All day chasing a fuel problem....

[Gary H NC]

At least it acted like a fuel issue.
Bogged down on hard accel...popped and backfired..died..

Merc 5.7
I replaced the filters...checked the fuel pickup,anti-siphon valve,ect,ect..
Was standing near the motor with it at idle speed..touched the spark arrester and the engine died??... Somehow i was the ground?

Started checking electrical..well after a few things i noticed the bolts were not real tight where the ignition box mounts to the riser..
Cleaned the wire terminals,put the bolt back in and it ran like a new one..
Live and learn...

 

[cooter2506]

Re: All day chasing a fuel problem....

Don needs to add that one to the Adult Only Sticky!!!!!! Well atleast you found it. Congrats!

 

[Don S]

Re: All day chasing a fuel problem....

There is a ground wire under one of those 3 bolts. Loose grounds in electronic parts make problems. No, it won't be a sticky. It's one of the basic things that all manuals tell you to look for. Loose, corroded connections.

 

[Gary H NC]

Re: All day chasing a fuel problem....

Yea,no need for a sticky...I was just upset it took me so long to find it.
Really sounded and felt like a fuel problem.
The guy said he had just filled up when the problem started so the first thing in my mind was start checking fuel system.
It did have some water and crud in the filters and rotted fuel lines so all of that needed replaced anyway.
Kinda of a messed up design,the grounds at the ignition box that is mounted to the riser have rubber grommets behind them so the bolts can't be real tight.
I have to go back and do some more work for him so i decided to get a longer bolt,double nut the one with the ground so it can't happen again.
May even run an extra ground to the block to be certain.
The way it is now it relies on the threads only to make ground on a bolt that can't be very tight.
I guess the rubber holds the box off of the riser so it does not get the heat transfer.

 

[Don S]

Re: All day chasing a fuel problem....

I've never seen a module with rubber spacers, they are usually a hard fiber spacer. If they are actually rubber, extend the ground wire and bolt it solidly to a good engine ground. Some of those modules had a longer ground wire and were wired to the engine and not the riser.

 

[Gary H NC]

Re: All day chasing a fuel problem....

Thanks Don.
I think the rubber spacers were an idea whoever worked on it before came up with?
I decided when i go back to do the other work to ground the box direct to the block..It will eliminate that problem of ever happening again..
Its actually 2 wires using that location for a ground..one from the coil and one coming out of the harness.

The customer was happy. He is a repeat customer so i knocked off some labor but he tipped me 50 bucks anyway.
He has also sent me a couple new customers..

 

[JustJason]

Re: All day chasing a fuel problem....

That works... good for you Gary.

If your talking about a TB4 module on the port riser then yes those rubber mounts are supposed to be there.

1 way to see if there is an issue with either the box or the ground is to throttle it up to 3k or so and see if the timing is steady or if it's walking all over the place. If the advance is all over the place its either a bad box or bad wiring.

 

[Gary H NC]

Re: All day chasing a fuel problem....

It was for sure the ground. This boat used to have a 4.3 in it and now has a Vortec 5.7...600 cfm 4 bbl.
After the ground fix it runs perfect..
18ft SeaRay...nice little boat and it will haul butt now..
A little under propped being it would turn 6200 at WOT..

Speedo was reading 54 mph...I will take my gps next time and see how close that was.
He is buying a higher pitched prop for it.
He has a list of stuff he wants me to do..I have already done a ton of work on it.