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Fuel leaking back to tank on a 3208 Cat
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dondozer
Posted 4/11/2017 21:26 (#5958419)
Subject: Fuel leaking back to tank on a 3208 Cat


NW Ohio,near Findlay
Have a 3208 Cat in a 84 L8000 with only 44,000 miles on it. Problem is slowly getting worse, fuel will drain back into tank if sets a week or more. I have to use hand pump, open bleed petcock at injector pump, pump fuel through fuel filter and it will start instantly, no missing. No fuel leaking out anywhere, and runs perfect after bleeding fuel. At work we had a 3208 that the injector pump shaft seal was bad, but it wasn't running good, would miss and low on power. Could it be leaking air at the hand primmer? Any one had this problem?
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Lone Wolf Picker
Posted 4/11/2017 21:37 (#5958455 - in reply to #5958419)
Subject: RE: Fuel leaking back to tank on a 3208 Cat


Black Hawk County, IA
I would check or replace every rubber hose from the tank to the pump. If original they are 33 years old. J
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4WD
Posted 4/11/2017 21:39 (#5958465 - in reply to #5958419)
Subject: RE: Fuel leaking back to tank on a 3208 Cat


Between Omaha and Des Moines, 7 miles South of I80

dondozer - 4/11/2017 21:26 Have a 3208 Cat in a 84 L8000 with only 44,000 miles on it. Problem is slowly getting worse, fuel will drain back into tank if sets a week or more. I have to use hand pump, open bleed petcock at injector pump, pump fuel through fuel filter and it will start instantly, no missing. No fuel leaking out anywhere, and runs perfect after bleeding fuel. At work we had a 3208 that the injector pump shaft seal was bad, but it wasn't running good, would miss and low on power. Could it be leaking air at the hand primmer? Any one had this problem?

 

Yes, it could be the hand priming pump(allow air into the system), and that would be easy to change; without a service call. (get a new gasket, also){reasonable first step}

I've seen "rub spots" on fuel filters, too, that create a very tiny pinhole (remember, on a CAT 3208, the majority of the fuel system is suction; thus you don't tend to see external leakage on the "fuel supply system")

Do you have the "glass" water separator element? {Seen problems there, too; poor sealing and/or their aluminum  bases and their valves}

 

Using fuel "sight glasses", is the best way to trouble-shoot, but you can afford to throw a few parts at it, first, before taking it to a mechanic/dealership.

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jloula
Posted 4/11/2017 21:43 (#5958472 - in reply to #5958419)
Subject: RE: Fuel leaking back to tank on a 3208 Cat


St Peter MN
This has happened twice on mine, and both times the glass fuel filter needed to be replaced.
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makar
Posted 4/11/2017 22:22 (#5958557 - in reply to #5958472)
Subject: RE: Fuel leaking back to tank on a 3208 Cat


Northern Alberta
I have fixed a few of these, there is check valve type of thing, it is in the v behind the fuel pump, there is a plate you remove. Easy fix.
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t-boss
Posted 4/12/2017 08:03 (#5958942 - in reply to #5958419)
Subject: RE: Fuel leaking back to tank on a 3208 Cat



sc ia
Most likely air is leaking in allowing the fuel to drain back. I've been able to find the leak sometimes, by pressurizing the fuel tank. Use an air hose and a rag at the filler neck to pressurize. Don't over do it with pressure but keep doing it for maybe a minute and then check for leaks. You're looking for a real small leak.
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dondozer
Posted 4/12/2017 11:10 (#5959176 - in reply to #5958419)
Subject: RE: Fuel leaking back to tank on a 3208 Cat


NW Ohio,near Findlay
maker, which fuel pump, the hand pump or fuel pump on engine, as of right now, don't know where it is? Thanks to all, will start at filters first and go from there.
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makar
Posted 4/12/2017 16:32 (#5959492 - in reply to #5959176)
Subject: RE: Fuel leaking back to tank on a 3208 Cat


Northern Alberta
The main pump, there should be a oval shaped plate with i think 2 bolts, under that is a check valve, done a few.
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dondozer
Posted 4/12/2017 17:51 (#5959587 - in reply to #5959492)
Subject: RE: Fuel leaking back to tank on a 3208 Cat


NW Ohio,near Findlay
Will find it, check it out, thanks. don
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4WD
Posted 4/12/2017 18:28 (#5959636 - in reply to #5959492)
Subject: RE: Fuel leaking back to tank on a 3208 Cat


Between Omaha and Des Moines, 7 miles South of I80

makar - 4/12/2017 16:32 The main pump, there should be a oval shaped plate with i think 2 bolts, under that is a check valve, done a few.

 

I'd like to know what "plate and check valve", you are talking about.

 (Remember this is a 3208 in a truck, not an industrial 3208) There are differences.

I'll throw a bunch of 3208 photos, on this post/thread and see if you can describe "your plate", in one of these photos.

 





(3208injpump.jpg)



(3208 pump top view.jpg)



(3208pump_2.jpg)



(3208 pump.jpg)



(3208injectionpumpgovernorhousingview_inpaint.jpg)



(3208fuelpressureplug_inpaint.jpg)



Attachments
----------------
Attachments 3208injpump.jpg (56KB - 748 downloads)
Attachments 3208 pump top view.jpg (53KB - 755 downloads)
Attachments 3208pump_2.jpg (56KB - 823 downloads)
Attachments 3208 pump.jpg (125KB - 700 downloads)
Attachments 3208injectionpumpgovernorhousingview_inpaint.jpg (67KB - 887 downloads)
Attachments 3208fuelpressureplug_inpaint.jpg (69KB - 753 downloads)
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makar
Posted 4/12/2017 19:34 (#5959726 - in reply to #5959636)
Subject: RE: Fuel leaking back to tank on a 3208 Cat


Northern Alberta
Its not in the pump, its in the v of the block behind the pump. If i remember in or close to the valve you open to pump up the filters.
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4WD
Posted 4/12/2017 19:43 (#5959744 - in reply to #5959726)
Subject: RE: Fuel leaking back to tank on a 3208 Cat


Between Omaha and Des Moines, 7 miles South of I80

I'm not familiar with what you are describing.(or I've never seen it)

Here's a picture of a CAT 3208 "TRUCK ENGINE " fuel injection pump's special fuel return line fitting/valve, that also has an "anti-siphon check valve" in its outlet. It is also used to bleed fuel filters, or bleed the front part, of this 3208 injection pump. {Note: To bleed the rear governor housing, normally, we remove or loosen the "pin timing plug" in the rear "fuel setting" cover.}

Image result for CAT 3208 injection pump new ag talk

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makar
Posted 4/12/2017 20:01 (#5959773 - in reply to #5959744)
Subject: RE: Fuel leaking back to tank on a 3208 Cat


Northern Alberta
Ok, my memory is wrong, good thing i have a manual, page 17, check valve and bypass valve. Check valve is in that housing you can see with 2 bolts behind the valve in your picture. Will try to send a page copy.
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4WD
Posted 4/12/2017 20:07 (#5959781 - in reply to #5959773)
Subject: RE: Fuel leaking back to tank on a 3208 Cat


Between Omaha and Des Moines, 7 miles South of I80

Ok, that is the by-pass "one-way check valve" that allows a person to use the "hand primer pump" ; because engine/fuel pump uses a gear type fuel transfer pump, thus the fuel needs a passage to "by-pass" the transfer pumps gears(non-running), so the hand primer pump can deliver a reasonable volume of fuel, while hand pumping.

The hand priming pump, also has 2- "one-way check valves", that should "stop" any drain back, if they are working correctly.

Image result for CAT 3208 fuel pump



Edited by 4WD 4/12/2017 20:12
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makar
Posted 4/12/2017 20:10 (#5959783 - in reply to #5958419)
Subject: RE: Fuel leaking back to tank on a 3208 Cat


Northern Alberta
page 17
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makar
Posted 4/12/2017 20:12 (#5959789 - in reply to #5959783)
Subject: RE: Fuel leaking back to tank on a 3208 Cat


Northern Alberta
oops, attempt 2.
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makar
Posted 4/12/2017 20:15 (#5959795 - in reply to #5959789)
Subject: RE: Fuel leaking back to tank on a 3208 Cat


Northern Alberta
attempt 3.
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makar
Posted 4/12/2017 20:16 (#5959800 - in reply to #5959789)
Subject: RE: Fuel leaking back to tank on a 3208 Cat


Northern Alberta
attempt 3.
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4WD
Posted 4/12/2017 20:20 (#5959809 - in reply to #5959789)
Subject: RE: Fuel leaking back to tank on a 3208 Cat


Between Omaha and Des Moines, 7 miles South of I80

That's Ok, I understand, now.

I would say, if this guy's engine didn't have a hand primer pump, installed; then the check valve that you describe, becomes way more important, to prevent a possible drain-back.

 

 I would have to say, it would be rare if I ever saw a CAT 3208 engine, without a hand primer pump. (but I'm sure there are probably some out there)

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makar
Posted 4/12/2017 20:21 (#5959813 - in reply to #5959800)
Subject: RE: Fuel leaking back to tank on a 3208 Cat


Northern Alberta
Attempt 4



(download (2).jpg)



Attachments
----------------
Attachments download (2).jpg (138KB - 730 downloads)
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makar
Posted 4/12/2017 20:25 (#5959829 - in reply to #5959809)
Subject: RE: Fuel leaking back to tank on a 3208 Cat


Northern Alberta
All my 3208 had hand primers and i have changed 2 or 3 of the check valves.
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dondozer
Posted 4/13/2017 08:26 (#5960587 - in reply to #5959829)
Subject: RE: Fuel leaking back to tank on a 3208 Cat


NW Ohio,near Findlay
Well I have info now, will start with filters first, hand pump check valve, last check valve on pump. Will give update when problem found. It doesn't do it all the time, can sit for days and be OK, then sometimes overnight will do it. Thanks to all for info.
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