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no power to the fuel pump. Next item to check / anyone with wiring diagrams?


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Hey guys,

I dropped the Bu in the water last weekend and it turned over and wouldn't fire up. Figured out after a bit that it wasn't getting fuel and the fuel pump wasn't turning on.

Just got back from going over and trouble shooting on the boat with my multimeter and the pump is getting no power when I cycle the ignition key switch. I ran a separate power and ground test lead to the batter real quick and the pump still works.

I'm not sure what part of the engine the saftey switch/lanyard disables but I checked that switch to be safe and it is still operating correctly.

This problem occurred from the boat just sitting about 4 weeks. Was working fine when I put it away before that.

So a couple of questions:

1) Like all MPFI engines I've worked on in cars the fuel pump should cycle on for 2-4 seconds when you turn the key to on correct?

2) Is there a fuel pump relay or fuse that I can check? The fuse pannel under the dash doesn't have anything for the engine or fuel pump.

3) Anyone have a wiring diagram for this boat or know where I can get my hands on one?

Thanks

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I scanned the diagrams you need. They are very large, color JPEGs. You need to PM me your email address so I can send them.

Besides that, you should buy this book. Heck, it's exactly where I got the diagrams from and the reviews on it aren't bad either.

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Ok I just got back from the boat. Found the fuel pump relay and fuse. All the wiring checked out using my ohm meter from the pump all the way to the computer (I took the computer plug off and checked literally from the pin onward).

I measured voltage on the signal wire from the computer two ways:

1) Initial key on gives 0.5 volts for well less than 1 second (I'd say 1/4 second or so).

2) Cranking for a while (oil pressure at 20 psi from cranking) I get about 0.01 voltage which I think is just noise more than anything.

So I've figured out the computer is not sending a signal to the fuel pump for initial key on and when cranking. Does this mean the computer is shot or is there something else I can check?

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Anyone know if this boat has an oil pressure switch to the ECU that cut's the fuel if no oil pressure?

Would that prevent the 2 second prime when you first turn the key to on?

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Well I read the Indmar manual for testing the fuel pump circuit though 1 or 2 pages were missing as it was the book preview on google.

But most of the section was there and it didn't mention anything about an oil pressure switch.

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I don't know much about your boat but I fixed a similar problem on a 99 SS LXI It was a carb motor but the fuel pump would shut down. the problem was the oil pressure shut down. I pulled the pressure sending unit next to the oil filter one wire on it flushed it with gas dried it reinstalled and have not had the problem

again! Dontknow.gif

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I had a similar issue on my 98 vlx it ended up being a connection issue with the plug (can't remember the name of it) that comes out from the ecm area. It is a round plug with 15+- wires in it you can't miss it on the port side of the metal protective case. I simply bypassed the wire from one side to the other and vola' fuel pump again. Give it a try.

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I had a similar issue on my 98 vlx it ended up being a connection issue with the plug (can't remember the name of it) that comes out from the ecm area. It is a round plug with 15+- wires in it you can't miss it on the port side of the metal protective case. I simply bypassed the wire from one side to the other and vola' fuel pump again. Give it a try.

How did you bypass it? I used an ohm meter on the plug there and is appeared to be totally fine.

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FYI based on excerpts from the Indmar manual I'm now pretty sure the signal wire from the ECU completes a ground circuit rather than sending voltage so I need to go back and retest. I may still have a relay problem.

In case it is a relay problem does anyone know where to get the special looking relays for this thing other than a dealer?

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Well I was so excited at the thought it still might be the relay I went over and tested it tonight. Just got back. No deal.

Testing under the presumption the signal wire from the ECU grounds to energize the fuel pump it still didn't work. Also, since I now knew what the other identical relay did I swapped the fuel pump relay into that harness and it worked so it was never the fuel pump relay.

So the fuse is good, the relay is good, my ohm meter testing says the wiring is good I will go play around some more when it's daylight and I have time. Will try to jumper the signal wire to get the fuel pump to energize manually just to be sure.

Which oil pressure switch does the ECU read? And does grounding it activate the switch or applying power? Basically how do I bypass the oil pressure switch to test if that's it or how do I use a multimeter to test it?

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FYI based on excerpts from the Indmar manual I'm now pretty sure the signal wire from the ECU completes a ground circuit rather than sending voltage so I need to go back and retest. I may still have a relay problem.

In case it is a relay problem does anyone know where to get the special looking relays for this thing other than a dealer?

dude,

IIRC, the +12 volts to turn on the fuel pump relay, comes thru a contact in the ECM relay first. This way the injectors get power at the same time as the fuel pump. So you have to be sure the ECM relay is also coming on at "key up". Therefore both relays have to be installed to test. You are correct about the 2 second priming run of the fuel pump on key up, then the fuel pump will not run again till the ECM see's a reference signal from the distributor showing the engine is cranking or running.

And yes, the ECM does indeed ground (complete) the fuel pump relay circuit thru a green (or green/white) wire. The ECM relay gets its power from the key switch and is solidly grounded on the block somewhere. EDIT; this only applies to MEFI 3 & 4.

The relays, if bad, can be purchased at auto parts stores. They are standard automotive relays, so if need be you can borrow some out of you car. There are a few in the fuse/relay box in the engine room.

Edited by electricjohn
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You are correct, the ECM relay has to be installed and working to provide power to the injectors, fuel pump and ignition coil/distributor. I've tested it and it's working fine. In fact I swapped the fuel pump relay into the ECU relay and verified that both relays are working properly.

I'm testing the green/white wire that goes to the ECM for the 2 second prime signal and also during cranking by connecting positive lead from the multimeter to 12v power and connecting the ground lead to the green/white wire. During both 2 second key on and cranking the green/white is not providing a ground.

Next test I'm going to do is figure out how to remove the green/white wire from the ECU plug so I can bypass the ecu and see if I can get the pump to energize.

The section of the manual I'm looking at is page 101 item 13 & 14.

13. Turn the key switch to OFF or STOP. connect the cord of the test lamp to the positive battery terminal. touch the test probe to the No. 85 terminal in the relay mounting bracket or harness plug. The lamp must not illuminate. If the lamp illuminates, the dark green/white wire connecting the No. 85 relay terminal to the ECU is shorted to ground, or the ECU is faulty. Either condition will cause the fuel pump relay to remain in the energized position, and the pumps will operate anytime the system relay is energized. Check wiring and terminals for shorts. Replace the ECI only if all other components and the wiring on the circuit are good. Failure of the ECU is extremely rare.

14. Touch the test lamp probe to the No. 85 terminal on the relay mounting bracket or harness plug. Observe the test lamp while an assistant turns the key switch to ON or RUN. The lamp must illuminate for 2 seconds and then extinguish. If not test the EFI system relay as described in this section. If the system relay operates correctly, the dark green/white wire connecting the No. 85 relay terminal to the ECU is open or the ECU is faulty. Check the wiring and terminal and correct as needed. Replace the ECU only if all other components and wiring in the circuit are good. Failure of the ECU is extremely rare.

I don't have pages 98 and 99 but it seems pretty clear to the above that based on the tests I've done it's the ECU and there is no mention of the oil pressure switch. After I bypass the ECU with the green/white wire I think that will be the final nail in the coffin so to speak.

Can you even buy MEFI 2 ECU's anymore and do I have to buy from Indmar to ensure it's flashed with the correct maps?

If bypassing the fuel pump signal allows the engine to start then I'm wondering if I can make up my own relay system to operate the fuel pump safely. If the ECU already uses a signal from the ignition to determine the engine is turning over, I wonder if I can splice that signal though I'd still have the issue of no 2 second prime when the key is turned. Oh well maybe I'm getting ahead of myself, need to try my last test.

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Dude,

Looking in clymers, page 101 deals with MEFI 3 & 4. You need pages 98 & 99 for MEFI 2. And looking at the wiring diagram for MEFI 1 & 2, the green/white wire appears to provides +12 volts to the fuel pump relays coil on terminal 85, and terminal 86 is connecting the coil to ground via a black wire. This is different than MEFI 3 & 4 where the ECM grounds the fuel pump relay circuit with the green/white wire.

If either of the ECM fuses are blown, there will be no +12 volts for the ECM to output to any of its peripherals. So also check them.

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Thanks John,

I've tested the ECU relay and fuse and they are working evidenced by power to the fuel pump fuse being off when key is off or when key is on but the ECU relay is removed. With key on and relay in place I get the power.

First thing I did this morning was order the Indmar manual for myself lol.

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There is a third fuse which is independent of the ECM relay. It's power comes from the hot side of the starter solinoid. The +12 volts from this fuse feeds into the ECM in two places and also provides power to an orange wire on the data link connector. This I think is the +12 volts for outputs from the ECM that I talked about in my last post.

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Hey John,

Any idea where that fuse is located?

I brought the boat home to try and eliminate all possibilities. I removed the green/white wire from the ECU plug and wired it directly to 12 volts. The fuel pump energizes perfectly with the key on.

There are three 15 amp fuses under the Monsoon cover where the ECU is. Labeled ECM, Fuel pump, injectors respectively. The three are powered only when the ECU relay energizes and all three fuses are in perfect shape.

If I pull the coil wire and turn the engine over I'm pretty sure I can here the arc but am going to verify once I get someone to turn the key for me.

The boat still doesn't start even with the fuel pump circuit bypassed and working.

Someone was kind enough to e mail me wiring diagrams of the circuit from the ECU to the engine but I don't have the wiring diagram from the ECU to the rest of the boat (ignition battery etc). But I don't know where to look for the fuse John mentioned. There is a panel under the dash and one item is labeled engine / horn / and something else. Since the horn works I'm assuming that whatever power that supplies to the engine works.

I ordered the manual from Amazon on Monday but it didn't even ship until yesterday.

Finally, the wiring diagram I mentioned above didn't have anything shown for an oil pressure switch. I don't know if a 97 even has this feature? Can someone confirm?

Help?

Thanks

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Ok more info.

I put some gas down the throttle body and the engine fires up and runs until it burns through that gas.

Since the ECU quit sending a signal to the fuel pump I'm guessing it also isn't firing the injectors. I did read that if oil pressure falls below 5 psi there is a safety switch that will sound the engine alarm (mine doesn't have one or it doesn't work) but not that it would keep it from running. According the parts of the manual I can read online it signals less than 5 psi by grounding the wire connected to it. So I removed that wire as that should be all I need to do to bypass the switch and it made no difference.

Is there anything else to try or is the ECU toast?

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Can you disconnect the fuel pump wires from the ECU and hard wire it to a temporary switch and battery. That way you can throw 12V to the fuel pump and try to start the motor and see if the ECU is controlling the injectors and timing. I'm not familiar with the Malibu ECU's. It might not play nice w/o the fuel pump attached, but if it's just a simple 12V digital output to run the pump you might be OK.

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Can you disconnect the fuel pump wires from the ECU and hard wire it to a temporary switch and battery. That way you can throw 12V to the fuel pump and try to start the motor and see if the ECU is controlling the injectors and timing. I'm not familiar with the Malibu ECU's. It might not play nice w/o the fuel pump attached, but if it's just a simple 12V digital output to run the pump you might be OK.

Yeah I dunno on the place nice part either. However, in post #16 above I already disconnected the fuel pump wire from the ECU and tried to start it. Though the fuel pump was working it still wouldn't start.

Since in the post above where I added gas down the throttle body it started the ECU is still controlling timing. I don't know how to test the injectors.

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There is a third fuse which is independent of the ECM relay. It's power comes from the hot side of the starter solinoid. The +12 volts from this fuse feeds into the ECM in two places and also provides power to an orange wire on the data link connector. This I think is the +12 volts for outputs from the ECM that I talked about in my last post.

I reread this post John and saw the reference to the orange wire at the data link connector. I am getting a full 12 volts at the orange wire here so I'm guessing the power from the starter solenoid is good?

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The oil pressure switch wired to the ECU is just for sounding the warning horn under your dash. On carbed motors it is tied into the fuel system, but not on FI engines.

The only other thing I can think of at the moment is to see if there is 12 volts on the red wire at one of the injectors when the key is on. There should be. The ECU controls the injectors by grounding the green and blue wires on the other terminal of the injectors.

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Getting 12v's to the red fuel injector wire. When g/f going to get home I'm going to have her turn the engine over while I try to test if the computer is sending a ground signal to the injectors.

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Go get a NOID light set from an autoparts store and check for pulse at the injectors, rather than just checking for power. That will tell you if the injectors are being fired. The set only costs like $20-30 at NAPA or Autozone. Otherwise I know mine were more from Snap-on. It wont do any good if you power your fuel pump manually if you cant fire the injectors.

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Don't know what kind of meter you are using, but the pulses happen every 10 milliseconds, and at cranking speed (idle), they will only last 1 to 2 milliseconds.

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