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Just finished tuning my WUR after rebuilding. My 1976 99 Federal Car was running super rough, I could barely keep it running after starting it. Had to feather the throttle to keep it from stalling. Out came the CIS test gauge.
Results showed the WUR pressure was same as line pressure. Line pressure was 69 psi which is in spec of 65.5 psi - 74.0 psi. Line leakdown was 20 psi after 20 mins (10 psi minimum spec). So the car was running super lean with high control pressure. This is mostly caused by clogged filter screen on the inlet of the WUR. So after much cleaning with carb cleaner, the pressure only dropped to 60 psi cold. Spec is roughly 20 psi. This WUR was a rebuilt unit that I got at O'Reilly Auto Parts (I think) so I thought it was in decent shape, but I decided to crack it open. It was a 0438 140 020.
Inside, a screw was missing from the diaphragm, wow. Closer inspection, the screw had been sheared off in the hole, so the diaphragm was held on by 3 of the 4 screws, and a new problem had to be solved. The rebuilder shipped it like this, it had never been opened as it still had the red sealant over one of the screws and the pin. At least it was pretty clean inside and the heater had the correct resistance. But I've had a hot start issue for ages.
I bought a rebuild kit from Germany off eBay, I think it was the nicest one since it had all the hardware and it was sourced from German parts. It took less than 2 weeks to arrive. Rebuild went smoothly, I followed instructions from the page I linked, although mine doesn't have any vacuum ports. And I drilled out the broken screw and used new screws from the kit. I also spent a long time cleaning the filter screen. Eventually, I could fill above the screen with carb cleaner and gravity would pull it through quickly. Disassembled, I could spray from both sides of the diaphragm to clean it.
Since I no longer trusted my rebuilt unit, I pushed out the pin that controls cold and pushed out the diaphragm so it was about 4mm proud of the housing. From here, I can use a 1/4" extension and hammer to bang on the pin to set cold, and bang on the diaphragm where the fuel lines attach to set warm. It's convenient that these pressures can be set by jumping the fuel pump relay socket. There is no need to start the car. To simulate warm conditions, apply 12v directly to the WUR and let the heater bend the bimetallic into hot state.
Here is the order I did it from first install. I went carefully so that I wouldn't have to disassemble and push the pin and diaphragm back out and start over.
1) Set cold pressure to top of the range. Ideally, use the nice chart in SI 6/77-272. There is a low res version in the factory manual too. From memory, I was at about 35 psi and tapped it down to about 22 psi.
2) Apply 12V to the WUR and watch the pressure climb, it takes about 10 mins to stabilize. Set the high pressure to the low end of the range of 49.8-55.5 psi. I think mine was around 45 and I hit the diaphragm in until it hit 51 psi.
3) Let the car sit overnight and the next day, check the cold. Mine was about 25 psi and I hit the pin carefully until about 20 psi.
4) I started the car and let it fully warm up. It warmed up a little rough, still lean maybe, but the warm pressure hit 52 psi which is perfect. No need to adjust hot.
5) Let the car sit overnight again and set the cold. Now I was really close, I was just out of range and I punched it down to the middle of the range, I think to about 17 psi. I checked hot by 12V to the WUR and the hot was still 52 psi. I started the car and ran it until fully warm.
6) Next morning, ran through the tests - cold pressure, 18 psi center of the range - perfect for the current temperature. 12V to the WUR, high pressure hits 52 psi. Keep 12V on the WUR and shut off the pump. Check leakdown after 20 mins - 21 psi.
Finally, drove the car and it ran as well as I can ever remember. Fired on the first throw, smooth warm up, idled perfectly, all the power is back.
posted by 66.75.233...
https://k-jet.biz/rebuild-manuals/
1
, Fri, 30 Apr 2021 17:08:06
, Thu, 18 Mar 2021 05:41:20
, Thu, 18 Mar 2021 04:08:53, Fri, 19 Mar 2021 04:07:50
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