Diesel Fuel Filters, once again.

[Bob Maguire]

I am looking for a 2 micron secondary fuel filter for a Volvo MD7A to replace a 10 micron WIX filter #33358 that is already in use. I intend to replace the old Fram type primary filter this spring with a Racor 500FG2 that will have a 10 micron filter and thus the need for a 2 micron filter down stream.

Is the use of the hand primer sufficient to fill this new filter with fuel as well as eliminate the air from the system? This has worked fine in the past when changing the secondary filter.

In looking at the Owners Manual for the MD7A, it states that there is a built-in cold-start device in the fuel injection pump. How do I know whether the engine is equipted with a CAV or a BOSCH pump and does this device aid in cold starting?

Your guidance in these matters would be greatly appreciated.

Bob Maguire

[Steve Laume]

Hi Bob, I can't answer any of your questions. I did install a Racor filter on my boat last year though. I did this while changing the fuel lines, which was recommended by my surveyor. I figured I was already disconnected and it seems like the Racor elements are easier to find and change than the Frams are and you can see in the bottom of the bowl. One more thing I did was to install a fuel vacuum gauge. I don't know how many people out there are using these but it just seemed like a good idea to me. Rather than just changing the primary filter at regular intervals which may be too soon or too late I can see if the fuel pump is starting to draw hard because the filter is beginning to clog. I got it at West and it tees off the filter connection. You might want to do those old hoses too. Have fun, Steve.

[Leo MacDonald]

Hi Bob,

I'll second Steve's suggestion. I've done exactly as he suggested - now changing the Racor per vacuum gauge reading (which now has been a few years?).

I have a 500 series that formally had a ‘T-handle’ on top to remove the cap. That handle is replaced with the Vacuum Gauge. They are available directly from Racor (1-800-C-PARKER), P/N; RK11-1669.

[Bob Maguire]

Am still trying to find a 2 micron secondary fuel filter for the MD7A. All I can find now is the 10 micron.

Anyone know anything about the built-in cold-start device in the fuel injection pump and how to tell whether the engine is equipted with a CAV or a BOSCH pump? Does this device actually aid in cold starting? I am confident that there are several of you out there that have the answer to my questions.

Thanks for the help.

Bob Maguire
CD30
Anacortes, WA

[Stan W.]

For the secondary fuel filter I have been using Fram cartridges from West Marine. I think these are 2 micron but I'm not sure.

If you go to the shop manual online at the CDSOA website, page 8 shows an MD6A with a Bosch pump and page 9 shows an MD7A with a CAV pump. My understanding is that Bosch pumps only came on early MD7As. My '79 (built in late '78) has a CAV pump.

The CAV pump cold start device is a little rod-like device that sticks out of the bottom of the pump body. I think you are supposed to pull down on it to aid cold starting. I guess it increases fuel flow but I don't know how it is any different from just giving the motor more throttle. Mine is frozen so I can't say whether it helps.

[Ron Turner]

Bob,

The 500FG Racor can have a 2 micron element in it. So could the smaller 200 series Racor and you could have a primer pump on the filter body. Remember the 500 element comes out the top and the 200 spin-on comes off the bottom, depending on how much space you have for changing filters. The 500 is a high capacity unit and the 200 has expensive elements. Lots of things to trade off in the selection process. I prefer the 500 given the room to manage it but I like the primer pump on the 200. I have plumbed in an electric fuel pump for priming, fuel transfer and emergency running.

[Derek Matheson]

After much research, the following was found:

Baldwin filters has just released for sale their BF7921 at $19.56 each or $14.71 each if you buy a box of 6.

As there were no 'micron' specifications given, I called the factory and the tech rep told me the following:

The BF7921 has an 'absolute' rating of 5 microns, meaning that more than 98.7% of particles 5 microns or larger are trapped. She also told me that it has a 'nominal' rating of 2 microns, meaning that more than 50% of particles 2 microns or larger are trapped.

I plan to buy and install one soon as the engine mounted fuel filter on the Volvo MD7A. Also, I plan to install a bypass line around the 2 micron Racor, so that I can switch over in an emergency.

[Wayne Grenier]

Ever see a commercial fishing boat set up? that's what they do-they have several filters lined up-when one clogs you shut the lines off and shunt it over to the next one-its overkill on a sailboat and with every connection you have a potential air leak-but once you get working you will have piece of mind-I though about it but never did it-I do carry spare filters and know how to replace them-You'd be surprsised how many boaters don't-

[Clay Stalker]

I may be mistaken, but I always thought that the primary filter was the Racor, Fram, or whatever you have installed between the tank and the engine, and that the secondary filter was that little guy on the engine. The Racor should be a 20 micron filter, and the little guy on the engine a 2 micron. That's how I have always set up my Yanmars, but it may be different for Volvos and others....maybe I've been lucky, but even in nasty weather, I've never had the filters clogged...at least not yet......