Fuel pressure gauge problem Help!

Post by **swoakes** » Wed Jul 25, 2018 6:25 pm

I have just fitted a new regulator to the Sprint car with a new sender and gauge.

I messed up on the gauge

The gauge maxes out at 10psi and the car runs at 2-3 bar (30-45psi)

Gauge and sender were expensive and fitted so I would like to use them

Josh reckons that we can fit a resistor in-line to the gauge input

I would like to alter the gauge reading by a factor of 10 so that 1 psi on gauge is in fact 10psi.

Can any electrical bright sparks confirm if this will work and if yes the size of the resistor required (or how to calculate it).

Post by **philhoward** » Wed Jul 25, 2018 6:34 pm

Short answer is no - need a sender with a different range (x10). A resistor won’t do it.

Post by **peter freeman** » Wed Jul 25, 2018 6:48 pm

Do you know what the output of the sender is and what the input the gauge is requiring. Of course you would need to alter the range shown on the gauge which would mean a new scale being fitted. If you bought the two together how come the seller did not notice that the gauge and sender did not match - have you tried to get them to exchange the gauge for one of the correct range.

Post by **philhoward** » Wed Jul 25, 2018 6:57 pm

Trouble with a quick answer - reading it too quickly

Might be possible but as instruments normally are specified to give full scale for their rated values have you got links to what you bought? If a matched set, then it’s probably not rescuable. If it’s two separate items you might be ok one way or another.

Post by **swoakes** » Wed Jul 25, 2018 7:01 pm

peter freeman wrote: ↑
Wed Jul 25, 2018 6:48 pm
Do you know what the output of the sender is and what the input the gauge is requiring. Of course you would need to alter the range shown on the gauge which would mean a new scale being fitted. If you bought the two together how come the seller did not notice that the gauge and sender did not match - have you tried to get them to exchange the gauge for one of the correct range.

Purchased from Merlin motor sport. The gauge and sender do match but when connected gauge just maxes out due to the high pressure. They don't seem to do a gauge for high pressure applications. Looks like I'll have to send them back. I can get a mechanical gauge that will do the job but really want one in the cockpit. The last gauge and sender were cheap Chinese rubbish really

Post by **peter freeman** » Wed Jul 25, 2018 7:37 pm

If the sender is made for 10psi then the higher pressure will just blow it apart. Sorry.

Post by **swoakes** » Wed Jul 25, 2018 8:13 pm

peter freeman wrote: ↑
Wed Jul 25, 2018 7:37 pm
If the sender is made for 10psi then the higher pressure will just blow it apart. Sorry.

Don't think it would Peter. Proper bit of kit £72+Vat

https://www.merlinmotorsport.co.uk/p/co ... r-cbc-ft-1

Post by **peter freeman** » Wed Jul 25, 2018 8:52 pm

Pressure transmitters are something I do know about - putting 4 times the pressure on it would at best distort the pressure head. In the marine world we used 100mv transmitters, 2v pressure transmitters and 4-20ma transmitters. All cost about £300 not that you can get anything but the 4-20ma type now.