stillsmokin209

So I installed the delphi hfp702 from Oregon fuel injection today on my 90 d250 along with modifying a banjo fitting to install a fuel prssure gauge. The truck is not heavily modified, ground fuel pin, afc adjustments, full power screw turned in a good bit, roughly 1-1 1/2 turns from runaway. Stock injectors. I used 5/16's fuel line to fit over the factory lines, and made my own block spacer out of 1/4" aluminum I had at the shop, since I didn't want to wait a week for the cummins spacer. No leaks at all, but the gauge only reads around 7psi, post filter. What gives? Is the spacer to thick and I'm not getting enough stroke on the pump? I read around on here and people said the spacer was around 3/16"~1/4", so I used the 1/4" I had around. I thought these pumps were making around 15psi at idle? Any ideas folks? I'm new to the first gen stuff, help me out.

cougar

My Cummins spacer is 3/16, add the gaskets and it's just under a 1/4. Is that 7psi at idle?

stillsmokin209

Yes that's at idle, I think the extra thickness is limiting stroke. I will make another or order the cummins spacer

cougar

What are you getting at WOT and cruise?
I know some one that holds 10-11 at WOT and 13 cruise. I have yet to install mine, but I chose it for not needing a regulator. It may not be the best choice for all out performance (volume), but it seems to be a good upgrade replacement over the diaphragm pump.

stillsmokin209

My gauge is mounted under hood, so I can't check WOT and cruise. I may try another gauge as well as add a length of hose so I can see it while driving. Although psi did not change when I raised rpm by the throttle under hood. Psi did go up if I pressed the pumps priming button, but would fall off after.

thrashingcows

Those are the reasons I went with the piston pump. When I ordered mine, I had no idea what Oregon Fuel injection would be sending me. But I'm happy enough with it.

cougar

Silly me, sitting here thinking on how I can taper the spacer to get more travel and maintain block clearance. I'm board.

bgilbert

1/4" is ~6mm. The Cummins spacer is supposed to be 7mm. So I'd say that's not your issue. My thoughts on this knockoff pump I've been reading about for awhile. It's not the same pump as the original 'upgrade' low pressure piston lift pump Cummins part number 3936320. There are many variations of this 'piston lift pump'. Different strokes, bores, volume and pressure outputs and part numbers. The 3936320 pump is definitely a ~12psi or more at idle pump. I'd say whoever the genius was that discovered this "delphi hfp702", didn't do many of you any favors. Sure it's a piston lift pump and it's cheaper than the Cummins pump. But it's not equivalent to the original low pressure pump in pressure and most likely, volume. Fail.

Bruce M

I was told by a Bosch Dealer that the HFP702 is rated at 8psi.
So after the filter it would be 1 or 2psi less as indicated by your reading.

stillsmokin209

I talked to Jeff at Mumau Diesel today, he said the Cummins spacer is 3/16", plus the gaskets the whole deal is around 1/4". My spacer alone is 1/4", plus two gaskets which are fairly thick, and it looks like I'm around 5/16"s or more. Jeff also told me that the Delphi pumps are fine, as are the Carters, which are both suppliers to Cummins. Delphi has been in the injection business awhile, I doubt making a lift pump is their biggest issue. I ordered the cummins spacer and cummins gaskets though so I will let you guys know what happens when I install it.

Exekiel69

I got My HFP702 and spacer from OFI, 10psi idle and 12psi wot, 9psi under heavy load. Gauge is in cab.

mhuppertz

That seems low to me. I wonder how low the stock diaphram pressures are...

BC847

Those numbers are like that I had with my Cummins LP piston lift-pump. With AN6 supply lines.

thrashingcows

I thought some guys were seeing close to Zero at WOT on the diaphragm pumps? Especially with tweaked pumps and big injectors the diaphragm just can't keep up.

stillsmokin209

12psi at WOT sounds good to me. I can always go bigger, but I think this should do fine.