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View Full Version : HELP...!! Calling all Gearheads....



DonziDave
06-21-2005, 09:13 PM
I am having a fuel supply problem that I cannot track down and have reached the limit of my technical ability.

Boat is 1986-18 Classic - 350 SBC w/ 4bbl. Quadrajet carb.

Boat will run up fine up to approx. 1500 rpm. If I throttle up to cruise speed or above, boat will run for 30 seconds or so then become gas starved and stumble to a stop. Hard to restart, but with some pumping it will fire back up.

Here's what I've done so far:
1. Pumped gas tank dry. No water, almost no trash/scale.
2. Poured pumped gas into glass container and let sit for 24 hrs. No water, but gas was cloudy and remained cloudy for the 24 hrs. Nothing settled out.
3. Tank pick-up tube, fuel line, and carb. filter is clean. Fuel system does not have an anti-siphon valve.
4. Tank vent line is clear.
5. Replaced gas filter that only had 2 hrs. time with new filter. Gas in filter was also cloudy.
6. Put in fresh gas and ran boat. Same problem.
7. Removed new filter. No trash or water. However, when I removed the filter, it sucked air as if it had a slight vacuum. THIS MAY BE A CLUE...????

What I haven't checked:
1. Mechanical fuel pump.
2. Carb. internals. Carb. was rebuilt 2 years ago and has operated fine.

I have done all that I can think of. Any ideas...???

Thanks for any help....
Dave

MOP
06-21-2005, 09:45 PM
THe vacuum created in the fuel filter proves the pump is trying to suck fuel, don't pick on the carb yet. If you still have the blue stiff braided hose that connects the copper line to the engine check to see if the inner layer has come loose. Your boat being an 86 the fuel line is suspect, lots of years of alcohol eating at the rubber.

Phil

RickR
06-22-2005, 09:18 AM
Make sure the pick up tube inlet is above the bottom of the fuel tank.

Cloudy fuel??? If you have an additive in it to remove water, it might be clogging the fuel filter. Fuel filters clogged with water can be reused if you turn them upside down and let the element dry out.

Donzigo
06-22-2005, 09:34 AM
The fuel tanks in 1986 were made in Perry, Fl. They are still in business. G. Carter bought a new tank frim them. Throw him a call. I'll put my money on a fuel tank that is full of corrosion and needs to be replaced.

I told George the same thing. Don't shoot me..............ask him if I gave him good advice, first.

Richard

Rootsy
06-22-2005, 09:59 AM
is there a fuel shutoff in line between tank and filter?

Morgan's Cloud
06-22-2005, 10:31 AM
I thought I'd throw this in while we're on the subject.
My friend Todd had the same problem shortly after he went back in the water last summer after a re-powering job. It was a new turbo diesel but the exact same problem.

He also had put in new tanks as part of the job ..

When he bypassed the tanks and ran off an auxilliary tank the engine was fine.

After much gnashing of teeth and hand wringing he took the engine AND tanks back out and took the fittings off the tanks and examined the insides.
There was a little dirt but not really enough to clog the pickups ...
Well , that is if the pickups did'nt have damn screens on the ends of them !

The micro fine screens had become clogged with the dirt and anything over 1000RPM or so and the engine was'nt gonna do it .

I don't actually think that after all these years this could be your problem but I bring it up for two reasons

1) I can't believe that anyone would be stupid enough to build tanks with screens on the pickups

2) A little info can go a long way .. maybe this will serve someone else later on .

S

Pismo
06-22-2005, 12:28 PM
Try an alternate fuel source. Unhook the gas line going from the tank from the input side of the filter/water separator and plug it off. Hook a two foot piece of fuel line onto the input fitting on the filter/separator which you just freed up. Stick the free end in a 5 gal can of gas and go for a ride and see what happens. This will immediately narrow it down to the tank/fuel line or the carb/filter/pump.

jstokes8407
06-22-2005, 08:07 PM
I have a 86 18 also and had the same problem as you did 2 years ago. I found the elbow on the tank clogged maybe a (1 way check valve also ). It was a long time ago. I put a new fuel pump, carb , lines, pick up and still died out. It would idle but when you punched it and the carb ran out of fuel it would starve and die out. My tank is still origional also and no signs of problems. It's worth a try also do what the other guys said and run it off a 5 gallon jug

Good luck

Pismo
06-23-2005, 05:56 AM
To be 100% sure you are running out of fuel you can wait until tou are having the problem and push just the accelerator pump on the quadrajet and feel if it is pushing gas. If no gas it will just push down easily. If there is gas it will push down hard and squirt gas into the barrells.

DONZI
06-23-2005, 02:21 PM
On the top of the tank there is an 90 deg. brass fitting w/ fuel line attached. Inside this fitting there is a ball/ spring (Anti-Syphon valve).Even a small amount of debris can partially clog it.Remove fitting from tank,ck.,clean.Re install ck. for leaks.

Cybercop
06-23-2005, 03:28 PM
I've been following this thread very closely, as it appears to tie into the same problem I posted about one engine running rough coming off idle.

Starboard engine is a GenVI, port is a GenIV. Did a complete top-end tear down of the GenVI. After jumping through hoops for top engine and carb gasket kits, getting the right plugs in the GenVI (Thank you Brian!!), swapping ignition coils to rule those out, I am still sputturing coming off idle. Have not tested vacuum (yet) but fuel pressure on the GenVI to the carb shows 5psi. While the service manual for this 1991 33Z Crossbow lists 7 - 8.5psi with the original mechanical pump on the GenIV, does anyone know if the electronic on the GENVI should also fall in that range? If so, then the info in this thread might clearly indicate my problem (I hope, I hope, I hope, I hope.....)

I am replacing the fuel filter and will test shortly. Of course additionally insight is GREATLY welcome/appreciated/begged for!

Thanks

DonziDave
06-23-2005, 09:10 PM
Hey Guys...Thanks for the great response and good tips...!!
I have rechecked the fuel system. No trash in the tank, fuel pick-up is clear, Checked the Areoquip fuel line (Thanks Phil) it is clear, fuel shut-off ball valve is clear, carb. filter is clear. I think that I am down to the fuel filter as the culprit. I have put on a fresh on and will run this weekend. I'll update you all on the outcome.
Thanks again....
Dave