Hobbs Switch Testing

[Leonidas514]

Anyone know how to test this style Hobbs switch? I tested with an ohm meter by both blowing and sucking on it but didn't get any change in ohms. I also tested each of my 3 fuel pumps my running 12 volts to them, all 3 worked. I tested on my Fore module pump #1 pump had constant voltage as it should. I tested both pumps 2 and 3 by smashing the gas (hoping to create a little boost and engage the pumps) neither pump kicked on and didn't get any voltage. I ordered a new switch for shits and giggles but this things starting to PISS me off.

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[TRP45ACP]

Not technically a hobbs test; however, I have found you can unplug the switch from its connection and short the male plug (the one to the hobbs) across its own leads with a paper clip for example. You should see a slight increase in your fuel pressure at your regulator verifying the second pump (in my system) is operational. Other than that, a data log at higher RPMs should reveal whether or not you are running lean. How does your trims and Lambse look?

 

[Leonidas514]

Not technically a hobbs test; however, I have found you can unplug the switch from its connection and short the male plug (the one to the hobbs) across its own leads with a paper clip for example. You should see a slight increase in your fuel pressure at your regulator verifying the second pump (in my system) is operational. Other than that, a data log at higher RPMs should reveal whether or not you are running lean. How does your trims and Lambse look?

Lamda and trims look fine according to the tuner. Lambda if I recall is between .73 and .80 around 6K

 

[TRP45ACP]

Why do you believe you are running out of fuel?

 

[Leonidas514]

Why do you believe you are running out of fuel?

Because when I get up high in the rpms the car surges really bad and doesn't seem to be pulling like it should. I honestly don't think I am, I just want to test everything to eliminate all possibilities.

 

[TRP45ACP]

Who is tuning the car? Have they looked at it? It may helpful to upload your latest log for comment.

 

[Leonidas514]

Who is tuning the car? Have they looked at it? It may helpful to upload your latest log for comment.

PBD is. Not sure if it's cool to post the log?

 

[TRP45ACP]

This may seem obvious but I would check with pbd where the rev limiter is set. More importantly, is pbd seeing anything on the log? What is their feedback?

 

[Leonidas514]

This may seem obvious but I would check with pbd where the rev limiter is set. More importantly, is pbd seeing anything on the log? What is their feedback?

Feedback. Lol

The limiter is set to 7500 but the car has never made it there. It usually hits about 7200 and then the rpms start to drop, then it will shift around 6500. I am putting in a fully built PBH trans on Thursday with a new Torque Convertor to make sure its not a trans or convertor issue. I actually reflashed the car today with the same tune and it started up fine and before it would take my foot on the pedal. Now I've had too many beers to test. Lol. I did another compression test today and all good there also. I also jumped the boost valve plug like you suggested and the fuel pressure did raise about 5 pounds. Thanks again!

 

[wazslow]

Did you ever try unplugging the "dyno" plug by the airbox? I had some weird breaking up, almost felt like a limiter, but it was the throttle body closing due to the traction/stability control.

 

[Leonidas514]

I just unplugged it. That's a good call, will try and see if that worked.

 

[TRP45ACP]

Old post I realize. Curious how this ended up.

 

[andrewtac]

To add, I test mine everything before I make a hit. I have an led in the pillar, I give enough fuel to trigger it. I realize all this indicates is voltage, but it is no different than assuming the pump is working if hard wired.

 

[TRP45ACP]

That’s a great idea. Your running an led off pump two with a Hobbs switch, no? If so, assuming once in boost, fc3 sends power to pump #2 while also lighting your led. I will add the same as that is the critical one.
I did replace my #1 267 pump today as it stopped producing pressure at 20mph, car died. Switched the leads in the fuel hat to make it home. Can’t believe the pump failed after 3000 miles. Grateful it was #1 however

 

[andrewtac]

That’s a great idea. Your running an led off pump two with a Hobbs switch, no? If so, assuming once in boost, fc3 sends power to pump #2 while also lighting your led. I will add the same as that is the critical one.
I did replace my #1 267 pump today as it stopped producing pressure at 20mph, car died. Switched the leads in the fuel hat to make it home. Can’t believe the pump failed after 3000 miles. Grateful it was #1 however

Correct I get pull voltage from the tap going to the pump and it lights the LED. I did get a lower pressure hobbs switch (2-3 psi I think). I do a quick small throttle stab while watching the light, then get out of it before I do any full pulls. Sort of like a quick systems check of everything. During a full hit, it is hard to watch for the light as I am usually more worried about going straight but I do notice it sometimes.

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