Fuel pump ?????

**Gorilla0178** · 03-08-2011, 08:02 AM

If the stock fuel pump runs off vacuum, if the idle is low will that effect the pumps pressure? And the volume of fuel pumped????? I was told that the idle should be at around 900 in the water, which it will be 700-800 in gear. If thats the case I need to raise it, its only around 600 in the water and stalls if you punch it at idle. Wondering if that could be why the upper bowls dont stay as full.

**Action Dave** · 03-08-2011, 03:46 PM

That's a good question. I think that the vacuum should remain consistent whether it's spinning a higher RPM or being pull-started. But I'm no pro. You're definatley a little low in the idle RPM range but lack of fuel in the bowls may be related to float hight. Once again, I'm just throwing it out there, I don't have a definate answer.

**Riverratt** · 03-08-2011, 04:26 PM

Did you do a link and sync? It sounds like maybe the butterflies are opening before it is getting any timing

**flabum1017** · 03-08-2011, 06:37 PM

The pump runs off the pulse, not vacuum. the fuel pump will deliver more fuel at low idle that what the motor can use, this is why there is pressure. I have had motors idle at 500 rpm in gear with no problems. Sounds like your proble lies elsewhere as Riverratt suggests

**Gorilla0178** · 03-08-2011, 10:40 PM

Ok I did some testing today, I put a clear hose on the top carb and ran the motor. At first, if I took thge hose off the carb and pointed it up, it wouldnt pump enough to even flow out of the hose. I'm not sure what was going on. I increased the idle a little and took the pump apart again to check inside again and it was all good. I reassembled it and it seems to be pumping plenty of fuel now. Not sure what is going on. There is alot of air being pumped through the line, not sure if thats normal. If I pump up the primer ball and run it there's no air, but as soon as I give it some gas then it starts pumping air through the line. Any ideas????? I'll have to check it out again.

**Gorilla0178** · 03-08-2011, 10:50 PM

I didn't do a link and sync, I've checked evetything I can, The issue I'm having is it was appearing that after a few min running
the upper bowls dont seem to be getting fuel. If you give it gas you dont see any being pumped into the carbs, and they run lean. just trying to figure out if its a pump problem, there doesnt seem to be any blockage anywhere.

**mn808gade** · 03-08-2011, 11:36 PM

eliminate your fuel system by takin motor connector off a known (workes properly)6 gal fuel tank,then install tank hose onto fuel inlet of fuelpump. now go thru tests.sounds like u may have air leak tank pickup/cracked fitting/petrified hose/other. good luck

**Forkin' Crazy** · 03-09-2011, 04:43 AM

Sounds like you may have a leak on the suction side of the fuel system. It shouldn't be pumping air.

**Gorilla0178** · 03-09-2011, 05:14 AM

I'll do the test with another tank and check. I've looked for leaks, and havent found any. I took the pickup tube out and its aluminum, and there's no cracks in it. All the hose is brand new. The little plastic filter in the motor always has a little air in it, I thought it might be pulling it from there. I'm going to test it without the filter in place to see if that may be where it's coming from. Test test test..........

**mrcrsr** · 03-09-2011, 07:04 AM

exactly, you've got an air leak somewhere. just disconnect the feed line from the fuel pump and use a different tank(or container) directly to the pump and see what you got. if it still has air then the pump itself is introducing it. usually if you have a vac leak at the pump though when you squeeze the primer bulb you'll see a fuel leak. as far as fuel press between idle and wot, the 2.5 mercs you usually see 2-3 psi at idle, and 6-9 at wot

**flabum1017** · 03-09-2011, 10:13 AM

what pump do you have? is it a standard fuel pump or a VRO pump? If it's a VRO pump, are you still running the oil side? If you have a VRO pump and have the oil side disconnected, make sure it's plugged off well at the pump and the cap your'e using to plug it off isn't cracked

**Gorilla0178** · 03-09-2011, 06:35 PM

The VRO is disconnected. I thought that would be the leak cuz its not plugged. I plugged it while it was running and didnt see a difference. I'll be sure to try all these ideas in the next few days. Its a standard fuel pump. I figured the oil port should be plugged but its wasn't. I'll cap off the port and run it on a seperate tank and see if that fixes it.

**mn808gade** · 03-09-2011, 09:31 PM

plz list yr. and mod.when askin 4 help.hard 2 guess@ what u have.old VRO pumps are known to fail/loose screws/over-under oil,etc.want your motor to last??? get rid of vro, mix oil and itwill live forever.replace w/regular fpump (ex. 88hp).

**flabum1017** · 03-09-2011, 10:20 PM

VRO pumps can be a problem....cracked housings, failed diaphragms etc.... I had a few over the years that hahd sucked the tiny rubber checkvalves through the openings due to fuel restrictions, also had a lot of diapragm and check valves get ruined by methanol and ethanol......

**Gorilla0178** · 03-10-2011, 07:18 AM

Sorry its a 99, 200HP johnson. VRO is disconnected. I took the pump apart 2 times and everything looks good inside. Are you saying I should get rid of the pump all together and put a stand alone fuel pump? If so any recomendations? I was thinking of removing the little plunger that pumps the oil in, its connected to the fuel side of the diaphram and just snaps off. It's not doing anything anyways.

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