Fuel pressure relief valve

[ffgb]

Can someone tell me where the fuel pressure relief valve is located on a 1985 300d California Model??? I saw a banjo bolt on the end of the hard plastic fuel line on the inside part of the I/P on the engine side. When I removed it, it was just a banjo bolt with a solid hex head and no internals. I did notice that there is another banjo bolt on the the other side of the I/P, the fender side, that looks more like the fuel pressure relief valve because I can see the ball bearing in the middle. Is this this the correct location for the two??? Is this a 1985 California model thing because of the OX-Cat? I am not the original owner of the vehicle so maybe they're in the wrong locations and I should switch them into there correct locations.

Does anyone hear have a picture of the I/P on the fender side???? So I can see if it is just a banjo bolt or a fuel pressure regulator valve???

Thanks!

[NZScott]

It's the one on the engine side, and it sounds like you've got a non-adjustable version. That other one is the fuel supply

[mach4]

Welcome to the club, I made exactly the same mistake when I put the fuel pressure sensor in my '85 Cali 617. I have a hunch they're less susceptible to weakening springs as my fuel pressure is very good...but who knows because you can't check.

[ffgb]

Hmmmmm, does the fuel supply suppose to have plain banjo bolt or one with a ball bearing in the middle, that is my question. The pics that I see of the non-adjustable fuel pressure relief valve isn't in the same area, i/p engine side, on my car, it is on the opposite side, fender side. I wanted to see here whoever has a 1984 or 1985 300d California model with OX-cat if their setup was like mine. If it isn't, then the previous owner or mechanic installed the pressure relief valve in the wrong location.

[mach4]

Read post 9 and 11 in this thread - http://www.peachparts.com/shopforum/diesel-discussion/362989-adding-fuel-pressure-gauge.html

.

Look close and you can see the ball bearing in the hole.

[ffgb]

I have that banjo bolt with ball bearing, but it is on the I/P fender side. Does that make sense???

[Phillytwotank]

Originally Posted by ffgb

. Does that make sense???

NO

[ffgb]

I had to search through the MB factory service manuals online. Apparently where the fuel pressure relieve valve is suppose to go, I/P engine side, there is just a banjo union. Where the banjo union is suppose to go, I/P fender side, there is the fuel pressure relief valve. Whoever worked on the car before I got it must have put this in the wrong order. So basically, there wasn't a fuel pressure relief valve there. I will flip flop them into the correct location.

[funola]

Originally Posted by ffgb

I have that banjo bolt with ball bearing, but it is on the I/P fender side. Does that make sense???

Some boneheadinstalled it in the wrong place.

[mach4]

^^What he said.

[BillGrissom]

Just to add a snippet, in engineering parlance it would be called a "back-pressure regulator" (BPR), i.e. it controls the pressure upstream of it. A "pressure relief valve" (PRV) is a similar spring-loaded poppet. The difference is that PRV is designed to hold open at a lower pressure once it pops. This is done by the upstream fluid being exposed to a larger plug area after it opens. A PRV is designed to reach a stable in-between state, more like the T-stat does in temperature control.

[OM617YOTA]

Have the hoses been moved around too, or just the bolt w/ the PRV?

[ffgb]

Just the bolts were moved around. I put a rebuildable Pressure Relief Valve with longer spring in. But having new rebuilt injectors with Bosio 314's made the most difference in performance! Lol

[OM617YOTA]

How could it have run before? The PRV also acts as a check valve. If it was on the INLET to the IP, it wouldn't have let fuel flow in. If it did, without any restriction on the outlet side, you'd have had almost no pressure in the fuel gallery in the IP.

[cooljjay]

If anyone reads this....pictures help...


http://www.peachparts.com/shopforum/diesel-discussion/234609-fuel-pressure-relief-valve-adjustment.html