2000 21V Fuel Pump not getting a signal

[Goofyr44]

Just checked the fuses, again, and they are all good. Also changed out the relays. Still no prime or power upon turning the key to ignition.


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[Goofyr44]

Sorry Goofy, been at the lake since Thursday morning and just now enjoying my coffee with internet service. If the relay is getting power but the pump harness connection doesn't get power, it's a blown fuse, bad really or a broken wire between the relay and fuel pump. Sometimes the fuse in the 3 pack of fuses will blow so Check that next. The fuse set has 6 wires, red, purple pink etc.., coming out of the fuse harness and is usually located near the relays. It has a black cap about three inches wide by 1/4" thick on it. Fuel pump is the middle fuse but check all of them.

So I think I am officially stumped. I don't know why my fuel pump won't receive a signal. I guess I am going to have to trace a ton of wires and hopefully find something/anything. Its just so strange how everything was running fine and then not. I am going to start tracing wires because everything else works. Is there anything else on this boat that would cause the fuel pump not to turn on /get a signal? Does the oil pressure sender cause this? Is there a crank position sensor that would cause this? Are the boat gods mad at me for taking hiatus from the water to have kids? I have always been a fan of Tige but this is really getting to me.

[boatwakes]

Nope, its a straight shot from the relay output to the fuel pump connector. Check the terminal connections at the fuel pump relay for power, i.e. stab the tester point into the output of the relay connection to check if there's power there. We've seen chafed wires on the block, bad grounds and even melted connections at the fuel pump connector but you'll just have to check every inch of the wire from the relay to the pump. Does your engine have the booster pump on top of the fuel filter?

[Goofyr44]

My plan tonight is the unwrap all the wires that lead to the fuel pump, fuel pump relay, and fuel pump fuse and look for something. Are you referring to a low pressure pump as a booster pump? If so I don’t think it has one on the filter thanks again for the advice. I need to fix this issue before I pull all of my hair out.

So just make sure I understand. Nothing else besides the fuel pump relay or the fuel pump fuse will cause an interference in the signal?
I m assuming Neutral safety switch would kill the starter not the fuel pump.


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[boatwakes]

Yes, certain model years had a booster pump mounted inline above the fuel filter to help avoid vapor lock. The fuel pump relay also controls that pump with an intermediate jumper wire set too. Without it, the search will be easier.

[Goofyr44]

So I did not find a booster pump mounted inline above the fuel filter. What I did do I jump the fuel pump relay and the fuel pump came on. That being so means that after I close the circuit on the relay the fuel pump gets a signal to turn on. That would explain why I wasn't getting a signal to the fuel pump. So now I need to find out what is causing the relay not to close. I did attempt to start the boat with the jumper in place, just to see if it would start, but it did not. I was hoping that It would start just to slightly ease my mind. So my new question is, does anything else between the ECM and the relay cause the fuel relay not to close and provide signal/power to the fuel pump? Just to reiterate the relays are new, I have a sufficient oil level, the fuel pump Fuse is good, and the starter turns over. Once again I really really really appreciate al the the time and help that you guys are giving me.

[Goofyr44]

Does anyone have any wiring schematics for the EFI and the wiring harness


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[boatwakes]

This is the generic Thunderbolt Mag 350 wiring diagram which is the same between the outdrive and inboard models, the only difference being the drive lube reservoir bottle.

[boatwakes]

Im leaning back to the ECM being the problem again. Check for spark with the jumper to the fuel pump in place (has your ignition module been replaced yet?, the 3 wire version is the updated unit replacing the old and problematic 2 wire unit.) because one of 2 things is happening; if spark is present, the injector driver is not receiving signal (ECM) and no fuel will be injected to the engine Or, if spark is not present, the ECM is not seeing ignition input from the distributor ignition sensor and not sending fuel either.

[Goofyr44]

Im leaning back to the ECM being the problem again. Check for spark with the jumper to the fuel pump in place (has your ignition module been replaced yet?, the 3 wire version is the updated unit replacing the old and problematic 2 wire unit.) because one of 2 things is happening; if spark is present, the injector driver is not receiving signal (ECM) and no fuel will be injected to the engine Or, if spark is not present, the ECM is not seeing ignition input from the distributor ignition sensor and not sending fuel either.

I will check for spark when I get home from work. I did that ECM check on J1 and received 12volts for seconds with the key in the on position. I figured that meant the fuel driver in the ECM was good. The ignition module in the distributor is the 3 wire system. I also checked voltage in the module and also got 12volts.

So are they any other checks on the ECM to verify if it is the culprit? I have read several threads on several different sites where people have changed out the ECM and it did not solve the problem.

I m assuming the relay is not receiving a ground signal to close the normally open switch to activate the fuel pump, which would make sense of the ECM fuel driver was toast.

Do they sell refurbished ECMs? I saw a few new ones but they are over $1,000. What’s a good source to get one from.


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[boatwakes]

Verify the fuel pump driver voltage from the ECM is making it to the relay connection, there could be a problem in that wire or the terminal connection at the relay or J1 backside of the connector. It is the Dark Green with white wire connected to the relay base. If good voltage for 2 seconds when key first on proceed. If not, check the terminal connections for continuity between backside of J1 and the slot where the relay installs. If no signal across there, find out why, bad wire, bad terminal connections etc...

If good voltage at dark green w/white, check for power on the pink terminal of the relay base with key on. There are two pink wires here, both come from the fuses, the fuse in the middle and the outside fuse which also is connected to the ignition module and supplies voltage to the injectors. Just for giggles, replace those fuses because we've seen some that look and test okay but are broken and will show continuity and voltage but not pass amperage. I'm going to PM you my number so we can walk through this while you're on the boat.

[Goofyr44]

Once again I can’t say it enough I really appreciate all the advice and help. I’m starting to get discouraged. I’m going to go through those checks when I get home. I’ll keep you updated.


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[Goofyr44]

This is the generic Thunderbolt Mag 350 wiring diagram which is the same between the outdrive and inboard models, the only difference being the drive lube reservoir bottle.

Hey buddy check your PM when get a chance. Thanks


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[rconner]

I'm having the same issue. Did you get it fixed?

[boatwakes]

Rconner, list exactly what your boat is doing and what you have done so far to diagnose it. Ill most likely have you start a new thread.