Lookes like you guys are on the right track....
thesameguy":9l6pbpcl said:
Also, Ford ran with that goofy low-pressure/high-pressure pump combo for a while. My '86 XR4Ti has the same setup. Long time ago I eliminated the under-belly high-pressure pump and replaced the in-tank low-pressure pump with a Walbro 255lph pump. Runs my XR at 20psi very nicely.
I never really understood that dual pump setup, but things like it were common on European cars of the time - Saab had a combo pump configuration up to 1987, although both pumps were mounted in the tank. I suspect they weren't confident in or motors weren't developed enough to perform both tasks (scavenging the tank and pressurizing the rail) reliably. Plenty of cars even had surge tanks ("fuel accumulators") and dampers in the system to ensure consistent pressure. By the late '80s or early '90s, most people abandoned both. This morning, in fact, I eliminated the dual pump and damper in my 1985 Saab and replaced it with a single in-tank pump.
Since you guys here are mostly American, there is a gas station everywhere. So you've not dealt with net postive suction head related matters caused by a pump not being able to scavenge down to the same almost empty level as a mechanical fuel pump can. And that is a major issue, because, if your in Noo Zeeland where the relief is sharp, or on, say, the Yukno Trail in your EFI Jeep, its a major issue.
The Lo and Hi pressure pump was the solution by the Swedes and Australian Fords, which had shallow tanks to maximise trunk space.
The change has been the modern, all in one, in tank module mounted, prescreened, prepriming , integrated modern pumps with check valves. GM Opel and MB and BMW got it together first, but Ford Germany with its Capri RS 2600, Granada 2.8 Injection, Sierra XR4I 2.8, Merkur took a lot longer due to a lack of gas tank height. Uwe Bahnsen and Cortina/pinto designer Ray Brown Jr decided on the same shallow fuel tank design. GM's T car just had the ages old Vauxhall style behind the rear seat upright fuel tank, and by the time the V car arrived in 1978, the tank was set down in a deap trunk, offset to the side, similar to the MB W123 series.
Due to the shallow nature of the Mustang gas tank before 1979, its impossiable to easily fit such a system in tank, so Ford started out with a copy of the GM V car Opel Commodore/Senator/Monza style fuel tank pickup, but a LO/HI two pump system for reliablity of fuel flow right down to dead empty.
I had no problems with my Mustang in getting down to the last ounce of gas, I had to do the 15 US gallon load up everytime I go for a 600 mile day trip, as the 12.4 US gallon tank was too small.
but in my Explorer, it wouldn't start on a tail up incline when stopped with less than 1/4 of a tank. That is fatal in some circumstances in the steeper than San Fransisco Shakey isles.
See this 9 minute video. Yeah, it is Airtech, but covers off some of the issues.
https://www.youtube.com/watch?v=QbzEeWy1b3o
And understand the
whole in tank module system assembly can fail
http://www.popularmechanics.com/cars/a2 ... -cop-cars/