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Topic: Gauges for Fuel Filters and Air Cleaners (Read 962 times) previous topic - next topic

Gauges for Fuel Filters and Air Cleaners

Posting a couple of EZ mods to stay ahead of the game for fuel filters and air cleaners.

The first photo shows a fuel pressure gauge I added on the discharge of the secondary fuel filter. As the filters clog, the pressure drops and this will eliminate 99% of other possibilities. I made the installation using only two components, the gauge (ebay delivered for $5) and the brass fitting (NAPA $9.95). The gauge has to be small so it can be installed without hitting the fuel filter mount. The engine is running in the photo and the gauge indicates about 36 psi at idle. For a 2 cycle Detroit, the pressure should be 15-20 min minimum at hot idle and 65-70 psi at max rpm. The fuel spill (diesel returned to the tank) should be about a gallon a minute at 2100 rpm. This is important as the ECU (engine computer) is bolted to the top of the engine and diesel fuel flows through it to cool it. A partially clogged filter could cause the computer to operate at a higher temp than recommended. A sender could be installed instead of the gauge and sent via the extra wires, up to the instrument panel where a new gauge could be mounted.

The second gauge I added just replaces the stock green/red air cleaner restriction tell-tale and is a 30 second installation without any additional parts. This shows the amount of restriction and can be used to figure out how soon to order that new air cleaner. 20" Hg for a 2 cycle Detroit, 25" for a Cummins and 30" for a CAT. Gauge was found on ebay for about $10 delivered. Air Filter Restriction Indicator Gauge ACDelco AFM4 Cat 3116 | eBay

This could also be sent to the instrument panel with a sender and gauge using the extra wires available in the engine compartment.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Gauges for Fuel Filters and Air Cleaners

Reply #1 –
Pierce,
Great ideas - thanks.
But I'm puzzeled - I would have thought the fuel line was in suction!  Can you explain?
John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho

Re: Gauges for Fuel Filters and Air Cleaners

Reply #2 –
Quote from: JohnFitz –
Pierce,
Great ideas - thanks.
But I'm puzzeled - I would have thought the fuel line was in suction!  Can you explain?

No, this is the low pressure fuel supply (70 psi) AFTER the fuel pump and right at the last (secondary) fuel filter outlet. From here, it goes into the cylinder head passages and to the individual pumps/injectors where it goes from about 70 psi to 3000 psi when it is sprayed/injected into the cylinders. The excess fuel heads back to the main fuel tank.

If you can't see from the photo, this is added to the filter outlet on the filter mount up high on the left side of the engine. The spin-on filter is right below.

The beauty of this gauge location is that if either fuel filter is clogged, an O ring leaks air or a fuel line from the tank is cracked, the pressure will be lower than the numbers I quoted in the post. That is also where a  cockpit gauge would be handy. For instance, if you were losing power on a hill, you could look at the fuel pressure gauge and instantly tell if the pressure was low that it was fuel supply related.

I was very careful with the installation to make sure that no paint chips or dirt was introduced into the system as there is no filter after the gauge. The hose clamp also has to be loosened and the hose slipped through a couple of inches so the hose line fitting can thread onto the brass adapter.

This same installation idea will also work on a Cummins or CAT.

With the rear radiator, it might have to be mounted slightly differently so you could read it.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Gauges for Fuel Filters and Air Cleaners

Reply #3 –
Does anyone know if the VMSpc is able to monitor fuel pressure on the Cummins M11?  Sure would be nice if the fuel pressure sensor was already installed.

Dave VanAmburg
David VanAmburg
'99 U320 42ft

Re: Gauges for Fuel Filters and Air Cleaners

Reply #4 –
Pierce, 

Thanks for the info and pics on the fuel pressure gauge mod.  Takes the guesswork out of detecting a low fuel pressure problem.  Easy and inexpensive  for everybody and a way to monitor fuel pressure either in the back or up front on the panel.  Does it work in tandem to the gauge on the other side as shown in the other pic you sent me?

Would a fuel pressure gauge be helpful on the generator?  A Low fuel pressure reading would certainly be helpful in diagnosing generator problems such as a clogged fuel filter or a cracked fuel line.

Karma coming your way,

Jerry
The selected media item is not currently available.
Jerry and Cindy Maddux
1993 U300/36WTBI DD6v92TA
build 4271  "Miss Lou"
1995 suzuki sidekick 4x4 toad
Gulfport, Ms

"Pride of Ownership"

Re: Gauges for Fuel Filters and Air Cleaners

Reply #5 –
Quote from: coastprt –
Pierce, 

Thanks for the info and pics on the fuel pressure gauge mod.  Takes the guesswork out of detecting a low fuel pressure problem.  Easy and inexpensive  for everybody and a way to monitor fuel pressure either in the back or up front on the panel.  Does it work in tandem to the gauge on the other side as shown in the other pic you sent me?

Would a fuel pressure gauge be helpful on the generator?  A Low fuel pressure reading would certainly be helpful in diagnosing generator problems such as a clogged fuel filter or a cracked fuel line.

Karma coming your way,

Jerry

Jerry,

A lot of big rigs have both fuel pressure as well as air restriction gauges in the cockpit. With the air restriction, it is a more gradual change so probably a glance to see where it indicates when you check oil would be sufficient. More work and expense for the sender and gauge to send it up forward.

The generator idea is very good. Lots of past posts from folks trying to figure out why their generator won't start, starts but dies, etc. etc. With a gauge mounted as shown in the photo, you can monitor the pressure and then if low, go backwards toward the fuel tank to find the problem. This is on my list to do. I would replace the fitting shown in the arrow and mount the gauge on top. That way, the metal line would be in the same place and would not have to be bent, etc. The fuel gauge should read 15 psi max as the electric pump probably puts out about 7 psi. Dave M. would know exactly.

At the same time, you could also install a temp gauge for the generator. The best spot would be as shown in the photo. The square plug could be removed with a 1/2 inch extension turned backwards with a adjustable wrench at the other end. Might be a little tricky as the gauge would have to be fairly small in diameter or you could just mount a sender and mount the gauge anywhere. As for the small, "T" handled fuel shut off, not all U300s have it so don't worry if you don't have one.

When you are looking at your generator, check the 4 rubber isolation mounts. You have to pull it out to check the underside as this is where the failures show up. A couple of mine need replacing.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Gauges for Fuel Filters and Air Cleaners

Reply #6 –
We have a generator coolant temperature sender installed where Jerry indicated in his photo. A single wire was run to dash, through a DPDT switch to the factory engine coolant dash gauge. We used the same VDO temp sender Foretravel used on our engine so it could drive our dash gauge correctly. Wiring is normal when DPDT switch is down. When switch is up, start battery and generator sender are connected to dash gauge. Our generator seems to run around 160 degrees. 10kv Gen/set U300 GV 1994 - temperature gauge

We also bought a VDO oil pressure sender for our generator, so we could do the same for gen oil pressure, but never got around to installing it because it is on the back side of our gen.

Re: Gauges for Fuel Filters and Air Cleaners

Reply #7 –
We did the same thing (for the temp sender) but installed a separate temp gauge below the dash.
Bought a 2 gauge dash top gauge pod and installed sideways.  (The ammeter watches the alternator.)
Dave and Nancy
1999/2013 U270 36' Xtreme
Motorcade # 16774
2013 Subaru Outback
KD0NIM

Re: Gauges for Fuel Filters and Air Cleaners

Reply #8 –
Quote from: Dave Katsuki –
The ammeter watches the alternator.
Does the ammeter work off a shunt in the alternate line?

My recollection is that the old style ammeters actually carried the generator current. That wouldn't work so well with a 160 amp alternator 30' away with another 30' to get back to the batteries.
J D Stevens
1997 U295 CAI 36' Build #5085
2002 Subaru Outback
Motorcade 16869
Bellville, TX
 

Re: Gauges for Fuel Filters and Air Cleaners

Reply #9 –
Yep.  The ammeter has a shunt in the ground wire of the alternator.  Thin twisted pair plus a reference ground wire runs from the shunt up to the meter. 

I think Barry and Cindy did this first, and we copied :)) .    (We've copied lots of things they've done...)  The meter is a CruzPro A-60 which I found on eBay with 500 Amp shunt. 
Dave and Nancy
1999/2013 U270 36' Xtreme
Motorcade # 16774
2013 Subaru Outback
KD0NIM