Electric fuel pump power

[Jctritoon1992]

I have a 1992 4.3 litre Jc Tritoon. The problem is the electric fuel pump, When i turn the ignition all the way to starter position It has power but when the key is in run position it has no voltage. So the boat just starts and dies. Any ideas why i do not have voltage in run position. Don't know if this helps but it has power to the gauges in run position. Thanks ahead for any help. First time posting and have found these forum a big help.

 

[havasuboatman]

Re: Electric fuel pump power

The fuel pump power supply goes thru a switch that is tripped with oil pressure. If the engine isn't running no power to the fuel pump. If the engine is running and loses oil pressure, the fuel pump shuts off.
If you are testing the fuel pump circuit without the motor running, you get the results you have gotten.

 

[Jctritoon1992]

Re: Electric fuel pump power

My oil pressure needle gauge is broke so i cant verify oil pressure. But your saying i will only have constant power if oil pressure is good, and only when boat is running? Just got the boat and trying to work out all the bugs and make sure its done right.

 

[180shabah]

Re: Electric fuel pump power

Yup, fuel pump gets power from two sources, the starter and an oil pressure switch (port side of the block, above the filter). Quick test, install a jumper to bypass the pressure switch. If the boats runs, replace the switch.

DO NOT opperate the boat with the switch bypassed.

Also, head up to the "adults only" sticky at the top and download the factory maual for you engine and drive - FREE

BTW - welcome to iboats.

 

[180shabah]

Re: Electric fuel pump power

CORRECTION - I should have said verify the oil pressure first, don't wan't to do any damage here.

 

[Jctritoon1992]

Re: Electric fuel pump power

Well i bypassed the oil pressure switch and no luck starts and dies. The boat hasn't been started in years so i guess ill check fuel pressure and take apart the carb and clean it. Thank for your help it has been very useful and i know what to check if i can get it to stay running.

 

[Bondo]

Re: Electric fuel pump power

Ayuh,... You have already checked the fuel filter for water,+ changed it,...
Right,..??

 

[havasuboatman]

Re: Electric fuel pump power

If it starts and dies immediately as soon as you release the key, I'm thinking there is a problem with the ignition wiring. Like maybe the coil wire is attached to the wrong post of the starter relay, or not at all, and only the 12 start up override is connected.
Do you have voltage at the positive (+) post of the coil when the key is in the run position?

 

[Don S]

Re: Electric fuel pump power

I have a 1992 4.3 litre Jc Tritoon.

That tells us nothing. What engine Mercrusier, Volvo, OMC ? Do you have any model or serial numbers that may help us?

 

[Jctritoon1992]

Re: Electric fuel pump power

Sorry about that Don S. It is a mercruiser and the serial number is OD841054. I can get it to start, and figured out if i keep bumping the throttle up and down i can get it to run but wont stay running. It only wants to run at WOT. When it is about to die i throttle it up again and it will rev high (about 3000 rpms) so i back off the throttle gradually and it starts to die. I am running on muffs and know I am not supposed to go past 1500 rpms.

 

[Silvertip]

Re: Electric fuel pump power

Wrong! If the engine starts and dies when you let go of the key the carburetor is not the problem. The problem is probably a bad oil pressure switch (remember that your gauge doesn't work) and these two issues are related. How did you bypass the oil pressure switch? Diagnose, diagnose, diagnose. DO NOT solve problems by throwing parts at a problem. It gets expensive and time consuming.


Edit: Sorry -- blew past the part about running at WOT.

 

[Don S]

Re: Electric fuel pump power

It's not a fuel delivery problem to the carb, or it wouldn't run at 3K+ rpm.
Sounds like you need some carb work.

 

[Jctritoon1992]

Re: Electric fuel pump power

I jumped the switch by taking the wires off the oil pressure switch and connected them together. And pulled the wires off the fuel pump and checked voltage with ignition in run position. And i had voltage so i know i had the switch bypassed correctly. And thank you Don S I guess its time for a good carb cleaning and rebuild.