Bad AFPR (reversed diaphram?)

[TWRViper]

Hey all,

I've got a AFPR that kinda looks like this

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7978581363&category=33553

I've noticed that when I step on the throttle, the fuel pressure decreases. This is strange since I have a 255 fuel pump and my guage seems to be working well. I would expect the pressure to increase when vacuum decreases.

It that normal? Could the diaphram have been reversed inside the regulator?

I wanted to make sure the problem was my AFPR rather than a plugged filter or a bad fuel pump. I tested my AFPR by turning on the ignition without the engine running. The fuel pump turned on like normal and the gauge showed about 35 psi of fuel pressure. I applied vacuum (by sucking with my mouth, it tasted like fuel fumes, not doing that again) and boost by using a pump. Both times the fuel pressure decreased by 2-5 psi then returned to the original position.

Thanks
Tom

 

[HISSIN50]

Tom, you are correct. that is not normal. The regulator supplies fuel inversely to manifold vac (when vac is high, pressure is less. when vac is low, like at WOT, pressure is higher).

A warm motor at idle should show ~32 psi with the vac line attached. remove the vac line and plug it and the pressure should go to ~38-39 PSI.

Is there fuel in the vac line to the regulator? some regulators (Kirban, IIRC) are rebuildable.

Good luck.