Stbd Engine Hard to Start, Dies at Idle

[drewc]

Apologize if this topic was recently covered, but I did a quick scan and didn't see this specific problem. The Starboard Lehman 120 (1978) is very hard to start after secondary Racor filter change and bowl clean out, requiring mid-3/4 throttle to catch. I did the normal priming at the injection pump bleed screws to bleed air from the system, at least enough to get her started. I'm now wondering if there is another step required to purge additional air that might be affecting proper engine fuel system operation, maybe on the primary filers? I've never had to do this in the past, and never on the (much easier to deal with) Port engine. Another symptom is that once started, the engine dies when pulled back to about 650 or so for idle, or when put in gear. Thanks for any advice.

 

[Marin]

Don't know if this has any bearing on your problem but I assume you are aware that older Racor 500 filters (if this is what you have) don't accept the current Racor 500 filter elements without the use of an adaptor. The adaptor is apparently included now with all the filter elements. They changed the configuration of the filter so that the new filter elements do not come all the way to the top of the newer Racor filters, so some fuel could go through the filter without being filtered.

I don't know if using the new element in an older Racor 500 would affect the starting and idle but I suppose it's a possibility.

If in your element changing and bleeding process something happened that is admitting a bit of air into the fuel line, this could certainly cause the symptoms you are experiencing. A washer left off a bleed screw, a bleed screw not properly seated. the top of the Racor not properly seated, an o-ring left out of the top of the Racor, or two o-rings where there should only be one, this sort of thing.

It the engine wasn't hard starting before and idled fine and now after changing the filter element and bleeding the system it's giving the problems you describe, the cause lies in something you did.

You might want to start over and do it all again, making sure you're following the correct process and not leaving any parts out or adding any extras.

 

[drewc]

Marin, thanks for thoughtful suggestions. I am still using old stock elements for my Racor 900s...I do realize there is an adaptor necessary to properly use the new elements. As far as i can tell, I am doing the filter replacement to spec - at least the way I have always done it!

This engine has always been "hard starting" in comparison to it's port-side companion. As I indicated, it typically takes a mid-postion throttle to turn it over. Once started, it idled fine. Not sure if there is a clue embedded here!

Your comment about admitting air into the fuel line is no doubt spot on, but I am at a loss to locate where it is. I will take your suggestion to repeat the filter change process to see if I can eliminate it this way. One question: do you recommend that I crack open the bleed screws on the primaries as well? I was thinking there might be residual air in there...

Drew

 

[Marin]

The setup on our boat is different in that we don't have to bleed the fuel system if we change the elements in the Racors. Our entire fuel system is gravity fed so filling the Racors to the top by opening a transfer valve on a tank is all that's needed.

However, if we change the two spin-on filters on the engine, I do need to bleed these filters and the injection pump. I do this from the rear of the engine forward using the manual lever on the engine's lift pump. We never have to bleed the injectors themselves.

If an engine will start, it will tend to "bleed" itself of any air trapped in the system. However, if you have a air leak, even a tiny one, at a fitting, for example, this could cause the problems you're having.

 

[kulas44]

Adding an electric primer pump ahead of the Racor "may" help you find a small air leak. At the least it makes filter changes much easier. I prefer the old style Walbro marine units but they are getting hard to find. I install the pump with a bypass valve but some folks just put it inline. Its a flow thru type so doesnt really add much restriction, especially on a low fuel flow engine.

 

[drewc]

Thanks to all for help. Turn out it was injection pump sticking due to low/old lube oil. Once changed out, she starts right up and idles nicely.