Fuel Delivery issues?

C

Cutty Sark

New member
Hey everyone, had something I can use a little help on. My 94 evinrude 70HP is having some issues with the primer bulb staying firm. I've already replaced the bulb and checked for obvious leaks, and replaced some of the lines. It will get firm if I bleed all the air out so it aint the carbs leaking. But after a run it will be from 3/4 to flat in firmness. And I mean flat, full of air. I do have a H20 fuel seperator but have primed it as manual says. My feeling is its on the motor somewhere? Could this be any guesses before I take it to the shop.

Sark
 
If the bulb is flat after running the engines it would suggest to me that the engine(s) are using fuel faster than the line can supply it and you are sucking the bulb flat. Something partially occluding the pick-up in the tank or stuck in the line, maybe at the connection to the bulb. Do you have a portable gas tank that you could run with to eliminate or confirm that it is on the tank side of the bulb?
 
Sounds like you have an air leak between the bulb and the fuel level in the tank. Could be old cracked hoses, a fitting needing thread sealant, a loose pick up tube inside the tank, or the tank selector valve packing. Likely a minute leak...tough to find.
 
After many years of repairing Johnson/Evinrude motors here is what I would do.

A restriction in the fuel system could cause the primer bulb to be sucked flat.

An air leak into the fuel system could cause the primer bulb to be mostly full of air, not fuel, and be its normal full, round shape.

For restrictions, I would check the, fuel tank vent and vent hose, the fuel pickup in the tank, anti syphon valves, fuel hoses, valves, and fuel filters.

For air leaks, check fittings, tank selector valves, hoses, hose clamps, fuel filter gaskets, and primer bulb.

One way to check for air leaks is to temporally install a section of clear hose in the fuel line between the primer bulb and motor. This is for testing only, remove it before operating the boat! Run the motor at the dock or on a flusher (remove the prop for safety!) and observe the fuel flow in the clear hose.
Any air leakage will show as bubbles. Very small bubbles(pin head size) are OK, large, continuous bubbles show air leakage into the fuel system.
Its possible for air to leak into the system, but not let gasoline leak out.

Please be safe working with gasoline, and running motors!!
 
If the bulb goes flat, the problem has to be between the bulb and the tank. The only way that bulb will go flat is depletion on the downstream side, with lack of filling on the upstream side. If there is an air leak in the system, the bulb won't go flat, it'll just get a lot of air in it.

What's the primary symptom? Is the engine quitting? Or do you just have a "Soft" bulb?

Ken
 
Ok let me speak clearer as I realize I phrased it wrong. My bulb is not sucking flat, but when I squeeze it, it is full of air and goes flat(no gas). It does this after running or sitting idle for a while. I have checked the vent, replaced the pickup tube(not clogged),replaced fuel lines to water seperator, tightened end fittings. When I replaced the pickup I didn't reseal it overly well, but the problem has been going on since before I did that. Could that be it. I dont think so but... I guess I'll get a new bulb and see if thats the problem. I had bought a new one but it didn't help and seemed to have its own valve issues, so I put the old one back on . Could it be possible that the air is coming in, from a fitting inside the motor and working its way back to the bulb? I will try another tank too I think to hmake sure it's not the tank or something back there.

thanks for the help
Sark
 
Sark, I've been through this problem a couple of times.

The first time it was a bad quick disconnect fitting at the end of my fuel line that connected to the Tempo fuel tank (sucking air).

The second time about a year later, I purchased a new 8 H.P. Honda and ran two fuel lines from a tee off the fuel filter/water separator. One line for the main and the other for the kicker. I thought I had a check valve in both lines, but one was just a fitting without the check valve in it.

This kind of stuff drives ya nuts, but it's usually something simple. The cost for both fixes was under $6 dollars. I'm not sure what kind of setup you have, but I hope this helps.

Jon
 
Sark,

If you run the motor on a separate six gallon tank and hose, you take your boat's fuel system out of the circuit.

Now, if the motor runs fine, suspect your boat's fuel system.

If the motor and squeeze bulb show the same problem, suspect the fuel system inside the motor cover.

A couple of comments about primer bulbs:

Primer bulbs have an arrow on the rubber which must point to the motor.

If a bulb doesn't want to prime, try pointing the "arrow to the sky" (up) and then squeezing. Gravity helps the internal valves to close.

The hose barb size on the bulb must match the fuel line size(I.D. of the hose).

Sometimes its the simple things! :teeth
 
Well I picked up a new 6 gallon tank and new primer bulb assembly. Will try to isolate the problem and then move foreward from there. Let you guys know what I find out. Thanks for the help. As I said before this site is one of the biggest reasons for my wanting a CD. Can't wait to crawl around in one at the boat show.

Sark
 
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