1989 4.3 V6 RPM's falling off

[Rick Stephens]

Whelp, they just called me, they said come pick it up. About a half dozen guys from two different marinas and they can't figure out what's wrong with it.

Fuel is good
Fuel system is good
Fuel pump is good
Carb is good
Coil is good

???

Holy cow. That's.... (loss for words)

This is not rocket science. We know something is happening. I think you need to stick a T in the fuel line and hook up a fuel pressure gauge right before the carburetor.

 

[jasoutside]

Holy cow. That's.... (loss for words)

This is not rocket science. We know something is happening. I think you need to stick a T in the fuel line and hook up a fuel pressure gauge right before the carburetor.

Yah he didn't want to keep running up the bill searching for something he can't find.

That's a rigid fuel line, I don't have the skills or the tools to install a gauge on there.

 

[Rick Stephens]

Yah he didn't want to keep running up the bill searching for something he can't find.

That's a rigid fuel line, I don't have the skills or the tools to install a gauge on there.

In that case I would probably remove the rigid line and cobble together a rubber line with the appropriate fittings on the ends and a T to an automotive vacuum/pressure test gauge. The gauges are cheap, as is the rubber hose and fittings you need.

 

[pckeen]

Following along

 

[achris]

With the portable tank in place see if squeezing the primer helps or hinders. If no primer, put one in, cheapest option for diagnostics so far.

 

[Patfromny]

It sure sounds like fuel to me and apparently alot of people but unless you can bring someone else out with you or install the fuel pressure gauge at the helm where you can see it, it's not going to do a whole lot of good. I personally would just change the fuel pump and call that a good expense just so you know when it was replaced. It might not solve the problem but you will know how old it is going forward. I would then change things one at a time. Any rubber fuel lines would be my next choice. This boat has been a long time in the making. Just because you put new fuel lines in 3 yrs ago doesn't mean they are new. I would also try a new coil. If it doesn't solve the problem you can return it. No moving parts. Just tell them you never installed it. If none of those work, I would disconnect and reconnect all ignition terminals. Maybe reinstall with some dielectric grease. If for no other reason but peace of mind, this is a good thing to do. When you were wiring the first time, you were excited to get the boat on the water, now you are looking more carefully at each connection because of this problem. You might find a crossed wire or a faulty ground. Basically, you should check your work. Chances are that the mechanics were just assuming you had everything right and we're troubleshooting from there. I know first hand how deflating these things can be but you have got to keep your eye on the prize here bud. Years and years of enjoyment with the family are worth a few hours of diagnostics. I'm sure you'll find it. One other idea is to throw the old carb back on. You changed ignition parts and the carb at the same time. The original problem could have been ignition. This option also costs you nothing. Good luck. Just about this whole site is as anxious as you are to see this topless islander fly.

 

[achris]

..... I personally would just change the fuel pump and call that a good expense just so you know when it was replaced. It might not solve the problem but you will know how old it is going forward. I would then change things one at a time. Any rubber fuel lines would be my next choice. This boat has been a long time in the making. Just because you put new fuel lines in 3 yrs ago doesn't mean they are new.

This is called 'shotgun mechanics'. It's an expensive and time consuming way to try to fix something, and usually introduces more faults than it cures. The quickest, cheapest and most reliable way to fix a problem is proper diagnosis and troubleshooting, not just throwing parts at it.

I would also try a new coil. If it doesn't solve the problem you can return it. No moving parts. Just tell them you never installed it.

This is called fraud, and gets you locked up with cell mates named 'Bubba'.... Also not a recommended troubleshooting technique.

.... Years and years of enjoyment with the family are worth a few hours of diagnostics.....

This is what you should be doing, not throwing money/parts at it, or pretending you didn't use something when you did.

jasoutside Just had another watch of the video. Definitely looks like a fuel issue. I didn't see any signs of ignition interruption. Quadrajet carb with mechanical fuel pump? I definitely think a remote tank with a primer in the line would help point you in the right direction. Does the carb have solid needles or sprung?

Chris.....

 

[saginawbayboater]

Fuel pressure should be 5 to 9 PSI at the carb. If your tank is lower then the pump, or the suction line is really long the pressure will be lower yet. I like the primer bulb idea chris has to pump it up as you drive when the sputtering starts. :thumb:

 

[Patfromny]

Kinda harsh there achris. Might not have been the most honest thing to do but no harm in using something for a few minutes and retuening. You can be honest and tell them it didn't do the trick. Most times the parts dealer will take back an item with no moving parts that was used breifly. I can see your point so no need to expound on it. The bubba statement although more for your benefit, was understood. Shotgun mechanics is putting all these things in at once and crossing your fingers. Changing parts one at a time is a valid way to find the problem. Especially since this boat has been checked by several experts with no answers. I disagree that putting new parts onto an engine one at a time would introduce more problems. The worst that could happen is that it might expose another problem. What is wrong with installing new parts onto an engine? Especially a fuel pump that has been sitting with ethanol in it for who knows how many years. If it isnt the problem now, it will be in the near future. I Don't want to start anything here. Just asking for a bit more courtesy. I kinda felt attacked there. Something I wouldn't expect from a moderator. Thought your job was to stop that sorta thing. You could have just disagreed with me and not quoted before making these statements. The objective here is to help Jas. Not try to discredit someone along the way to pushing your idea.

 

[Watermann]

Pat don't take it personally, we know you're trying to help. I've been frequenting the MC forum for a while now and was put in my place too. :lol:

I was wondering Jason did you replace the barb fitting on the tank that has the anti-siphon in it? Just another thing to check and test if it's a restriction or maybe becomes one since we all seem to think it's a fuel delivery issue. Something could be getting sucked into the anti-siphon gizmo.

 

[achris]

Another thing to check on the fuel system is to put a vacuum gauge on the line just before the fuel pump. If the reading it more than 2", it's too high. Also, putting a temporary section of clear hose just before the carb. You'd be looking for a solid stream of fuel, no air bubbles.

Chris......

 

[saginawbayboater]

No doubt about it waterman that check valve is suspect. There should always be a sock or screen or filter on the suction tube in the tank, but not everyone used them. With any gas engine that sits around for long periods of time the gas goes bad. Gas can turn to varnish and that varnish can turn to flaky particles that plug everything. I like to use a product like seafoam in gas to melt that varnish away. if its foreign matter like additive seals or other junk it will have to be dismantled.

 

[saginawbayboater]

I also am with patfromny on changing out the fuel pump and here is why. If you don't like to get stranded, then changing out the parts that will let you down is preventative maintenance. For example Batteries 4 years and I don't trust them. Fuel pumps, water pumps, starters, alternators, belts and hoses, plugs, wires, cap and rotor. These will all let you down! It puts the mind at ease, and is safer to have the bases covered. It's also easier to work on in dry dock, then out to sea.

 

[jasoutside]

Hi Guys, first off, thank you all very much for chipping in to try and help me figure out this whole issue! I really do appreciate your time, thank you.

All right, so, let me see if I can catch the bulk of your comments, comments and suggestions here.

So, Friday after I picked up the boat, in my desperation and defeat, I immediataly ordered a fuel pump. It will be here tomorrow. Another couple of pieces of the puzzel for ya: I just spent a whole week on vacation, without a boat that took many years to build. Lake Huron was flat calm for three straight days, the kids kept asking "when can we go tubing?" Heartbreaker. On Friday I leave for the U.P. for another vacation on the lake. I sure hope i can get this figured.

All right, anyhow, on Saturday morning I took out the Islander attempting to diagnose this fuel system. Specifically the two fuel tanks, the 3 way valve, the fuel filter and all the lines that go with them. Check out the video...

https://www.youtube.com/watch?v=INykM4qRpR0

The wind kicked up the night before so I was dealing with 2'-4' swells out of the harbor. No way I could get to WOT. But the boat ran awesome, beautiful in the chop, and the engine was as smooth as could be.

Drove home Saturday night, church and family time today. This afternoon I took the boat over to our local lake to try the test again. Of course I'm dealing with weekend boat traffic as I'm very carefully trying to handle some very specific tests, with the boat going from full speed to stalling out.. Launch ramp mosh pit, jet skis, go fast boats, pontoons, sheriffs patrol (with my non marine approved jerry can on my deck) ugh, what a mess.

Anyway, I did conduct the few tests that I wanted to and needed to:

1. Run through WOT on the bow tank
2. Run through WOT on the midships tank
3. Run through WOT on the jerry can directly connected to the fuel pump

All three tests yielded the same results, loss in RPM's at WOT.

Now I did this test a while back with the old carb and assumed the results would be the same.....and they were.....but I should not have assumed that. Now, no assumptions. I was especially curious when SBB mentioned long runs between the tanks and pump, I do have that. But, the distance between the jerry can and pump was about 16", with the same exact results, so that rules that out. Good thinking though.

Something else worth mentioned here...

After a few WOT tests I eased back to around 2800 - 3000 RPM and just rand for a while. All of the sudden she wanted to stall right out. I eased back to 1000 and it continued to run fine. I moved it back up to 3000, stalled right out. I tried to restart, no good, tried again, no good. Gave the throttle a couple of good pumps and it started right up. So, I think that tells me that carb is running dry. Is that what it tells you guys too? Maybe it's obvious huh.

I feel confident in saying everything up stream of the fuel pump is good to go. While the fuel tanks certainly did come from donor boats they were cleaned thoroughly, fittings too, and all brand new fuel lines were installed. All the fuel in this boat is brand new too, as in the last couple of weeks. So, if that part of the system is all good, I think it's reasonable to be eyeing the fuel pump, or the carb. (Or maybe something much worse like engine failure? Man I sure hope not.)

Chris, the fellas at the marina did test the fuel, no water in it. They also ran a clear line up to the fuel pump, no bubbles or gaps or anything like that. I don't have all the lines, bulb and fittings here on hand or I would definitely try as you suggest. Very smart! I am guessing it'll cost me a good chunk of $ to get all that stuff together from the marine dealer. Plus two hour long round trips as undoubtedly I would get the wrong size fitting or something dumb like that.

I may shoot to install the new fuel pump tomorrow afternoon if I can find the time, I'm booked up through the day. Man, that would be great if that actually solved this issue straight away. We will see.

Thanks again for helping out guys:thumb:

 

[Rick Stephens]

Fingers crossed for you. Gotta get the kids back in good graces :^)

 

[achris]

If you're confident in everything north of the fuel pump and you were running off a known good can and line to the fuel pump, then it's the fuel pump. The primer bulb would have proved that. But as you have a pump on its way, just go ahead and change it.

As for 'long runs' of the fuel line, as long as the pump is good, and the lines are not too small, nothing bad. My brother has a bow tank and uses 3/8" lines, works a treat. If you have questions over the lines, the easiest way to check it to hook a vacuum gauge to the suction side of the pump and see how hard the pump is working. You don't want to see any more than 2" of vacuum on the suck side. If it is, you have some form of restriction, be it the anti-syphon valve or the lines being too small.

Chris....

 

[jasoutside]

Fingers crossed for you. Gotta get the kids back in good graces :^)

Too right. They really have been so patient over the years watching this boat so slowly being built, often talking about tubing fishing and all that. They have been great to me, I really need to get this wrapped up and flyen over the water for them.

If you're confident in everything north of the fuel pump and you were running off a known good can and line to the fuel pump, then it's the fuel pump. The primer bulb would have proved that. But as you have a pump on its way, just go ahead and change it.

As for 'long runs' of the fuel line, as long as the pump is good, and the lines are not too small, nothing bad. My brother has a bow tank and uses 3/8" lines, works a treat. If you have questions over the lines, the easiest way to check it to hook a vacuum gauge to the suction side of the pump and see how hard the pump is working. You don't want to see any more than 2" of vacuum on the suck side. If it is, you have some form of restriction, be it the anti-syphon valve or the lines being too small.

Chris....

Hey Chris, the long runs were a minor concern of mine. See this is my set up...

The bow tank and midships tank lines run all the way back, under the engine, up to the transom, over to the 3 way valve, down through the fuel filter then on to the fuel pump. All the lines are 3/8". The fuel should be running downhill from the tanks most of the time so the pump shouldn't be working that hard to pull. But, then it goes uphill a bit to run through that 3 way valve. Of course running off of the jerry can sitting right next to the pump eliminated all of that business and the engine still cut out. So, I think it's reasonable to say that shouldn't be the issue here.

I set up the valve and fuel filter there for two reasons, 1) At the time I built that all out the engine wasn't yet in place and I didn't have the doghouse built, so, I had know idea what kind of space I had to work with surrounding the engine. 2) I wanted the valve conveniently located so I can easily switch tanks when I need to. Now that the engine is installed and the doghouse is built I can see I have just enough space inside of the doghouse, right next to the fuel pump, that I can relocate that fuel filter and 3 way valve. That should eliminate about 7' of fuel line (round trip) and an extra 6" - 8" of uphill pull. Again, that shouldn't be the issue here but it's worth considering as I move along.

Yup, the fuel pump will be delivered right to my door by the guy in the big brown truck. Installing a primer bulb, lines, fittings and gauges is probably the correct method of diagnosis but I know I'd spend a lot more time putting all that together. Plus I'd probably be at about half the cost of a fuel pump (or more). So, we will give this a shot. Man I hope it works.

 

[NHGuy]

I haven't been following your thread. Just came across it. But I do think you are following a good trail. IF the fuel pump fixes her up you can just chalk it up to the engine had more demand than the old pump supplied.
I have a couple of ideas for you installing the fuel pump. First off put some absorbent pig mats in your clean new bilge to catch the oil that will drop.
Get a longer bolt that will fit the hole in the front side of the block by the pump. With that bolt you can lock the pump rod against the block so it does not fall out when you remove the old pump. It's a time and cuss saver. Wrestling the pump rod in before the pump can be a bear.
Be very certain that you put all the fuel lines onto the barbs well and clamp them enough to seal. But don't clamp them so hard they can split and allow air into the fuel. I was thinking your fuel supply might have had air in it at high RPM til you told us the marine shop did the clear line test.
If your carburetor is a quadrajet and it still does the same thing you could have a carb for a smaller version of your engine. There are upgrades possible. This is way out there, but if the fuel is air free you may want to go to the next size up on your needle and seat.

 

[jasoutside]

Allrighty, fuel pump is off. Now obviously some gas ran out of there, but, I also had oil come out...

All over my nice clean deck, rats.

Duh!

Then I read your post....

First off put some absorbent pig mats in your clean new bilge to catch the oil that will drop.

 

[Watermann]

A crescent wrench and vice grips?