Quite a specific question but here it goes. Just looking for some input on a fuel pump I recently bought. It is a sierra style mechanical fuel pump part# 18-7278 for my 1986 mercruiser 3.0 140hp. My old fuel pump did pump fuel but was all gummed up with junk and had a small tear in the middle gasket so I took the liberty of replacing it as well as cleaning my gas tank as best I could. Only problem is the new one isn't working.....
I noticed there was a slight play in the new fuel pump lever that gets pushed in by the cam lobe before I installed it, but thought nothing of it. It works fine by hand at the bench once you get passed the "play" in the lever but when installed I get zero fuel even when I prime with a outboard fuel line bubble connected to a portable gas can with new clean gas. The old fuel pump had zero play in the lever and had 2 gaskets between it an the engine block. I'm guessing the 2 gaskets were used as a sort of spacer to decrease the fuel psi on the old pump so i tried only using 1 gasket on the new pump. Still nothing. So I took apart the new pump to inspect the diaphragm and noticed that when apart there was no play in the lever. When compared to the old pump the spring underneath the diaphragm on the new is much longer holding the diaphragm up much higher. This is causing the lever to have play when reassembled.
I'm assuming the play in the lever is too much and the cam lob can press it in far enough to initiate a pump. I've ruled out a vacuum leak by checking and rechecking thread fittings and by using new fuel lines. Soooo....faulty fuel pump? right?
Any input is helpful! Thanks!
I noticed there was a slight play in the new fuel pump lever that gets pushed in by the cam lobe before I installed it, but thought nothing of it. It works fine by hand at the bench once you get passed the "play" in the lever but when installed I get zero fuel even when I prime with a outboard fuel line bubble connected to a portable gas can with new clean gas. The old fuel pump had zero play in the lever and had 2 gaskets between it an the engine block. I'm guessing the 2 gaskets were used as a sort of spacer to decrease the fuel psi on the old pump so i tried only using 1 gasket on the new pump. Still nothing. So I took apart the new pump to inspect the diaphragm and noticed that when apart there was no play in the lever. When compared to the old pump the spring underneath the diaphragm on the new is much longer holding the diaphragm up much higher. This is causing the lever to have play when reassembled.
I'm assuming the play in the lever is too much and the cam lob can press it in far enough to initiate a pump. I've ruled out a vacuum leak by checking and rechecking thread fittings and by using new fuel lines. Soooo....faulty fuel pump? right?
Any input is helpful! Thanks!
