Test three: Facet at source direct current from battery 7 psi. Test four: switch circuits measure after regulator bendix 6.5 psi at idle 4 psi at 3000 rpm. Facet 7 psi at idle .5 psi at 3000 rpm. Notice after shut down Bendix retains pressure, Facet does not.
The regulator is on the engine compartment, close to the fuel rail. I agree, 7 psi after the regulator is too high. The Facet pump dropping to .5 psi at 3000 rpm is an indication that the pump is not delivering enough volume to meet the demands of the carbs. Joe: did you test hot wiring the Facet pump and checking pressure at 3000 rpms? Ivan
Have not direct wired the facet and ran the engine as of yet, may try that tomorrow. However that would be only be masking the problem which is the fact that the facet pumps are under performing under load.
Joe, Trust me on this one, this is the voice of experience talking Webers like the fuel pressure to be between 2.5 and 3 psi. You may also have to replace the regulator, but first lets get the Facet pump pressure to be above .5psi, after the regulator, when running at 3000 rps. I really think your problem is not enough amperage going to the Facet pump. You might be making the wrong assumption that the Facet pump is identical to the Bendix pump and that simply is not the case. They are electrically different therefore do not expect them to behave the same way. The Facet pump is most likely not defective, it is simply not getting enough amperage to work properly. I think you will find that if you give the Facet pump enough amperage it will work fine. As a test, you need to hot wire it using at least a 16 gauge wire. If this fixes the problem then we can talk about how to permanently wire the pumps using a couple of relays. Ivan
Might as well check that off the list of possible causes. Checking the voltage level during these tests at both pumps old & new would tell you if there's not enough current too. It doesn't take all that long but I'd be surprised if the two pumps are that different. You need to check everything because you haven't fixed it yet. Before you claim the pump isn't working properly measure it's performance - outside of the car. If you never do that then you're just pissing in the wind.
Joe, Bench-test the lot, measure flow and amperage taken up. The Facets are either not performing to spec or you have too little current to make them operate properly. I'd be surprised if both Facets turn out to be bad, but I'd also be surprised if a more modern pump than the Bendix would take up way more current to produce the same flow. If the latter is the case, I'd certainly consider putting a relay in the car to feed the pumps, as you may be overloading the existing circuit. First thing to check though is if the switchgear is functioning properly and at the right voltage. You may simply have a dirty ort corroded connection somewhere. Best, Jack.
That's strange. Another Italian-English or just plain old typo? You're in danger of overwhelming the float needle valves. BTW, I noticed that the old Bendix held the pressure once turned off. That tells me that it has an integral shut off valve. That model of Facet pump does not. Once this pump problems been solved you might want to think about why Maserati had that in there. Fuel can't errantly flow from the tank that way so not knowing the layout of that fuel system I don't know how important that is. You can add a fuel cutoff solenoid valve like I did on my Espada. I don't know if you'd need a pair like the Espada does to prevent tank to tank cross flow which then leads to an over flow,and ruined paint when you park on an incline. At one point you said that the union has a check valve for each side? The description just says union? You might also want to try an bypass that check valve #14 and block out the other tank to see if that's somehow involved here. If that doesn't have a check valve internal to it then one pump will always be pumping against the other and if the pump also has no check valve or cut off the perhaps fuel could be pushed backwards through it by the other pump? My old Bendix does have a check valve as a part of design of the pump mechanism. If the new ones don't then that might explain your problem if you've actually got the new pump on when you think it's the old one? But they sound very different right? Keep check everything ... Image Unavailable, Please Login
Bob, You make a good point there: If the union doesn't have a valve and neither do the pumps, part of the flow will be lost transferring it from one tank to the other. Easy to try, with a Bendix pump on one side and a Facet on the other. The Facet should then work fine. Unless of course the valve in the Bendix is not tight, which then moves the problem to the other Bendix pump rather than the primary suspect, i.e. the first pump is fine but the valve in the other is gone. Best, Jack.
The union also acts as a check valve. There is a flap inside that moves depending on which of the two pumps is running. Sometimes the flap fails but if there is proper pressure using the Bendix pump then I really doubt this is the problem. Joe: what year is your Ghibli? Does it have a single fuel line or does it have a second line going back to the tank? Earlier cars had a single line and keeping fuel pressure once the engine is off helps avoid vapor lock. Later Ghiblis used a recirculating fuel system where excess fuel returns to the tank. On these cars maintaining fuel pressure after shut off is less important. My money continues to be on a lack of sufficient amperage to the Facet pump as the culprit. But what do I know, I've only owned and worked on 30+ Ghiblis Ivan
A couple of interesting points on that union. At least in the parts books the same number goes in a Biora and looks like an ordiray tee to me. I ripped mine out many moons ago. That's a single tank/pump system. So the parts manual may be in error. My old original Bendix pump does not allow reverse flow but it has no flow cutoff in the other direction. Joe has move the various pumps, there have been 5 now from one side to the other and the problem moves which has me wondering if he does indeed have a union with one of those flap valves maybe the new pumps don't have enough pressure to push it open? Sounds weird I know but it's hard to envision why the Bendix pump works fine on both circuits and the new one does not. But I agree he should try it as it doesn't take that long.
I agree with Ivan. A poor electrical connection will produce low pressure. The connection is not only the power supplied but could also be a poor or weak ground. Perhaps the newer pump is more sensitive than the older Bendix units. Also, a weakened battery itself may create problems with fuel pump pressure. I know that this is a concern when converting the Lucas fuel pumps used on the Sebrings to the modern Bosch conversion supplied by Power Props. I would suggest that you charge the battery overnight. It may have become drained during all of the testing.
Ivan, It is a 71 Euro SS, the car before the Black US spec SS you had. It has many early spec feature fans in front and a single fuel line. I have no doubt that you are correct in that putting more power to the pumps will help them keep up with the performance of the bendix. I spent a good amount of time on the phone today with facet, they were shocked that their pumps would drop to .5 or less under load and the bendix did not. Their operating amperage is minimum of 1.4 and a max of 1.6. When I get a chance I will test the circuit.
That's a very low load then. I remain dubious. But the only thing that matters is if the pump meets Facet's specs in a virgin environment Joe. If it does then your car's environment is the problem. Why not start with that and potentially eliminate one half or identify the correct part of the problem?
