Stus-List M-35 electrical fuel lift pump
rickbrass at earthlink.net
Tue May 21 21:03:55 EDT 2019
The OEM fuel filter for my Universal M35B is 10 microns, plus there is a small “strainer” filter near the inlet to the lift pump. IIRC, the spare “strainer” that comes in the parts kit is marked as being something like 70 microns.
The installation manual for the engine suggests using a primary filter (the Racor) of about 30 microns should you want to add one. Which is consistent with the advice you gave.
But because I’m anal about abrasive material getting into the high pressure pump, and because the design flow rate of the Racor filter is literally 10s ( maybe 100s) of times the 3 to 5 GPH flow rate of the M35B fuel pump, I’ve elected to use a 5 micron Racor as the primary.
I had to replace the 1st Racor while enroute to Annapolis last fall, with something over 900 engine hours on the filter, after apparently getting a tank of crappy fuel the previous day. The engine coughed once while approaching a marina, then ran for about 15 minutes. When restarted the next day, it ran a few seconds, stopped, and could not be restarted. The clear bowl below the filter was totally black with crud.
The failure mode was not that described in Pierre’s post (gradual fuel starvation after long run period) and seems more consistent with the overheating lift pump I mentioned in my other comment.
I suppose that an almost plugged filter could cause fuel starvation for a short while. But once the filter is plugged, the engine will stop and not restart.
From: CnC-List [mailto:cnc-list-bounces at cnc-list.com] On Behalf Of Andrew Burton via CnC-List
Sent: Tuesday, May 21, 2019 5:03 PM.
To: cnc-list at cnc-list.com
Cc: Andrew Burton <a.burton.sailor at gmail.com>
Subject: Re: Stus-List M-35 electrical fuel lift pump
2 micron might be part of your problem. There’s no need to go that fine on your filter element. 30 micron is perfectly adequate. Remember you have a finer filter on your engine.
The 2 micron can easily clog up and leave the bowl of your Racor clear.
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On May 21, 2019, at 11:46, Pierre Tremblay via CnC-List <cnc-list at cnc-list.com <mailto:cnc-list at cnc-list.com> > wrote:
After suffering few fuel starving, I decided to have spare part for everything between fuel tank and engine fuel injection pump. Engine is a Universal M-35. RPM would slowly drop down then engine dies. I am able to start it back by just opening the fuel blead valve on the injection pump. It happened after 4 hours motoring in dead calm sea with a full tank, and the Racor glass is clear. I had no problem when the engine is cold. I suspect the fuel lift pump.
The electrical fuel lift pump I actually have is a CARTER 7H15A 504. Google cannot find it, and the only look alike from Carter is #P60504 or #P76438 superseded by #P90091. Can someone tell me what you have for lift pump.
>From the spare fuel filter I have, primary (Racor 200FG) is 2 micron, and secondary is 10 micron. I know it is wrong and I will go with 10 / 10. The 2 micron might also start to be dirty.
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