Your Air Dog would , I'm sure pump enough fuel to compensate for the return line being wide open at idle. But at higher demands for fuel with the RPM's it would start falling off as they climbed until the VP was running itself dry between the injector lines taking up what they need and the return line taking all it would carry at the same time.

Maybe the fuel cutoff in the VP malfunctioned?

well i went ahead and just went and pullled the supply line off the pump and pulled the fitting. i didnt see a check valve in it.

Bet you just found your problem.:U:

so it is supposed to have a check valve in the fitting that goes into the pump or is it the 90 degree fitting that is supposed to have the check valve init.

Been to long since i was stock to remember. You have two lines coming from the VP right next to each other. One comes from the tank/filter and goes into the VP and the other one comes out of the VP and back to the return line to the tank. It runs right next to the head and comes to a T by the back corner of the block. This is the one that should have the check valve in it.

i didnt look in the IP to see if there was a check valve. i thought you were talking about the fittings that came with the airdog haveing th check valve. i didnt unhook the return line from the IP, so unless they switched them when it was built it shouldnt be a problem.

It's just a banjo bolt that you had to hook up to connect your fuel lines. The bolt has the check valve inside of it. All the other banjo's just have an open hole and this one has a bearing in it the block fuel flow.

it doesnt use a banjo bolt for the air dog fitting on the one im using. it replaces it on the supply line.

I think were comin to an impass here. I'm not explaining it right. You are looking for the fitting that connects the fuel return line to the VP. This fitting can't be replaced, it has to be the regulator bolt. If it's anything else it won't work. For a short while I put a straight High pressure fitting on it and installed a real fuel regulator on it but even that didn't work quit right. Again, this fitting has to be the regulator banjo. If it was daylight out I'd go take a picture.

The Air Dog may have come with a fitting to replace the Banjo Bolt on the line that supplies fuel to the VP but you can't replace the fitting on the return to tank line.:deal: