Which Filter To Install?

mvtofino · May 11, 2011

Hello Forum!

This is my first posting on this forum, and wouldn't you know it - I need some help!

I am upgrading my current fuel filtration system to the Stanadyne FM100 series, but I'm not sure which part number is more suitable to the application.

Some background:

The company who will be doing the install first recommended the Stanadyne 33945 combination electric fuel pump/water separator/5 micron secondary fuel filter together with an in-line, disposable pre-filter and high quality fuel hose connecting it all up.

As cost became an issue, we considered other options. If we were to keep the existing mechanical lift pump (new with only a hundred miles on it), they recommended a Stanadyne 33642 water separator/5 micron secondary fuel filter with the same in-line pre-filter and hose as noted above, but no electric fuel pump.

I then did some further research and discovered that the 33642 can also be supplied with a wide selection of options, including an electric fuel pump.

The project has now become more complicated (and expensive) as the Stanadyne DB2 injector pump's serviceability is now in doubt, and I'm likely facing the installation of a remanufactured unit as well. Also, I think it would be wise to eliminate the mechanical lift pump altogether at this point seeing as we will be replacing/upgrading all the other components and a simplification of the system is desired.

The application:

The 1983 GM 6.2 liter diesel engine and forward controls chassis is mounted under a 27 foot 1984 Pace Arrow Elegante "J" Class A motorhome with only 55,000 original miles on it. The engine runs like a top with no mechanical problems itself, however I have had a lot of trouble with the battery charging and storing systems (which have now been extensively upgraded to industry state-of-the-art status) as well as recent on-going problems with the fuel delivery system, more specifically, both a water-in-fuel problem (now resolved) and an air leak located somewhere within the original OEM two filter/mechanical lift pump configuration.

The objective is a high quality, reliable fuel delivery system that includes an in-line pre-filter, a water separator with sight bowl, a 5 micron secondary fuel filter, and an electric fuel pump that is all connected with the shortest length of high quality diesel fuel hose (replacing the existing steel fuel lines) and the fewest number of high quality fittings.

I would prefer the fuel pump was manually operated by a dashboard-mounted toggle switch (joining other after-market toggle switches controlling as many engine and coach functions as possible) instead of it being wired into a switched source of 12VDC power. I also want to make provision for the future installation of a fuel pressure gauge mounted in the cab, which requires a (plugged) tee fitting being inserted in the pump housing's outlet port.

My questions:

Which of the 2 recommended Stanadyne FM100 fuel filter/water separator/fuel pumps would be the more suitable choice for my application - the model 33945 or the model 33642? (Both would be ordered with the optional glass or plastic sight bowl, and a manual primer pump.)

What are their specific differences?

Any idea why the installer/supplier would have first recommended the 33945, and then switched to the 33642 (without the electric pump) when they could have selected the 33642 with the same electric fuel pump instead of the 33945? That is the mystery to me.

I would appreciate as much detailed information as possible, especially anything from other members who have had personal experience with either of these Stanadyne combination units.

Thanks in advance for your input, commentary or suggestions.

Best regards,

JT

markw8 · June 15, 2011

Hello Forum!

This is my first posting on this forum, and wouldn't you know it - I need some help!

I am upgrading my current fuel filtration system to the Stanadyne FM100 series, but I'm not sure which part number is more suitable to the application.

Some background:

The company who will be doing the install first recommended the Stanadyne 33945 combination electric fuel pump/water separator/5 micron secondary fuel filter together with an in-line, disposable pre-filter and high quality fuel hose connecting it all up.

As cost became an issue, we considered other options. If we were to keep the existing mechanical lift pump (new with only a hundred miles on it), they recommended a Stanadyne 33642 water separator/5 micron secondary fuel filter with the same in-line pre-filter and hose as noted above, but no electric fuel pump.

I then did some further research and discovered that the 33642 can also be supplied with a wide selection of options, including an electric fuel pump.

The project has now become more complicated (and expensive) as the Stanadyne DB2 injector pump's serviceability is now in doubt, and I'm likely facing the installation of a remanufactured unit as well. Also, I think it would be wise to eliminate the mechanical lift pump altogether at this point seeing as we will be replacing/upgrading all the other components and a simplification of the system is desired.

The application:

The 1983 GM 6.2 liter diesel engine and forward controls chassis is mounted under a 27 foot 1984 Pace Arrow Elegante "J" Class A motorhome with only 55,000 original miles on it. The engine runs like a top with no mechanical problems itself, however I have had a lot of trouble with the battery charging and storing systems (which have now been extensively upgraded to industry state-of-the-art status) as well as recent on-going problems with the fuel delivery system, more specifically, both a water-in-fuel problem (now resolved) and an air leak located somewhere within the original OEM two filter/mechanical lift pump configuration.

The objective is a high quality, reliable fuel delivery system that includes an in-line pre-filter, a water separator with sight bowl, a 5 micron secondary fuel filter, and an electric fuel pump that is all connected with the shortest length of high quality diesel fuel hose (replacing the existing steel fuel lines) and the fewest number of high quality fittings.

I would prefer the fuel pump was manually operated by a dashboard-mounted toggle switch (joining other after-market toggle switches controlling as many engine and coach functions as possible) instead of it being wired into a switched source of 12VDC power. I also want to make provision for the future installation of a fuel pressure gauge mounted in the cab, which requires a (plugged) tee fitting being inserted in the pump housing's outlet port.

My questions:

Which of the 2 recommended Stanadyne FM100 fuel filter/water separator/fuel pumps would be the more suitable choice for my application - the model 33945 or the model 33642? (Both would be ordered with the optional glass or plastic sight bowl, and a manual primer pump.)

What are their specific differences?

Any idea why the installer/supplier would have first recommended the 33945, and then switched to the 33642 (without the electric pump) when they could have selected the 33642 with the same electric fuel pump instead of the 33945? That is the mystery to me.

I would appreciate as much detailed information as possible, especially anything from other members who have had personal experience with either of these Stanadyne combination units.

Thanks in advance for your input, commentary or suggestions.

Best regards,

JT