Low voltage to Fuel Pumps

[wepucci]

I just bought a 1997 Natique with the GT-40 engine. Currently it is not operational. I found a copy of the diagnostic service manual online and have been trying to troubleshoot the problem myself as the nearest dealer is ~3 hours away. I have spark, but the fuel pumps will not run. When I take the pumps off and put 12V to them, they work. With the leads to both fuel pumps disconnected, I get 12V to each for the first second or two, then I get about half that. However, when I connect the leads back to either pump, and then turn the key on and check for voltage on the leads to the other pump, I get nothing. My current thinking is that it may be something with either the fuel pump relay or the 15AMP circuit breaker that the power to the pumps passes through. I should mention that this started as an intermittent failure to start, then progressed to it dying on me at 25 mph. Any help is appreciated. As you might guess, it has been extremely frustrating to look at the boat in front of my house and not be able to use it. Not to mention blowing several weekend afternoons so far working on it. The summer is NE here is ticking away and I'm about ready to drive it up to NH for service but just figured I would take a stab at posting here and see if anyone had any ideas. Thanks.

- Bill

[DanielC]

RE: Low voltage to Fuel Pumps

Thank you for taking the time to download the manual. The fuel pump electrical circuit is on page 6-8 of the manual.
Do this test:
http://planetnautique.com/index.php?...amp;highlight=
Grounding the wire on the six hole plug should make your fuel pumps come on whenever the key is on, do not start the engine.
May as well check the fuel pressure while you are there.
There are two Bosch type relays on your engine. One powers the engine's computer, the ignition system, and also supplies power to the coil of the fuel pump relay. The other relay is for the fuel pumps only, after it gets power supplied to the coil, the engine's computer completes a ground, and turns that relay on, and your fuel pumps turn on.
If the engine's computer does not receive a signal that the engine is turning, the fuel pumps only run about a second, and switch off. This is normal. The fuel pumps start running when the engine is cranked, or the engine is running, normally.
If you suspect the fuel pump relay is bad, you can temporarly replace it with an automotive relay FOR TESTING PURPOSES ONLY
You can also make a short fused jumper with 1/4 male spade ends, and jump on the fuel pump relay socket where relay pin 30 and 87 go. This will also force your fuel pumps on until you break this connection.
www.skidim.com has the relays, the item number is R130011, they are about $13.00 plus shipping when I wrote this. If you have a GT-40 engine, go and order the relay now, so you will have it when yours goes bad. the most recent GT-40 engine is now 6 years old.

[AirTool]

RE: Low voltage to Fuel Pumps

I don't know much about the gt-40 configuration...but I have chased a few fuel pump problems on other vehicles.

I don't know how that pump is grounded....but, as usual, you need to check all the grounds.

Your relays may be week. Here are some ideas to test the pump and relay. These are all a lot of trouble......but that's what I've had to do before.

You can build a test loop with a good multi-meter that has a DC current feature and run the pumps through the meter to check the amp load. Be sure to have a fuse in this loop. Chose the size based on your fuel pump fuse or the limit of your meter...whichever is smaller. You could also measure the voltage drop at the same time with another meter. Amp load should be only 1 or 2 amps.

You can also check the motor and the ground by measuring the resistance of the pump to ground. Clip the ohm meter to the hot and to the engine ground/pump ground. I'm guessing for that pump the resistance should be 10 or less. I had one measure 60 ohms....it was dead and would not run.

You can also use the test loop you made to put a fake load on your relays. I did this once with a small spot light. With the test loop, I measured the light's load at 5 amps....low enough to not overload the fuel pump relay. Powered the light through the pump relay...had to manually power the relay since it doesn't stay energized when the engine isn't running. It would come on for two seconds when the ignition was energized...that's the GM way...not sure about Ford.

If you can jump your pump and keep it running and you can't get your engine to run...you'll need to test your injectors with a NOID light to see if they are getting pulsed by the ECM. You may have a bad ECM.

If you could describe the set up and tests you do more, I might be able to help more...but there are probably people out there who know the gt-40 better and can help you.


AirTool

[DanielC]

RE: Low voltage to Fuel Pumps

A little additional info. Both fuel pumps are grounded all the time, they are switched on the positive side by the fuel pump relay.
The GT-40 manual has specifications for ground circuit resistance, I think.
Air tool, the fuel pumps on a Ford engine shut off the same as a GM engine, they run about two seconds, and if the engine is not being cranked, or is running, the fuel pumps shut off.
The GT-40 service manual also has a very good troubleshooting section in it.

[wepucci]

Thanks for the responses. I am getting ready to order the relays, and just wanted to make sure that R130011 is the part number for both the fuel pump relay and the eec/igntion coil. They appear to the be the same to me, and I just figured I would replace both of them while I was at it. In looking at the ones in my boat, they each have a unique number engraved on the front. But the relays look identical.

Thanks.

- Bill

[wepucci]

A little more info. Grounding the wire on the six hole plug (with the key on) does not turn the fuel pumps on. With one or the other pump disconnected, it sends 12V to the other pumps for a split second, then the voltage drops to about 6V.

I also jumped pin 30 and 87 as suggested and the fuel pumps ran. I'm wondering if the problem is more likely a relay issue or a computer issue. I have two new relays on the way that I will install on Thursday. If that doesn't work then I'm stumped again.

- Bill

[AirTool]

Are 30 and 87 the load and line side of the relay? not the coil connections?

If so, you probably have corroded contacts on the relay. You could try that fake load trick I told you about with a lamp and in-line DC amp meter.

Run the test directly on the battery then through the relay and note the difference in amps and the voltage drop across 30 and 87.

AirTool

[slob02]

Relays were a problem on my 1997!! Cheap fix if it is the problem.

[wepucci]

Thanks to everyone for their input. Just wanted to post that it was indeed a relay. Honestly, I don't know if it was just the fuel pump relay or both the fuel pump and the eec relays - I replaced them both, and full power to both fuel pumps was restored. I replaced the eec relay first, then tried it and had no power to the pumps. I then replaced the fuel pump relay and it worked like a charm. I was so happy I didn't bother to put the old eec relay back in.