Won't start after rebuild

[Mike81]

I bought a 97 SN 5.8 gt40 in not running condition and rebuilt it. Supposedly the engine ran rough before he disassembled and decided not to fix.

Problem now is that it won't crank. I've troubleshot everything I can think of. Both fuel pumps are new and delivering 40 psi to injectors. I've tested all injectors and they have 15 ohm resistence. Injector plugs are getting power from ecm. Plugs are getting spark. Double checked distributor position and timing should be close.

So engines at their simplest just need fuel spark and compression. Mine should be getting all three. Even if the timing were off I should be getting SOME popping/combustion but I get nothing at all.

Any ideas/tips please I'm going crazy!

[scottb7]

Well if you verified spark while cranking that only leaves fuel and air to test for...can you check for signal to a couple injectors while cranking?

[xlwater01]

Play around with the timing on the distributor. It probably needs to be advanced. I ran into the same thing when I rebuilt a GT-40


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[Mike81]

Scott I did check and the injectors get signal during crank.

xlwater thanks that's my thought too and I'm gonna play with it more tomorrow just thought I might be missing something.

[scottb7]

Yep, then timing is probably good to check next. Good luck.

[Mike81]

Another question...this is my first inboard boat I've always had outboards. The engine seems to turn over really slow on cranking...is that normal? Brand new "high torque" starter and new battery. Compared to a car engine it just turns over much slower.

[xlwater01]

Yes, they are slow compared to a car.


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[Mike81]

thank you

[functionoverfashion]

I've just gotta ask, since I did this to myself: I rebuilt a GT-40 (a machine shop did the block, heads, etc.) years ago and in putting it all back together, I was careful to get the wires on in the right order; only to find that I put them on in the wrong direction of rotation on the distributor. It doesn't seem likely to be your problem, but I double-checked everything and missed that detail.

There's also a power wire that in some years was connected directly to the battery and without power to that wire, the engine would not run. When I put the GT-40 in my older Supra, we had to locate this wire and give it power, which we did by adding a breaker near the other main breaker on the engine. Sorry I can't recall what it did. If I get a minute later on I'll try to be more clear. I do recall that was the only wire that didn't plug in directly to the old harness on my '89!

Also, check out this thread, it's a great resource on these engines.

[Mike81]

I did connect the plugs wires in right order but ill double check today. As for wiring it was all cut by P.O. so I tried tracking and connecting it all properly but ill double check today. I have a heavy positive wire going to starter solenoid and a smaller one in the main wiring harness.

[functionoverfashion]

I can't find the information I'm looking for, but it could be this (?) that I was missing completely, again, as I was retrofitting this in an older boat. This was power to the EEC that Correct Craft wired direct to the battery; of course you may have already addressed this as you're starting from cut wires, but this would keep the boat from running even with fuel and spark, as far as I can recall.

Disclaimer - it was 2007 when I did the swap, and I can't remember the exact circumstances. But when we first installed the engine, it wouldn't run because of no power to... something. THEN, after the rebuild a few years later, it wouldn't run because the wires were on in the right order but reverse direction. I'm hoping you're just missing some little thing like that.

[Mike81]

Thank you sir I'll look at the wiring diagram again and verify. The benefit of these troubles is I've learned a lot about how this engine works and is wired!