4.3 Mercruiser Crank, No Start

[Joey9851]

TL;DR: I have replaced the starter, fuel pump, changed the oil and filter, oil pressure sensor and sending unit, ignition system (went with Delco EST from Mocassin Marine), fuel/water separator, spark plugs, and plug wires. Checked all wiring for corrosion and couldn't find anything. The neutral switch is working (if I put it in gear, it will not turn over). The only thing I can think is that a wire on the starter is not in the right place (I hired someone to replace it and don't know what wire went where) or there is a wire or loose connection somewhere, but I don't know where to begin looking. What else could be preventing it from firing up? What am I overlooking? The oil pressure gauge on the dash is maxed at 80 psi as well. All fuses are good and have continuity on the terminals.

I've been chasing a crank, no start issue since Christmas last year on a 4.3 Mercruiser in my 2011 Bayliner 195BR. I live in Hawaii so we took it out for Christmas when my mother in law was visiting. It ran fine for the trip to and back from our destination, we loaded it on the trailer and brought it home to prep for the next day to take my wife out for her birthday. We got to the ramp, and it would not turn over, it just clicked like the starter was locked up. We brought it home, I hooked it up to the muffs and tried again and it clicked again so I hired a mechanic to replace the starter. It would turn over but not start so I started small and checked the basics; fuel, spark, air, timing. I was getting fuel, and obviously air, but no spark. I replaced the spark plugs, no dice so I replaced the plug wires, still no dice. Then I replaced distributor cap and rotor, nothing. After consulting with my local mechanic, he told me to replace the oil pressure sender, that didn't fix it. Then the oil pressure sensor (what tells the fuel pump to kick on), no change. Then I replaced the fuel pump after making sure the sensor worked by jumping the contacts, no change. Then I stopped getting spark so it was back to the ignition system. I ended up replacing the thunderbolt V ignition with the Delco EST ignition system. I set the engine to TDC on compression stroke, set the EST up but still nothing. I am honestly just trying to get my boat running again and really need some guidance or help.

 

[Scott Danforth]

welcome aboard

since you have a Delco EST, make sure you have power to the distributor (not wired to the starter at all).

make sure you have +12 volts on the purple wires when the key is on. if not, check the key switch and the MOB switch

since your motor cranks as normal, forget about the starter, that part is wired ok.

grab a plug wire end and have someone crank it. you will know if you have spark. if you have spark, do you have fuel? is the spark timed right.

since you also fired the parts cannon without dianosing the issues. does the fuel pump run when cranking, yes or no? if yes, then its wired to the R terminal correctly on the starter. if no, then look there.

does the oil pressure switch work - you can test this when cranking with a DVM

you state you have fuel. however lets verify.

doubt any of the parts you threw at it were needed.

stop throwing parts at it, and start diagnosing

 

[Scott06]

The fuel pump gets power from the starter during cranking, which bypasses the oil pressure switch during cranking, mechanic should have know that. If the Oil switch was bad Fuel pump would run during cranking, engine would run for a short time until fuel bowl is empty, cranking again would refill bowl...

Not sure how 12v to coil is supplied during cranking as if you trip your MOB switch it will run briefly until you let the key go from start to run.

Check for 12 v at + side of coil when cranking and when in run. Likely don't have that so stop and do some diagnosis

Disconnect shift interrupt switch I think with EST you have to change this around - TBV ground thru the interrupt switch and est uses a 12v+ thru the switch - might be grounding out the coil ?

If you have 12 v at coil try disconnecting the tach at negative side of coil (grey wire )

What's your serial number ? I'll see if I can pull the wiring diagram

 

[Joey9851]

welcome aboard

since you have a Delco EST, make sure you have power to the distributor (not wired to the starter at all).

make sure you have +12 volts on the purple wires when the key is on. if not, check the key switch and the MOB switch

since your motor cranks as normal, forget about the starter, that part is wired ok.

grab a plug wire end and have someone crank it. you will know if you have spark. if you have spark, do you have fuel? is the spark timed right.

since you also fired the parts cannon without dianosing the issues. does the fuel pump run when cranking, yes or no? if yes, then its wired to the R terminal correctly on the starter. if no, then look there.

does the oil pressure switch work - you can test this when cranking with a DVM

you state you have fuel. however lets verify.

doubt any of the parts you threw at it were needed.

stop throwing parts at it, and start diagnosing

The fuel pump runs when cranking, or at least I think it does because I can hear fuel going into the carb after I stop turning the key. How do I get power to the distributor and not wired to the starter?

 

[Joey9851]

The fuel pump gets power from the starter during cranking, which bypasses the oil pressure switch during cranking, mechanic should have know that. If the Oil switch was bad Fuel pump would run during cranking, engine would run for a short time until fuel bowl is empty, cranking again would refill bowl...

Not sure how 12v to coil is supplied during cranking as if you trip your MOB switch it will run briefly until you let the key go from start to run.

Check for 12 v at + side of coil when cranking and when in run. Likely don't have that so stop and do some diagnosis

Disconnect shift interrupt switch I think with EST you have to change this around - TBV ground thru the interrupt switch and est uses a 12v+ thru the switch - might be grounding out the coil ?

If you have 12 v at coil try disconnecting the tach at negative side of coil (grey wire )

What's your serial number ? I'll see if I can pull the wiring diagram

1A633081

 

[Scott Danforth]

The fuel pump runs when cranking, or at least I think it does because I can hear fuel going into the carb after I stop turning the key. How do I get power to the distributor and not wired to the starter?

The Delco EST has 3 wires. A purple wire that is 12 volt, a grey wire that is the tach feed and a black wire that is ground

Do you have 12 volts on the purple wire when the key is on......yes or no

 

[Scott06]

The fuel pump runs when cranking, or at least I think it does because I can hear fuel going into the carb after I stop turning the key. How do I get power to the distributor and not wired to the starter?

check with a volt meter if you have 12 v on + post of coil ... Do you have that? Electrical drawings are below.to test you can jumper 12v from battery to positive side of coil if you get spark solve why you dont have 12 v there by chasing it down with a volt meter.

 

[Scott06]

1A633081

I think that is a repower serial number which has a different parts look up.

@Fun Times I think knows where to get the parts breakdown

 

[Fun Times]

I think that is a repower serial number which has a different parts look up.

@Fun Times I think knows where to get the parts breakdown

For reference, this serial number is a normal factory number/engine we're used to seeing here...Just a newer series being 2011+ model year indicated by the 1A starting number vs 0F, 0L, etc.... I believe they are even in the 2A's now or higher by 2023.

4.3L CARB ALPHA/BRAVO - 1A063240 & Up

4.3L CARB ALPHA/BRAVO - 1A063240 & Up

www.mercruiserparts.com

I believe this would be a first being that the OP (Joey9851) went from replacing OEM thunderbolt V ignition with/to the Delco EST ignition system.

I would have to think he lost at a minimum the warning horn control for the temp overheat sensor as it runs through the TB5 ignition control module. The Delco has it's own timing module mounted to the distributor...Not to sure if it would have had any effect to the turn key start system of the carburetor or not.

Being the oil pressure gauge is maxed suggest something might be grounded or bad connection such as the main 10 pin wiring harness at the engine.. might want to give the harness an inspection and wiggle it around with the key on, engine off and see if the gauge goes to normal then try to start.
Edit: Is the gauge maxed out with the key on only or all the time even key off?

Own a timing light by chance? Just for quicker reference, Connect it to the high tension coil wire between the coil and distributor and see if it's consistently flashing when cranking over the engine to start... Or not...

 

[Joey9851]

For reference, this serial number is a normal factory number/engine we're used to seeing here...Just a newer series being 2011+ model year indicated by the 1A starting number vs 0F, 0L, etc.... I believe they are even in the 2A's now or higher by 2023.

4.3L CARB ALPHA/BRAVO - 1A063240 & Up

4.3L CARB ALPHA/BRAVO - 1A063240 & Up

www.mercruiserparts.com

I believe this would be a first being that the OP (Joey9851) went from replacing OEM thunderbolt V ignition with/to the Delco EST ignition system.

I would have to think he lost at a minimum the warning horn control for the temp overheat sensor as it runs through the TB5 ignition control module. The Delco has it's own timing module mounted to the distributor...Not to sure if it would have had any effect to the turn key start system of the carburetor or not.

Being the oil pressure gauge is maxed suggest something might be grounded or bad connection such as the main 10 pin wiring harness at the engine.. might want to give the harness an inspection and wiggle it around with the key on, engine off and see if the gauge goes to normal then try to start.
Edit: Is the gauge maxed out with the key on only or all the time even key off?

Own a timing light by chance? Just for quicker reference, Connect it to the high tension coil wire between the coil and distributor and see if it's consistently flashing when cranking over the engine to start... Or not...

Gauge is only maxed out with key on. I inspected the harness and there’s no corrosion at the 10-pin plug, and all the female connections look good. I do own a timing light

 

[Joey9851]

The Delco EST has 3 wires. A purple wire that is 12 volt, a grey wire that is the tach feed and a black wire that is ground

Do you have 12 volts on the purple wire when the key is on......yes or no

I have 12 volts on the purple wire with the key on.

 

[Joey9851]

For reference, this serial number is a normal factory number/engine we're used to seeing here...Just a newer series being 2011+ model year indicated by the 1A starting number vs 0F, 0L, etc.... I believe they are even in the 2A's now or higher by 2023.

4.3L CARB ALPHA/BRAVO - 1A063240 & Up

4.3L CARB ALPHA/BRAVO - 1A063240 & Up

www.mercruiserparts.com

I believe this would be a first being that the OP (Joey9851) went from replacing OEM thunderbolt V ignition with/to the Delco EST ignition system.

I would have to think he lost at a minimum the warning horn control for the temp overheat sensor as it runs through the TB5 ignition control module. The Delco has it's own timing module mounted to the distributor...Not to sure if it would have had any effect to the turn key start system of the carburetor or not.

Being the oil pressure gauge is maxed suggest something might be grounded or bad connection such as the main 10 pin wiring harness at the engine.. might want to give the harness an inspection and wiggle it around with the key on, engine off and see if the gauge goes to normal then try to start.
Edit: Is the gauge maxed out with the key on only or all the time even key off?

Own a timing light by chance? Just for quicker reference, Connect it to the high tension coil wire between the coil and distributor and see if it's consistently flashing when cranking over the engine to start... Or not...

So I tested the coil like you said, and my timing light does not flash at all when cranking.

 

[Joey9851]

However, when I use a spark tester, i get a steady blue spark. I started testing some of the wires and tracing them, and I’m not getting any power on the purple wire at the plug to the fuel pump.

So I tested the coil like you said, and my timing light does not flash at all when cranking.

 

[Fun Times]

However, when I use a spark tester, i get a steady blue spark. I started testing some of the wires and tracing them, and I’m not getting any power on the purple wire at the plug to the fuel pump.

Can you snap a photo of the wiring at the engine starter? maybe it will help see if it's connected right or not.

 

[Joey9851]

Can you snap a photo of the wiring at the engine starter? maybe it will help see if it's connected right or not.

I will get one tomorrow. Do you happen to know how it is supposed to be connected?

 

[Fun Times]

While it's often mentioned using a timing light is not a good way to confirm spark, i myself have done it multiple times with good success for a quick reference point...So with that mentioned either it won't be a good test for your situation or maybe the coil wire is bad if/depending on spark tester type/design you have...Meaning does your spark tester use the existing coil wire or does it have its own wire bypassing the high-tension coil wire normally used?

Are the plug wires new or old?

 

[Fun Times]

 

[Joey9851]

While it's often mentioned using a timing light is not a good way to confirm spark, i myself have done it multiple times with good success for a quick reference point...So with that mentioned either it won't be a good test for your situation or maybe the coil wire is bad if/depending on spark tester type/design you have...Meaning does your spark tester use the existing coil wire or does it have its own wire bypassing the high-tension coil wire normally used?

Are the plug wires new or old?

It uses the existing coil wire. It’s the in-line style. The plugs and plug wires are new. I replaced them when I put the Delco EST ignition system in last month. What I find is weird is that there’s no power to the purple wire for the fuel pump but there’s power everywhere else along that wire.

 

[Fun Times]

To get power at the purple wire at the pump the engine needs to be cranking over as the starter is delivering the power.

If just testing with key on, you won't see power there.

 

[stresspoint]

long shot .? have you tested the wires to the key switch and the switch itself.

sorry if this has been covered ,iv just chimed in and not read though the entire thread.