Fuel Pump Question

[janpetemar]

My Chevy engine is an in-line 4 cyl with dual RBG carbs. The boat came with an alternative electric fuel pump mounted on the inboard transom with a fuel selector for running from main forward tank or reserve 6 gallon tank in rear. It also includes a fuel flow regulator mounted after the water seperator. The original or oem fuel pump mounted on the port side, between the oil filter and the starter appears to be a single diaphram mechanically driven pump.

Question is, when I changed the oil, there was fuel found, that I can assume is coming from a bad pump. Would I be better off in replacing the original pump with a dual-diaphram pump, installing fuel filters at the carbs, which there are none currently, and taking out the alternative system, and being able to provide proper fuel pressure required? I figure I should solve this problem prior to rebuilding the carbs, which sat too long between use.

 

[mkast]

Re: Fuel Pump Question

Are you assuming the fuel is coming from the pump? I would rebuild the carburetors first to isolate the source of the fuel.

 

[janpetemar]

Re: Fuel Pump Question

I have checked fuel flow to the old fuel pump, good. I checked from the old fuel pump to the rear carb, good. Checked fuel flow to the forward carb, good. But do not know if I am loosing pressure through the old pump into the lower engine?

 

[mkast]

Re: Fuel Pump Question

You state that you want to rebuild the carburetors anyway. Do that first, if fuel is still present in the crankcase then start looking at the pump, eliminate one or the other. That can be accomplished by rebuilding the carburetors.

 

[Don S]

Re: Fuel Pump Question

I'm not sure how the carbs could put gas in the oil, unless it was running very rich and leaking all the gas out of the carbs and leaking into the cylinders and going past the rings while it sets. Which I would think would be noticed by black smoke and hard starting cause the carbs were empty.

Fuel pumps are a very common cause for fuel in the oil. Especially if it's a LOT of fuel.

 

[Maclin]

Re: Fuel Pump Question

This may be another clue for your quest.....:
Are you running the boat a lot now? If you are and the carbs are draining enough to seep fuel past the rings and into the crankcase then it would would wet-foul the spark plugs and be very difficult to start and would not idle well in my opinion.

I do have some advice on your setup. If the auxiliary fuel pump is wired to an oil pressure safety switch, then GOOD! It willl not run if the engine is not running. If it is wired to be on all the time then that is not good. While I understand the dual tank plumbing adds value, I would definitely want it to supply fuel only during engine cranking or only while the engine is running. An alternate wiring would be to definitely have the oil pressure safety switch wired in but have a momentary switch to run the rear pump for a bit to prime the rest of the system, then when the engine starts the rear pump would stay running The mechanical pump on the engine should be the marine dual diaphragm model with the fuel vent hose fitting plumbed to go up to one of the carb's throat.

Good luck with your issues

 

[Maclin]

Re: Fuel Pump Question

The post from DonS was not there when I started, takes me too long to get my posts ready sometimes....:redface:

 

[janpetemar]

Re: Fuel Pump Question

The quantity of gas in the oil was greater than expected. Further investigation into the engine fuel pump indicated an automotive pump, which I am definitely going to change. The question on the aux fuel pump being wired into the oil pressure switch is grudgingly no....it runs all the time unless it is shut down manually.

I agree that the carbs should be rebuilt first, which rebuild kits have been ordered for. The only part(s) I can not locate are the idle mixture screws and springs, which are damaged from forcing against the throttle body. Any ideas where I can locate them for a Carter RBS. In addition I am also looking for the throttle adjusting screws and springs for same....