Cold start primer pump information

[ryansuperbee]

Hi guys! I am new to steel soldiers and this has been a HUGE help to me whenever I had a question regarding my truck. I own a 1984 M812A1. I have been slowly making it very nice and replacing ALL sorts of part on it! Anyway, I have a question regarding the "cold start primer pump" I have replaced the pump handle but it does not pressurize. I have also replaced the hose and connections. One hose goes to the bottom of the fuel pump itself and the other hose goes to the top of the intake. I have also taken the pump out and temporarily replaced it with an air hose. When i applied some air pressure to it, the air pressure gauge goes up. I would like to know what I should try nest to get this to work! I would really like to completely bypass this somehow... (maybe an electric primer pump or something???) Any help with this is GREATLY appreciated! Thanks guys!

 

[ryansuperbee]

Can someone tell me what the hand pump for the cold start even does exactly? Does it pressurize the fuel? Or does it pressurize air? I was thinking about putting a small electric air pump on the fuel tank and whenever I needed to pressurize the fuel, I would simply flip a switch in the cab to turn on the air pump, the air would press down on the fuel in the tank and force it through the lines. Anybody have thoughts on a system like that? Pros and cons? Would it even work!?!? Thanks!

 

[98G]

Can someone tell me what the hand pump for the cold start even does exactly? Does it pressurize the fuel? Or does it pressurize air? I was thinking about putting a small electric air pump on the fuel tank and whenever I needed to pressurize the fuel, I would simply flip a switch in the cab to turn on the air pump, the air would press down on the fuel in the tank and force it through the lines. Anybody have thoughts on a system like that? Pros and cons? Would it even work!?!? Thanks!

It should work.

There's yet a simpler solution though - make a fuel cap with a Schrader valve and just pressurize it from your glad hand when needed. $2 in parts and some time....

 

[nk14zp]

Bad o rings in primer pump.

 

[nk14zp]

Found this.

FYI to all 809 owners for your part number lists:

O-rings for manual fuel pump...
Brasscraft #0562, 3/8" I.D. (1/2" O.D.) X 1/16" Wall purchased from Lowes

 

[Floridianson]

It should work.

There's yet a simpler solution though - make a fuel cap with a Schrader valve and just pressurize it from your glad hand when needed. $2 in parts and some time....

Bad idea. Just fix the pump as it is a simple system. Pump, atomizer, glow plug. It is simple so keep it simple.
98g how would you get air to begin with out of the glad hand? The truck would not be running and it would more than likely be out of air and cold. Just fix the cold start system what ever it takes. Fix pump, check atomizer, check glow plug.

Ryan you need to use the search and read as this is not a uncommon problem and a simple one.

 

[ryansuperbee]

Thank you for the reply James. Trust me when I say that I have searched high and low for literature on the cold start system. Been on it for a couple months on and off now and there's honestly not much I can find on it. I have founds lots of stories about people needing to use this system! But not much on the actual functionality of it. One thing that would be a BIG help is to know is what that pump is pressurizing? Is it pressurizing air and pushing on the fuel? Or is it pressurizing fuel? If it is supposed to be pressurizing fuel, then I would have to think that I should be seeing fuel come out if I take apart the pump on the dash. When I take the pump apart, it is dry inside. Is that normal? or should I see fuel? Also, I did replace the O-rings as the previous ones were bone dry. I will say that I need to get a little better fitting O-rings as the ones I have now are from Auto-zone and they are very tight. I will try out the rings that nk14zp suggested tomorrow, but I have a feeling that I am still going to run into the same problem...

 

[Floridianson]

No problem and yes it takes fuel out of the PT and pushes it through the atomizer. It sound like you are thinking but one thing you don't want to do is over load the intake with fuel as it could cause problems. If the hand pump is working but you have bad fuel lines from the tank to filter or filter to PT that can cause an air leak and the lines/filter drain back to the tank. So when you go to pressure up the cold start system it does not come up to pressure. Yes you can pump the cold start primer and top off the canister or even after a filter change but it takes a long time and many strokes. On a truck with a good tight fuel system and primer working good the pressure gage comes up within a couple of strokes. You should be able to get fuel out of the cold start system if you just open the bleeder on the intake. I have never had a problem with the two check valves in the primer but that can happen too.

 

[USAFSS-ColdWarrior]

Quick reference help?
Can someone please post the page in the TM that shows the assembly or parts breakdown of the Fuel Primer Pump for the M809 Series Trucks?
Thanks in advance.
(Scrolling through 1338 pages on a small screen is a booger.)

 

[jhooah]

I think I need O-rings too, and doubt there's an exploded view, only the part swap which is TM 9-2320-260-34P-1 section II figure 76 page 76-1 (somewhere around Page 164 of the whole manual from what my printer said)
O-rings are cheaper than a $35 part, you can Google the stock number 5110760
NEW DETROIT DIESEL / CATERPILLAR / CUMMINS HAND pump

V/R W. Winget

 

[Scar59]

take it to a good NAPA, counter guy pulled the SAE O ring selection out and found replacements, fit and functional. (3/8" I.D. (1/2" O.D.) X 1/16" thickness)

 

[TurboJoe]

I have to hijack this thread just a tad, but it seems the best place to ask this. My primer pumps up and gets exceptionally stiff in one or two pumps. The pressure gauge never moves, and it gets so hard I can't push it in by hand. Once I start cranking the pressure drops and I can pump again.

Any ideas?