2nd Gen Non-Engine/Transmission Negative Numbers on SPA Fuel Pressure Gauge!

[RADdodge]

Since I installed a SPA gauge for fuel pressure and transmission temperature, the fuel pressure would occasionally and intermittently flash the negative sign next to the number. Needless to say, this bothered me. I really thought it was just a gauge issue, but I tried replacing first the gauge, then the sender with no change. It’s hard to just ignore it since the effects of no fuel to the injection pump are well known. Anyway, I also tried a separate ground wire from the intake manifold to the bracket that holds the sender. I have a good connection to ground. At first I thought that fixed it, but then noticed that it still flashed negative numbers. I finally disconnected the setup and hooked up a mechanical pressure gauge. The gauge only reads to 7 psi, but it was steady and I couldn’t see it go less than 7psi much less to suction! I also tried setting the Alarm to 3 psi. The alarm LED constantly flashes. Much more than the negative pressure indicator. Anyway, I’m at Wits End. Anybody have any ideas about what might be going on? I. e. HELP! Thanks...

 

[HC]

SPA's seem to me to require very good (perfect) electrical connections; I had to solder some of my connections to get good numbers.



Call SPA at 317-271-7941 and they'll help you "debug" your problem.

 

[illflem]

Your sender is probably shot. It has always been my opinion that no fuel pressure sender will last long in a diesel. That's why mechanical is the only way to go.

 

[Ron Bissett]

You may have a good gauger and a bad lift pump . looks like the pump is not doing the job , you need at least 10 to 16 at idle and not less than eight under load see others post on lift pumps , you stated that the mechanical gauger had a reading of 7psi then that is all it pump is putting out the injector pump is sucking the fuel and that is causing the neg reading . Dc will replace if low power power towing or heavy load is stated by owner star has to approve all pump replacements. Take it from here ,LOL Ron in LOUISVILLE KY:-{} Oo.

 

[Powder Extreme]

I had that exact same problem, it isn't a bad sender, and it isn't a bad lift pump, it's a bad connection. Clean the connection at the sender and wire, then apply a liberal amount of di-electric grease and put it back together. If you aren't familiar with this stuff, any electronics supply store or Radio Shack will have it as well as electrical contact cleaner (be sure to get stuff safe for use on plastics).



Spa sent me new senders etc. trying to fix the problem, finally I did it myself with this grease. I wish I had thought of it sooner.



P. S. It will also fix alot of the issues people are having with the Comp Box.



Jerry

 

[TomGolden]

First, I'm sorry to hear of your problems. Secondly, man, am I glad I am not the only one with this same problem!!



I had 3 new SPA Series 2 gauges installed about 2 months ago: EGT/boost, oil temp/fuel pressure, transmission temp/rear diff temp. As soon as I got the fuel pressure gauge in (all 3 done at same time), I discovered my original lift pump was dead, so I immediately replaced it. Until last week, I had never seen any erratic readings from any of the gauges, then suddenly, my fuel gauge started reading large negative numbers, and violently skipping all over the place from -6 to 16 PSI and every value in between. Then, 3 days ago, the oil temp gauge started doing the same thing! Even when I just start out in the morning, I might suddenly see 270*F on the oil temp!



I'll have to get to Radio Shack and get some di-electric greas and try this with all the sending unit connections.



Tom

 

[Bigsaint]

Ditto on the above. I had vacuum numbers on my SPA FP gauge once, turned out to be the Mallory lift pump DOA. Just for the heck of it, pull the elbow off the sender and disassemble same. All you need to do is to remove the center screw, then depress with a small but blunt tool where the screw was seated. This will allow you to view the SPA connections. You will see that they aren't held in place by much exposed wire.



Scott W.

 

[Brandon]

tom let me know if i can assist, they should not be doing that





adios, B... ... ... ... ... ... .....

 

[Sled Puller]

My boost guage does the same thing. I don't think SPA and Diesels mix well.

 

[DHRA]

reset

maybe it's not an option anymore, but I can zero mine out. After a long period of time, mine reads -. 00. I can turn the power on, go til it says "pr" on the screen and hold the button in for a couple of seconds. Then just key back on and it is reset.

 

[HVAC]

I have found the potential to read negative numbers to be helpful. When my Mallory pooped out on me over a year ago I was warned by my gauge going negative. This was the first clue as to the problem developing. The pump was inconsistant but the gauge was right on and warned me at times when the Mallory stopped working.



I have also seen negative boost at idle. Rezeroing the gauge cured that problem.

 

[JR2]

I finally got fed up with the poor connections on the SPA's and hard wired them in with a cannon plug style connector. Once I did that I have had zero problems... .

 

[RADdodge]

Thanks For The Help Guys...

Well the last thing I tried was replacing my original ground wire from the intake manifold with a 6 AWG wire from the sensor to the single point ground on the chassis on the left side. I did that for several reasons, but anyway the gauge started to work correctly. But since the connector was reseated, I'm not sure if it was the new ground wire or reseating the connector that fixed the problem. I'm going to get some of that grease so I'll be prepared the next time it starts acting up. I love the SPA gauges, but they have to be trustworthy. I wish SPA made a Pressure/Pressure gauge so we could monitor two spots at once. Thanks again

 

[HC]

Re: Thanks For The Help Guys...

I wish SPA made a Pressure/Pressure gauge so we could monitor two spots at once. Thanks again

Several months they had a pressure / pressure gauge in production; but it was on backorder. By now, you should be able to get one. Another good source of gages is Dakota Digital...

 

[GotDiesel]

HC

Do you have a link to Dakota Digital??

Thanks,

Later...

 

[JR2]

You can always install two spa press senders and a switch to one gauge... ...



John

 

[RADdodge]

Boy, do I feel dumb! That's an excellent idea! Has anyone done this with a SPA gauge? I guess you would have to switch both leads. I believe it’s a differential circuit if I remember right. Has anyone added a switch between two sensors and one SPA gauge? DPDT I suppose. P. S. – Nice pictures John…

 

[TxDieselKid]

negitive boost numbers.....

Whenever I see this, I pop the hood, and jiggle the connection of the 2 wires, and then there is no problem.



Andrew

 

[TomGolden]

Yep,



I opened the hood yesterday morning before going to work, un-did the connections for fuel pressure and oil temp, re-seated them, and have not seen the slightest bogus reading since. Will be picking up some dielectric grease this week and thoroughly re-seating all my SPA and Comp box connections.



Thanks for the suggestion!



Tom

 

[Powder Extreme]

Glad I could help, it sure cured my problem. Spa told me they were glad to hear it too and were going to start recommending it to people.



Jerry