350 mag mpi strange fuel pump relay problem

[nigb]

Boat started from cold ok but after turning off for hour refused to restart. Fuel pump not coming on when ignition turned on. What I have found so far.
1. Both fuel pump & MPR relays audibly click when inserted into MPR socket with power on.
2. Both relays don't click when inserted into fuel pump relay socket with power on.
3. If I bridge terminals 30 & 87 on fuel pump relay socket pump comes on & engine runs.
4. I have 12 volts across FPR socket terminals 85 & 86 so coils on relays should energise.
5. I can't see any burnt terminals on relay socket.
Would appreciate any suggestions on what to check next. I am wondering perhaps the relay terminals aren't connecting properly in the sockets? Thanks

 

[alldodge]

4. I have 12 volts across FPR socket terminals 85 & 86 so coils on relays should energise.

Should not see 12V on both sides for pump to run. The ECM applies a ground to pin 86 when key is turned ON for a couple seconds to prime fuel rail. Once pump stops running 12V will be seen on both 85 and 85

 

[Grub54891]

Not sure on yours, I was working on a volvo once. Had an issue with the same thing. Diagnosing was doing similar things. Replaced both relays, it still acted up. Located another relay, in the front of the motor not in the box up top, it was on the right side looking from the front. Replaced that relay and it worked perfectly. It may be different on yours. Even went so far as swapping computers from one motor to the other and it didn.t change before I found the other relay.

 

[dubs283]

Have you checked the fuses located in part A of the wiring diagram you posted ?

 

[nigb]

Have you checked the fuses located in part A of the wiring diagram you posted ?

Yes checked those thanks

 

[nigb]

Should not see 12V on both sides for pump to run. The ECM applies a ground to pin 86 when key is turned ON for a couple seconds to prime fuel rail. Once pump stops running 12V will be seen on both 85 and 85

Thanks for the replies. This YouTube video really helped

With ignition on & multimeter leads in FPR socket 85 & 86 ecm switch side I get 12.5 v.
Given I have power to 85 & 30, 86 grounds through ecm & relays are good I am pretty sure there is a contact fault with the relay base. I have purchased an automotive relay & base which I will try tomorrow. Weather permitting as boat is on mooring & rain is forecast. I will report back.

 

[nigb]

Update. FPR relay although clicking when put in MPR base had internal fault & was not connecting MPR 30 & 87. This is where it gets strange. I connected wires & pins to the automotive relay allowing me to connect the pins to the harness socket. With ignition on the relay would only work if I shorted the 86 ECM ground connection to an external ground. I then put a brand new Zettler relay in the FPR socket & again nothing. I plugged & unplugged the relay several times & same thing. I had 2 friends helping me a retired motor vehicle engineer & a retired electrician. I am a retired engineer. We all agreed there was a problem with the ECM earth connection. I was getting a 15 ohm reading on the meter on the ECM ground wires. Not much but should have been zero. I then plugged new relay back in again & tried again & pump burst into life & engine started. Turned ignition on & off a few times & pump/engine started. Tomorrow I will take it for a run.
I did find a similar post on another site where the person had exactly same symptoms with the new relay where it wouldn't work but after inserting & removing the relay a few times the pump would suddenly burst into life.
Hopefully it's not an intermittent connection time will tell. At least I know now I can jumper FPR contacts 30 & 87 to run pump to get boat home.

 

[alldodge]

I would guess its a bad connection, don't see it being the relay

 

[nigb]

I would guess its a bad connection, don't see it being the relay

The original FPR relay was bad I bench tested it. It appeared I had 2 faults the relay & a bad connection which would be unusual. Unless the spring contact in the relay base was faulty. If the fault remanifests itself I will post. Appreciate your response Alldodge.