Low primary pressure - no symptoms - even worth getting into?

[82DMC12]

I'm getting about 68 PSI primary pressure. I had this reading prior to doing a LOT of fuel system work (clean tank, replace pump with DPI kit, replace fuel filter and accumulator, and replace all 13 lines) and I still have it. I know the accumulator was going bad (failed leakdown test and confirmed by removing rear flex line) and my Bosch-style pump had a slight leak / seep at one of the electrical studs. I was hoping the new parts would tighten everything up but alas, no dice. That's OK though, all parts needed to be replaced anyway no matter what.

But I still want to figure out this pressure problem. I have no driveability issues and the idle is very nice with only the occasional burble when fully warmed up (possibly due to one fuel injector with a not-quite-perfect spray). Because of this I hesitate to even mess around with it (and open my wallet).

Also I have the green label 076 distributor which is apparently not correct but was also often used in the early days as a replacement.

I suppose my gauge could be off a few lbs. If my pressure is indeed 68 PSI would there be any symptoms of a problem? Am I missing out on anything or having lower performance with 6 to 8 PSI lower pressure?

I know there are shims etc in the PPR but I don't want to go in there unless I really should.

Attachment 66970

[82DMC12]

PXL_20210804_021500698.jpg

[Helirich]

I don't have an answer for you, but I can tell you I played with shims and didn't seem to make any differnce. My problems turned out to be elsewhere, so I went back to the original shims. Changing the shims is easy, but everytime you remove that valve, you risk cutting the o-rings. I wouldn't attempt it without having extra O-rings.

[82DMC12]

I don't have an answer for you, but I can tell you I played with shims and didn't seem to make any differnce. My problems turned out to be elsewhere, so I went back to the original shims. Changing the shims is easy, but everytime you remove that valve, you risk cutting the o-rings. I wouldn't attempt it without having extra O-rings.

Thanks. I'm leaning towards leaving it well enough alone unless other symptoms pop up... I assume an adjustment in primary pressure also means having to go through the CO /dwell meter setting again too. I'm nearly done buttoning everything back up and should be able to start the car again by Friday (waiting on some injector boots).

As a side note, this DPI pump is super quiet running. When I re-pressurized for the first time last night to do a leak-check I could hear the fuel rushing through the lines and the accumulator pressurizing (spring compressing). That was an interesting sound. The Bosch pump was far louder.

[Bitsyncmaster]

Very common to have 69 or 70 PSI. Mine was 71 PSI and I shimmed it up to 75 PSI and did not notice any change in engine performance. It takes a lot of shim to move it that 4 PSI I did.

[DMC-Ron]

I think your good. I'm seeing 70 on the gauge picture. With no adverse symptoms, don't fix what's not broke.
Ron

[Acmetowers]

Also I wouldn't trust the gauge if it's come from a red box. I've seen those out by half a bar as they're not calibrated.

Sent from my SM-N950F using Tapatalk

[82DMC12]

Thanks guys. For the record, I have this gauge and have owned it for about 20 years.

https://www.ebay.com/p/1801278814

I'm going to leave the fuel pressure as-is and finish putting everything back together. It could be a touch low but I'm not experiencing any other symptoms and would prefer to avoid opening a can of worms.

[Ron]

FWIW- If you want to raise it in the future, you can use a thinner copper washer instead of thicker shims. This can help you avoid damaging the PPR o-ring, since it often stays inside with the piston when you remove the rest. And it also allows you to get it close in bigger steps....
(Not saying you should do it now...I agree with the others -- Those are best left alone, even when a bit out of spec.)

[Helirich]

FWIW- If you want to raise it in the future, you can use a thinner copper washer instead of thicker shims. This can help you avoid damaging the PPR o-ring, since it often stays inside with the piston when you remove the rest. And it also allows you to get it close in bigger steps....
(Not saying you should do it now...I agree with the others -- Those are best left alone, even when a bit out of spec.)

Ron reminded me of something. If you pull the valve and the piston stays inside, place a cloth there to catch the piston if it pops out later. You can be fooling around with the spring and the rasidule pressure will push the piston out when your not ready. Maybe your not even the vicinity. You don't want that piston to be rolling around the intake or all the hoses in that area.