So i have two working fuel pumps, and can’t decide which to use on my 88 XJS V12.
Walbro GSL391 - Flow rate 190LPH @43.5psi
Bosch 69536 (580464008 with turbine tech.) - Flow rate 130LPH @43.5psi
I’ve heard the Bosch turbine is better tech and quieter, and 130LPH should be fine for up to 350hp, so I’m leaning towards the Bosch.
130 lph is puhlenty for your street engine.
And too much is not good here. Just puts more heat into the fuel.
I would go with Bosch. Reliable quality and sufficient flow rate. Extra flow rate will not give you any benefit on stock engine except extra heat.
Thanks for all the advice guys. I will go with Bosch, especially since I removed my A/C fuel cooler.
Follow up…the Bosch pump I bought and installed back in Dec, 18, it intermittently made loud whining sounds over the first few months. Some days it was quiet. Well, lately it’s noisy 50% of the time, every day. But fuel pressure is good, and so is acceleration. I looked everywhere for kinks or plugged filters, found none. Today I put my previous Walbro back in, whining noises gone!
I guess I either got a bad Bosch, or it was compromised when I ran it back in Dec on a bad tank of gas?
One thing though, when the Bosch is not whining, its very quiet. I can hear the hum of the Walbro if windows are up and radio is off.
My belated two cents.
Walbro and Bosch are quality products. Each has been around for over a century,I think!!
Aye, the Bosch may have a bit of detritus. As you suggested, from the bad gas. Back spinit and flush it on the bench.
But, leave the Walbro in. It works!! Bosch as a spare.
Carl
Greg,
The Bosch fuel pump in our 1990 XJ-S convertible (5.3L V12) would occassionally whine, particularly on very hot 100F+ days after a long drive and when low on gas. The whine was not normally noticeable from inside the car while driving with the top down, but when stopped it could be clearly heard particularly with the radio off. There was also a slight stumble while accelerating up a steep hill while the whinning occurred. But whenever this happened, the following cool morning when the car was driven again the fuel pump would be very quiet. I drained the fuel tank and inspected the fuel strainer (that I replaced a couple of years ago in the surge tank) and everything was fine there. When I inspected the molded OEM fuel hose that I got from list member Ed Sowell a couple of years ago it had a definite kink at the pump end. So I purchased a 1/2 inch EZ COIL, some 1/2" fuel injection hose (I know that was overkill) and installed them as shown in the attached pictures. We drove the car in recent 100F+ temperatures and the fuel pump remained quiet. I am not ready to declare victory over the fuel pump whine, but so far it looks pretty good.
My conclusion so far was that the fuel pump whine was caused by internal cavitation due to the kinked hose and fuel blockage. The kink was made worse when the hose softened due to elevated fuel tank temperatures. Although this car had functioning air conditioning and a fuel cooler, it is not functioning now do to a refrigerant leak that is on my list to fix.
Paul
Hi Paul,
Going with a little longer hose will also alleviate the kinking tendency.
I sent you a request earlier this morning for a copy of your legend that gives the coding for the colors of the wires out of the ECU.
Do you or anyone know the resistance of the Power Resistors?
Paul
The thing about that kinked hose is that it’s also likely to pull the fuel pump out of position. That foam mount does not hold it securely, and a bit of dislocation in nearly any direction can cause it to transmit more noise into the car. Worst of all is sliding downward until the outlet end jams into the floor of the trunk. I had to fab a stop with a hose clamp around the pump to prevent it from sliding downward to put a stop to this.
Paul,
The fuel hose in the first picture was a New Old Stock OEM molded hose, C46109/1 that I got from a fellow lister. It’s a little difficult to lengthen an OEM molded hose. 
The hose that I used with the EZ COIL was plain 1/2" fuel injection hose that I got from the local NAPA auto parts store. Because of that 90 degree bend it too would have kinked without the EZ COIL especially when the fuel temperature rose. There is a sweet spot when it comes to hose length and bend radius for a 90 degree bend. Cut it too short and it will kink, cut it too long and it will kink. I started with a length that was too long and shortened until I found what looked like the sweet spot. Then I put the EZ COIL on and hopefully that will continue to work well. As Kirby points out it is a tight space with little room to maneuver.
Did you get my PM with the information you requested on the S57 legends?
Sorry, but I don’t know the resistance of the Power Resistors. That info might be in the XJ-S ROM. I am headed out the door now but will check my hard copy ROM for that tonight, unless someone provides it sooner.
Paul
If they both exceed specification, then go with the fuel pump which draws least current, i.e. the one whose measured resistance is highest. The logic here is that the excess current draw goes into producing heat. The only thing stopping the pump from overheating is the fuel flow and so you can load the odds in your favour by choosing the pump which generates the least wasted heat.
kind regards
Marek
Follow up, the walbro has not whined like the Bosch for a week now.
And the slight hum I could hear from the cabin is gone now that I installed a new foam sleeve for it.
Great to know. Appreciate you coming back to let us know
