new report on fuel pump (Walbro inline) for fuel injection

[jaywithtype3]

New report on fuel pump for type 3
Altho no one has said why new/rebuilt working 3-port pumps cannot be found, I have verified in testing an inline 2-port Walbro pump GSL392 for replacement . It requires ~7 volts & ~5 amps for good flow & 28 psi+ pressure. I put 1 ohm resistor in series to take up extra power rather than overdrive pump & fuel, as seen & heard.
Instructions with pump give no specs & are short on electrical & plumbing. Need to rig water-proof connection to 6-32 thread terminals with #12 wire splicers & maybe add silicone. Use spades to go in original pump connector. Couple on J-bend of 15 inches of 5/16 copper tubing to bring outlet around near inlet for connection to VW’s fuel damper & to main line. Inlet connects to filter & tank. (Pump has 1/8 FIP threads; use their pipe to barb adapters & copper seal, or other 1/8 plumbing. VW system does regulation & only returns to tank) .
Room under tank to rig clamp to put pump where old one was, BUT pump needs ~11 inches & must mount higher, farther back, and closer to car center, by ~ 2 inches each, with new hole in plate, standoff, & redone clamp.
For a good short illustrated report on theory & rebuild of 3-port pump, see document on British Type 3&4 Forum. It doesnt cover all issues. A link is in post after my post, on their Workshop.
Thanks to several advisors under my first fuel pump topic to get this far.

[supaninja]

I don't understand why you dropped the voltage to the pump. The more voltage to the pump the less current it draws and ultimately the longer it lasts. I originally ran a walbro through a Ljet regulator (fixed 30 psi) and it worked just fine. Any excess flow just gets returned to the tank. BTW- walbro's are rather whiny, that is normal. I have a filter to the inlet of mine and it gets real loud when it's time to clean it.

[aircooledtechguy]

More over thinking and back yard over engineering for problems that really don't exist. . . Brought to you by jaywithtype3

[jaywithtype3]

overlooking backyard sniping, easy to see, using variable voltage supply, that increasing V to pump is accompanied with increasing I (& flow) in real test with kerosene.

[Piledriver]

MS3 can actually do variable fuel pressure regulation via PWM if you are inclined to go for absolute overkill...
PWM alternator voltage control too.

[gearheadgreg]

Can MS3 handle the amp load to PWM a pump?

[Piledriver]

Can MS3 handle the amp load to PWM a pump?

Using the proper driver transistor, yes.
(This is a real feature folks are using...)

In fact, the 2 std mainboard injector drivers each are rated to IIRC 10-12A, if you have an MS3X they are available for ~any other purpose, and probably ~ideal for that purpose, possibly need a mod for reverse voltage spikes, but it's been done.

Unless you are running a roller cell pump, one channel would likely be more than sufficient.

I would personally be inclined to use an external DC solid state relay if only to keep the electrical noise out of the ECU, same as ignition coils.