That is one tough lift pump you have !!! Sick ones would not pull the skin off custard.
I guess though that the low pressure was all the way around the fuel system so it was your IP high pressure elements doing the work.

I have seen fuel tanks expanded a little with air pressure to increase their capacity. You are lucky it didnt go bang !!
As a kid we once piped up 150 # to a 50 gal drum for fun. We ended up with 3 sheets of flat steel & a hole in the shed wall. Lucky we were not hurt. Our ears were ringing for a few days & our backsides were sore after dad found out what we had done !!!

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving