Fuel filters

DieselSJ · Post by **DieselSJ** » Tue Feb 14, 2006 10:21 am

We had a little problem on our racer where we clogged the filters. We are using a couple in-line 35 micron units. We have 2 pumps, mounted parallel so that we can switch between them if a pump fails or a filter gets plugged. We think some of the bladder material was coming apart and that is what plugged the filters. Now we have a problem in that one of the pumps totally failed and the other is not sounding good, so I think the debris from the tank is eating the pumps.

So, what I want to do is move the filters so that they are between the fuel cell and the pumps. Along with that, we are going to change to something like a Fram HPG1, which has a much bigger element than what we have now, and filters down to 10 micron.

After all that, I have 2 simple questions -
1) Anyone have any problems running the filter on the supply side of the pumps?
B) Should we also run a filter after the pumps?

Thanks!

Jack · Post by **Jack** » Tue Feb 14, 2006 12:25 pm

If you clog up the filter on the supply side of the pump, you have the potential to cause caviation in your pump. This can destroy your pump. Most pumps do not like having to pull against suction, they prefer to push.

In my opinion, you would be best off by opening up your fuel cell and replacing the foam and/or bladder.

To learn more about why not to put a filter before your pump, search the web for "cavitation" and "NPSH"

Jack

DieselSJ · Post by **DieselSJ** » Tue Feb 14, 2006 2:07 pm

Well, after talking to the guys at the shop, I had it wrong in that we have the filters between the tank and pumps now. I'll bet that when the filters clogged is what caused the pump to fail.

Yes, we are pulling the cell apart and replacing the guts. Just something that goes along with buying a used racer.

OK, so let me ask this - how durable are the pumps? How much stuff can they ingest before they fail? We are using the Ford external EFI pumps. In off-road racing, it is inevitable that dirt will get into the cell - it is a fact of life in the desert. I'd like to put something in there to protect the pumps.

BottleFed70 · Post by **BottleFed70** » Tue Feb 14, 2006 6:09 pm

If it's bladder material, then it probably wasn't the material itself that killed the pump.

Fuel pumps rely on the fuel flowing through them for cooling. If the filter was plugged, then you would have no fuel flow and could easily burn out the motor.

What I did with my install is use a large diameter high-flow "prefilter" before the pump, then installed a smaller + finer filter after the pump. The prefilter will remove most particles while not restricting flow very much, while the 2nd filter can concentrate on just removing the finer particles.

Jack · Post by **Jack** » Tue Feb 14, 2006 8:32 pm

DieselSJ wrote:OK, so let me ask this - how durable are the pumps? How much stuff can they ingest before they fail? We are using the Ford external EFI pumps. In off-road racing, it is inevitable that dirt will get into the cell - it is a fact of life in the desert. I'd like to put something in there to protect the pumps.

I'm going to guess that the pumps can pass a lot of particles before failing; it depends on the particle size, shape and material, as well as the impeller material and design. These particles will wear the impeller, whereas the low flow can fail the pump on cavitation or as suggested, overheating.

When a pump impeller is wearing out, it just won't provide the flow and/or pressure to do it's job right.

The suggestion for a large coarse pre-filter is a good one. I'm wondering if a pressure gage, that goes negative, on the pump inlet would be a good idea.

Jack

Jack