My fuel pump has no fuse? Interesting 5.0 fuel problem.

This question kinda fits between engine and electrical, so I guess I'll post it here first:<br /><br />I had an interesting problem last weekend... there was no fuel getting to the engine...<br /><br />2001 5.0 Mercruiser in 21' Bayliner.<br /><br />The only thing I did prior to the fuel problem was to install a larger-gauge wire to my trolling motor.<br />I figured I just knocked something loose, but it appeared all connections were fine.<br /><br />In the search for the problem, I noticed I didn't have a fuse anywhere for the fuel pump... Shouldn't I have one?<br /> <br />I looked through my engine manual, and sure enough... it doesn't show a fuse other than the 50 amp breaker that sits on top of the engine.<br /><br /><br />I finally loosened the fuel line at the carburetor (bumped the key) and it started pumping gas again... Was it a vapor lock or was it the poking and prodding on the wire harness?<br /><br />I'm not exactly sure why it started working again... A problem that seemed to fix itself... which is nice, but I'm worried that it will happen again.<br /><br />Vapor lock? Maybe the needle valve stuck closed and shut the fuel pump off until I released the pressure? <br />I haven't had one problem with this boat... this is the first time.<br /><br /> <br /><br /><br />H.

Re: My fuel pump has no fuse? Interesting 5.0 fuel problem.

Being in electronics I can only guess that while poking around, you made the connection again. I would be concerned about ventureing to far away from shore with a "self fixxing" problem. I would go thru the wiring for the fuel pump and see if you can't duplicate it with no power if so I would re-wire fuel pump.<br /><br />Good luck, and as I said only a guess.

Re: My fuel pump has no fuse? Interesting 5.0 fuel problem.

Thanks for the help...<br /><br />I kinda doubt it's a wiring issue, but I'm going to TRIPLE check again.<br /><br />I'm also going to run some carb/treatment/cleaner through it. It's very possible it just got a piece of varnish or something to stick the needle valve shut.<br />It only sat a week prior before this happened.<br />( and the new trolling wire)<br /><br />H.

Re: My fuel pump has no fuse? Interesting 5.0 fuel problem.

** UPDATE **<br /><br /><br />Well, I had the problem repeat this evening.<br /><br />I figured I'd start it up before I hit the lake tomorrow. It started fine, but quickly died. No fuel.<br /><br />I tapped on the carb where the fuel line connects, and it fired right up.<br /><br />Obviously a stuck float. Strange thing is, I've never had a needle valve stick closed... only open.<br /><br />I took the top of the carb off, and the needle and seat didn't look varnished or anything.<br />Everything looked OK.<br /><br />What could cause this?<br /><br />You'd think the fuel pump would have enough pressure to blast the valve open if it was slightly stuck.<br />Do marine fuel pumps have some kind of shut-off when they feel back-pressure?<br /><br />After I put it all back together, I ran the motor for a while, and it seems fine. Purrs like a kitten.<br /><br />??<br /><br />H.

Re: My fuel pump has no fuse? Interesting 5.0 fuel problem.

there is a fuse that controls the pump. the pump may have a bad connection. there is no stall feature on the pump but if the current draw on the pump exceeds what caan be pulled past aa bad connection it stops. the normal bad spot is at the oil pressure switch on the side of the block just above the oil filter pad. next time it happens take a voltage reading at the purple wire on the choke coil without disturbing anything else. carefully inspect/study the harness diagram for the current flow path for the pump, start at the battery positive and trace it all the way to ground. you will see the fuse then.

Re: My fuel pump has no fuse? Interesting 5.0 fuel problem.

Check your fuel pressure also. My 5.7L seemed to be running OK, but started cutting off at idle intermittently when the engine was warm. I found that the fuel pressure was under 3 PSI from my Carter marine fuel pump, although it still had good flow. Replaced it and pressure was back over 5 PSI and problem was gone. I guess the low pressure wasn't enough to open the float needle valve of the Q-Jet all the time.

Re: My fuel pump has no fuse? Interesting 5.0 fuel problem.

Similar situation today bayliner 21 with 5.0 have never had any troubel whatsoever in 207 hours. left the boatramp made it about a quarter mile and the boat died Sprayed with starting fluid and boat would run on starting fluid. Got the boat home and same thing would run on starting fluid sprayed directly into the air intake. checked fuel filter etc. took off fuel line and turned over seemed to pump fuel but with fuel line hooked up not pumping enough into carb to stay running. So Fuel Pump? I suppose I will replace the fuel pump and start from here. Any suggestions comments appreciated.
Jason

Re: My fuel pump has no fuse? Interesting 5.0 fuel problem.

I have a 1997 4.3 and was having intermitting stalls on the boat. It would start and run for less than a minute at idle, shorter with the throttle open. I check the fuel for water, changed the filter and check the carb. Everything seemed fine. I got a hose and ran it from a gas can to the filter intake. Still had the same problem. Because I used a clear hose on the last test I could see the fuel pump start and then it was cutting off. I started to search for the price on a new fuel pump and run into pricing for a fuel pressure switch. I notice my fuel pressure switch had oil on it. I jumped the wires together and the engine run fine in my driveway for at least 5 minutes. I disconnect the the jumper and soon the engine died. I am going to order a fuel pressure switch for $25 instead of a fuel pump for $200. The only question I have is if I just jumper the Fuel switch out is there going to be a problem. The oil pressure gauge seems to work and is setting at 40 when the engine is running.

Thanks

Re: My fuel pump has no fuse? Interesting 5.0 fuel problem.

There are better minds then mine here on this topic....but, from what I understand the reason behind the fuel pump being wired thru the oil pressure sensor is if there is no oil pressure present, (engine not running)the pump will not run it is a safety issue....if you bypass the oil pressure sensor, the pump will continually run if the engine is off but the ignition key is in the ON position.

Re: My fuel pump has no fuse? Interesting 5.0 fuel problem.

This is an OLD 2005 Post

Start a new thread with your questions guys so everyone knows who is replying to what post