Jpzaluski

I am nearly at my wits end with this motor. 1999 Scarab AVS w/ 2001 500EFI's (170 hours). Starboard motor starts, runs, flawlessly, everytime I hit the key, no matter the situation. The port motor could only be so lucky. These problems I am going to describe generally ONLY happen first start of the day, and rarely once it's been started once. The port motor for weeks only intermittently sounds the horn when keyed on and at times had been a bit difficult to start. I really paid it very little mind at the time. Well this problem has begun to progress, and I'm beginning to dig deeper and deeper each time it happens.

Last Saturday I put the boat in the water, starboard motor cranks up and idles, port motor cranks and cranks with no start/no horns. Fuel pump runs as I cycle key no problems. I attempt cranking a few times and all of the sudden the fuel pump decides not to run. Key on multiple times, cranks fine, but fuel pump never runs, horns never sound. I go poke around the motor and underdash, and try the key one last time and low and behold fires right up. Gave me no more problems the rest of the day.

This evening I decide to go through everything obvious and try to eliminate any potential problems. I look at all the underdash wiring, all ignition cylinder wiring etc. was inspected for corrosion or loose terminals, none were found. I then located the two grounds on the bellhousing of the port motor. Got a wrench on both of them and insured they were both tight. No evident corrosion there. Got to the helm, keyed on the motor quite a few times. Horns sounded every time, fuel pump ran every time (horns hardly EVER sound). I think I might have nipped the problem and hook up the hose to fire up the motor. Cranks and cranks no fire. I pull the nearest plug, confirm no spark. So I went to the ignition box (it does have MSD ignition), check all connectors, etc.) I find nothing wrong, so go to the helm, key on the boat, no horns, fuel pump runs and the boat starts right up. Turned motor on and off about 20 times and never gave me a problem starting again.


WHAT GIVES HERE GUYS? It kills me because the problem doesn't exist long enough to diagnose, and it has so many different symptoms. At any given time the fuel pump, ignition, or horns may not work... but they never fail for any rhyme or reason. Am I being an idiot here? I need some pros... please help.... it's driving me half insane

gripit

Sounds to me like something electronic like a computer chip in one of the moduals.

getrdunn

iTrader: (7)

i know you mentioned you checked all the connections, harness's etc. i assume you checked the main merc harness at the rear of the engin. the one about 1 1/8 diameter with a hose clamp on it. i don't mean to insult you in any way shape or form however those plugs will do weird things if they go bad and or are get seperated. seems like you may have done something near or in the area of what you recently did when it fired for you.

cloudmaster_321

I don't know how each motor is tied into the safety lanyard switch, but maybe there is a connectivity issue with it.

stevesxm

throw the msd in the garbage to start with. the factory ignition was better in all respects and these intermittent problems are an msd trademark.

if that doesn't fix it ( which will really surprise me ) the easiest thing to is swap components motor to motor until the problem moves. this serves the obvious purpose of back to backing known good pieces as well as forcing you to have apart those connectins for examination. you are really only talking about the dist trigger, the coil and the ecu and the crank angle sensor if that motor has one...

Jpzaluski

gtrdunn... I'm going to check this plug tonight. Any help in locating it or should it be fairly obvious?

steve.... do you think the MSD box is in anyway related to my fuel pump/horn issue?

mookymonkey

i agree with steve. good advice. in my dealings with msd it stands for "must self destruct". factory stuff is always the best. i recently had some electric problems also and after about 8 hours of mass confusion it turned out to be an inline fuse holder. the plus of it was that i learned alot and got to bulletproff some things. my thoughts are with you. mark

28Eliminator

I help a guy at our lake 2 years ago because he had a similair problem with his 38 formula. We tracked it down to the safety lanyard switches, as cloudmaster suggested above. This guy would go to the doc and one motor wouldn't start, bring it home and it would start, but the other one wouldn't. I verified that there was no continuity on the switch, so we bypassed both for the weekend, and it ran flawless. He replaced both lanyard switches and all was good. Not sure if that is your problem, but those do go bad.

By the way those lanyards connect to the engine harness through that same main merc harness also, so either could cause this type of problem.

getrdunn

iTrader: (7)

you can't miss it. it is the main harness plug (lanyard) in the rear of each engine. it's ussually mounted on a plate that bolts to your bell housing or the back of one of your heads. they vary a lot depending on year, manufacture, etc.

good luck!

john

Blueabyss

Sounds like a bad Neutral Position Switch. Esp since it acts up early and then gets better.. IE the corrosion gets wiped off from moving the stick. BUT this is only a guess.

Chris