'97 SS quits after 5-10 minutes full throttle

[NautiqueSS]

Hey, I have been trying to figure out whats wrong with my '97 Super Sport GT40 for about 4 months now. I have figured out that it is running through the fuel that's in the fuel control cell and then dying, not completely but to a rough idle. Both pumps are working at least they make noise and at first I thought I was having an overheating problem and the computer was cutting the fuel but I now know that is not the case. I'm going to try to find a fuel pressure gauge and check that but other than that is their anything else to look for? Also the boat will run fine for up to 45 min. just wakeboarding with no weight, about 20-30 mins with weight and less than 10 minutes full throttle and I've checked the FCC bowl and it's always empty after it stalls and is full just 1 minute after letting it idle so I know it's running out of fuel. Could one of the fuel pumps be working but not good enough if so which one. Also I took the bowl off and turned the key on and it pumped gas down through the pump inside the FCC.

[NautiqueJeff]

Have you replaced the filter element in the FCC? If not, I'd start there.



If that isn't the problem, my guess would be the low pressure fuel pump.

[tryan]

i would suspect the low pressure pump if it can suck the fcc tank dry. is there a filter/screen up stream (tank side or in the tank) that will protect the low presure pump from debris?

i would say you have a volume not pressure issue.
the pumps sound okay, but your fuel lines are blocked somewhere.

even if the filter looks 'clean' , it could be saturated with water impeeding fuel flow. is it the original filter? i would ask vince at skidim if there are any other filters or screens in the tank or pre-low pressure pump.

[NautiqueSS]

Yes I have replaced the FCC filter, that was one of the first things I did back in November when the problem arose, the original filter looked pretty bad (but was obviously working) and there was a few of what looked to be rust particles in the bottom of the FCC but all is clean now. The new filter wouldn't have already gotten gummed up would it. It still looks new. And to Tryan I believe you posted something before about upgrading the fuel lines coming out of the FCC. What is that all about? Could that be my problem? There doesn't seem to be any filters before the pumps only after up by the fuel rails correct me if I'm wrong and I'll check them.

[tryan]

i would disassemble everything from the prepump back to the fuel tank. it could be something simple like a pick up screen clogged with rust particles or a stopped up tank vent.

(i know older carbed boats have a check valve in the tank that keeps fuel from flowing back into the tank when the motor is shut off and fi motors will have one, but i'm not sure where it would be on your set up. i have never had an outboard die because the tank vent was closed. never. NOT)

it seems silly to me to not have some type of a filter or screen before the fuel pump. one chunk would just chew it up. is the diagram marked correctly? take the supply line off the prepump and see if there is a screen in the hole.

it's probably just a tablespoon of rust particles giving you the headache


what years had recall issues with the pre pump? 94-95? was 96 the first year for the fcc?

[GC]

When you encounter the problem you might want to check the voltage coming out of the fuel pump relay. I have seen a lot of the O.E.M. (Hella) relays go bad.

[skinautique]

I would check out the fuel pump relay and see if it has a bad connection or the relay itself has gone bad.

[tryan]

if the pre pump is still humming when the boat dies, i would still assume it's getting power. you should swap out the hella relay and try it.
(i pack a spare hella ice cube in the glove box of the truck. they are a pretty common ten dollar item even on newer american cars.) is there another relay on the boat he can swap it with?


is the prepump controled by oil pressure, fuel pressure or a counter? (my old carbed honda 'lude counted engine revolutions) it might be an electrical issue, but rust in the previous filter and the fact that it making noise leads me to believe the inlet to the pre pump is blocked (or the impeller has sheared). it would be nice to know the fuel pressure and the suction pressure of the prepump.

[GC]

I usually replace both the fuel pump relay and the main relay with a standard Bosch relays. I've also seen a couple of problems similar to this caused by a poor power connection for the ECM at the battery. Make sure the connection is clean and tight. For extra measure solder a new ring terminal on in place of the original. Also, make sure all of the ground locations are clean and tight as well.

[NautiqueSS]

checked everything, now what?

Well I checked everything, battery connection, blew air through the fuel line replaced relays with working hatch relays (original relay was working, hooked it up to the hatch motor) I also straight wired the low pressure pump to the battery and it pumped an inch or so of fuel into a gallon ice cream bucket in 1.5-2 minutes. It also dribbled most of the fuel and about every thirty seconds (did it 3 times) shot a lot of fuel out in a heavy stream for 2 or 3 seconds. Is this normal or should it be shooting in that fast all the time. Otherwise it was mainly just dribbling about what you could get through a straw. When I was doing this the key wasn't on so the high pressure pump wasn't on as I had the bucket underneath it to catch the fuel. Also as I was disconnecting the FCC bowl I noticed the high pressure pump was a making a high pitched whine with no power going to it I had already disconnected the battery and then unplugged the relay and at that point it quit but I don't know that the relay being unplugged caused it to quit. It was very faint I had to have my ear right to it to hear it but it was coming from the high pressure pump for sure. This led me to believe maybe it is the high presure pump but once again the FCC bowl was empty after the boat stalled as usual. So I am defintately clueless now. Except for maybe having computer problems?

[skinautique]

If the pump is making a high pitched squeeling noise, it is on the verge of failing. Have you used gas with alcohol in it? This will deteriorate the fuel pump in a real hurry.

[tryan]

i think you have narrowed it down to a fuel line restriction or a sheared impeller on the pre-pump. blowing air back into the tank might blow the crap off the pick up screen, but turning the pump on could suck it right back onto it.

the dribble effect can't be narrowed down untill you can put an unrestricted supply and outlet to the pre pump to see if it will shoot a solid stream. was there a screen on the inlet side of the pre-pump?


i believe the 'buzz' that you hear at the high pressure pump is the check valve returning the fuel to the tank.

[NautiqueSS]

Fixed It!!!

I don't know specifically what I did but it must have been junk on whatever is at the end of the hose in the fuel tank because I tried pumping fuel from another tank but I didn't have the right size hose and it was sucking air and leaking so I did what I didn't want to have to do and take up the floor (which was not difficult at all) and take the hose of the gas tank to use in the other tank. When I did this the pump worked fine. That surge of fuel I had every 30 seconds before was the way it was supposed to flow all the time (16 ounces every 10 seconds according to Vince at Discount Inboard Marine) So I was going to pull up the fuel line and clean it out but there is something on the end of it, maybe a filter but I couldn't pull it out so I just blew air through it and knocked against the bottom of the tank and put everything back together and it worked perfectly. Oh and there is a screen right before the check valve thing which was clean So I don't know exactly what fixed it but it's working good now so I'm happy. Does anyone know if there is a filter in the tank and if so how would you get to it? Maybe at the end of the year I'll take the tank out and clean it out now that I know how easy it is to get to. So Thanks everyone for their suggestions, without you guys help I would have just gone out and bought pumps and filters and still wouldn't have fixed it. Oh and he (Vince) also said fuel pressure should be 40psi which I never did check but is good to know.

[tryan]

the crap you knocked off the pick up will eventually find its way back and clog the pick up. it would take a few hours, but i would think about removing the fuel tank. if there is enough crap in there to stop up the pick up completely, it would be a worthwhile endeavor.

if its rust, see if there is enough iron in it to make it stick to a magnet. you might try to go fishing. if you have a poly tank, put a magnet on a string or a telescoping magnet and remove as much as you can. 8)

you got a bad batch of fuel from old metal tanks. try to use newer stations with the fiberglass mixing tanks from now on.

[tryan]

if its a flexable line in the tank, you might try to grab it with a coat hanger and clean it off through the access port or sender port periodicaly.