I'm working on a '93 940 with Regina fuel system. The owner replaced the fuel pump and reported that he drove around the block and then it died and wouldn't restart.

I checked the fuel pressure at the test point just before the filter and there is 0 PSI. I pulled the pump and it runs when energized, and everything looks OK. I'm sort of at a loss as to why there isn't any fuel getting out of the tank. I'm curious as to what the piece that goes between pump and the sender hose...see photo below. It appears to be some sort of regulator that has o-rings in it.

I'm really at a loss as to what the true problem is as I've never worked on a Regina car, but suspect that something may be wrong with the way that this piece was installed.

Any ideas?

Dear WrenWright,

Hope you're well. I just did one of these and had trouble re-installing the send unit into the tank.

What Chris Mullet highlights is correct. The steel bracket - that holds the "buffer unit" (black plastic with metal twin-cap) tight to the pump's output nipple - has not been installed correctly. The steel bracket's arm is supposed to fit squarely in the slot, on the left side of the photo. One side of the bracket's arm is not in the slot. It is wedged between the white plastic pump base and the wall of the pump.

Further, because the bracket is not seated squarely in the slot, the "finger" at the bottom of the white plastic base cannot snap into a recess in the bracket's arm. As a result, the pump is not locked to the buffer unit. Instead, pumped fuel has pushed the "buffer" unit upwards, so that fuel is not entering the buffer unit. Rather, the fuel is pouring from the pump's output nipple, back into the tank.

The car started the first time, likely because the fuel pump's output nipple was partly into the buffer unit. The force of the pumped fuel pushed the buffer unit upward (and the pump itself downward), until the nipple came out of the buffer unit. As a result, no fuel entered the hose and so soon as the engine had used the fuel in the line, the engine died and would not re-start.

If the bracket is installed squarely into the slot in the white plastic base, the bracket will lock the buffer unit to the top of the pump, and the pumped fuel will go into the hose, and thence to the engine.

Hope this helps.

Yours faithfully,

Spook

"...I'm curious as to what the piece that goes between pump and the sender hose...see photo below. It appears to be some sort of regulator that has o-rings in it...."

I believe that is a sort of buffer that absorbs the pump pulsations in order to achieve a smoother fuel delivery to the pressure regulator.

Looking at your photo, what is that open brass looking piece on top of the pump? The reason I ask is because when I replaced the Regina system pump in our 740, I didn't get the pump properly locked into the metal bracket. So I had the same results as your car's owner - it started the first time OK, but when I shut it off it wouldn't restart even though could hear the pump running. Since the pump wasn't properly locked into the bracket, the fuel pressure blew the pump downward so that it disconnected from the "gizmo" above it.

I'm not certain what you mean by open brass-looking thing. can you clarify?
Also, how does one know when the pump is engaged with the holder and dampener?
Thanks!

I'm attaching a picture with areas of concern circled. Maybe I'm just imagining something wierd about that brass thing. However, something is for sure not right at the bottom where the metal strap isn't resting back in its proper notch in the plastic part.

Just to close out this thread, as mentioned above, the real problem was the aftermarket fuel pump that was installed previously. I was able to remedy the problem by placing a hose clamp on the pump body to ensure that it would stay up tight against the pulsation damper.

Thanks for all of the inputs, guys!