1983 Mercruiser 350 5.7L Won't Ground Start

[lmorefield41]

Hello fellas,

I just finished rebuilding my 350 (260hp) and I cannot get it to start. I have it in my garage. I wanted to test it out for leaks and any nonsense before I stick it back into the boat and then have to work on it in there for any reason. This engine has a Thunderbolt IV ignition system. I've used the troubleshooting guide for the Thunderbolt system and I believe that in order for this to properly work, the harness has to be connected and the setup has to be just like it's in the boat with a key switch and all. We have fuel, we have compression (147+ on all cylinders), but we're missing spark. My setup includes, Jumping #5 and 6 on the harness and running a positive to #7 on the harness (through an ignition switch). The engine cranks and cranks but won't start. I've also tried running a positive lead straight to the coil as well as run a positive lead straight to the red/wht terminal on the distributor, and still won't start. I've hooked the switch up directly to the starter and it has no different result from putting it in #7. I took a spark plug out (#1) and tried turning the engine over while I have it connected to a ground and there was NO Spark. Also, when I had the timing light hooked up to the #1 plug, the light did not come on at all. My thoughts are that I have to either replace the ignition sensor, the coil, both, or that I cannot ground start this engine because of the ignition system. I would've included the amplifier as a possible replacement item, but it should have no effect since I'm directly running leads to all of the proper components. My engine Serial Number is 6261004. I've added a pic so you can see what the engine looks like after the rebuild. I have the thing looking like a champ, Now I just need it to Run like a champ. I'd prefer it to look like crap but run good rather than look great and not run. Any help is greatly appreciated.

 

[Bt Doctur]

Re: 1983 Mercruiser 350 5.7L Won't Ground Start

If you havent blown anything by random jumpers all you need to do is run a jumper from the + battery to the + side of the coil.short the slave solenoid to fire the starter.

 

[lmorefield41]

Re: 1983 Mercruiser 350 5.7L Won't Ground Start

If you havent blown anything by random jumpers all you need to do is run a jumper from the + battery to the + side of the coil.short the slave solenoid to fire the starter.

I tried this initially, when it didn't work, I started researching online and found that if you jump port 5 and 6 together, then run the positive lead to port 7, it's the same. I have no problem sticking with the way you mentioned. Is there any for sure way to rule out the ignition sensor or coil?

 

[Bt Doctur]

Re: 1983 Mercruiser 350 5.7L Won't Ground Start

Heres how i do mine. I hook cables to the starter and block ,attach to battery. i take a jumper from the red/purple of the slave to the plus side of the coil. The jumper clip is big enough to contact the Yel/red that fires the starter solenoid from the red/purple.
Use the TB IV trouble shooting guide to test the ign system.

 

[lmorefield41]

Re: 1983 Mercruiser 350 5.7L Won't Ground Start

I'm able to get the starter to turn without a problem. The issue is something with the ignition. I'm not getting any spark and I've troubleshot using the TB IV guide, to no avail. I believe either the coil or the ignition sensor inside of the distributor is bad, if not both.

 

[Bt Doctur]

Re: 1983 Mercruiser 350 5.7L Won't Ground Start

12v to the Red/White may have blown the sensor.doubt the coil.Do you have 12v at the + side of the coil the way your jumpimg?
Did you reconnect any wires at the shift interupter? The upper bolt that takes the black wire supplies a ground thru the bolt, the white wire goes to the insulated lower screw.

 

[lmorefield41]

Re: 1983 Mercruiser 350 5.7L Won't Ground Start

I do Have 12v at the + side of the coil. I did not have any voltage at the wht/red side of the distributor, therefore I jumped 12v directly to it to see if it'd change anything, as the TB IV guide says that if you're getting 12v and still no spark, change the ignition sensor.

 

[Bt Doctur]

Re: 1983 Mercruiser 350 5.7L Won't Ground Start

http://www.boatfix.com/merc/Bullet/83/83_24.pdf
http://www.boatfix.com/merc/Techbk/94/94hsa2.pdf page 2A-12

 

[lmorefield41]

Re: 1983 Mercruiser 350 5.7L Won't Ground Start

I've ordered a new ignition sensor as well as a harness that way I can try to start it how it's supposed to be started. If this does not work, what are the next steps that I should take?

 

[Bondo]

Re: 1983 Mercruiser 350 5.7L Won't Ground Start

I've ordered a new ignition sensor as well as a harness that way I can try to start it how it's supposed to be started. If this does not work, what are the next steps that I should take?

Ayuh,.... That's a big step,.... Let's see what it does 1st, 'n go from There,....

 

[lmorefield41]

Re: 1983 Mercruiser 350 5.7L Won't Ground Start

Ok, So I got the new ignition sensor (ignition control module) and the harness that hooks up to it, and it still won't start. I am getting spark now though. So I have all 3 keys: spark, fuel, and combustion, but still no luck. Even though I can see the fuel in the carb, I still tried to spray starting fluid in there to see if it would start then, still no luck. I got 1 loud pop in the exhaust as if it were about to start, however, it didn't turn over. Now that I have the harness, I troubleshot the Thunderbolt IV using the TB Troubleshooting guide, and everything checked out. Any suggestions on what to do next? Thanks for the help guys, I'm still a rookie, but I'm learning.

 

[NHGuy]

Re: 1983 Mercruiser 350 5.7L Won't Ground Start

Well if you are getting fuel, spark and no start, recheck that your wires are right, your coil wire is on and that #1 is on the compression stroke.

 

[NHGuy]

Re: 1983 Mercruiser 350 5.7L Won't Ground Start

You rebuilt it right? How did you adjust the valves?

 

[lmorefield41]

Re: 1983 Mercruiser 350 5.7L Won't Ground Start

You rebuilt it right? How did you adjust the valves?

I took both heads to the local Napa and had them recondition and resurface them. They actually did the full adjustment and re-seating. I've been tinkering with the engine all day and I just recently was able to get actually exhaust to come out, it sounds like the engine wants to start, however, it's just not starting. The exhaust are popping and it's nearly there, but something's missing. Each plug is getting gasoline on it. I re-checked compression on each cylinder, I checked each plug/wire for spark, I took the distributor out and reinstalled it the proper way (putting the timing at 8 degrees before TDC, then seating it so that the rotor is facing the #1 cylinder, then adjusting the distributor so that the #1 plug cap is directly above the rotor), I've done literally everything that I can think of as far as troubleshoot and I'm still coming up short.

 

[Bt Doctur]

Re: 1983 Mercruiser 350 5.7L Won't Ground Start

I took the distributor out and reinstalled it the proper way (putting the timing at 8 degrees before TDC, then seating it so that the rotor is facing the #1 cylinder, then adjusting the distributor so that the #1 plug cap is directly above the rotor), I've done literally everything that I can think of as far as troubleshoot and I'm still coming up short.
????????????????? You rotate the motor untill #1 is coming up on compression, slowly turn motor untill timing mark is set to "0" at the tab,install dist with rotor facing #1 position in the cap, in a clockwise rotation from #1 wires go 1,8,4,3,6,5,7,2.
Start motor ,then adjust timing.

 

[H2Onut]

Re: 1983 Mercruiser 350 5.7L Won't Ground Start

Have you put a timing light on the motor and verified the ignition timing is right? Even cranking you should be able to see the ignition timing mark.

 

[lmorefield41]

Re: 1983 Mercruiser 350 5.7L Won't Ground Start

????????????????? You rotate the motor untill #1 is coming up on compression, slowly turn motor untill timing mark is set to "0" at the tab,install dist with rotor facing #1 position in the cap, in a clockwise rotation from #1 wires go 1,8,4,3,6,5,7,2.
Start motor ,then adjust timing.

I did it that way so that I don't have to adjust the timing, when I hook the timing light up, it's dead on at 8 degrees before TDC.

Have you put a timing light on the motor and verified the ignition timing is right? Even cranking you should be able to see the ignition timing mark.

I did, it's dead on.

 

[Bt Doctur]

Re: 1983 Mercruiser 350 5.7L Won't Ground Start

Simply amazing that the crank gear, cam gear, timing chain, timing chain slack,gear slop in the cam teeth and dist teeth
dont matter for timing a non running engine.

 

[lmorefield41]

Re: 1983 Mercruiser 350 5.7L Won't Ground Start

I took the distributor out and reinstalled it the proper way (putting the timing at 8 degrees before TDC, then seating it so that the rotor is facing the #1 cylinder, then adjusting the distributor so that the #1 plug cap is directly above the rotor), I've done literally everything that I can think of as far as troubleshoot and I'm still coming up short.
????????????????? You rotate the motor untill #1 is coming up on compression, slowly turn motor untill timing mark is set to "0" at the tab,install dist with rotor facing #1 position in the cap, in a clockwise rotation from #1 wires go 1,8,4,3,6,5,7,2.
Start motor ,then adjust timing.

So I just went out and did as you said, I adjusted the timing to 8 degrees BTDC after installing the distributor as you said, gave it some throttle while starting it, and it somewhat came to life! :laugh: It's 11:00 where I'm at now so I don't want to wake the neighbors up or ever worse, have the police show up at my door. I will get back to this bad boy in the morning and update you as to whether I can keep it running or not. Thanks for the assistance, I have a feeling that did the trick!!!! @Bt Doctur.

 

[lmorefield41]

Re: 1983 Mercruiser 350 5.7L Won't Ground Start

She's purring like a lion now. Thanks for the small fix @Bt Doctur! So just to break down the problem for future problems for other boaters, I wasn't getting any spark. I have the Thunderbolt IV Ignition Amplifier. I troubleshot the Ignition system using the Thunderbolt IV guide above. I came to the conclusion that my ignition sensor was bad, and therefore replaced the ignition sensor (ignition control module) and the spark was back. However, the engine still would not start. I then followed the directions that Bt Doctur gave me in post #15 to a T, even though I thought I did it properly the 1st time, I took the distributor out and did it his way which was obviously the right way, I started cranking it while giving it some throttle, it started right up and was roaring like a beast. Thanks for all of the help!:laugh: