OMC 95 50FAPHUE Fuel Starvation

DaveNix · Jul 22, 2011

I have been trying to find the source of fuel starvation for a couple of years. I have gone through the fuel system testing in the manual and determined there is no fuel blockage before or after the LP fuel pump which seems to be the issue. The pressure on the high side was inline and the FP regulator checked out. The pressure on the low side was at 1 psi. All tests seem to piont to the LP fuel pump being bad. I replaced the LP pump and it will work until it heats up. It gets very hot after a minute of use and then will not suck the fuel necessary. The engine will keep running because the HP pump is pulling the fuel into the reservoir. One thing I noticed on the electrical side is that the voltage to the pump is at 14.5 v. The manual asks if the voltage is at least 10.5 v to the pump but doesn't specify a maximum. Could this be causing the pump to run hot and fail?

Don S · Jul 22, 2011

Re: OMC 95 50FAPHUE Fuel Starvation

Hook up a remote fuel tank (6 gal outboard tank) and run the engine and see if the fuel pump runs cooler. Usually air is the cause of fuel pump problems.
Simple things like not using mini hose clamps on the fuel lines between the tank and engine can cause air leaks. Did you use the clear hose method test to look for air bubbles going into the engine fuel filter?

DaveNix · Jul 22, 2011

Re: OMC 95 50FAPHUE Fuel Starvation

I did. There were no bubbles when the pump was working. Once the fuel pump ran for a minute and heated up, the fuel went back down the clear hose into the tank.

mcleaves · Jul 22, 2011

Re: OMC 95 50FAPHUE Fuel Starvation

While it might not explain the hot low pressure pump, is it possible you got debris in the system past the filters and clogged the injectors? Wouldn't that act like a starvation problem? I have the exact same engine and fuel system. I replaced both my pumps AND my VST tank last year. It was shocking how much debris had made it into the old VST tank. After that it's just the regulator and the injectors. I also had my injectors serviced this year and I have all the old baskets in front of me. Quite a bit of debris in them.

But Don't suggestion of a separate tank and tight connections is the first test.. And trust me, the connections are not something to dismiss. Don't ask me (or Don

) how I know! Check them!

DaveNix · Jul 23, 2011

Re: OMC 95 50FAPHUE Fuel Starvation

I had the VST tank apart last week and it was clean. The screens are clean on both pumps. I did replace the FPR while I had it all apart. The engine runs great as long as the LP fuel pump is cool and working. I experience the fuel starvation when the LP fuel pump heats up and doesn't pump fuel. I saw this when I had the clear the hose coming from a gas can. I don't want to replace the LP pump until I know why it is heating up.

Don S · Jul 23, 2011

Re: OMC 95 50FAPHUE Fuel Starvation

Did the pump heat up with the remote fuel tank hooked up? If it did, replace the pump.

DaveNix · Jul 23, 2011

Re: OMC 95 50FAPHUE Fuel Starvation

Yes, It did heat up. Do you think the 14.5v when running has anything to do with it? You has posted a diagram of the electrical circuit showing diodes before going to the relay. Do the diodes have any resistance accross them to lower the voltage? I was reading that some do, but it was on the internet and I am not an electrical engineer so I don't know if that is true. I don't want to throw $150 at another pump and it still heat up. Thanks for the quick reply Don!

mcleaves · Jul 23, 2011

Re: OMC 95 50FAPHUE Fuel Starvation

I agree with Don. I don't think the voltage is an issue. Let me look at my efi and electical manual and see what says. Sometimes new parts are just bad. I bought mine from Autozone. They tend to have decent warranties.

EDIT: meant to say "DON'T think the voltage is an issue"

DaveNix · Jul 25, 2011

Re: OMC 95 50FAPHUE Fuel Starvation

How much did you pay at Autozone? I didn't realize they had marine parts.

mcleaves · Jul 25, 2011

Re: OMC 95 50FAPHUE Fuel Starvation

Those pumps are not marine specific.. If I recall it was around 60.00 for one and 90.00 for the other. let me see if I can dig out the old receipts. If you pull the pumps and look at the numbers (or if you can see them installed) you can google or look them up right on Autozone's site. Other places have them too.

DaveNix · Jul 25, 2011

Re: OMC 95 50FAPHUE Fuel Starvation

Thanks mcleaves! Did you have a chance to look at the efi and electrical manual to see if the voltage is too high?

DaveNix · Jul 26, 2011

Re: OMC 95 50FAPHUE Fuel Starvation

Do you happen to have the part number through AutoZone? I went into my local store and the kid could not find it without a part number....

mcleaves · Jul 26, 2011

Re: OMC 95 50FAPHUE Fuel Starvation

I looked last night and couldn't find it. There is a long discussion on here where others posted the part numbers. I am headed out to wrnce on the engine and will look at the pumps and grab the numbers by hand..

mcleaves · Jul 26, 2011

Re: OMC 95 50FAPHUE Fuel Starvation

Hi Dave.. The part numbers on my pumps are useless, but I found the iboats thread with the good info. I have both these pumps in my 5.0 EFI. Here is the link to the iboats thread:

http://forums.iboats.com/showthread.php?t=298952&page=1

And here is the relevant post from jdblya:
"The High-Pressure is a Carter # p61171 and the low pressure is a #P60965 or a Airtex/Master E8263. Autzone and Advance sell the low pressure for $72.99. I ended up getting the high pressure from napa for $123. Both of them are not normal stock, of course and took a day to show up.

The low pressure sits on top of the fuel filter on the front of the engine where the feed line from the tank is, and the high pressure mounts on top of the fuel reservoir on top of the engine behind the intake manifold. "

mcleaves · Jul 26, 2011

Re: OMC 95 50FAPHUE Fuel Starvation

DaveNix said:
Thanks mcleaves! Did you have a chance to look at the efi and electrical manual to see if the voltage is too high?

The only thing the manual has in the diagnostic section is to make sure the voltage is at least 10.5 to each pump. No upper limit. I don't think that's an issue

OMC 95 50FAPHUE Fuel Starvation

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