MerCruiser 5.0 TBI to 5.7 Carb Swap

[BajabossJD]

Hey guys!

Can someone help me figure out a weird ignition / spark problem I'm having after swapping a 2004 5.0 TBI engine to a 5.7 engine w/ #1409 Carb setup? Everything is in and hooked up.. I replaced the stock Merc electronic pump with an electronic pump for a carb (7 psi). I'm getting fuel, I have spark, the long block is new (880 Block). Cranked it up and it sounds like the ignition is not letting it fire. There may be a backfire through exhaust but it cranks and cranks. Set #1 to TDC. Cap and rotor pointed at #1. The swapped over Distributor, Coil and Ignition were working perfect on the boat before the 5.0 lost a cylinder due to water through manifolds / risers.

In the engine swap process I installed new Pioneer timing cover without the crank sensor port. I knew the carb setup didn't need it but now I'm thinking the ignition is in limp or error mode without a sensor connected to it. Timing light shows I'm getting spark but it refuses to fire up.. Do I need an older style distributor for this setup? I assume the Thunderbolt V ignition is fine with the carb setup? I have a scan tool for the Thunderbolt V system but I had to order a different connector to hook up to this one.

Thanks!

Joe

 

[alldodge]

No crank sensor needed for TBV

Remove plug #1
Use your thumb or a cork to cover plug #1 hole. Bump starter over slowly until cork or thumb gets pushed out by pressure.

Look at timing notch on damper and see if it lines up with Distributor #1

 

[BajabossJD]

Thanks for the fast response. You've always been helpful to my troubleshooting over the last few years.

I agree it does sound like it's 180 out ..

I checked TDC with threaded tool TDC tool (twice..timing tape is in good shape and visible..marks showed up in correct spot). I did have an issue with the rusted bolts in the distributor cap.. I may have put the cap on differently than it came off. I'll check first thing in the AM. Is the distributor the same for TBI and Carb setup?

 

[alldodge]

Is the distributor the same for TBI and Carb setup?

Yes, if its a TBV its the same

 

[Scott06]

Any backfire means timing is off do the timing as recommended above. Leave the distributor loose have someone crank it and twist a bit one way or the other see if it fires. Use a timing light while cranking to see if timing is at least near 8-10 deg BTDC

 

[achris]

TDC occurs twice in a 4 cycle engine. Once for the compression stroke (when the spark fires) and once at exhaust/inlet overlap... It's no good just finding TDC, it has to be the right one (for when the spark fires)... You need to do as Alldodge says, find TDC on the COMPRESSION stroke.

Chris.......

 

[QBhoy]

Hope you get it sorted. Didn’t know there was a 2004 5.0 tbi.

 

[achris]

Hope you get it sorted. Didn’t know there was a 2004 5.0 tbi.

I suspect the boat is 2004. And the engine is ????? (As TBI was only available 1995-2000, then that'll be the engine year)

 

[BajabossJD]

Thanks for all the tips guys. I am headed to the shop now to see if I can get the engine in time. It's a friends 2004 24' Bayliner. I offered to do the swap for him. I was also surprised to see the TBI setup on such a new boat. Who knows how it got in there..

Thanks again,
Joe

 

[BajabossJD]

I just wanted to update everyone on this. Sure enough the distributor was 180 off. Set the timing again and it fired up right away. Thanks again!