SW FUEL PRESSURE READINGS

[ROAD WARRIOR]

I was wondering if any of you guys had any ideas on this?

I purchased and installed the same SW sender and gauge part numbers that Steve St. Laurent installed on his truck. I have only one sender and it is mounted on the incoming test port, pre filter.

After installing the gauge, it would read 12 psi at idle and about 11 psi down the road. Once in a while the gauge would start jumping all around down to zero and back. I figured my pump was going out so I replaced it with a JRE pump. After that it was fine for a while and then I started losing pressure at idle until I goosed the accelerator. This didn't make sense so SW sent me another sender unit. Now that I put this one on, I am getting 13psi at idle, but as soon as I reach highway speeds in 4th or 5th, I am reading -5psi. It will remain like this unless I floor the engine or depress the clutch at which point it will come back to 13psi.

I checked all of my connections and all seem to be good. I measured the signal voltage at the sender and get 6VDC(13psi) at idle and when I raise the idle, I get 11VDC(-5psi). I think my pump is ok, i believe the problem is with the SW gauge or sender.

Sorry about the long post, but I could use some ideas. I can't get through to the tech. service at SW, and I am paranoid driving my truck around at -5psi. Thanks for any help.

Dan

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'99 2500 4x4 QC, 5SP, 4. 10, LSD, SLT, DR. PERFORMANCE PHASE III, BANKS 4" EXHAUST(no muffler), BANKS BOOST& EGT GAUGES, SW FUEL PRESSURE GAUGE, BILLET ALUMINUM TURBO INTAKE HORN, AMSOIL AIR FILTER, ROCKFORD FOSGATE AUDIO SYSTEM, DMI QUICK & EASY HITCH, BD 2 LOW KIT, NRA MEMBER

 

[illflem]

Dan, I went though two S-W senders before I gave up and went with a mechanical gauge. The first one read 25 psi (which is ok for 12 valve) all the time, when I checked it with a mechanical gauge I found that it should have been moving around much more. I replaced the sender and the next one read 22 at first then after a few months crept slowly down to zero. Since I installed a mechanical gauge I'm happy to say that it stays at 22 psi much of the time with minor movement.

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95' 25004X4,AT,Driftwood,Banks Stinger,Warn fender flairs and running boards(work truck)
95 3500,5 speed 3:54,BD E-brake,Driftwood,Banks&Psycotty,34,000 GCVW apple and tractor hauler(works harder truck)

 

[BigCarl64]

You do realize that the sender must be well grounded. I have the same setup from SW(bought from XK's) and had the same problems described. I then ran a separate ground wire from the sender to the frame and my problems went away. The gauge has worked perfectly since.

 

[ROAD WARRIOR]

Well, I found my problem today. I hooked the sender unit up to an adjustable air regulator and checked the resistance. At 0psi it read 240 ohms and swept to 8 ohms at 20psi. But, from 66 ohms it opened and then came back at 53 ohms. This was right around 13 psi. I'm glad these are assembled in Mexico. I guess i'll try my luck with a third sender.

Thanks for your replies. If I can't get this resolved, what is a good mechanical gauge?

Yes, I did check my ground and it is good. I even ran a second ground wire to the gauge ground and this made no difference.

Thanks again, Dan