Carb Rebuild and New OEM Fuel Pump Install

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audiocontr
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Re: Successful Carb Rebuild and New OEM Fuel Pump Install

Post by audiocontr » Sun Apr 30, 2017 11:17 am

easy enough to disconnect the linkages and rev one separate from the other. I suspect this is more of a timing issue than the carbs if both carbs are equal.
1973 712m
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bbolander
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Re: Successful Carb Rebuild and New OEM Fuel Pump Install

Post by bbolander » Sun Apr 30, 2017 4:02 pm

Did some more testing today. When I noticed the fuel line from the pump to the carbs vibrating so badly during the sputter, I thought maybe the 5 mm new line from the filter to the pump might be too small. My brother tried the specified 7 mm line for that location but it was so loose on the fuel pump inlet that he changed it to a 5 mm. I took the 5 mm out and my brother is correct, the 7 mm line just slips on and off the fuel pump connection. So I put an SAE 1/4" line (6.3 mm) in. After the engine warmed up, that seemed to help a lot with being able to accelerate without the stumble.

I also noticed the carbs are definitely not working the same. The front carb around the accelerator pump nozzles, at the base of the nozzles and underneath the nozzles are dry.

The back carb I saw fuel coming out at the base of the accelerator pump nozzles in addition to the tip, and fuel puddling beneath the base of the nozzles. Once when pressing on the gas to accelerate I heard a backfire pop out of that carb.

What would need to be done about the fuel coming out at the accelerator pump nozzle base?

I haven't tried disconnecting one carb at a time yet to see what each one does.

I took a video but it just doesn't show what happened at the nozzle base on the rear carb well.
1971 Pinzgauer 710M, all stock including 245-16 Maloya tires, taken off and stored for show
BFG MT KM2 265/75R16's on Black SAV replacement rims on now

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David Dunn
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Re: Successful Carb Rebuild and New OEM Fuel Pump Install

Post by David Dunn » Sun Apr 30, 2017 4:35 pm

I'm sorry, but you need to re-title the thread to "Unsuccessful carb rebuild."
The Pinz runs very strong after it gets past the coming off of idle stumble.
The whole point to the accelerator pump is to dump lots of fuel down the carb in a abrupt acceleration and avoid the stumble and falling on it's face!
In the videos, you're not getting by an easy acceleration without a load on the engine, I'd hate to see what it would take to drive it.

It's been a long time since I've rebuilt a carb, but without the engine running, you should get a large amount of fuel visible being sprayed into the venturis as soon as the pedal is depressed. If you don't get the immediate fuel spray down the venturi, your pumps are either bad, adjusted wrong or parts installed wrong, or all the above

Also don't think you're smarter than the engineers, changing the fuel lines to a larger size is a good way to set your engine on fire. You're not going to get more fuel through inlet pipes but more likely have the hoses leak at the fittings.
.
The Trojan Horse... the 1st Pinz used to covertly carry troops into battle .




ATL Pinzgauer XM 718K TUM(HD) 6x6 FFR (aka The Green Grail)

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bbolander
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Re: Successful Carb Rebuild and New OEM Fuel Pump Install

Post by bbolander » Sun Apr 30, 2017 5:23 pm

David Dunn wrote:I'm sorry, but you need to re-title the thread to "Unsuccessful carb rebuild."
The Pinz runs very strong after it gets past the coming off of idle stumble.
The whole point to the accelerator pump is to dump lots of fuel down the carb in a abrupt acceleration and avoid the stumble and falling on it's face!
In the videos, you're not getting by an easy acceleration without a load on the engine, I'd hate to see what it would take to drive it.

It's been a long time since I've rebuilt a carb, but without the engine running, you should get a large amount of fuel visible being sprayed into the venturis as soon as the pedal is depressed. If you don't get the immediate fuel spray down the venturi, your pumps are either bad, adjusted wrong or parts installed wrong, or all the above

Also don't think you're smarter than the engineers, changing the fuel lines to a larger size is a good way to set your engine on fire. You're not going to get more fuel through inlet pipes but more likely have the hoses leak at the fittings.
Ha! I've been wondering about how to change the title and just figured out how to do that. We were so excited to have an extremely high float level corrected, smooth idle with no smell or smoke that it was successful, until we tried to accelerate!

I make a point and pay through the nose for good OEM parts that are correct from our Suppliers. My brother has many years of experience rebuilding carburetors so I don't think the rebuild is the problem.

It is very disappointing to buy a new OEM fuel pump, OEM spec fuel lines and OEM carburetor rebuild kits and have this kind of a problem. The top cover gaskets in the kit were too small, SAV sent new ones and they were correct. We had a devil of a time getting the pump to pump fuel, so since the 7 mm supply fuel line fit so loosely on the fuel pump nozzle we thought it might be sucking air. So we changed it to 5 mm. I saw it vibrating in the videos and just changed it again to 6.3 mm and it is better. Now that the fuel pump is pumping I might try changing it again to the specified 7 mm and see if that can be done without leaks or sucking air. So we haven't increased the fuel line size over what the OEM engineers specified. Why they'd match a fuel line that slips so loosely on the pump connection is a reasonable question. I am an engineer by the way.

The SAV carburetor kit is a Pierburg kit. Every kit my Brother has installed in the past has had all of the necessary parts, including the pump suction and pump pressure valves. The SAV kit did not include these pump valves and we think the pump valves are likely the problem of not getting a strong accelerator pump stream. I have ordered them and should have them on Tuesday. That's another disappointment in the SAV kit. It means we have to tear the carburetors down again!

The Pinz actually does run strong after it's off of idle around town. We haven't tried it on a steep grade yet since we're still trying to work out the stumble and accelerator stream issue.

So we're doing our best to sort out an unexpected problem!
1971 Pinzgauer 710M, all stock including 245-16 Maloya tires, taken off and stored for show
BFG MT KM2 265/75R16's on Black SAV replacement rims on now

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Jimm391730
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Re: Carb Rebuild and New OEM Fuel Pump Install

Post by Jimm391730 » Sun Apr 30, 2017 7:24 pm

Depending on the kit, the accelerator pump pistons are either leather or plastic. I've heard that the leather is the (much) better of the two choices. Which came in your kit?
Jim M.
712W and 710M

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bbolander
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Re: Carb Rebuild and New OEM Fuel Pump Install

Post by bbolander » Sun Apr 30, 2017 7:39 pm

Jimm391730 wrote:Depending on the kit, the accelerator pump pistons are either leather or plastic. I've heard that the leather is the (much) better of the two choices. Which came in your kit?
Ours came with the plastic ones. I only looked at SAV, the one we bought, and at EI who doesn't even show a kit on their website. Maybe there are other sources for better an more complete kits, like vintage VW suppliers.
1971 Pinzgauer 710M, all stock including 245-16 Maloya tires, taken off and stored for show
BFG MT KM2 265/75R16's on Black SAV replacement rims on now

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Hotzenplotz
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Re: Carb Rebuild and New OEM Fuel Pump Install

Post by Hotzenplotz » Mon May 01, 2017 5:08 am

Jimm391730 wrote:Depending on the kit, the accelerator pump pistons are either leather or plastic. I've heard that the leather is the (much) better of the two choices. Which came in your kit?
depending on the history of the vehicle, the currently installed pistons are either the initial leather or the later introduced rummer material.
the factory ReHab Manal clearly stated to replace any leather with plastic, irrespective of its state.

So i am really surprised that any rebuild kit would contain leather pistons at all ....
Cheers
Albert
========================
My Pinz has NEVER been with any army

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bbolander
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Re: Carb Rebuild and New OEM Fuel Pump Install

Post by bbolander » Sat May 20, 2017 5:26 pm

We finally had great success with our carb rebuild and fuel pump. The Pinz ran like a top with good power at our Grand Staircase Escalante National Monument adventure based out of Escalante Utah. Never a problem even at around 8,000 ft elevation on the highway with steep grades or the off-road trails with steep grades as well. We got 11.3 mpg on an often steep grade trip with it in 3rd gear most of the way, and got 15 mpg on the highway trips to and from Escalante. The most we'd ever gotten before the rebuild on the highway was 11 mpg.

We ended up putting in new pump suction and pressure valves, accelerator pump jets and nozzles. We could blow through the old nozzles much easier than the new ones, so we think the ports on the old ones had worn larger contributing to the fuel tumble on acceleration. We have nice strong spray through the nozzles now.

We ended using the same NAPA M60175 fuel pump that was on the Pinz before we started the re-build and it works fine. We filled the pump with fuel with a vacuum pump before re-installing it. We had trouble getting fuel delivery with both the OEM fuel pump from SAV and the new Carter M60175 fuel pump. We think they were just stiff and perhaps with some pre-tensioning per the manual or filling them with fuel before installation they might have worked.

We enriched the idle mixture slightly and raised the idle speed slightly. The stumble on acceleration is gone. The exhaust smells slightly from the idle enrichment, but not nearly as bad as before.

Oil level is up and has not increased, no gas smell in the oil.
1971 Pinzgauer 710M, all stock including 245-16 Maloya tires, taken off and stored for show
BFG MT KM2 265/75R16's on Black SAV replacement rims on now

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