on about a 10 mile drive today and by the end it was behaving like it used to.

I started taking apart hoses starting at the electric pump -- got a nice good stream of fuel out of the pump, then through the filter (had some air in there still). Was not getting any out of the return line from the injection pump though.... but after purging all the air out of the filter, it at least would run enough to rev a tiny bit. So, I ran it for a while with the return hose off -- mostly nothing coming out, then a little bit of foam, then eventually a weak stream of fuel, and it would rev up, though a bit reluctantly. So, I took it for a drive -- to begin with it was quite sluggish and wouldn't rev above about 2k, and I couldn't get it to more than about 3psi of boost. Just felt like it wasn't getting enough fuel under higher throttle. But after 4 or 5 miles it started getting better. Eventually, it became normal again. I'm thinking that either something was stuck and managed to unstuck itself... or that it had air stuck inside the injection pump and eventually it finally worked its way out. I also put a can of BK244 cleaner in the tank before the little drive, so maybe that had something to do with it too. Perhaps the truck was just mad about not being used for 5 years.

[camoit]

hahaha. If you did not get "any" for 5 years you would be mad too, wouldn't you?
But it sounds like it's coming back to life. Now drive the crap out of it and see what happens. It should come back to life. Nothing like old gelled fuel to cause an issue. Good to here you are getting it going. Keep us up to date on it. This will help the next guy.

I sure like the Radio we have. It plays some good tunes. Link at the top of every page. MMD5 Radio.

[recian]

Yeah 5 years. I've got a diesel that sat for about 2 years now and I'm scared to pull the fuel system apart and drain the tank so I'd say 5 is pushing it.

[mikewarme]

Hey guys, also USING DIESEL ADDITIVE IS A MUST WITH LOW SULFUR DIESEL!!!! These fuel pumps are wearing out quicker than ever without lubricity due to low sulfur content. Don't be cheap get a couple bottles it does not the much. Also ***** is right about the governor getting stuck. And if you have to have an electric fuel pump on these 4d55's than your pump is toast anyways as they have a mechanical vane which pulls the fuel up and you run the risk of blowing out seals with an electric pump that is too strong.