Carter to Walbro:

Yeah, another "Walbro" install ‑ but with a few minor twists.

My OEM LP and added Carter pusher have been operating flawlessly for 50K miles ‑ and no REAL need to change ‑ but I do also have a Frantz sub‑micron fuel filter installed, which adds significant restriction to fuel flow, especially under high engine loads such as mountain grades towing our 5th wheel.

SO, after hearing a year or more of enthusiastic claims about the Walbro pumps, I decided to try one myself. First, I made up and installed a homebrew regulator valve to bleed off the Walbro's excessive flow and PSI



That is installed immediately in front of the VP‑44 where my fuel PSI is also monitored, since it's the PSI my VP‑44 sees that I am most interested in keeping as proper and constant as possible. I ran this setup with the OEM LP, relocated to the frame rail near the added pusher, for several weeks to make certain the regulator functioned properly ‑ I got a steady 15 PSI under most normal operation ‑ but higher loads would see PSI drop to 10 PSI ‑ sometimes a bit lower. It was OK, but I wanted steadier and higher PSI, especially at higher engine loads ‑ so it was time for the Walbro.

I removed the Carter 7 PSI pusher I had been using, and swapped in the Walbro ‑ which also included the same added automatic fuel bypass valving I have used on both the OEM LP and pusher to avoid fuel flow failure if the pump fails:



The OEM LP is still in the fuel line further up the line from the Walbro, but is disconnected electrically, and the fuel flow is routed around it by it's included automatic bypass valve. If the Walbro should fail, all I need do is disconnect the power lead from the Walbro, and connect the OEM LP ‑ which would probably take only a minute or 2.

Result at this point is a typical 20 PSI as measured right at the VP‑44 ‑ dropping slightly to 18 under most driving situations. Heavy, WOT operation when towing our 5er up a steep grade drops PSI to about 14 ‑ which is entirely adequate and acceptable in my opinion ‑ undoubtedly the spread in PSI would be considerably less without the added Frantz restrictive fuel filter ‑ but the combination of Walbro and Frantz gives me excellent fuel filtration, combined with excellent fuel flow and PSI.

OH, do the added bypass valves really work? YUP! Immediately after installing the Walbro, I started the truck to make a run into town ‑ and my low PSI alarm and warning light activated. The engine was running fine, but PSI was at ZERO! I wiggled the power relay that controls the power to the fuel pump(s) ‑ and the Walbro started up as it should, with normal PSI.

This happened a couple of more times before I got time to closely inspect the connections at the base of the relay, and found a loosened solder connection ‑ which was quickly fixed.

Without that added bypass valve at the Walbro, the total fuel flow would have been shut off, and the engine would not have operated. As it was, It might not have operated well at any significant load, but WOULD at least get me to a safe place to provide an inspection and fix!