Thread: New 5.7L setup WON'T START ... need your expertise

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Since I was born 77 years ago, I've been a life-long hot rodder and record-holding drag racer. But for my 22' boat I got a 5.7l Blueprint long block from Summit (5.7, 373 HP, Vortec heads, one piece main seal, roller rockers) and the marina mechanic installed it. All of the good parts from the original engine were transferred plus an Edlebrock dual-plan intake, a rebuilt Rochester Qjet (replaced the Holley), a new marine starter, new plugs, new quality spark plug wires, and new Mercruiser manifold exhaust system ($$$ ).

The engine didn't run well from the start. Initial 3-minute test run was pretty good at first, reaching 4800 RPMs at one burst, then the RPMs dropped, wouldn't take throttle, and stalled out. It would run then stall out. Thinking it was a fuel delivery problem, I continued to start and run and stall out ...until I went a short distance to the marina.

The mechanic ruled out a fuel problem, and then had a very difficult time starting the engine. It finally started and the timing was rechecked and my guess is the timing was off before. Not being able to pay more for the marina work, I have been working on it myself for 2+ weeks (I'm fairly capable, and have learned a great deal more from videos and advice online).

Here's what's up and I'm stumped. I've gone over the entire drill many times;

1. TDC on #1 (blows thumb off with aggression, so compression is good on that cyl at least).
2. Dizzy rotor is correctly in time, pointing to #1 tab in the cap.
3. Carb is getting fuel.
3. I removed the DUI dizzy and installed another HEI to see if things would change, but they didn't.
4. New wires are quality, new plugs could be a little fouled now, but not enough to prevent firing.
5. Dizzy is seated properly and the rotor turns when cranking.
6. Wires are on right plugs and terminals 1-8-4-3-6-5-7-2 (this firing order shows up in my sleep).
7. Ignition switch is wired and installed correctly (unless I've got something wrong. 4-terminals; IGN to dist., battery to BAT terminal, wire to solenoid, and gauge connections to ACC terminal).
8. There's 12.6 v at both the ign switch and the dist. terminal.
9. When cranking, voltage drops to 10v, which I understand a good reading.
10. Along the way, I tested spark with a 4-plug tester, and there was ONLY a very weak spark on cyl. 6.

When the engine was first cranked it seemed a few cylinders wanted to start for a moment, but no start. And when I moved the dizzy to maybe catch better timing, it had no effect on trying to start (I'm using a remote starter switch). After the initial 'try to start' mode, it wouldn't try any more, just cranked at any timing adjustment. It turns over at what seems to be the normal speed.

Again, when #1 plug wire is checked for spark with the clip-on tester there is no spark. But it has compression.

Left to do today is run a jumper wire directly from the battery to the dizzy and see what happens. Also check all battery cable and wire grounds and check resistance ohms.

Can you guys understand I'm at my wits end. Working on this engine in the unmovable center console is nearly impossible except for the Qjet and the dizzy. Because of the new risers and elbows on the Vortec heads the plugs are a nightmare to reach, and working in the 92-degree FL sun is no picnic (poor me, eh).

Your help is invaluable. Thanks so much! Larry

Hi Larry,
Another Florida guy here. Are you SURE it is getting enough fuel? My boat was acting similar a few years ago, and it ended up being the fuel anti siphon valve was restricting the fuel flow.

You say no spark with the clip on tester, try an actual spark plug, laying on something it can ground on. NOT near the carb please. Spin the motor, look for spark. If no spark, confirm 12V to dizzy. If 12V is good and no spark, you have an issue under the cap. Did you install the rotor? Rotor button? Try swapping in a new spark module. I had a dodge that would randomly blow out the module for no apparent reason. (Used the same module as Chevy HEI)

What is the negative post of the battery attached to?

.

FOLLOW UP: Thank you all for your insights. It's been over a month since I started this thread, and the pain continues. The only concern at this point is why no spark. I feel I've done everything I can think of. And yes, the two batteries are grounded on the engine block.

Recap: Had no spark in any cylinder except for a very weak spark in #4. Pulled #1 plug and it was black with soot from cranking and stumbling I suppose ; unusual on a new set of Iridium plugs.

I installed a new ignition module and no difference. Pulled the DUI unit and replaced it with a good, standard HEI and got it to run, although badly. It was obviously dropping cylinders.

Checked spark and it's sparking on cylinders 1-3-5-7 (left bank), and only #4 on the right bank.

It has new wires, and there's no mix-up. Cap and rotor look fine.

The ohm meter registers 12.6 Volts at the ignition and the dizzy, and 10 volts when cranking. But that was checked earlier in this long process, so I will check it again for sure.

Any more ideas? I'm heading for the looney ward!

A friend of mine had this problem with his IO. What we finely found was water getting into the cylinders through the exhaust. It didn't happen all the time. We ran it with out the water cooled manifolds and just a set of headers. It ran just like it should. put the water cooled manifolds back on and back to the problem. there was a rubber flap at the rear of the boat at the exhaust exit that was bad. I'm not saying that's your problem BUT. I know first hand there is not a lot of room to work on these. In the beginning we took the engine out thinking it had a cracked block. We fought it for two boating seasons. It runs fine now. Good luck

Check the resistance on all the spark plug wires. I'm not a fan of anything over 500 ohms and if they're accell I'd toss them in the trash.

I don't generally give advice, usually just come to read and look at hotrod builds. This problem seems familiar though. If the boat sat up any period of time with old fuel in it(even if you added fresh fuel) the old crap gas in the lines and bottom of the tank will varnish the spark plugs when you first run it. When you shut it down the first time the bad gas will bake onto the plugs in the form of varnish, which is an insulator. No ignition system will fire through it. Now that you've likely ran most of the bad gas through it, put a fresh set of plugs in it.
I also had a 454 mercruiser with a weird random misfire one time. Everything was new on it and I discovered the new rotor cap center blade where it contacts the distributor cap button looked flattened out. I carefully bent it up some to make sure it was firmly contacting the button and the random misfire was cured.