nordic95

EFI gurus,I need help


I'm working on a mercruiser,1988 320HP 5.7 liter.The problem I'm having is that when the boat sits for a week or two it is very hard to get started,but once fired it starts and runs great all day.I installed a jumper cable to the fuel pump,if I prime the sytem with the jumper it fires right up.This old EFI system has no prime mode when you turn the key on,it only has a safety shut off with an oil pressure switch.Is there a way to put a timed relay,or a fuel pressure switch in?One that would prime before I start?Im not sure if its the injectors or the pump causing the loss of prime over time,any way to test?I attached some pics so you can see the set up.

Thanks
Nordic95

nordic95

I cant beleave with all the motor heads on this site no one has an answer??



Nordic95

Ted G

iTrader: (1)

I have never seen an EFI engine like that, but here goes. It looks like the feed hose to the fuel rail from the pump is rubber. If it is you can clamp it off with a fuel pressure guage installed and see if it holds pressure, if it does the leak is at the fuel pump. If it still leaks then it is either the pressure regulator or 1 or more injectors leaking. If you clamp off the return line from the pressure regulator and it still leaks then it is one or more injectors. On my 96 502 MPIs I can set the ECU to either run the fuel pump to prime with key on or not, it's possible that that ECU may be able to be programmed like that also. If not the easiest thing to do would be wire a momentary switch to energize the fuel pump manually before starting.

Sonic30ss

I had two of them, it is an issue with the stock wiring. The fuel pump WILL NOT run if there is no oil pressure.The fuel pump is not controlled by the ECM, the only things that control it are the oil pump and the key switch I used a jumper to power the pump and prime the fuel rails and it would start on first try. I just learned to live with it.

nordic95

I am using the jumper wire now and it works great.I was wondering if any one has any kind of momentary,or timed relay I could wire into the circuit so that it will bypass oil pressure switch till engine starts.

Thanks Nordic95

mattee

Hi
.
I have a liberator 26 with twin 320 motors and ss drives witch I have own for nine years and tried to improve for each season. First the jumper is a must, I use a time relay from cars indoor light connected to the ignition and it work perfect. Another improvement is to lower the fuel pressure because these motors runs to rich, to fix that you need an adjustable fuel regulator. I custom fabricated my stock regulators to adjustable but I guess you can find some aftermarket stuff. You can connect one of these small 1, 5 inch fuel gauge at the front of the right fuel rail, disconnect the valve and the gauge will fit right on. Fuel pressure should be about 40 psi (stock over 45) and you got a motor that runs much nicer. Good luck from Sweden