Bad Fuel Pump Symptoms? (DT40)

Hi all... new to the group and new to the Suzuki outbout motors. :^

I bought an 85 model, DT40 a while back and have slowly been resurrecting it from 3 years of storage. It's on a 16ft runabout. Gone right though everything that needed, or might need doing, (impeller, carb recondition, gear oil, plugs, timing, etc,). I had it on the water for the first time today and it seamed to run ok (nothing spectacular) at low to medium speed, but when I run it full throttle the motor dies after about 2 minutes. It starts again after a fair bit of cranking but the same thing happens again each time I run it at close full throttle.

I suspect the fuel pump is not working at full capacity. The last time it stopped I saw that the bowl under the fuel filter was just half full. I disconnected the hose from the pump to the carb and cranked the engine over but no fuel came from the pump until I primed it by squeezing the hand pump on the fuel tank line.

I ulled the pump and stripped it down but cannot see any obvious problem with the diaphragm. I did notice that one of the metal flapper valves (on th eintake side I think)was not fully closed against the pump body. I'm not sure if this is relevant....

So... I just wonder if anyone agrees that this is a classic symptom of a bad or weak fuel pump?

Thanks! and greeting from the fjords of Norway!


Bill Carr

Re: Bad Fuel Pump Symptoms? (DT40)

Sure sounds like an insufficient fuel flow to support WOT, scooper.

The fuel pump is the prime suspect, and if that check valve isn't closing reliably it needs replacing. I don't know if a pump overhaul kit includes the check valves.

Inspect the whole system, though. I have found pinched fuel hoses causing the same symptoms.

Good luck, and welcome to iboats.

Re: Bad Fuel Pump Symptoms? (DT40)

Something doesn't quite make sense here... The fuel bowl that holds the fuel filter was almost empty after the motor cut out at wot. The fuel pump draws fuel from the filter. If the pump stop working or works at less than it should then why would the filter be empty when the filter is upstream?

Doesn't make sense.. I'm now more inclined to look for points on the fuel line that might be sucking air into the system.

DogScoop

Re: Bad Fuel Pump Symptoms? (DT40)

it's pulling more fuel than it can deliver, when you shut the engine off, the fuel that was sucked out is replaced with air as everything balances out again.

Rebuild your fuel pump. The only other plausible cause would be a fuel line restriction.

Re: Bad Fuel Pump Symptoms? (DT40)

Make sure that your tank has proper ventilation also ....

Re: Bad Fuel Pump Symptoms? (DT40)

deejaycee_2000 said:

Make sure that your tank has proper ventilation also ....

Click to expand...

Right on! This whole thing could boil down to a faulty breather vent on the tank..... Of coures I might never know, since I've allready done the pump, filter, tank hose connectors and a feul line.... The next trial on the water will tell. Sheessh... The spare parts market just love people like me... :|:|


DogScoop


DogScoop

Re: Bad Fuel Pump Symptoms? (DT40)

Ha, wouldn't that be something if it was the breather on the tank :/

Sometimes it's hard to KISS ( keep it simple, stupid! ) d

Re: Bad Fuel Pump Symptoms? (DT40)

redfury said:

Ha, wouldn't that be something if it was the breather on the tank :/

Sometimes it's hard to KISS ( keep it simple, stupid! ) d

Click to expand...

Yes.. but on the other hand.. a 22 year old motor with original pump and fuel lines has gotta be a breakdown waiting to happen. I probably would have changed them in any case. Preventative maintenance?? o


DogScoop

Re: Bad Fuel Pump Symptoms? (DT40)

Problem solved! She running nicely now. Starts within 2 seconds cold and at the slightest flick of the starter when warm. Pulls well through all power range and runs at full throttle without cutting out.

I'm pretty sure the problem was a cheap replacement squeeze pump the last owner put on it. I suspect the valve on the pump was sticking and cutting the flow of fuel to the motor. There was enough getting through to run at up to 3/4 speed but at full throttle she was starving for gas.

The only small problem I'm having now is that idle is sometimes a bit fast when the motor is warm, but mostly it's ok... I can live with that.

Thanks to all of you who helped me sort this out!

Cheers

DogScoop