I have had a question come up in my mind awhile back, and then come to find out OTC tools had the same idea. Every now and then we will have an engine come in the shop that has common rail fuel system, and we need to check the rail pressure (no start/hard start/low power). And of course, it will be a brand that we don't have a scan tool for (Deere, Cat, etc.). I have wondered how hard it would be to back-probe the fuel pressure sensor and read the voltage and get an idea of fuel pressure. Then I see that OTC has a tool to do this (p/n 3674). So apparently it can be done. My question is how much difference is there between the signals of different manufactureres? As in, if I have one engine running at 18,000 psi and a reading of 2.5 volts (just a # I pulled out of my head) would a different brand of engine running at the same pressure have the same voltage reading?
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Common rail fuel pressure reading?
- Thread starter inthedirt
- Start date
YukonJeff
Active Member
from my experience, the systems are close enough that you can at least diagnose your no starts. 0.5-4.5 Volts, typically require minimum 4000psi rail pressure to start, peak pressures are usually 18-26ish,000psi.
Most are a re-branded Bosch fuel system now anyways.
Does the OTC tool just show voltage? or does it translate to pressure?
Most are a re-branded Bosch fuel system now anyways.
Does the OTC tool just show voltage? or does it translate to pressure?
It says it alternates between voltage and pressure readings. It might be a fairly cheap alternative to having to have the MFG electronic software and tooling... and it might be fairly inaccurate. ? I just wasn't sure what everyone else uses to check out oddball equipment for fuel pressures.
YukonJeff
Active Member
not a ton of Common Rail stuff here, and that stuff that is I've got the software for. I think that OTC tool would work well though, doesn't need to be perfectly accurate, so long as it's within a couple hundred psi you'll be able to tell if you've got a rail pressure issue on a no start.
Tractorguy
Well-Known Member
Most all Deere machines with a rail you can look at it through the monitors. I’m not familiar a enough with other brands but skid steers, loaders, dozers, large excavators, skidders, cutters, log loaders, backhoes, graders, can all be viewed in screen
