No ignition... hmmm

[Choppo21]

Gday from Australia! Weekend here, so no shops open to diagnose and i prefer to do it myself anyway.

Just installed a second hand 300x (2005 model #OT999451) and she no workie: Thought i'd get some input as i try to fault find over the weekend.

So, here goes;

Fuel
- low pressure pickup pump works fine, lines bled and fuel confirmed at HP fuel pump
- HP FUEL PUMP NOT WORKING when ignition on and/or cranking - i've jury rigged it and it actually works fine when direct connected to 12v

Electrical
- Motor cranks fine on the key
- Unable to see if spark at plugs as no helper at the moment - i suspect there is, as it did fire for 1sec when i first tried it (i suspect some residual fuel rail)

So, my current thought is it is electrical. Well electrical at least in terms of the HP fuel system ain't turning on, therefore probably other electrical probably the same...

Reviewed the factory wiring diagram last night, and it appears the red/blue is rather fundamental. Will check relay connections today.

It's likely ignition signal wire related (and i have not connect something correctly), but the starter works off the key, so why not the fuel pump?

Any suggestions appreciated as i have 2 days to play around and see if i can solve this puzzle.

First steps will be - bypass kill switch (even though it shouldn't matter as it works), check outputs rear of key (again shouldn't matter as it works).

Is there a single wire that you guys could suggest i've missed engine side? Gut feel is i've missed one ignition connection somewhere under the cowl. But the weirdest thing ever.... it actually kicked at one point (even with no fuel pump running).

Now i think about it, the ignition and starter must be 2 different wires... maybe the key barrel has an intermittent fault... hmmmm

[Choppo21]

Talking to myself here, but helps me think lol.

so get to boat, try turning over and she backfired and runs for 4secs.

So I’ve got ignition, low pressure fuel just no hp fuel pump… can’t hear it prime or run at all. Little bicycle air valve thingo above fuel rail has no pressure (obviously).

So, looks like I’m chasing power to fuel pump issue.

[Choppo21]

Jury rig HP fuel pump - she work!

Now why not off the ignition switch? Checked the 4 little fuses down back, all good.

Any other hp fuel pump fuses anywhere guys?

[rock]

Bad fuel pump driver in ECU. Happens often. The ECU switches ground when you activate key. You can run it like you rigged it or get ECU repaired.

Rock

[Choppo21]

Bad fuel pump driver in ECU. Happens often. The ECU switches ground when you activate key. You can run it like you rigged it or get ECU repaired.

Rock

Thanks Rock. Man that sounds spot on.

Good news is I got it running.

The bad news is I didn’t really do much. Pulled fuses, checked and put back in. Pulled main power relay, looked hard at it and put it back in �� Generally moved wiring around looking like I knew what I was doing….. then tried the key again, could hear the hp fuel pump run and bingo! She works!

Now, even more frustrating. Trailed it around to where I could hook it up to water, and she ran fine for a couple minutes then cough, splutter, fart died. Sure enough, hp fuel pump not working. Super random. So again, I didn’t really do much. Pulled relay in/out, moved wiring around, bingo she works again.

Pre your comment Rock, the only thing I could see that could possibly be a reason is the 4 pin main relay. It was something I had removed, replugged to get it going. So I have one on order due early next week (@ $47 $AU mind you ����).

Rock, with the ECU driver repair, what is involved? It it a bad driver as in plug it into a Merc diagnostic tool, unload and reload the software driver like a regular PC, or a more serious hardware issue than needs a part replaced? If the former I might give it a shot. If the later, I’ll jury rig to ignition power via a seperate relay.

Thamks!

[rock]

Couple guys here in the states that do them but in Australia????? I don't think it is a simple fix but really have no idea. Call Tony Brucato and get the real information.

Rock

[Choppo21]

Thanks rock - think I’ll make life easy and just make up a power & earth connection off ignition and be done with it.

[LakeFever]

It might be worthwhile to add a few ground straps. One from the ecu chassis and the fuel pump to the block and loosen/tighten all the little ground straps from factory as well. Ive chased a lot of electrical gremlins over the years and many of them end up being poor ground connections somewhere

[Choppo21]

It might be worthwhile to add a few ground straps. One from the ecu chassis and the fuel pump to the block and loosen/tighten all the little ground straps from factory as well. Ive chased a lot of electrical gremlins over the years and many of them end up being poor ground connections somewhere

Yep, I hear you. These older engines have had ground point added/deleted/moved/stacked high over the years. Can never hurt to ensure they are all tight and add add an additional strap! Thanks!