1999 4.3 carb (elec pump) fuel problem

Joined
Feb 26, 2010
Messages
13
I know you guys see a lot of these and I think I have narrowed it down to a bad fuel pump. But I'd like to be a little more sure before I lay down $200+ for a new one.

Last year,just once, the boat started fine but would not run under load when pulling a tube. I changed the fuel filter and it worked fine up until last week (several trouble free outings in between)

Last weekend it was hard to start cold,at the time I thought I had flooded it. Cranked and cranked with the throttle in various positions and it finally caught and ran. We put about 60 miles on the boat that day cruising @ 25 +/- mph. Once during the day I had to crank it for a few seconds before it ran (it usually starts immediately once warm).

Yesterday I went to start it an it fired died, fired again caught and ran for a few seconds and died. No amount of cranking would get a pop out of it. Assuming I flooded it, I pulled a spark plug and found it dry, same with 2 more, put new plugs in anyway as I had them.

Tried again no pops. I do have good spark by the way.

I have since then:

Changed the fuel filter (filled new one with gas first).

checked that fuel is available to the filter pump from the tank ( pulled line from tank to filter at filter and fuel flows freely).

Also tried using a 5 gal can temporarily as the fuel source with the same result.

Checked the filter at the carb (perfectly clean).

Confirmed the engine will run fine as long as gas is manually fed through the carb (squirt bottle).

Cranked the engine with line disconnected from carb and got No fuel. Checked it 3 more time and did get fuel once but then none again.

During all this the fuel pump runs (you can just hear it while cranking) and stops when key is released.

All this I feel, points to a bad pump. But I don't know if a pump can still run and be bad/intermittently bad. I did remove the pump from the boat and direct wired it and can feel vacuum when I put my finger over the intake.

Bottom line is , money is tight and I can't afford to throw $ and parts at a problem like this. I'd like to get it right the first time.

Any insight would be a big help.

Thanks

Jim
 
Last edited:

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,468
Re: 1999 4.3 carb (elec pump) fuel problem

During all this the fuel pump runs (you can just hear it while cranking) and stops when key is released.
Ayuh,...
While Cranking on the starter, the fuelpump is powered by the little outside lug on the starter...
When it starts,.. It's powered by the igntion circuit....Through an oil pressure Switch,...
My guess is, that Switch is Bad...
It's probably located just foreward of the oil filter boss on the portside of the block, down low...
Should be a Cheap Fix,...;)
 
Joined
Feb 26, 2010
Messages
13
Re: 1999 4.3 carb (elec pump) fuel problem

I am 99% sure that we can hear/feel the pump running while cranking though....not that I wouldn't prefer to buy a switch vs/pump. The engine never catches and runs and no fuel is pumped while cranking.

Thank You by the way :)
 
Last edited:

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,093
Re: 1999 4.3 carb (elec pump) fuel problem

it will while cranking .you need to inspect/ check the fuel pump pressure switch. should be just above and slightly foward of the oil filter
 

180shabah

Rear Admiral
Joined
Mar 26, 2005
Messages
4,995
Re: 1999 4.3 carb (elec pump) fuel problem

Disconnect the oil pressure switch and jumper the leads together - now the pump will run whenever the key is in the on position.

if it starts and runs, replace the switch if it doesn't replace the pump.


FYI - these pumps frequently fail intermittently before they die completely. Also, I think everything you felt and heard was not the pump, just vibration from the starter. These pumps are pretty quite. I have a priming switch for mine, and even with the hatch up, I can barely hear the pump from the helm.
 

whitney

Seaman
Joined
Jul 26, 2010
Messages
69
Re: 1999 4.3 carb (elec pump) fuel problem

Hi Jim, please let us know what you find. Your symptoms sound very similar to what I am going through with a 1996 4.3 and Holley 2bbl.

I just completed fuel system testing and can find no problems, including fuel pump. I used a pressure gauge, test light, and a bypass switch on the water. Always running at 6-7psi. Flows great and I'm pretty confident the float chamber is staying full. I'm looking at carb issues now for my no-start and WOT power issues (which may not be related but I suspect now are both carb)

http://forums.iboats.com/showthread.php?p=2850139#post2850139
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: 1999 4.3 carb (elec pump) fuel problem

Well Jim
I think the one piece of information most needed is rather you have a Mercruiser or a Volvo. Both have 4.3L V6 Chevy engines, but the fuel pump setups are completely different. No oil pressure switch on Volvo's.
 
Top