onesickpantera

iTrader: (1)

Yesterday I went out and when I turned the key my fuel pressure didn't come up. Popped the hatch and tried it a couple more times. The fuel pump wasn't kicking on. Unplugged the main harness and plugged it in again and tried it again and bingo pump kicked on with the key.

Once running all was good. Went for a 30 mile rip and shut it off and it happened again. I followed the wires from the pump as best I could and the go to a cluster with some tiny selenoids and small "electrical" boxes and one of them clicks when I turn the key. I hit reset buttons, checked fuses, unhooked batteries, checked the key switch wires and nothing. Then all of the sudden it works. And worked fine once running again.

I assume there is something that tells the pump when to kick on??? What should I be checking? This is a MPI motor.

onesickpantera

iTrader: (1)

I have been going out and turning the key on about every hour and the fuel pump kicked on 5 times in a row. Now nothing just a click from this thing. The wires go through a fuse then into this thing and then to the fuel pump.

stevesxm

two things...
one, the new fuels are quite "dry" ... not a lot of lubricant in them at all and if your pump is one of those where it uses the fuel to cool it, they quite often " stick" for lack of lubrication. cure for this is some top end lube in the fuel... marvel mystery oil or something like that.

two... there are two types of high pressure pump. vane type and g roter (sp) type. the vane type can pas some tiny junk very easily but the g roter type can not and will jam if anything at all gets in them. you can pull the pump heads apart and check for this.

all of these pumps are prone to this if they sit around dry for a long time.

what i have done to revive them is take them out and let then pump wd 40 for a while ... re circulate it in a gallon can and then run the top end lube, keep the filters clean and thats that.
and thats that.

i also don't run relays. on an efi system, the pump runs for some number of seconds before the engine starts and then shuts off. thats a relay controlled by the ecu.. this is all easy to isolate. switch pumps from motor to motor. if the problem follows the pump, thats the problem. if the problem stays with the motor then thats the answer.

onesickpantera

iTrader: (1)

Thanks for the reply. Unfortunately it's a single so I can't swap. I just got in from the garage and checked the voltage at the pump with the key on and nothing. So, I bypassed everything and used a jumper to go straight to the battery and the pump worked.

So, for whatever reason I am not getting voltage to the pump. The relay has 4 wires, 2 pink wires One large(about 10gauge) and one small(about 20 gauge) that both have voltage all the time. There is also a larger grey wire(same color as pump lead) and a small green wire. They are both dead with the relay unplugged. But maybe it has to be plugged in to transfer voltage???

I have no idea how the relay works??? But, obviously something isn't transferring power to the pump like it should.

onesickpantera

iTrader: (1)

I think i am starting to get this. It lloks like the relay is very similar to a selenoid. So, when i turn power on it should transfer power through the relay and to the fuel pump.

I was thinking it was probably a bad relay. But then I realized that there has to be a power source to the relay when the key is on, which is probably the small green wire. Turn the key on and the green wire "triggers" the relay to transfer power from the pink wire to the grey and in turn supplying the pump with voltage. Does this sound right? I actually hope not cause that means i need to track that wire down! I was hoping it was just a bad relay!

I can't get any voltage from the green wire when the key is on???

It is a Hella 4RD 960 388-15 relay.

stevesxm

if its an efi motor, that relay gets signal from the ecu. it is supposed to see it when key on for 5 secs, and then shut off until the motor cranks or starts. only sees it when the crank sensor says to the ecu that the motor is spinning fast enough to start or run.

i preach having the FACTORY workshop manual for just this reason. the aftermarket books don't deal with this effectively but the merc books deal with it in such detail that would never have had to ask this question. you would have your answer in minutes. it litterally was the best money i ever spent on my boat.

onesickpantera

iTrader: (1)

It is an EFI motor. Since the fuel pump only kicks on when when it needs pressure I am assuming there is some type of sensor to tell the relay when to kick the pump on? Once the pump kicks on it starts and runs perfect.

Not sure how much the Merc manual would help since it is an Innovation Marine motor. But it would be nice to get a basic understanding of how it works. I'll call Dave in the morning and see if he has any ideas.

Thanks for the info.

speedreeder

I really believe your problem might be in your engine wiring harness connector. Turn on your key, Go grab a hold of the big plug where they join together and slowly pull up and down and side to side and see if the pump kicks on while you are doing this. I have had several harnesses go bad. Good luck

onesickpantera

iTrader: (1)

I tried that when out on the water and it didn't help. But, then again I have no idea why it finally kicked on so it is a good possibility.

onesickpantera

iTrader: (1)

A local auto parts store has the relay for $12 so I will start there and hope for the best.