GT-40 Fuel Pump Issue

The last couple of times I started the boat up I had erratic fuel pressure that leads to an eventually stall. Now, the fuel pumps will not prime with key on or inconsistently prime. Pumps will not/inconsistently prime even when grounded to STO.

I worked through Lewy's fuel pump thread:

lewy-amb

I cleaned all the grounds. With meter set on 200 ohms, I have a reading of .01 on pin 40 and 60 at ECM.

I have proper voltage on pin 37 and 57 at ECM with key on.

The one thing I noticed is that on 85 terminal of the fuel pump relay, voltage is less than 2.0v. The funny thing is that I sometimes get proper voltage and the fuel pumps work. Pressure is 32 psi when pumps work.

What would you recommend from here.

Also, no codes from tester. I did have to jump STI to ground to get code reader to work.

99 GT-40 and I do not have the fuse at the battery box. Power goes directly to starter relay. I swapped the relays and tried a spare that I have (cheap e-bay bosch style) and no difference in voltage. I'm getting 12+v on terminal 30 of ECC relay. Wouldn't the 11+v reading on pin 37 and 57 confirm the ECC relay is working?

I noticed that if I wiggle the wire (85 on fuel pump relay) I sometimes get a jump in voltage. Could it be possible there is a bad connection somewhere?

Alright, I jumped terminal 30 to 87 on ECC relay harness and I have less than 2.0v on each pin. When I remove the wire voltage goes back to 12v on terminal 30. I guess I need to check some components and/or wire down the line.

lewy2001 wrote: James, all jumpering terminals 30 to 87 of the EEC relay does is simulate a activated relay. If it drops to 2V at terminal 85 of FP relay and 87 & 30 of EEC relay you have a problem somewhere in the circuit after the EEC relay.

Any recommendation on where to start troubleshooting?

lewy2001 wrote: Did you measure the voltage at fuel pump relay with the relay removed? It could be a faulty relay or pump.

Yes, it was under 2.0v. (I ordered two relays anyway. They should be here this weekend.)

lewy2001 wrote: If you tested voltage with FP relay removed the voltage drop is coming from elsewhere in the EEC power circuit. Remove the big connector at the bottom of ECM (computer). Mentioned in AMB's old thread how to do this. Is the voltage at terminal 85 of fuel pump relay harness now 12V? Also test the voltage on pins 37 & 57 of the ECM connector.

Still 2.0v with ECM removed at both terminal 85 and pins 37 & 57 (check with grounds 20, 40 and 60. I also checked voltage on TFI module and ignition coil connector and got the same reading.

lewy2001 wrote: I assume you are working from the circuit diagrams in the reference section.

I was able to print everything out so I can look at it while I work.

Thanks for the help Lewy. Everything was running great until I brought the boat back from its last trip. I was flushing the engine and it starting having problems.


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05-11-13 - Edit Post: Just to update. I ended up replacing the 12.5 AMP breaker which helped resolve my problem. Had a .40 resistance with ohm meter. Voltage was fine with key off, but dropped with key on.