1999 Mercruiser 4.3L won't start!

[Samcent]

My buddy and I have a 1999 Capri Bayliner with a Mercruiser 4.3L, carb engine, sterndrive. We bought it a few months ago and it started/ran fine but was having some idling problems and stalling out. We knew this when we bought it but we consider ourselves somewhat handy so we started troubleshooting it. Basically we rebuilt the carb (twice) and it didn’t fix it, next we replaced the distributor cap. When we did this it would no longer start at all. Firing order was matched and triple checked. We proceeded to replace the spark plugs, ignition coil, oil pressure sensor, and the fuel pump (in that order). Nothing. We used a timing light to assure the 1 cylinder is firing and it is. We did some minor electrical troubleshooting and it appears the fuel pump was getting power so we assumed it was a bad pump. We replaced that and still nothing. She’s cranking fine so we don’t think it’s an issue with the starter. So we’re out of ideas... help!

 

[dingdongs]

have you run through the ignition system for your boat which maybe a thunderbolt v.obviously throwing parts is not the problem.are you getting spark????

 

[MikDee]

Did you move the Distributor, or take it out? Sure, you say #1 is firing, But is the engine on the compression stroke, or exhaust stroke? One more thing, under the middle of the Dist. cap, the carbon rod, has to touch the spring on top of the rotor for spark delivery.

 

[dingdongs]

change the cap back to the original

 

[Samcent]

dingdongs: Yeah it's getting good spark. Unfortunately I stupidly threw away the original cap. Looked identical the new one so I didnt think there was any use in keeping it... In retrospect I should've.

MikDee: Didn't remove the distributor. Just the cap. We we're getting backfire for a while but we turned the distributor about 45 degrees and timed the ignition and it's right at TDC. Doing that stopped the backfiring. I'll check the carbon rod to see if its making a connection. And if it's not?

Could it just be a bad cap even though it was brand new? I'm sick of just switching out parts hoping for the best. I'm still very concerned that we're not hearing the fuel pump click on...

 

[Bt Doctur]

~~Didn't remove the distributor. Just the cap. We we're getting backfire for a while but we turned the distributor about 45 degrees and timed the ignition and it's right at TDC. Doing that stopped the backfiring. I'll check the carbon rod to see if its making a connection. And if it's not?

That dosent make sense unless you have the firing order all screwed up. The cap should be marked with 1,6,5,4,3,2. You cant time the engine unless its running ,has to be put in base mode first.

 

[Samcent]

Right right. I take that back. I had that confused. I did not set any timing. All I did was check that it was getting spark and it was. We traced all the spark plug wires from the cylinder to the right marking on the cap so the firing order should be correct no? 1-6-5-4-3-2.

 

[dingdongs]

are you sure the leads are correct and if so was it running b4

 

[cliffblue]

Do you see a squirt of gas in the carb when the throttle is worked? If it is a fuel issue, you could dribble a little fuel into the carb and it would start for a second if everything else was close, timing, etc. Just don't dribble while starting in case of a backfire. I can't hear my pump either, but it is running. If you didn't turn the distributer, and it was running before than it has to be a part you changed or replaced incorrectly. You might check and see if the distributer will turn relatively easy. You might have turned it accidentally. Good luck!