View Full Version : 2000 Mobius V will not stay running

06-05-2006, 02:21 AM
This is my 2nd attempt to post this info, something did not work the first time. . . My 2000 Mobius V started right away this spring, but letting it warm up I noticed after about 5 min the voltage gauge was reading 13.8 volts, then suddenly dropped to about 10-11 volts and then the engine quit. I had to reset the main 20 A breaker on the integrated circuit board, wait about 2 minutes and it started right back up, but then would trip the breaker again. The longer I waited would allow it to run longer.

I disconnected everything but the gauges and wiring harness from the main circuit panel and even switched to my truck battery to be safe, but it would still stop running at random times. It did appear to be better, so I took it to the lake, and it stopped after 2 min. Frustrated, I bypassed the 20 A fuse and it started right up, and I then proceeded to idle on the trailer and occasionally rev it to 3-5 k and it ran like a champ for about 3 min. It then died and I have been unable to start it even after a day of rest. It might have been in my head, but the wires on the circuit board appeared warm to the touch.

At this point, I've verified I'm getting spark on several cylinders. I pulled the distributor cap and noticed a fair amount of corrosion on the terminals, yet it's creating spark. I can smell fuel, yet the plugs did not seem overly wet. Another odd bit is two of the 8 plugs were quite black, but the other 6 were very clean, since they are new MR43LTS plugs.

I'm concerned this could some wire that is shorting, but I'm not sure how to go about finding this. I think the hint is that the volt gauge showed a drop right before it died. I was watching the battery with a meter and noticed it also took a drop but still stayed around 12.3.

Any help or more troubleshooting steps would be very appreciated. I hate electrical problems.


06-06-2006, 01:29 AM
After digging more, it appeared that the main carb venturies were not injecting the usual spurts of gas, that would happen if you pumped the gas. I looked at the floats and the main float level was very low, while the secondary was full, which makes sense since it's only used at loads.

I jumped the purple and red wires on the oil pressure sender to activate the pump with the key in the on position. Before I did this the voltage was 12.4 at the battery. After the pump started to run, which I could hear, it dropped the voltage at the battery to 11.8. However, the purple wire, which is what the voltmeter and coil run off of, was down to 8.1. On top of that the jumper wire, which is 14 gauge, was hot to the touch after running the pump for no more than 30 seconds. I did the same test with the pump disconnected but still jumping the wires and the purple wire voltage was 12.05, after taking away the jumper there was no change in the purple wire voltage, leading me to believe the wire might be ok.

So my question is, could the fuel pump have a short that is pulling extra voltage, which could have been tripping the ignition's 20A fuse? Or is the fuel pump ok, but there is some short in the purple wire, which is what appears to power the fuel pump? When I do a continuity test on the fuel pump wires to the battery I get a beep with the ground wire, but not with the red wire at the pump.

My plan is to order a new pump and see if it also drops the voltage or not. If not problem fixed, if it does then it must be a wire. Any other suggestions would be very welcome. It's either this or wait 2 weeks to have a dealer even look at it.


06-10-2006, 01:01 AM
I think you are on to something with the fuel pump. It would make since that if the pump is overheating and shorting that it could trip the breaker and cause your short. I would try getting a turkey baster and try to keep the engine running with the fuel pump disconected. When the fuel pump went out in the truck the way we tested it before doing all that work was to see if we could keep it running on an artificial fuel source. Be very careful if you try this...backfires can prover very interesting. Hope this helps.

06-12-2006, 12:54 AM
Well it appears the fuel pump was problem #1. I started the boat last night after installing the new pump, exact same Carter model, and it worked great, no electrical issues. I did test my old pump on my battery charger hooked up to some water and there was nothing out of it and my charger was working very hard to keep up with the draw.

Now I have a new fuel related problem. Tonight I was going to let it run for 10 min, but it died after about 30 seconds of rough idleing. When I looked at the carb I could see gas just pouring in via the overflow tube on the secondaries, which is why it died. I let it sit for 30 minutes and the same probem. I unscrewed the float bowl window and you can imagine how much gas came out. I did the same to the primary and it also had gas come pouring out.

So what is the next step? I assume the float is stuck and it just keeps pumping as into the bowls, or could the new fuel pump be too strong? I doubt it but had to ask. My last question is what kind of carb do I have? The model # on the air horn is 75021-1. From what I can tell this is the 4150 Holley. Any advice on carb rebuilds or where to get one I'd appreciate it.

Thanks everyone,


06-12-2006, 09:16 PM
You are getting out of my expertise. I have rebuilt a few "simple" holly carbs, but never one of the double pumper carbs. Seems like it would be as easy, but just twice the parts. i would check to see if Summit or Jegs offerred the rebuild kits. I will look around as well. Good luck.

Jegs has one for 84.99

Summit offers these kits
http://store.summitracing.com/egnsearch.asp?Ntt=holley+4150+rebuild&searchinresu lts=false&Ntk=KeywordSearch&DDS=1&N=306368+115