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Fuel line check valve

Posted: Mon Aug 12, 2013 8:41 pm
by pinzinator
I bought a fuel line check valve and installed it on the Pinzgauer last weekend. I don't drive mine that often, so it can start hard after sitting a while. This might solve the problem, might not, but time will tell. The device didn't produce any restriction, as the Pinz ran normally afterward. I wasn't sure if it should go before or after the fuel pump, this location seems to work OK.

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The check valve is available on eBay for about $18 delivered from Alabama. It took 2 days for delivery.

Re: Fuel line check valve

Posted: Mon Aug 12, 2013 9:14 pm
by Twin Pinzies
Pardon my ignorance but what exactly does a check valve do? Does it keep the fuel from all flowing back into the tank?

Re: Fuel line check valve

Posted: Mon Aug 12, 2013 9:41 pm
by compunerdy
Exactly..

Re: Fuel line check valve

Posted: Mon Aug 12, 2013 9:58 pm
by waterdog
I have the same valve! Waiting to install next time i go under the dog house... Report back your experience...!!

Re: Fuel line check valve

Posted: Tue Aug 13, 2013 6:32 am
by Stekay
Th fuel pump is a check valve if you look at the cut-a-way in the manual. That being said, pumps push much better than they pull, so I'd tend to put it after the pump, but I don't see the value in that. I do see the potential for problems if put between the tank and pump so I personally would stay with the current set-up.(no check valve). A little extra cranking is no big deal to me.

Re: Fuel line check valve

Posted: Tue Aug 13, 2013 11:38 am
by Jimm391730
If it doesn't start right away after sitting for a few days, it is because the gas in the carburetors has evaporated, NOT because fuel in the carb bowls has leaked back into the tank (it can't). The fuel in the lines could leak back, but the amount of gas in the lines is less than what is held in the carbs.

Point is, loss of gas in the carbs will always result in cranking needed to get them filled before it will start. Whether the fuel in the lines seeped back into the tank is pretty inconsequential.

Now if it starts but dies after starting, that might be a symptom of not getting fuel pumped up to keep the carb bowls filled as quickly as needed. But since the fuel pump valves should be keeping the fuel from draining back, wouldn't a better idea be to correct the fuel pump problem?

Re: Fuel line check valve

Posted: Tue Sep 03, 2013 8:24 pm
by pinzinator
I removed the engine cover after the Pinzgauer had not been started for 2 weeks. The fuel filter was completely full, which meant that the check valve did its job by stopping the reverse fuel flow. Normally the fuel filter is 90% empty when the engine is running. This clear filter is available at NAPA (5/16" fittings, which is about 8mm. I think the part number is 3002).
The truck started up right away and didn't stall. With the pump still primed in this situation, I assume it was able to fill the fuel lines and carb much faster than if they had been empty after sitting for weeks. The check valve only requires 1 pound of pressure to open, which was a factor in my decision to install it on the suction side of the pump. I don't believe the pump has a check valve, but I could be wrong.
Conclusion- the check valve works and does make for easier starts after long periods of time.

Re: Fuel line check valve

Posted: Wed Sep 04, 2013 4:28 pm
by undysworld
Thanks for the follow-up with the results of the modification.

Re: Fuel line check valve

Posted: Wed Sep 04, 2013 7:13 pm
by pinzinator
Do a search on EBay for this item number if you want one- 171116165224
5/16" or 8mm inlet is correct.

Re: Fuel line check valve

Posted: Wed Sep 04, 2013 7:15 pm
by Jimm391730
I don't believe the pump has a check valve, but I could be wrong.
The pump has two valves: one to prevent gas from flowing back to the tank, and one to prevent gas from flowing back from the carbs. The pump diaphragm is between them and as it works in and out it sucks the fuel from the tank and pushes that fuel into the carburetors. Both valves prevent fuel from flowing back to the tank, IF the valves are working properly. As I haven't actually rebuilt the fuel pump I cannot say if these valves get replaced when the pump is rebuilt.

Re: Fuel line check valve

Posted: Sat Jan 18, 2014 9:56 am
by pinzinator
I am going to reverse my recommendation to install a check valve before the fuel pump. My Pinz has quit on me twice due to the valve malfunctioning, there simply is not enough pressure to open it up on that side of the pump. A mechanical pump has little draw capability (suction), but creates a lot of pressure on the outlet side. Any check valve should always be placed on the outlet side of a fuel pump. I was able to start the engine after shaking the valve, but that just isn't practical or even safe at times.

Re: Fuel line check valve

Posted: Sat Jan 18, 2014 2:20 pm
by edzz
My 710k had been getting harder to start after sitting for a week or so, to the point that I had to prime the carbs repeatedly to get it started.

Was thinking that the fuel pump maybe at fault however I decided to replace the fuel lines and filter before working on the pump. Long story short after replacing the fuel lines it starts and runs great.

Seems I had enough of an air leak in the lines that fuel leaked back to the tank. When trying to start the fuel pump had to be pumping fast enough to overcome the air leak.

Re: Fuel line check valve

Posted: Sun Jan 19, 2014 12:04 pm
by captxmas
I found I had the same staring problem after the vehicle sat for a while. The fix? Seems the fuel line running from the fuel pump to the esparcher heater (which had been removed and crimped, was leaking air allowing fuel to run back to the tank due to the lack of a proper air seal/vacuum . Sealed the line tightened the system and all has been fine. Never had any visible fuel leaks because the line was above the level of the carbs. Simple stuff is always the hardest to figure out....lol.

Re: Fuel line check valve

Posted: Mon Jul 14, 2014 7:16 pm
by pinzinator
Jimm was right, the gas does evaporate out of the vent in the middle of the carb throat, AKA the backfire screen. I checked my float level after about 2 weeks of sitting without starting, and the carb bowl was almost empty. The gas cannot siphon back to the tank since it can't get past the needle valve in reverse, like the air gap for a dishwasher.
I didn't think the gas could evaporate that fast, but it does! The fuel pump fills the bowl up rather quickly, but that takes some cranking for a few seconds. It's difficult to resist the urge to pump the pedal in the meantime, like cars from pre-85 or so, but that goes with the territory. Until the carb bowl is full the accelerator pump is quite useless.

Also, don't install a check valve like my original posting suggested. Leave good enough alone!

Re: Fuel line check valve

Posted: Tue Jul 15, 2014 9:34 pm
by Jimm391730
Jimm was right...
Oh, if only my wife could believe that! :cry: