Fuel pump relay clicking

[shaunsm_uk]

Hi All,

I have a query relating to my 5.0 MPI (s/n 0W611440) with regards to the fuel pump relay clicking constantly when the ignition is turned on but the engine hasnt been started, A while ago I discovered that someone had cut one of the wires to the alarm and now I think I know why, basically when the ignition is turned on the alarm beeps at a high frequency and after further investigation I've found the fuel pump relay clicks at the same frequency, the engine still starts when the key is turned but doesnt fire up straight away,

Both batteries are fully charged and I've tried a third known good battery, occasionally the fuel pump will prime on the first turn of the key and the alarm will beep once as expected, my guess would be a bad conncetion or something causing low voltage, are there any sensors on the MPI that can cause this, any info or wiring diagrams would be helpful,

Thanks in advance

 

[alldodge]

Do you have digital or mechanical shift, and is this an Alpha or Bravo drive?

The fuel pump relay is energized by the PCM applying a ground (Dark Green). With the alarm going on/off quickly would tell me the issue might be with the main power relay (Pink/Dark Green), and that may be causing the issue. This can be from a bad connection or a failing relay.

All relays on the motor of the same type are the same part and can be swapped. Many get tired of hearing the alarm during start up so they disconnect it. Main issue with that is they won't hear it when running if something happens

 

[shaunsm_uk]

Hi AllDodge,

The drive is a Bravo 3 and mechanical shift, I had another quick look over the weekend and the relay next to the FPR which I believe is the system relay is doing exactly the same, you mentioned a main power relay, do you know the location of this relay?
I'll try trace power to the relays in the next few days and see what I can find,
Makes sense why the alarm was disconnected although not a good idea

Thanks,

Shaun.

 

[alldodge]

Both relays should be side by side, they are square looking ones. Check also the engine and battery grounds

 

[shaunsm_uk]

Ah thats the one labled as the Ignition/System relay in the diagram, I'll try check them this evening, also good point about the engine ground as the motor had been removed not so long ago for fixing up bravoitis, battery connections are all clean and tight, hopefully an easy fix that I'd rather find on dry land!

Will let you know what I find out

 

[shaunsm_uk]

I did some more troubleshooting tonight, It turns out both the FPR and system/ignition relays are doing the same, measured voltage on the supply to the ignition switch, 12.6v measured the switched ignition and its sitting around 8v them measured voltage at both relays, surprise they're also around 8v so something is either drawing current when the ignition is on or theres a massive voltage drop happening, between the ignition key and the relays, I've started disconnecting everything I can from the batteries and will have to keep unplugging things till I get a decent reading, at least it explains why the relays are clicking on and off, if anyone has heard of anything similar or knows a starting point that would be good otherwise I'll keep unplugging things,
The motor ground is secure and all connections look clean and good, the mystery continues...

 

[Bondo]

The motor ground is secure and all connections look clean and good,

Ayuh,..... Welcome Aboard,..... Lookin', 'n wigglin' ain't good enough,.....

The connection needs to be taken apart, sanded to shiny metal Clean, 'n put back together,....

I slather 'em with grease after, to stop any possible corrosion,....

 

[shaunsm_uk]

Thanks Bondo, I'll definitley be cleaning up every connection I can along the way I have limited time to work on the boat at the moment so little bits at a time aslong as I can remember what I've done!

 

[shaunsm_uk]

I may have found the source of my voltage drop I'm going to clean up the connections and do away with the 90A fuse atleast to test

 

[alldodge]

That could do it, and for test would be good. Do suggest replacing just in case the alternator does short out

 

[shaunsm_uk]

Good news! Cleaned up the connections and connected back to the starter and I now have a healthy 12.6v at the relays, I've replaced the fuse even though it was an extortionate price from the local dealer, I know there are discussions about whether its needed or not but I don't like the idea of the alternator shorting and frying wiring or the cable form the fuse to the circuit breaker for that matter rather play it safe especially when in the ocean!
Cleaned up and greased every other connection I could find along the way so very happy,

Thanks for all the suggestions