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D12 losing fuel prime

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The past couple weeks my truck has become hard to start.  After sitting for a few days I have to resort to manually priming it with the plunger on the fuel filter housing.  I kind of suspect this primer and fuel filter housing might also be the source of my air leak.  I have a question about this primer plunger.... 

How many pumps are you supposed to do? 

Is the resistance on the plunger supposed to increase as air is forced out because I don't notice any difference in the feel of the plunger.

I see fuel/air bubble out from a hole next to the primer plunger.  Normal?

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I believe there is a check valve on the front of the engine, at the top, that has caused problems for folks.

We have a D13 engine, though I remember reading about the D12 issue.  You might look on YouTube, as well as the Resource Guide on this site.

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Check valve was one of my issues and also the filter housing primer pump combo. After replacing it no more issues. 

I also suspected the housing when having to pump to start   It got harder to start after a few times  

Yours may be elsewhere. 

Edited by billr

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As you can see there are lots of possibilities to losing prime or having a fuel-based hard start. Another is a bad injector cup. It can be very difficult to find the problem, but look at the most likely things first....the list above is a good start. 

On a hard starting truck pumping the primer 100 times is not that unusual. You should be able to feel it pushing fuel when it finally "gets prime". I always assume I'm going to pump at least 100 times....sometimes I'm surprised.

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Thanks Jack.  I will pump it more to see if I get better results.  I usually pump it about 10-15 times and the truck will stumble to a start but the primer pump never felt like it was moving fuel so I thought perhaps the pump itself wasn't sealing well.  Now that I know 100 pumps might  be required, I will try that. I have heard those filter housing/pump assemblies can be troublesome.  

All,. Thanks for the other ideas.  I replaced the Davco filter and o-rings yesterday. It was time for them anyway.  Today I am going to replace the spin-on filter and play with the primer pump more.  

I am in Albuquerque this week near the Volvo dealer so I really want to get this resolved before heading back out into the desert!

 

 

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17 minutes ago, chooseopen said:

Thanks Jack.  I will pump it more to see if I get better results.  I usually pump it about 10-15 times and the truck will stumble to a start but the primer pump never felt like it was moving fuel so I thought perhaps the pump itself wasn't sealing well.  Now that I know 100 pumps might  be required, I will try that. I have heard those filter housing/pump assemblies can be troublesome.  

2

Definitely, you are not pumping it enough. You could have a pump problem, but you'll never get it with 10-15 pumps if you have a prime issue. At least I never have. If you can do it in 10 pumps, then the truck would have started with a 10-15 second key-turn.

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Must be a relatively minor leak.  As indicated by Jack, 10-15 pumps is nothing.  Standard service on my Detroit is a recommended 220 pumps after replacing the secondary fuel filter  or until you feel resistance.

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Ok.  I changed my spin-on fuel filter this morning and afterwards pumped till my arm hurt, lol.  Took about 60 pumps and I could feel the difference and the truck fired right up.

Probably wishful thinking that a filter change would fix my leak, but I like to try the easy stuff before throwing parts at it.  At least now I feel more comfortable with the manual priming procedure until I find the leak.

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Sorry I'm seeing this late, but with that spin on filter, there have been problems with the prior o-ring still being there!  Hopefully it came out with the filter when you changed it out.

The other look for is when it does start, what are you getting out of the exhaust?  Any changes in color?

Good luck.

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The issue causing the loss of prime with my Volvo d12 looks to have been the lower fuel filter.

While manually priming the truck I built enough pressure for fuel to spray out between the fuel filter and the housing.

When I removed the fuel filter, I observed the rubber gasket was "swollen", and not sitting in it's groove on top of the fuel filter.

Hope this helps someone else.

Michael

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I am still experiencing a fuel pressure problem, when I can get the truck to start it runs and drives fine.

I have replaced both filters, made sure all o-rings and seals were new and no o-rings left behind from original filter.

When priming the truck with the Bosch manual primer the pressure comes up quickly, like three or four pumps. Sometimes it will start right up, sometimes not at all.  I quickly find that the pump is again in need of a few strokes to get the pressure back.  While pumping, I can hear clicks in the head like something is closing/opening/filling.

After four or five pumps, the hand pump is to hard to physically move by hand.

I think I want to replace the overflow valve next, seems like a simple repair.  I have replaced one in my Dodge Cummins to fix a low fuel pressure issue.

May I ask if this Overflow Valve is at the front side of the valve cover, and does anyone know if there is a check valve in the fuel pump as well?

When replacing the fuel filter in the Davco, I found that there was enough crap in the bottom of the housing to prevent fuel from being released out of the water drain bowl valve.

I completely emptied and cleaned the housing until it was spotless. put the new filter in, filled with fuel, couple pumps with the primer and truck started and ran fine.

I shut it off, went inside for a celebratory beverage, and lunch.  Came out decided to move the truck of the slight incline hill it is currently sitting upon, and no joy.

Pumped the primer as much as I could but unable to start again.

I  found the check ball in the Davco, the spring is still present as well as the ball, spring seems week, but don't suspect it needs to be tighter, it closes up when you release the spring, I suspect it is fine.

I am hoping you will tell me the overflow valve is worn out and not keeping pressure high enough to always start the truck.
 

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