I have diesel truck here with a mechanical injection pump. It was un-used for nearly a year...it was running perfectly before I took it off the road, but now that I've started it up and I'm having a problem with it.
It starts up and idles fine, but when I rev it the revs go back down really slowly. If I rev it high enough then the revs won't drop down at all but instead the engine wants to redline and I have to turn the key off. I've disconnected the fuel supply and return pipes and run it off a small can of diesel. I noticed that there was barely a drop of fuel coming out the return line. I tried taking the return banjo bolt out and putting in a different bolt with a larger hole in it...like that there is plenty of fuel coming out the return line, and the revs go back down normally when I rev the engine. I tried cleaning out the original return bolt and replacing it but there is still the same problem.
Can anybody offer any idea as to what the problem is or anything else I could try?

 

Additional Info: I'm also having a problem with the braking system which I suspect might be something to do with the vacuum pump/lines. Could a problem with the vacuum be the reason for the fuel problem?

 

 

Water in the fuel?
I'll fix your title for you. A year of vehicle helps too and what diesel you have helps too..

 

I've well a truely flushed it out by now....so I can't see there being any water in there. I'm wondering now if it's the actual outlet bolt itself....Could that cause the problem on it's own?

the engine is from a 95 4runner...it's a 1kzt

 

update: just answered one question myself...just drilled out the filter from inside the return bolt to see if that was clogging it up. I put that in and started it up. I got a sort of decent flow coming from the return pipe for a few seconds...reved it a bit and then the flow from the return droped down to nothing again.

 

I had sorta the same issue when i first installed my Td engine into my truck. What i learned is that mechanical injector pumps dont like sitting for a while especially if they have had old fuel run through them. Im not saying this is your issue but get your pump serviced and ill bet it runs like new. I rebuilt my vw 1.6 td from top to bottom but never screwed with the pump. After running it for the first time i couldnt figure out what the surging, and wacky idle was caused by, thought it was a timing issue. After many wasted hours i decided to just get the pump looked at to rule it out and turns out the pump was dirty. If you dont know anyone look up Jeff at York Diesel in Medina Oh. All he does is service Bosch pumps. Smart guy and knows injector pumps. Good luck