fuel pump problem

[jrrrr]

Hi, my dad recently bought a '98 Moomba Mobius and it had been running fine until recently when it would not start. I am 3 hours away at school so all the info I have was relayed to me over the phone but he said he was not getting voltage at the fuel pump and when he put some fuel in the carburetor and tried to started that fuel burned but it didn't get any more after that. The only thing at all wrong with the boat when he bought it that we were aware of was the guy told us how he had left the cap lose to the fuel tank and some water got in, but that was supposed to have been taken care of before we bought it. If anyone has any advice on what the problem might be I would be greatly appreciative.

[Buttafewcoe]

:?

[98outback]

I had this problem one time with my 98 outback. If you are not getting power to the fuel pump it could be due to low oil pressure. On the back of the engine there is a pressure sensor that has 3 wires connecting on top of it. One of the wires goes to the fuel pump. The oil pressure is what makes the power to the pump. Its hard to explain by typing. I hope you understand this.

[lowdrag]

How does the oil pressure effect the operation of the fuel pump? I'm not saying you're wrong, just that I don't get it. When the motor is not running there is no oil pressure, but when you turn the key the fuel pump should spin up even without oil pressure. To my knowledge, the oil pumps on these motors are mechanical and cannot produce oil pressure until the motor turns over.

One way to test the pump for sure is to get another 12v battery. When I had this problem I used the one out of my motorcycle. Use some jumper wires and see if the pump spins. If it does spin, then it's probably an electrical problem. If not, I'd say you need a new pump. I had a similar problem with my '03 Mobius. Pouring gas in the carb would get it to start for a few seconds. It ended up being a fuel pump that had seized over the winter. When the dealer was messing with it, it started pumping again when the bolts hold it together were loosened slightly, but he ended up swapping it out for a new one anyway.

[Brian Raymond]

Jrrrr, hope all is well. There is a 3 prong oil pressure/fuel pump switch just port and under the distributor. It is a safety device threaded into a oil pressure port. There is a Orange (batt), purple(ign), red(fuel pump hot), wire on the switch. When the engine is running (and the switch working properly), and there is oil press., it will activate the fuel pump and the motor will run. If no oil press. is detected, no voltage is sent to the pump and the motor won't run, hence the safety feature from locking a motor up. There are a few things to look for. First, verify your ground at the fuel pump, and the wires are firmly on. With a test light on the red post of the switch, while cranking, the light should come on and power should be at the pump. If the light comes on at the switch, verify with the same test on the gray wire on the pump. If no light present there, it is a wiring issue between the pump and switch. While cranking with the light on the red post, and it doesn't light, it is 1 of 2 things. There is debris in the small intake port of the switch, which may or may not be cleaned out by removing and shaking and inspecting (DO NOT USE A SOLVENT TO CLEAN). If this does not work, order the 2 prong Hobbes replacement switch through your dealer or Indmar. Hope this helps, keep us posted. Brian Raymond

[lowdrag]

Thanks for clarifying the pressure switch thing for me as well. Just one question though. By the way you described how the switch works, the fuel pump would still spin and pressurize the system on start up and then shut the pump down just after start up if it detected low pressure. Am I correct in my thinking on this? If so, what kind of delay is there on start up before it shuts down?

[Engine Nut]

Thanks for clarifying the pressure switch thing for me as well. Just one question though. By the way you described how the switch works, the fuel pump would still spin and pressurize the system on start up and then shut the pump down just after start up if it detected low pressure. Am I correct in my thinking on this? If so, what kind of delay is there on start up before it shuts down?

Boat Boy didn't give you the whole story. There is a connection on the starter solenoid that is "hot" only when the starter is cranking the engine. The fuel pump is connected to this terminal so the pump comes on during the crank cycle. Once the engine starts, the oil pressure activated fuel pump safety switch closes and supplies power to the fuel pump while the engine is running.

Engine Nut

[lowdrag]

Thanks. You can never know too much about these things especially when you're on the water trying to troubleshoot a problem.

[BensonWdby]

So here is another one from left field. At the beginning of the season, first time in the water, my 99 Mobius (carb) fired enough to burn the winterizer oil and then nothing. Could not get it to fire. So I went back and put in new plugs and went back to the landing.

Fearing the worst, I left the boat strapped to the trailer to avoid launching for no reason. I pulled the AC and used almost a full can of Ether on it. It would try to run and then fizzle out. Apparently the additional depth of being strapped to the trailer instead of floating caused enough back pressure on the engine that it would not stay running.

I drug it back to the dealer (only 35 miles), the guy put it on the hose and it fired right off.

Oone other thing I learned. The mechanic said that in addition to using the cold start position for the throttle, that I was supposed to pump the throttle full range 2-3 times to push the accelerator pump. I have never done this in the 6 years I have had the boat. He said I should be doing it every time it is cold. Go figure ....

Hope you got it figured out ...
Dave

[Jack Ellsworth]

We seem to have the same or similar issue with our 98 Mobius. We were out yesterday and the boat stalled when dropping off at the dock. We couldn't get it started again. So we pulled it out. Today at home in the driveway hooked up to the hose, we find that there is only 9 volts at the fuel pump when cranking (It did start right up today, but died shortly after running.) Fuel is being pumped, but then it seems to stop pumping. We were thinking maybe it was the oil pressure relay switch, but we still measured 12v at the fuel pump just before it stalled and no fuel seemed to be pumping. We did this twice. We are thinking it is the fuel pump now and it just isn't pumping enough fuel???? Also, it will start right up when hooked directly to the battery and not otherwise. Any suggestions?

[AaronWhitt82]

This thread is almost 5 years old... You should start your own thread and you will get more replies.

[Deanw]

I have the exact opposite problem. I just fired my 99' möbius up for the first time this season and I noticed as soon as I hooked up my battery the fuel pump started running. Never shut off even with key off. It totally filled my cylinders and fuel locked the motor. I would easily assume float stuck but why would the pump start pumping even with key off?

[zabooda]

It shouldn't. In fact, the pump is off until the oil pressure sensor energizes the circuit.

[Deanw]

It shouldn't. In fact, the pump is off until the oil pressure sensor energizes the circuit.

Your absolutely right. It shouldn't. But apparently when the dealer put my battery cable onto the starter there was no boot covering the post to the fuel pump safety switch somover time the batttery cable loosened enough to turn an 1/16 of an inch and make contact with that post. After further investigation I noticed that even with a boot over the terminal, the close proximity between the two terminals it would only be a matter of time before one of the wires would wear a hole in the boot. I ended up making an HDPE "barrier" to keep them separated. Works great now. Thanks for the forum. Lots of useful info here

[zabooda]

I'll have to check mine. Thanks for the feedback.