270 fuel pump

I have a 78 Carver with twin 270's and a single fuel tank. Last fall as I was headed to have it pulled for winter the port engine lost power and eventually stalled and would not start. Checked canister fuel filter and that was about 1/2 full from what I recall and seemed fine. If I filled carb through the vent tube it would start and run until carb was empty. I swaped pickup lines at tank for the port to starboard and issue stayed with the port engine, so pick ups are both fine.

This spring i pulled fuel pump thinking it was the issue. If I push the pump actuator the fuel in pump does push fuel out the output port and it seems to draw vaccum on input port. I understand that with slow pushing it may seem to be fine but a small pin hole could cause A problem. I was going to take it apart to check diaphragms, but when I turned to first svrew to bore lose with very little effort. Checked a couple more and the same thing. I then tightened the remainder of the bolts and I could tighten each one a 1/4 turn. Could the bolts being that loose cause the pump to not pull fuel through the filter and from rank?

Thanks horse input.

Only way to find out is to try it, but considering safety and the low cost (relativly) I would just replace it. You said you swapped the pick up lines, did you check the line from the pump to the carb and do you have the small filter in the carb itself?

I thought of the line after posting this, but no I did not check the line from the canister filter to the pick up. I believe I checked the carb filter but not positive. That was last Sept., lucky if I can remember last month. Will check both, as well as replace them.

Sounds to me that you have properly taken advantage of having twin engines by swapping this and that for testing.

I'm with missnancy....... simply replace it..... and you may as well replace both fuel pumps while at it.

As for your question

I then tightened the remainder of the bolts and I could tighten each one a 1/4 turn. Could the bolts being that loose cause the pump to not pull fuel through the filter and from tank?

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If the screws had loosened and caused enough separation to create an issue, I think that you would have seen or noticed a gasoline leak.


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If the diaphragm is leaking, you should have fuel in the sight tube (the tygon tube going back to the carb).

I'd be inclined to make sure the cam lobe is intact before replacing the pump....

Well tightened all the bolts, mounted the pump in a vise so I could actuate the pump and hold a thumb over the inlet of the outlet. While hold over the inlet it would draw and hold vacuum, while holding over outlet it would hold pressure. I then showed it to a marine mechanic and he said seems to be fine.

I replaced the rubber line from water separator and replaced a clamp that I realized was missing and reinstalled. But fuel within about 10 seconds of cranking engine. Seems good, but will confirm after it goes in the water I guess.

Thanks for for the input.

Well the fuel pump appears fine, struggling to get everything to run good. At launch the port which appeared to fuel pump issues last year. The port would not start for the marina. When I got there and tried it, it had fuel and spark and would pop a bit but not start. As I continued and started eliminating possibilities I relieazes the starter was struggling to turn it over. Pulled the starter had it rebuilt and was much better but still would start. Eventually put a little oil in each cylinder and fired up but would not idle smooth. After manually operating the chock by hand until it was warmed up and run with out chock it surged badly. Long and short I switched carbs motor to motor and problem stayed with the carb, but the starboard does run a little better with thus carb but does surge.

Opened carb and checked float height, it is right at 9/32" as spec sheet calls for. Tried setting at 5/16" and it was worse do I reset to 9/32". At idle a little fuel does come out of main jets and idle mice screws don't have much affect. Both carbs were rebuilt a couple years ago and the idle mix hole were drilled out.

Any suggestions as what may be causing the surging.

Thanks Steve

Are you running last years fuel?

leiniemann said:

....At idle a little fuel does come out of main jets and idle mice screws don't have much affect. Both carbs were rebuilt a couple years ago and the idle mix hole were drilled out.

Any suggestions as what may be causing the surging.

Thanks Steve

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that's know as nozzle drip....and typically happens when the idle speed is elevated.....which will also cause the 'no effect' syndrome with the idle mixture screws....what rpm is "idle"?

also, you need to make sure the choke functions properly or the carb will never function properly....

any idea why the mixture screws were drilled out and to what diameter??

Mark

The chocks have not been functional for 8 or 9 years. When cold bring up RPMs to 700 to 800 rpm's for 20 to 30 seconds and then back down to normal and they have run fine.

The idle passages were drilled out too. 040" less than the largest diameter of the needle.

Thanks

Steve

as long as they are open and the engine is warm you'll be ok.....I'd guess after 5+ years, you have a good handle on startup, etc.

Most people drill out the idle passage to get more fuel flow....and it really shouldn't be necessary on a small block.....any idea why they were drilled?

Surge could be due to a number of issues-old fuel, dirt in carb, vacuum leak......when was the last complete tuneup?

One idle tube was completely plugged and the one was partially plugged. Cleaned with copper wire twisted together. The one that was partly plugged started with 3 strands twisted together and was evenly able to get 5 strands through. The completely plugged started with 2 strands one longer than the other and kept pocking and twisting until it got though. And kept adding strands until could get 4 strands twisted though it. Would gently push in and out working like a brush.

Back to idle fine. Won't be putting away for winter with an empty carbs again.

Thanks for help.