View Full Version : Oil Pressure Switch to Fuel Pump
06-11-2012, 03:24 PM
Is it possible that a weak battery w/resultant slower turning might prevent the oil pressure switch from reaching the set point (5psi?) to shut and send power to the elec. fuel pump (Carter pump)?
(1998 Sportstar 19)
When this was happening the fuel pump was not pumping/energized (no sound).
I changed the battery and all is well now. I'm just trying to figure out if this is the problem and if I need to change that oil pressure switch which is right under the tranny cooler and looks like a bear to replace. Hints on this job? Yeah, I'll do that anyway to ensure she's fit to fight!
06-11-2012, 04:21 PM
Take a look at this thread.
Just so you know, the "Fuel Pressure Switch" as it's called has two variations. An OLD three prong and the newer 2 prong. The Old Three prong on my boat had one wire from the "S" post of the starter that went to the Switch (yellow wire with red stripe), the second wire from the Fuel Pump to the Switch (red wire), and the third was a purple wire (constant power). To test to see if my fuel pressure switch was bad I connected the yellow wire with red stripe from teh S post and the red wire to the fuel pump, then connected the purple wire to them. It started but the starter was staying ingauged. I talked to Vince at SKIDIM and he said to move the yellow/red stripe wire on the starter to teh "I" post. I did this and it worked fine.
What you have to understand is that the yellow/red stripe wire only gives the fuel pump power when you are actually turning the motor over, as soon as you let go of the key that juice stops and if teh motor starts you will have oil pressure and the switch takes over allowing the purple wire supply power back, joining all three wires together.
Working off of the "S" post with the 3 prong switch it worked fine as when you get oil pressure it would switch off of the Yellow/Red wire and join the purple and red together. With the new style. 2 prong switch it joins all three wires together sending power back down the red wire and the yellow/red stripe wire from the purple. If you have th eyellow/red stripe on teh "S" post your starter will stay engauged... Make since? lol
They sent me this one
but I really needed this one
Hope this helps...
06-11-2012, 06:48 PM
Thanks so much for the good info! I'm researching all this now.
I do have the 2-prong type installed now and a new one of the same type from Skidim ;- ), who are always helpful.
BUT, there are just two wires connecting to it. I "simply" assumed that one wire comes from the ignition switch, and once oil pressure is up (psi?) the switch shuts and sends power out thru other connection to the Carter fuel pump "+" terminal. This made sense to me because when the engine stops the oil pressure goes to zero, the switch opens, and wahla the fuel pump stops (a good safety thing). The other connection to the fuel pump "-" terminal I assumed was ground.
I've had fuel pump problems lately, so my simple minded understanding may be messed up as is my wiring.... I'll check the wire colors and see if I can learn more.