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D12 losing fuel prime


chooseopen
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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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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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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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  • 1 year later...

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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  • 1 month later...

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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  • 2 weeks later...

Sooo.....

Finally need to readdress this D12 Volvo losing Prime.

 I have replaced both filters, the Davco, and the one mounted on the motor.

I checked the ball and spring, in the Davco, looks good and spring is intact.  Spring does not seem very strong but does push the ball back when you release it.

I replaced the Overflow Valve.

I am not sure what would be the best procedure going forward for adding clear lines to try and see the air bubbles in the fuel lines.

Must I purchase the kit, or can I cobble something together to do this.

Would any of you have experience with using a mobile mechanic, would this be among their services.

I now am having trouble getting the truck started.  I can pump the primer 3 or 4 times and the pressure gets hard.

Waiting a minute or two and the hand primer will once again need 3 or 4 pumps to pump it back up.

The pump does not take 75 or 100 pumps to prime solid, just a 1/2 dozen will make it to hard to continue to pump.

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Let's do some quick math. The volume of the pump chamber, multiplied by the number of strokes, equals a very small volume to return the lines to pressurized status. The quick bleed down corroborates this. What's the closest thing to the plunger pump? The Davco? You've changed the filter, and looked at the check ball, but have you installed a rebuild kit? New ball, spring, and seat ring. It doesn't take a very big spot on the o-ring to cause a complete failure. 

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I have changed all the o-rings with the Davco.  I have not replaced anything with the spring and ball.

I will order one tomorrow.  

I will give the video a check see, YouTube is definately my go too source with new projects.  

We have been remodeling the kitchen, and I am struggling to find time to concentrate on the truck issue.

I am hoping it is not the injector cups.

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The sight glasses if it helps (no idea if they work on Volvo)

#10 draw https://www.apexinds.com/tools/M50043.html

#8 Return https://www.apexinds.com/tools/M50042.html

Compucheck fitting hooker upper if Volvo puts them in https://www.apexinds.com/tools/ATCL-TU-32-25.html

Mityvac to suck from the Compucheck https://www.amazon.com/Mityvac-6830-Brake-Bleeder/dp/B000JFN9WC/ref=sr_1_1?keywords=6830&qid=1580878400&s=industrial&sr=1-1

 

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I am happy to say Darryl was right, in between work and kitchen remodels and auto repair, wife's car, abmbd auto repair, son's Jeep, and auto repair, my pick up truck, and plumbing, outside spigot steel pipe broken inside the block, I ordered and received the check ball kit for the Davco fuel filter assembly.

I took a break from all the other exciting work I am currently doing and R&R'ed the kit.  I refilled the filter assembly and reprimed the truck, and it fired off as normal.  I was optimistic but wanted to be sure this was indeed the fix so I drove it for 4 miles, parked it and started it back up.  😄

Started it two more times last night, then went out and started it and drove it this am.  All good.

Darryl was right.

Darryl was right.

The existing ball from the Davco was black, and about 5/8ths the size of the white ball that came in the new kit.  Am I to assume it was worn down that much, or is the bigger ball an update?

 

Thanks all, especially Darryl, I was becoming a little frantic and overwhelmed.  I got to go back and install some new kitchen cabinets now.

Michael

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