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9.9 Evinrude fuel issue

J

jdb0367

New member
Hi evryone! I have been thru most of this forum trying to find some help with an issue I'm having. Any help and info would be greatly appreciated.
I recently aquired a 79 9.9 evinrude that was to be in "excellent working order".
After intalling all new seals in the lower unit due to water intrusion I fired it up on muffs. The motor started and ran fine up to 3/4 throttle. If I hold it at 3/4 or wide open for a few minutes, it will miss and blow a puff of smoke out the exhaust and it runs out of fuel.
Squeezing the primer bulb verifies this as the motor will continue to run at full throttle.
I've rebuilt the carb and fuel pump, Installed all new fuel lines including the primer hose and still no results.
I installed a clear fuel line from the pump to carb and when I hold the throttle at full, air bubbles gradually build in the fuel line until you can eventually watch it stop flowing into the float bowl.
I did a compression test and found both cylinders to be at 45psi. I have since pulled the power head and disassembled it to install new rings, seals and gaskets. After removing the head, I could move the pistons around in the cylinders pretty easy. The cylinders look real good and actually still have some visible cross hatch in them.
Am I on the right track here or am I simply spending money on something I've overlooked??
Again......any help would be appreciated.
 
The only comment I can make is that testing should be done on a boat or good size test tank.------Running that motor wide open with no load is a mistake.---45 psi is way too low and I suspect your tester is not calibrated properly.
 
racerone said:
The only comment I can make is that testing should be done on a boat or good size test tank.------Running that motor wide open with no load is a mistake.---45 psi is way too low and I suspect your tester is not calibrated properly.
Click to expand...
I did run the boat in the water with the same results.
My compression tester has always been accurate for me in the past and even putting a finger in a plug hole and cranking it, does not blow your finger out of the hole. I figured the low compression simply wasnt enough to pulse the pump at higher rpms...
 
If you can borrow a tank and hose from a running motor, you could easily rule out those two components. Double check the fuel pump rebuild....it is a simple mechanism but several things can cause it to malfunction. One way to verify if low compression was the problem would have been to run the motor on a 16 to 1 fuel oil mix. If the motor runs better on 16 to 1, suspect low compression.
 
When you rebuilt the fuel pump did you do the blow test. One end will allow air to blow through and the other should restrict it. If not, you know you did something wrong. I concur that if you can borrow another tank and hose you could rule those out. You could also try running it with the tank cap off to ensure tank venting is not the problem.

It sure sounds like you have a fuel pumping problem, you just need to verify where the problem is originating.

As for the compression. I find it pecular that both cylinders would be low at the exact same level. That is why the other poster was curious about the tester. I suspect if your cylinders were indeed at 45psi, when they should be in the 110 psi range, you would see this as a very poorly running motor with reduced top end performance. It sounds to me that you are saying that it runs OK at WOT until it runs out of fuel. Perhaps I midread it, but if I am correct, I would focus on your fuel pumping problem and when corrected, see how it runs after that.
 
Thanks for the responses so far everyone. I did, in fact run the motor on 2 brand new hoses as well as 2 known good used ones. I also tried 2 different tanks and even with the fill caps off. I wouldnt say this engine ran perfect until it runs out of fuel but it will rev up and if held at 3/4 to full for approx. 30 seconds to a minute, it will miss, backfire and blow a puff of smoke out the exhaust. At the same time, the fuel pump slows to bubbling in the clear line until it becomes empty all the way to the carb bowl. I went thru the fuel pump a second time and didn't find anything obvious. When I do a blow test, one way is free, the other has restriction but still passes air thru to an extent. I feel pretty confident on the 45psi compression because with both plugs installed you can turn the flywheel with the palm of your hand and meet no resistance at all. I have the motor completely torn down to hone, ring, gaskets and seals. Both crank seals seem pretty hard. Maybe it was low in crankase pressure?? The cylinder walls look good and so do all the bearings. I guess we'll see once my parts come and I get it back together.
I've been an auto mechanic for 20 years and this little bugger has me stumped!!
 
Ok guys.....First, thanks for all the replies!
I got the little 9.9 back together. Cylinders honed, new rings, bearings, seals and gaskets. Threw 2 new coils on while I was at it and she fired on the first pull. No more lack of fuel to the carb at mid/high rpms like before. Compression is back up to 110 each cylinder.
I honestly believe someone over heated the engine at some point and took the temper out of the rings? Any comments????
I think this was causing a lack of crank case pressure and therefor couldn't run the fuel pump at higher rpms.
The question I have now is.....the motor still has 1 issue that it had prior to the rebuild. If I hold the throttle at 1/4 to 1/2 in neutral, the motor has an occasional miss and blows a puff of smoke out the exhaust. It doesn't do it at higher rpm's or if I put it in gear and rev it.
Gonna try to get out on the water next weekend with it, but I was hoping for some insight before then....
 
Thanks Kim! You were right on the money! Sync was off a bit and I adjusted it. Seems to have eliminated the intermitten missfire.
Thanks so much to all of you and this forum for all you do!!!
 
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