Switch?for dual sender Fuel pressure Gauge

[Fuzz]

I have a SW fuel pressure gauge with two senders,one before the filter and one after.
The switch I used is a small Radio Shack rated 10A@110V. It is 3 position ON-OFF-ON.
I used the ON-ON terminals to each sender the center terminal to gauge. Now one side of switch goes to full scale to left,if I increase engine speed. Other side reads normal.
Switched the wires and the problem switched with it. So don't think it is the senders or the gauge. What the heck kind of switch to I want to get for this.
Possible I screwed this one up soldering wires to it,but I thought it worked until just recently.
Fuzz,y2k 3500 4x4

 

[illflem]

Fuzz,your wiring and switch sound like they are done right,I would suspect a bad ground at one of the senders. SW senders are the single wire type,right?If you used Teflon tape to seal the senders it could be causing the problem,I always use anti-seize to seal the threads.

 

[Fuzz]

Illflem,thanks will check out the grounds tomorrow. SW senders are the single wire.

 

[Fuzz]

Checked the ground,thought sure it might be that. No luck.
So here is what I did today:
1. Unhooked both senders from switch and gauge.
2. Hooked suspect sender direct to gauge. (used new wire). This sender is after Fuel Filter. (Shouldn't matter?).
3. Started engine,gauge indicates OK at idle,
rev up engine and gauge goes to full scales to LEFT.
Seems that the sender may be bad,as other sender works OK with gauge,and the switch out of ckt,it still acts up.

I placed a call to SW tech line and left message. . they didn't call back(they could of tried and line was busy).

What else should I check. .
I did not switch locations with the sensors,couln't see that,that would help. ?
I did run separate wire from suspected sensor case to ground.
Thanks for any comments
Fuzz

 

[Steve St.Laurent]

When you say it goes full scale to the left are you saying that it indicates normally at idle and when you rev it up it goes to zero? If so you may have a restriction in either the lines, fuel filter head, or fuel filter. I'd swap the senders since one seems to be working fine and see if it still does the same thing - if so I'd change the fuel filter right away and check again. If it still goes to 0 then you have a restriction somewhere - do you have a prime-loc installed on your truck?



------------------
-Steve St. Laurent - President of the Great Lakes TDR
'98 QC LB (CMNSPWR), 4x4, ISB, 5sp, 4. 10 LSD, TST Powermax, 275hp RV injectors, SW fuel pressure gauge, BD exhaust brake, Isspro turbo temp monitor, front Draw-Tite receiver, rear Draw-Tite class V receiver, BFG 285/75R16 AT KO's, (all the common stuff clipped)

 

[Fuzz]

Steve,no I don't have a prime loc. When it goes to the left it buries the needle to the left. . off scale past zero. Truck is running fine... I kinda assumed it was something electrical,the way the darn gauge acts. It goes immediately to the peg on the left when engine is reved. I will switch the sensors tomorrow to be sure. Fuel Filter only has about 5000 miles on it and all Fuel bought from Busy truck stop. But could be. Will let you know.

 

[Fuzz]

I got the sensors switched around this AM.
The problem follows the sensor.
Good news is I don't have a fuel restriction.
The offending sensor when moved to pre-filter
does the same thing,ie,full scale deflection to the left when revving up the engine. The sensor that was there is now after filter and it reads steady.
Put these on in Nov. so guess it might be under warranty. . will start calling around.
Any ideas on whether my setup could of caused this?
Doesn't seem like it would just affect one.
Thanks for all the suggestions... Made me check things more thoroughly. I have a tendancy to shotgun stuff.
Thnx again,
Fuzz

 

[Steve St.Laurent]

Glad to see you figured it out. If the sender isn't covered under warranty at least it's just a $25 part. I don't see how your setup could have done anything.

-Steve

 

[illflem]

Fuzz,great to have a problem solved,eh?. The gauge zapping below zero sounded like the polarity was reversed,but that's impossible with a grounded body. Really had me wondering,in fact it still does. If you had a double pole switch with the wires reversed to the gauge that would explain it,but I gathered from your post it was single pole. If you take the sender to an auto parts that sells SW they might exchange it for you even though you didn't buy it there.

 

[Fuzz]

The switch is single pole double throw,I think. It is ON-OFF-ON. I used the center connection to the gauge. The ON connections to the sensors.
Called a local distributor here and they have a sensor and will swap out under warranty. Probably do that tomorrow.
Thanks for all the help