working out bugs on the road - Questions

weelsey · Post by **weelsey** » Thu Dec 21, 2017 4:45 pm

May be the bigger issue would be driveability because of the lessened pressures in the body.

I can't quite picture how vacuum and pressure then mix together on the supply side. All that comes to mind is a starved delivery side.
Any explanations for fuel tanks pressurizing?

Post by **Growlerbearnz** » Thu Dec 21, 2017 6:16 pm

weelsey wrote:I can't quite picture how vacuum and pressure then mix together on the supply side. All that comes to mind is a starved delivery side.
Any explanations for fuel tanks pressurizing?

The pressure regulator plunger is pushed down by a spring, blocking the bleed port (the line that goes from the regulator back to the pump's inlet). The rotary fuel pump creates pressure against the underside of the regulator plunger (and in the IP body). Once IP body pressure is high enough it overcomes the spring, lifting the plunger, exposing the bleed port. The pump now just circulates fuel through the pump, out the bleed port, and back into the pump again. When the IP internal pressure drops (because the fuel's been used by the injectors) the spring closes the plunger again, and the pump's output goes into the IP body.

It doesn't actually work *quite* like that, of course. The plunger will actually settle at an equilibrium where it's exposing just enough bleed port to keep the IP body pressurised, adjusting slightly up or down as engine speed and fuel use change.

Not sure what you're asking about the fuel tanks, they should always be near atmospheric pressure.

weelsey · Post by **weelsey** » Fri Dec 22, 2017 9:40 am

I was speculating that the 'hiss' of escaping air from the fuel filler upon opening the cap could relate to a pressure bleed from the pump body. But don't understand how you could have both fuel delivery and pressure throughout the supply side.

Pressurizing tanks isn't new. Its happened with a couple of my diesel vehicles. The delica's filler cap is redish. Perhaps its for a gas unit.

i've read on another non-delica forum where pump body pressures are being adjusted. One argument i encountered is that the ULSD has had the effect of lowering pump pressures and that the thing to do is to drive the plug down in the regulator so there is some more pressure on the valve spring. Mainly its about getting more fuel delivery to old trucks. They are measuring pressure at the overflow port before the restriction.

I'm not consdering doing this. All i want to do at this point is see the valve is functioning. May be I can push upwards from the bottom to see about spring pressure. I could hear a rattle.

Post by **Growlerbearnz** » Fri Dec 22, 2017 2:22 pm

Oh, right, the pressure that comes out the fuel filler sometimes. I always presumed that was just due to expansion- sometimes it happens, sometimes it doesn't.

Though now I think about it, the tanks vent through an anti-spill valve which is supposed to keep the fuel in during a rollover. I presume it takes a certain amount of pressure to open the valve to let air in (as the tanks empty) or out (as heat expands the fuel), so a small amount of pressure buildup in the tanks makes sense. I've only ever seen red fuel filler caps on diesel Delicas, so I think yours is correct.

If ULSD is thinner than old diesel then I guess raising the pressure would put the timing back where it's supposed to be (since internal pressure is controlled by the outlet restriction).

Raising internal pressure by, say, 20psi would also cause the injectors to open a little sooner and close a little later, which would increase the amount of fuel being injected, but since injection pressure is about 1200psi I'm not sure it would be significant.

weelsey · Post by **weelsey** » Sat Dec 23, 2017 8:02 pm

https://youtu.be/uePRl2oQ1S8
Does this give an indication of the severity of the bushing wear?

Post by **Growlerbearnz** » Sun Dec 24, 2017 3:56 pm

Ouch. The limit's something like 0.2mm, that looks excessive. How many kms has this pump (allegedly) done? My old pump had done 250,000km and it was fine.

I think you need to track down a Bosch service manual and check everything else, especially the rollers and cam plate, and the high-pressure plunger. If they need replacing it might work out cheaper to find a rebuilt replacement.

weelsey · Post by **weelsey** » Thu Dec 28, 2017 1:01 pm

I'm inclinded to send for my replacment. I can't imagine this is a 200k pump as is shown on the odometer bsed on busing wear. though I've not had rubberband drive diesels much.

Wondering about the motor, also. If I had the replacement pump that came with the van I'd be trying to build the best pump with what I have. But since I don't know what the other is like entirely, I've opted not to invest in this one until I do. I've been informed that bushings are not readily available. I'd be happy just to have a working van again at this stage, even if I have to wait for warm days to start it. I'd rather invest in injector work.

Fingers crossed the re-seal will make an improvement. this is what the bottom pressure regulator o-ring soon looked like:

: IMG_1367.JPG (584.46 KiB) Viewed 4050 times

Very brittle and loose, although still intact, after pulling the regulator. I replaced all the rubbers in cluded in the kit. And am reassembling with cam seal, belts, tensioners. At negative 20C. Bleck.

weelsey · Post by **weelsey** » Sat Jan 06, 2018 10:29 am

It starts and runs quite good after reassembly. I suspected the work to the pump and rubber bands would have the effect of advancing the timing so I pushed it back a bit from where it was set (by me). Seems to start and run better but I haven't been able to make much observation before heading out of province. We managed to get it out of the garage and go for dinner friday, at -30c.
There was a change in the idle. I backed the accelerator arm to where it was before leaving NB to bring the idle down. Then another. Then I backed off the full speed screw. I left it so that the idle adjuster was backed off to the point it didn't even contact the lever to get the idle about where I wanted it with as little full speed. Is there an proper orientation for the governor shaft so that the holes in it go the right way? I failed to make sufficient registration marks.

Lots of power. Lots of smoke. or was that vapor. I'll probably get it properly timed if it's not leaking. But I'll return with the MD171460 which appears "less used" and figure it all out then.