Fuel Shortage

[Rob Dog]

New here.... I have a 1996 GTX that seems to be getting very weak fuel flow. I have replaced all fuel lines, selector, and the carbs were rebuilt last year. It starts fine and revs up to 3300 and that is it. At that point it starts spitting a higher RPM as though it is getting a splash of fuel. I installed an in-line fuel filter and watched it while running on the water. It starts with about 1/8 capacity and then when throttle is applied it sucks all the fuel and remains empty. I cannot see any fuel flowing but I know some must be. Thinking maybe fuel pump or an air leak that I have seen on these threads.... Any other thoughts?? Thanks in advance!!

 

[artr]

Did you use genuine Mikuni kits and follow the sticky thread for the carb rebuilds? I would check the condition of the pulse line hose and its connections to the mag carb and engine. The mag carb pumps the fuel on this model. Does it still have the original fuel filter/water separator under the hood near the fuel selector? Was that cleaned and the o-ring replaced/inspected? That should be used and not an inline filter. Even though you replaced the fuel selector, some can still have problems. You can rule that out by temporarily bypassing it and running fuel directly to the carbs. The fuel sender unit in the tank has a screen on the bottom that may be dirty.

 

[Rob Dog]

The rebuild was done at a shop and I believe they used those kits. The filter was replaced but I thought I should replace the O-ring again. I got the same results with the selector in Norm and Reserve. I will try to bypass and check that screen. What is the "Mag" carb? Thanks much!

 

[artr]

The carb in the front of the engine where the Magneto is. The rear carb is called the PTO carb.

 

[etemplet]

I can tell you from experience that they inline filter will restrict the fuel supply all by itself. My 587 ski kept giving me trouble till I was advised to discard the inline filter.... I never had that issue again. Very strange but I don't do inline filters.

If your problem existed before you installed the filter I'd suggest pressurizing the system and checking for leaks. I use about 8 PSI. I prefer to pull a vacuum test as I think it more readily shows where the problem is

 

[Rob Dog]

I can tell you from experience that they inline filter will restrict the fuel supply all by itself. My 587 ski kept giving me trouble till I was advised to discard the inline filter.... I never had that issue again. Very strange but I don't do inline filters.

If your problem existed before you installed the filter I'd suggest pressurizing the system and checking for leaks. I use about 8 PSI. I prefer to pull a vacuum test as I think it more readily shows where the problem is

Thanks for the reply! Assuming the filter is replaced by a clear tube, how much fuel should I be seeing passing thru? Seems like just a trickle at this point... Thanks again!

 

[Rob Dog]

I can tell you from experience that they inline filter will restrict the fuel supply all by itself. My 587 ski kept giving me trouble till I was advised to discard the inline filter.... I never had that issue again. Very strange but I don't do inline filters.

If your problem existed before you installed the filter I'd suggest pressurizing the system and checking for leaks. I use about 8 PSI. I prefer to pull a vacuum test as I think it more readily shows where the problem is

I replaced the grey fuel lines 2 years ago with black rubber. I am seeing notes about Napa vs Marine grade and also see clear blue lines. Do you have an opinion on the blue hoses? Thanks!

 

[etemplet]

I buy a 25' roll of the black 1/4" fuel line from Amazon. I don't really watch the fuel flow but if you suspect a flow problem I'd check for air leaks as well as blow some air through the hose to make sure it is OK.

 

[mikidymac]

Do not use the colored hose, it will get hard and leak in about a year.

 

[Rob Dog]

I am about to part this guy out!..... Did all the above and still not running. I put a new voltage reg in and it started, backfired and died... Now will not start. Fuel filter is filling so I am pretty sure it is getting fuel. It fires once in a while so I think it has spark.. Thinking of taking it in and putting a max on time spent. I just don't want to fall into a money pit hole with no escape. Thanks for the help!

 

[artr]

You don't seem 100% positive about if it getting fuel and spark. I would check for a consistant spark while cranking with some type of tester. I have an inline tester with a light that will let the engine start and run with the tester in series with the plug. You could check for fuel by disconnecting the plug wires and grounding the wires on the shorting bar on the rear electrical Box, crank the engine and remove the plugs to see if they are wet with gas.

 

[POPPS]

I'm with "artr",,,load test the battery,, check for charging,,,check compression,,,and then check for a good bright consistent spark.,,

 

[Nichols]

Also, genuine Mikuni parts DO make a difference. Check the diaphragms, each should show a red dot in the center. There is a noticeable difference in the feel of the cheapo and Mikuni parts. I can speak from experience.