Fuel Pump testing

[John Evans]

I got the gauge and other materials as outlined in the instructions for testing your fuel system. I went down to the boat ready to pull off the fuel line from the engine side of the fuel water separator and found the line to be connected directly to it. Can anyone list the specific sizes of brass fittings to bring both the filter and fuel line to barbed ends so that the test rig can be installed?

 

[Bondo]

Re: Fuel Pump testing

Ayuh,... Filter housings like the 1 pictured take either 1/4" pipe, or 3/8" pipe threaded fittings...

 

[John Evans]

Re: Fuel Pump testing

I just had and idea, maybe a bad one. There are 2 in's and 2 out's on the housing. Could I just remove the plug from the unused out, engine side, of the housing and replace it with a nipple for the vacuum gauge?

 

[dubs283]

Re: Fuel Pump testing

Could I just remove the plug from the unused out, engine side, of the housing and replace it with a nipple for the vacuum gauge?

no, your guage for reading either pressure or vacuum must be in-line with the fuel line

 

[Bondo]

Re: Fuel Pump testing

Could I just remove the plug from the unused out, engine side, of the housing and replace it with a nipple for the vacuum gauge?

Ayuh,... That would show filter, 'n tank restrictions....

"T"ed at the carb, or anywhere downstream from the fuelpump tells pressure....

 

[John Evans]

Re: Fuel Pump testing

Going by this procedure I should be testing vacuum on the engine side of the filter.

http://forums.iboats.com/showthread.php?t=283269

Here's my plan. I'll make a barbed nipple fitting for the unused fuel out port of the filter housing. At idle I should have 0-4 in hg. Take the boat out and run it. If the boat leans out under load and I still read 0-4 in hg my fuel pump is suspect if the reading goes up I have a fuel restriction. Then I'll collapse the fuel line input to the fuel filter at idle and see if my pump can deliver 6-9 in hg, per the procedure, if it can I'll focus on the tank/boat side of the system over the winter to fix my lean/backfire issue.

 

[John Evans]

Re: Fuel Pump testing

I ran the test and at idle I had fluctuations between 1 and 2 inches of hg. Under load she seemed bogged down, no power, and was steady at 1 inch of hg. I guess I'll do the fuel pump over the winter.

Any thoughts on replacing just the pump or the whole cool fuel assembly?

 

[John Evans]

Re: Fuel Pump testing

Any thoughts on replacing just the pump or the whole cool fuel assembly?

 

[Dshow]

Re: Fuel Pump testing

What do you have...

Edit: I would just replace the pump if that is the issue. The whole cool fuel system for my boat is $300+ on Ebay. Just the pump can be purchased at Summit for $117... can't beat that.

I would start at -> http://www.showmetheparts.com/airtex/
Select the 'Med/Heavy Duty/Marine' tab.
Under Type select 'Fuel Pump Marine'
Select your 'Make' (Mine is Mercury Marine)
Select your engine.
It will show your the Airtex pump part number you need, then search and find the best price!

 

[John Evans]

Re: Fuel Pump testing

Ok, I ordered the Airtex from Summit Racing, http://www.summitracing.com/parts/ATX-E11004/, for $116. We'll see how it goes.

 

[John Evans]

Re: Fuel Pump testing

They canceled the order, found one at rockauto.com. They indicate they have 1 left, I hope that's true.

The next step is the Mallory Marine Electric Fuel Pump - 9-35433, around $60 more.

 

[Dshow]

Re: Fuel Pump testing

So, I'm trying to follow your last post... You ordered the Mallory pump from rockauto, which is OEM, and it was about $176?

 

[John Evans]

Re: Fuel Pump testing

I ordered the airtex from rockauto for around $100.

I have the fuel pump and was following this thread on installation issues. http://forums.iboats.com/showthread.php?t=458904&highlight=cool+fuel+sytem

I pulled everything out of the boat that i could even the deck plates for better access to the cool fuel system. I was discouraged by the cool fuel thread thinking that i might have to pull the motor as nuts #28 are attached to the motor mount and almost inaccessible.

The nut is a 9/16 and the flange on the cool fuel mount make it impossible to get a box end on it. If you get a socket on it the motor mount is too close to use a ratchet without a universal adapter and with it you just roll off the nut. I found a solution today at O'reilly's, a 9/16 spark plug socket that has hex end that i could get a box end on. I broke those #28 nuts loose. Earlier a friend suggest a marine mechanic and now that i have proven to myself that the motor wont have to come out I think I'll let a pro break all the lines loose and install the new pump.

I'll let you know how it goes.

 

[John Evans]

Re: Fuel Pump testing

I hired a local guy to install the pump, he did it in around an hour. I'll run it, check fuel pressure and let you know how that goes.

 

[Pete104]

Re: Fuel Pump testing

Best wishes!

 

[John Evans]

Re: Fuel Pump testing

She started and ran great on muffs. I put a vacuum gauge in the fuel line and saw a little bump when I turned the key and a little at idle. I then collapsed the fuel line and the vacuum crept up to 5in of hg. I never did that before, before the pump change I hardly got any vacuum with a collapsed hose. I think I have a new problem with the cooling system but I'll start a new thread for that.

 

[John Evans]

Re: Fuel Pump testing

I got it the water today. Just past the no wake buoy I take it easy up to 4k rpm then the banging starts and I lose power. After i let go of the idea of following an anchor to the bottom i idled out of the cove I gave it another try. She ran great 5 miles to my dock. I picked up the wife and kid and we ran down river 3 or so miles to an island and she ran great. Coming home it knocked a few times but not enough to come off plane and she ran fine the rest of the way home.

I'm a bit lost, it seems 90% fixed. Any ideas on the last 10%?

 

[John Evans]

Re: Fuel Pump testing

Any ideas on the next step?

 

[John Evans]

Re: Fuel Pump testing

Another year into this problem. I had the same guy change the fuel pressure regulator hoping that it's fix the last bit of the issue. As I said before the backfire issue was mostly solved but after the latest repair I anticipated no problems, I was wrong. After a winter and spring on the trailer the backfire and power loss was back bad as ever. So once again in a depression I settled in for the hour long idle speed run to our dock. After around 30 min I tired it again and she got on plane a bit quicker then backfired and bogged down. I kept trying ans each time it seemed to get better until the last 1/2 mile she ran and I felt a few ticks but she never backed down and I stayed in the gas. I'm not saying it's fixed I full expect to have a frustrating summer chasing this down again.

I'v always had a jumpy tach which I never considered a cause or symptom, as it's done it from the time I bought the boat and several years of good service but I have seen some suggestions that this could indicate some timing issues. I can't imagine though how a timing issue could be intermittent. Then again I can't wrap my head around how any cause can be bad then get better and go away and come back worse. It is very frustrating.

 

[Failproof]

Re: Fuel Pump testing

Could be ignition cutting out, or tach causing the problem. Disconect tach at coil and run again to rule out tach/tach wiring. Could be a wire shorting out/loosing connection as well. Best of luck!