Trying an electric fuel pump...

capecodder116

Petty Officer 2nd Class
Joined
Jan 15, 2007
Messages
104
I have a 1984/260 mercrusier. Long story short...I've been having an ongoing, intermittent problem with engine quitting for lack of fuel....

Have replaced all filiters and water seperators, removed fuel tank and checked for blockage and cleaned tank, installed new vent and vent line and all fuel lines, rebuilt the Quadrajet 4 barrel carb, and replaced the mechanical fuel pump and problem still exists so decided to try an electric pump.

My question is can I leave the mechanical pump attached to the engine while I use the electric pump? If it's OK to do, should I plug off the fittings at mechanical pump?.......
 

Robj

Lieutenant
Joined
Mar 22, 2007
Messages
1,441
Re: Trying an electric fuel pump...

I would remove it and get a plate from your autoparts supplier to block off the hole. Why have it there if it is not required? Also if you block off the ports, the pump is still pumping despite not being hooked up and you will probably destroy the pump in no time. You can also plug where the vent line goes into the carb, it is no longer required with an electric fuel pump.

Have a great day,

Rob.
 

Haut Medoc

Supreme Mariner
Joined
Jun 29, 2004
Messages
10,645
Re: Trying an electric fuel pump...


If you replaced the fuel pump & you still have issues, you are wasting your time & money by installing an electric fuel pump.....
Your problem lies elsewhere........;)
 

Haut Medoc

Supreme Mariner
Joined
Jun 29, 2004
Messages
10,645
Re: Trying an electric fuel pump...


Assuming that you checked the pick up screen, & anti-siphon valve & cleaned the tank, I would say the problem is your carb......
You need to do a fuel pressure test........
If you replaced all of the components like you say, a fuel test will rule out everything up to the carb.....;)
 

capecodder116

Petty Officer 2nd Class
Joined
Jan 15, 2007
Messages
104
Re: Trying an electric fuel pump...

Thanks for your input Rob and Haut....

Haut, would you have any thoughts on the problem?? By the way, I have also changed out the anti-siphon valve and tired running without one as well....
 

capecodder116

Petty Officer 2nd Class
Joined
Jan 15, 2007
Messages
104
Re: Trying an electric fuel pump...

Ok....can you advise what tests, and testing procedures...also, what I'm looking for in the results...as this is a very intermittent problem, what would base line readings be for normal operations..??....

You suggest the carb would be bad....have had it rebuilt and was told everything looked fine inside....what makes you think the problem is the carb?
thanks..
 

Haut Medoc

Supreme Mariner
Joined
Jun 29, 2004
Messages
10,645
Re: Trying an electric fuel pump...

I'm assuming that the problem is that the engine quits under sustained load?....
It will idle all day long, but quit or stumble when under prolonged load?.....
Two things I would try......
1.......Get a portable six gallon tank & connect it & see if you can recreate the condition........
If it does not show the symptom, then the symptom lies somewhere before where you hooked it up....
If it persists, it will tell you to look after that hook-up.....
Perform a fuel pressure test......
Don S has a most excellent post on how to perform the test.....
You will have to find it in the advanced search function.....
I think your problem is in your carb.....
That said, I would perform the two tests above before I threw any more parts at it.....
A mechanical fuel pump should deliver all the fuel that engine needs.....:)
If you replaced all of the components like you said, I can't see it being in the delivery system or tank.....
It depends on how well you cleaned the tank.......
Debris can collect at the pick up screen & reduce flow, then fall of when the engine quits, then reaccumulate when load is applied.....
How clean is your tank?​
 

capecodder116

Petty Officer 2nd Class
Joined
Jan 15, 2007
Messages
104
Re: Trying an electric fuel pump...

I have gone out and run the engine under load for an hour or two, let it idle an everything is fine....could be OK for two, three or four weekends....Then I could be running along and problem starts out of the blue...engine reacts with a few surges as if it were running out of fuel then I'll pull back on the throttle and it will be fine for maybe 10 seconds or so, like the carb is refilling with fuel, then it will act up again, then finally stall out....extremely intermittent problem...

Have tried the 6 gallon tank experiment when she'd act up...the problem went away so we went back to the main fuel tank and problem happened again went back to the 6 gallon tank and she ran good again...that's when we figured we had a problem in the main tank so we drained it an cut an inspection hole (aluminum tank) in it as it did not have one. Thought the problem might be pick up screen clog or something of that nature but surprisingly there was nothing clogging pick up...so we throughly cleaned the tank..

I am not familiar with the advanced search...can you advise how would I do this search...thanks
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Trying an electric fuel pump...

Are you sure it's a fuel problem?
Intermittant can also be electrical. Had one about a month ago, would run fine for a while then start missing like crazy. All it was was a bad wiring harness from the distributor to the ignition module mounted on the port riser.
A wiggle test with the engine running will tell the story.
 

Haut Medoc

Supreme Mariner
Joined
Jun 29, 2004
Messages
10,645
Re: Trying an electric fuel pump...


Hmmmm........
Intermittant problems are the worst......
Anyway to 'search', go to the previous page with where all of the threads are listed.....
At the top it says, 'search this forum'....
Click on advanced, put in Don S & fuel test & see if that works.......:)
 

Coors

Captain
Joined
Dec 8, 2006
Messages
3,367
Re: Trying an electric fuel pump...

yep; hose sucking air? Don knows.
 
Top